Notice Medi ci ne i s a n ever-cha ngi ng s ci ence. As new res ea rch a nd cl i ni ca l experi ence broa den our knowl edge, cha nges i n trea tment a nd drug thera py a re requi red. The a uthors a nd the publ i s her of thi s work ha ve checked wi th s ources bel i eved to be rel i a bl e i n thei r efforts to provi de i nforma ti on tha t i s compl ete a nd genera l l y i n a ccord wi th the s ta nda rds a ccepted a t the ti me of publ i ca ti on. However, i n vi ew of the pos s i bi l i ty of huma n error or cha nges i n medi ca l s ci ences , nei ther the a uthors nor the publ i s her nor a ny other pa rty who ha s been i nvol ved i n the prepa ra ti on or publ i ca ti on of thi s work wa rra nts tha t the i nforma ti on conta i ned herei n i s i n every res pect a ccura te or compl ete, a nd they di s cl a i m a l l res pons i bi l i ty for a ny errors or omi s s i ons or for the res ul ts obta i ned from us e of the i nforma ti on conta i ned i n thi s work. Rea ders a re encoura ged to confi rm the i nforma ti on conta i ned herei n wi th other s ources . For exa mpl e a nd i n pa rti cul a r, rea ders a re a dvi s ed to check the product i nforma ti on s heet i ncl uded i n the pa cka ge of ea ch drug they pl a n to a dmi ni s ter to be certa i n tha t the i nforma ti on conta i ned i n thi s work i s a ccura te a nd tha t cha nges ha ve not been ma de i n the recommended dos e or i n the contra i ndi ca ti ons for a dmi ni s tra ti on. Thi s recommenda ti on i s of pa rti cul a r i mporta nce i n connecti on wi th new or i nfrequentl y us ed drugs .
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Student Reviewers Constance Mennella Uni vers i ty of Medi ci ne a nd Denti s try of New Jers ey School of Medi ci ne Cl a s s of 2010 Leland Stillman Uni vers i ty of Vi rgi ni a School of Medi ci ne Cl a s s of 2014
Contents Contributors Introduction Acknowledgments High-Yield Facts High-Yield Facts in Microbiology Physiology and Molecular Microbiology Questions Answers Virology Questions Answers Bacteriology Questions Answers Rickettsiae, Chlamydiae, and Mycoplasma Questions Answers Mycology Questions Answers Parasitology Questions Answers Immunology Questions Answers Bibliography Index
Contributors Robert K. Bright, PhD As s oci a te Profes s or Depa rtment of Immunol ogy a nd Mol ecul a r Mi crobi ol ogy School of Medi cne Texa s Tech Uni vers i ty Hea l th Sci ences Center Lubbock, Texa s Immunology Relevant High Yield Facts and Revisions W. LaJean Chaffin, PhD Profes s or Depa rtment of Immunol ogy a nd Mol ecul a r Mi crobi ol ogy School of Medi ci ne Texa s Tech Uni vers i ty Hea l th Sci ences Center Lubbock, Texa s Mycology Relevant High Yield Facts and Revisions Jane A. Colmer-Hamood, BS, PhD As s oci a te Profes s or Depa rtment of Immunol ogy a nd Mol ecul a r Mi crobi ol ogy Texa s Tech Uni vers i ty Hea l th Sci ences Center Lubbock, Texa s Physiology and Molecular Microbiology Virology Relevant High Yield Facts and Revisions Abdul N. Hamood, MS, PhD Profes s or Depa rtment of Immunol ogy a nd Mol ecul a r Mi crobi ol ogy School of Medi ci ne Texa s Tech Uni vers i ty Hea l th Sci ences Center Lubbock, Texa s Physiology and Molecular Microbiology Bacteriology Relevant High Yield Facts and Revisions Afzal A. Siddiqui, MPhil, PhD Grover E. Murra y Profes s or Depa rtments of Immunol ogy a nd Mol ecul a r Mi crobi ol ogy; Interna l Medi ci ne; Pa thol ogy Cl i ni ca l Profes s or, Pha rma cy Pra cti ce Di rector, Center for Tropi ca l Medi ci ne a nd Infecti ous Di s ea s es Texa s Tech Uni vers i ty Hea l th Sci ences Center Lubbock, Texa s Parasitology Relevant High Yield Facts and Revisions David C. Straus, PhD Profes s or Depa rtment of Immunol ogy a nd Mol ecul a r Mi crobi ol ogy Texa s Tech Uni vers i ty Hea l th Sci ences Center Lubbock, Texa s Bacteriology Rickettsiae, Chlamydiae, and Mycoplasma Relevant High Yield Facts and Revisions
Introduction Microbiology: PreTest™ Self-Assessment and Review, 14th Edition, a l l ows medi ca l s tudents to comprehens i vel y a nd conveni entl y a s s es s a nd revi ew thei r knowl edge of mi crobi ol ogy a nd i mmunol ogy. The 500 ques ti ons provi ded here ha ve been wri tten wi th the goa l to pa ra l l el the topi cs , forma t, a nd degree of di ffi cul ty of the ques ti ons found i n the Uni ted Sta tes Medi ca l Li cens i ng Exa mi na ti on (USMLE) Step 1. The Hi gh-Yi el d Fa cts i n the begi nni ng of the book a re provi ded to fa ci l i ta te a ra pi d revi ew of mi crobi ol ogy. It i s a nti ci pa ted tha t the rea der wi l l us e thes e Hi gh-Yi el d Fa cts a s a qui ck overvi ew pri or to proceedi ng through the ques ti ons . Ea ch ques ti on i n the book i s fol l owed by four or more a ns wer opti ons to choos e from. In ea ch ca s e, s el ect the bes t res pons e to the ques ti on. Ea ch a ns wer i s a ccompa ni ed by a s peci fi c pa ge reference to a text tha t provi des ba ckground to the a ns wer a nd a s hort di s cus s i on of i s s ues ra i s ed by the ques ti on a nd a ns wer. A bi bl i ogra phy l i s ti ng a l l the s ources ca n be found fol l owi ng the l a s t cha pter. To s i mul a te the ti me cons tra i nts i mpos ed by the l i cens i ng exa m, a n effecti ve wa y to us e thi s book i s to a l l ow yours el f one mi nute to a ns wer ea ch ques ti on i n a gi ven cha pter. After you fi ni s h goi ng through the ques ti ons i n the s ecti on, s pend a s much ti me a s you need veri fyi ng your a ns wers a nd ca reful l y rea di ng the expl a na ti ons provi ded. Speci a l a ttenti on s houl d be gi ven to the expl a na ti ons for the ques ti ons you a ns wered i ncorrectl y; however, you s houl d rea d every expl a na ti on even i f you’ve a ns wered correctl y. The expl a na ti ons a re des i gned to rei nforce a nd s uppl ement the i nforma ti on tes ted by the ques ti ons . For thos e s eeki ng further i nforma ti on a bout the ma teri a l covered, cons ul t the references l i s ted i n the bi bl i ogra phy or other s ta nda rd medi ca l texts .
Acknowledgments The a uthors wi s h to tha nk Ms . Al i ci a Ga una a nd Ms . Jenni fer Bri ght for thei r hel p i n the prepa ra ti on of the ma nus cri pt. The a uthors woul d a l s o l i ke to a cknowl edge the us e of the Publ i c Hea l th Ima ge Li bra ry offered by the Centers for Di s ea s e Control a nd Preventi on.
High-Yield Facts PHYSIOLOGY AND MOLECULAR BIOLOGY • Koch pos tul a tes : (1) s peci fi c orga ni s m mus t be i n di s ea s ed a ni ma l ; (2) orga ni s m mus t be i s ol a ted i n pure cul ture; (3) orga ni s m s houl d produce exa ct di s ea s e i n hea l thy, s us cepti bl e a ni ma l ; a nd (4) orga ni s m mus t be re-i s ol a ted from i nfected a ni ma l . • Gra m s ta i n: (1) fi xa ti on; (2) crys ta l vi ol et; (3) i odi ne trea tment; (4) decol ori za ti on (a l cohol /a cetone); a nd (5) counters ta i n (s a fra ni n). Gra mpos i ti ve when the col or i s purpl e; gra m-nega ti ve when the col or turns red. • Gra m s ta i n poor for: Chlamydia (i ntra cel l ul a r l oca ti on), Mycoplasma (no cel l wa l l ), Rickettsia (s ma l l s i ze), Treponema (too thi n, s pi rochete, us e da rkfi el d mi cros cope), Mycobacterium (us e a ci d-fa s t s ta i n), a nd Legionella (us e s i l ver s ta i n). • Ba cteri a l s ha pes : ba ci l l i (rod), cocci (s pheri ca l ), a nd s pi ri l l a (s pi ra l ). • Ba cteri a l a ggrega tes : di pl ococci (eg, Neisseriae), s treptococci (cha i ns ), tetra ds (fours ), s ta phyl ococci (cl us ters ), a nd s a rci na e (cubes ). • Fl a gel l a : monotri chous —s i ngl e pol a r fl a gel l um; l ophotri chous —cl us ter of fl a gel l a a t pol e; a mphi tri chous —fl a gel l a a t both pol es ; a nd peri tri chous —fl a gel l a enci rcl i ng the cel l . • Type VII pi l i = F (s ex) pi l i ; i mporta nt i n ba cteri a l conjuga ti on. • Conjuga ti on—DNA tra ns ferred from one ba cteri um to a nother; tra ns ducti on—vi ra l tra ns fer of DNA from one cel l to a nother; a nd tra ns forma ti on— cel l ul a r upta ke of puri fi ed DNA or na ked DNA from the envi ronment. • Pepti dogl yca n (murei n or mucopepti de) l a yer: uni que to proka ryotes (gl yca n pol ymers of s uga r N-a cetyl gl ucos a mi ne [NAG] a nd N-a cetyl mura mi c a ci d [NAM] cros s -l i nked by a s hort pepti de). Cros s -l i nki ng enzymes a re tra ns pepti da s es (ta rgets for β-l a cta m a nti bi oti cs ). • Ba cteri a l s tructures : pepti dogl yca n (s upport); cel l wa l l /membra ne (a nti geni c); outer membra ne (l i popol ys a ccha ri de [LPS]/endotoxi n); pl a s ma membra ne (oxi da ti ve/tra ns port enzymes ); ri bos ome (protei n s ynthes i s ); peri pl a s mi c s pa ce (hydrol yti c enzymes a nd β-l a cta ma s es ); ca ps ul e (a nti pha gocyti c pol ys a ccha ri de except Bacillus anthracis, whi ch i s D-gl uta ma te); pi l us /fi mbri a (a dherence, conjuga ti on); fl a gel l um (moti l i ty); s pore (hea t, chemi ca l , dehydra ti on res i s ta nce, cons i s ts of di pi col i ni c a ci d); pl a s mi d (genes for toxi ns , enzymes , a nti bi oti c res i s ta nce); gl ycoca l yx (a dherence, ma de of pol ys a ccha ri de); a nd i ncl us i on bodi es (no membra ne; s tore gl ycogen, pol yphos pha te, pol y-β-hydroxybutyri c a ci d). • Gra m-pos i ti ve: tei choi c a ci d uni que. • Gra m-nega ti ve: LPS/endotoxi n uni que. • LPS/endotoxi n: l i pi d A cova l entl y l i nked to pol ys a ccha ri de core outer membra ne a nd then uni que “O a nti gen” pol ys a ccha ri de repea t; LPS/endotoxi n ca us es a n a cute-pha s e protei n res pons e i n vi vo (rel ea s e of TNF-α, IL-1, a nd IL-6), ca us i ng fever, a nd the l i ke. • Lys ozyme: brea ks down gl yca n ba ckbone bonds of pepti dogl yca n. Spheropl a s t: pa rti a l cel l wa l l l ys ozyme di ges ti on. • Protopl a s t: compl ete cel l wa l l l ys ozyme di ges ti on, ca us i ng a s pheri ca l s ha pe of ba cteri a . • Exponenti a l or geometri c growth: cel l number = a(2n), where a i s number of s ta rti ng cel l s a nd n equa l s number of genera ti ons . • Ba cteri a l growth curves (four pha s es ): (1) l a g (no cel l ul a r di vi s i on, cel l s i ze i ncrea s es ); (2) exponenti a l (regul a r doubl i ng ti me, es s enti a l nutri ents decrea s e, toxi ns i ncrea s e); (3) s ta ti ona ry (cel l di vi s i on ra te = cel l dea th ra te) s ta ge a t whi ch s pores a re formed; a nd (4) dea th (cel l energy s tores depl ete, exponenti a l dea th due to l ow popul a ti on equi l i bri um). • Ba cteri os ta ti c: a gent inhibits mul ti pl i ca ti on; growth res umes upon remova l of a gent. • Ba cteri ci da l : a gent kills ba cteri a ; i rrevers i bl e. • Steri l e: free from a l l forms of l i fe. • Di s i nfecta nt: chemi ca l ki l l s ba cteri a but i s toxi c to ti s s ue. • Septi c: pa thogeni c orga ni s m i s pres ent i n l i vi ng ti s s ue. • As epti c: pa thogeni c orga ni s m i s not pres ent i n l i vi ng ti s s ue. (vi rol ogy—no ba cteri a l a gents a re pres ent.) • Pa s s i ve tra ns port: no energy requi red, movement down the concentra ti on gra di ent, no ca rri er mol ecul e (protei n mol ecul e tha t a tta ches to meta bol i c mol ecul e needed i ns i de the ba cteri um) tha t ca n cros s the cel l wa l l a nd cel l membra ne. The food goes i n a nd the wa s te goes out. • Acti ve tra ns port: requi res energy, movement a ga i ns t the concentra ti on gra di ent. • Ba cteri a l pa thogenes i s : (1) a nti pha gocyti c (cel l wa l l protei ns —protei n A i n Staphylococcus aureus a nd protei n M i n Streptococcus pyogenes, ca ps ul es , pi l i /fi mbri a e Neisseria gonorrhoeae); (2) a dherence fa ctors (pi l i /fi mbri a e, l i potei choi c a ci d, gl ycoca l yx, a dhes i on); (3) enzymes (coa gul a s e, col l a gena s e, fi bri nol ys i n, hya l uroni da s e, l eci thi na s e, muci na s e); a nd (4) toxi ns (exotoxi ns , endotoxi ns /LPS). • Exotoxi ns : pol ypepti de, hi ghl y fa ta l even i n l ow dos es , toxoi ds a s va cci nes , mos tl y hea t l a bi l e, s ecreted, both gra m-nega ti ve a nd gra m-pos i ti ve. • Endotoxi ns : LPS, l ow toxi ci ty, no toxoi ds , no va cci nes , hea t s ta bl e, rel ea s ed on l ys i s , onl y gra m-nega ti ve. • Free ra di ca l s of oxygen (s uperoxi des ) ki l l a na erobi c ba cteri a expos ed to a i r. Superoxi de di s muta s e i s a potent ba cteri a l a nti oxi da nt. The peroxi da s es i n ba cteri a a re protecti ve. • Obl i ga te a na erobes : l a ck ca ta l a s e a nd/or s uperoxi de di s muta s e a nd a re s us cepti bl e to oxi da ti ve da ma ge, foul s mel l i ng, produce ga s i n ti s s ue (eg, Actinomyces, Bacteroides, a nd Clostridium). • Superoxi de di s muta s e ca ta l yzes : • Ca ta l a s e ca ta l yzes : • Myel operoxi da s e ca ta l yzes : • Si tes of a cti on of a nti mi crobi a l a gents i ncl ude cel l wa l l s ynthes i s , cel l -membra ne i ntegri ty, DNA repl i ca ti on, protei n s ynthes i s , DNA-dependent RNA pol ymera s e, a nd fol i c a ci d meta bol i s m.
VIROLOGY • Virology terminology: vi ri on, ca ps i d, ca ps omere, nucl eoca ps i d, a nd genome. • Vi ra l genomes : • DNA viruses: • Herpes vi rus es , hepa dna vi rus es , poxvi rus es , a denovi rus es , pa pi l l oma vi rus es , pol yoma vi rus es , a nd pa rvovi rus es . • Al l DNA vi rus es a re doubl e-s tra nded (ds ), except pa rvovi rus es (s s ). • Al l DNA vi rus es ha ve l i nea r DNA, except pa pi l l oma vi rus es a nd pol yoma vi rus es (ds , ci rcul a r) a nd hepa dna vi rus es (i ncompl ete ds , ci rcul a r).
• RNA viruses: • (+)s s RNA (s a me a s mRNA) vi rus es : pi corna vi rus es , ca l i ci vi rus es , fl a vi vi rus es , toga vi rus es , hepevi rus es , a s trovi rus es , a nd corona vi rus es . • Retrovi rus es conta i n two s tra nds of (+)s s RNA tha t i s NOT mRNA (di pl oi d). • (–)s s RNA vi rus es : orthomyxovi rus es , pa ra myxovi rus es , rha bdovi rus es , bunya vi rus es , a rena vi rus es , fi l ovi rus es , hepa ti ti s D vi rus ; requi re vi ra l RNA pol ymera s e wi thi n the vi ri ons . • ds RNA vi rus es : reovi rus es ; requi re vi ra l RNA pol ymera s e wi thi n the vi ri ons . • Segmented RNA vi rus es : orthomyxovi rus es , reovi rus es , bunya vi rus es , a nd a rena vi rus es . • Viral replication: • Obl i ga te i ntra cel l ul a r pa ra s i tes , us e vi ra l a tta chment protei ns to a tta ch to hos t cel l receptors . • Growth cycl e: a tta chment, entry, uncoa ti ng, ma cromol ecul a r s ynthes i s , a s s embl y, a nd rel ea s e. • Vi ra l di s ea s e pa tterns : a cute, chroni c, pers i s tent (vi ri ons produced), a nd l a tent (no vi ri ons produced). • DNA vi rus es repl i ca te i n the hos t nucl eus EXCEPT poxvi rus es . • RNA vi rus es repl i ca te i n the hos t cytopl a s m EXCEPT i nfl uenza vi rus es . • Vi rus es tha t us e revers e tra ns cri pta s e (RT) ha ve cytopl a s mi c a nd nucl ea r repl i ca ti on pha s es : • Retrovi rus es : vRNA–RT → vDNA i n cytopl a s m; vDNA i ntegra tes i nto hos t chromos ome; hos t RNA pol ymera s e (RNAP) produces vRNA i n nucl eus . • Hepa dna vi rus es : vDNA to nucl eus ; hos t RNAP produces vRNA genome templ a te; vRNA–RT → vDNA i n cytopl a s m. Hepatitis Viruses • Hepa ti ti s A vi rus (HAV): Pi corna vi rus ; (+)s s RNA; feca l –ora l tra ns mi s s i on, no chroni c ca rri ers ; ki l l ed vi rus va cci ne. • Hepa ti ti s B vi rus (HBV): Hepa dna vi rus ; pa rti a l l y compl ete ci rcul a r ds DNA; pa renta l , s exua l , verti ca l (i ntra pa rtum, pos tpa rtum) tra ns mi s s i on; a cute a nd chroni c di s ea s e; hepa tocel l ul a r ca rci noma ; a nd recombi na nt HBs Ag va cci ne. • Hepa ti ti s C vi rus (HCV): Fl a vi vi rus ; (+)s s RNA; pa renta l or s exua l tra ns mi s s i on; a cute a nd chroni c di s ea s e; a nd hepa tocel l ul a r ca rci noma . • Hepa ti ti s D vi rus (HDV): Del ta vi rus ; (-)s s RNA; defecti ve vi rus , requi res HBV coi nfecti on; a cute a nd chroni c i nfecti ons . • Hepa ti ti s E vi rus (HEV): Hepevi rus ; (+)s s RNA; feca l –ora l tra ns mi s s i on; no chroni c ca rri ers ; hi gh morta l i ty i n pregna nt women. DNA Viruses • Pa rvovi rus B19: s s DNA; ca us es fi fth di s ea s e/erythema i nfecti os um (s l a pped cheek a ppea ra nce). • Pa pi l l oma vi rus (HPV): ci rcul a r ds DNA; ca us es common wa rts , HVP types 1, 4; condyl oma a ccumi na tum, HPV 6, 11; cervi ca l a nd other geni ta l ca rci noma s , HPV 16, 18; recombi na nt va cci nes for HPV 6/11/16/18 a nd HPV 16/18. • Pol yoma vi rus es : ci rcul a r ds DNA; BK vi rus , hemorrha gi c cys ti ti s ; JC vi rus , progres s i ve mul ti foca l l eukoencepa l opa thy; di s ea s e occurs onl y i n i mmunocompromi s ed. • Adenovi rus es : ds DNA; pha ryngoconjuncti vi ti s i n chi l dren, ARDS i n young a dul ts (es peci a l l y mi l i ta ry), a nd ga s troenteri ti s (s erotypes 40/41). • Herpes vi rus es : ds DNA; l a tent i nfecti ons occur wi th a l l ; rea cti va ti on i nfecti ons occur wi th i mmunocompromi s a ti on. • Herpes s i mpl ex vi rus type 1: pri ma ri l y ora l ; l a tent i n neurons , es peci a l l y tri gemi na l ga ngl i a ; col d s ores , kera ti ti s , s pora di c encepha l i ti s (tempora l l obe); a nd a cycl ovi r. • HSV 2: pri ma ri l y geni ta l ; l a tent i n neurons , es peci a l l y s a cra l ga ngl i a ; herpes geni ta l i s ; neona ta l di s ea s e; s exua l l y tra ns mi tted; a nd a cycl ovi r. • Va ri cel l a -zos ter vi rus (VZV): l a tent i n neurons ; pri ma ry i nfecti on, chi ckenpox, l es i ons occur i n crops ; rea cti va ti on i nfecti on, s hi ngl es , l es i ons occur i n derma toma l di s tri buti on; a cycl ovi r, va l a cycl ovi r; a nd l i ve a ttenua ted vi rus va cci ne. • Cytomega l ovi rus (CMV): ubi qui tous ; di rect conta ct, s exua l , verti ca l tra ns mi s s i on; ca us es reti ni ti s a nd pneumoni ti s i n i mmunocompromi s ed; neona tes s uffer from CMV i ncl us i on di s ea s e; ga nci cl ovi r, a nd fos ca rnet. • Eps tei n–Ba rr vi rus (EBV): i nfects B l ymphocytes ; i nfecti ous mononucl eos i s , pos i ti ve for heterophi l e a nti bodi es (monos pot tes t); s peci fi c EBV a nti gens a l s o us ed to di a gnos e i nfecti on—ea rl y a nti gen (EA), vi ra l ca ps i d a nti gen (VCA), Eps tei n–Ba rr nucl ea r a nti gen (EBNA). • HHV6: ros eol a i nfa ntum. • HHV8: Ka pos i s a rcoma i n AIDS. • Poxvi rus es : l a rges t, mos t compl ex vi rus es , a nd ds DNA. • Va ri ol a vi rus : s ma l l pox, exti nct s i nce 1977; potenti a l bi oterrori s m a gent. • Va cci ni a vi rus : va cci ne s tra i n a ga i ns t s ma l l pox; ca n ca us e i nfecti on es peci a l l y i n i mmunocompromi s ed. • Mol l us ci poxvi rus : mol l us cum conta gi os um; pea rl y nodul a r l es i ons . Positive ssRNA Viruses • Pi corna vi rus es (+s s RNA): pol i ovi rus es , coxs a cki evi rus es A a nd B, echo-vi rus es , enterovi rus es , HAV, a nd rhi novi rus es . • Al l enterovi rus es mul ti pl y i n upper res pi ra tory a nd ga s troi ntes ti na l tra cts ; mi l d upper res pi ra tory i nfecti ons (URI), ra s hes , a s epti c meni ngi ti s (l ymphocyti c pl eocytos i s , norma l gl ucos e, a nd norma l /s l i ghtl y el eva ted protei n). • Pol i ovi rus : pa ra l yti c pol i omyel i ti s ; era di ca ted i n the Uni ted Sta tes ; two va cci nes , Sa l k i na cti va ted a nd Sa bi n l i ve a ttenua ted va cci nes ; US now us es ki l l ed va cci ne onl y. • Coxs a cki evi rus A: herpa ngi na , ha nd-foot-a nd-mouth di s ea s e. • Coxs a cki evi rus B: myoca rdi ti s . • Rhi novi rus es : mul ti pl y onl y i n URT; common col d. • Fl a vi vi rus es : a l l a rthropod-borne EXCEPT HCV. • Encepha l i ti s (meni ngi ti s ): Wes t Ni l e vi rus , St. Loui s encepha l i ti s vi rus . • Fever wi th ra s h, hemorrha gi c fever: dengue vi rus es , yel l ow fever vi rus es . • Toga vi rus es : a l l a rthropod-borne EXCEPT rubel l a vi rus • Encepha l i ti s : a l pha vi rus es —Ea s tern equi ne encepha l i ti s vi rus , Wes tern equi ne encepha l i ti s vi rus , a nd Venezuel a n equi ne encepha l i ti s vi rus . • Rubel l a vi rus : rubel l a or Germa n mea s l es ; ca us es s evere bi rth defects ; l i ve a ttenua ted va cci ne. • Corona vi rus es : mos t s tra i ns ca us e common col d; a l s o s evere a cute res pi ra tory s yndrome (SARS). • Retrovi rus es : • HIV-1: di pl oi d genome, gag, env, pol genes ; ma jor protei ns , p24 (di a gnos i s ), gp120 a nd gp 41 a tta chment, revers e tra ns cri pta s e (RT), i ntegra s e
(IN), protea s e (PR); RT, IN, PR ta rgets for a nti retrovi ra l thera py; a cute retrovi ra l s yndrome, AIDS (CD4 T-cel l count <200/µL), a nd/or AIDS-defi ni ng opportuni s ti c i nfecti ons (Cryptosporidium, Pneumocystis, Mycobacterium avium-intracellular, ma ny others ), ca ncers (Ka pos i s a rcoma , others ), dementi a , or wa s ti ng. • HTLV-1: a cute T-cel l l eukemi a /l ymphoma ; tropi ca l s pa s ti c pa ra pa res i s . Negative ssRNA Viruses • Requi re vi ri on-a s s oci a ted RNA-dependent RNA pol ymera s e. • Pa ra myxovi rus es : • Mea s l es vi rus : mea s l es (rubeol a or ha rd mea s l es )—cough, coryza , conjuncti vi ti s , photophobi a , Kopl i k s pots ; ma cul opa pul a r ra s h; pneumoni a , encepha l i ti s ; SSPE; a nd l i ve a ttenua ted va cci ne. • Mumps vi rus : mumps (s wel l i ng of s a l i va ry, pa roti d gl a nds ); a s epti c meni ngi ti s , orchi ti s ; a nd l i ve a ttenua ted va cci ne. • Res pi ra tory s yncyti a l vi rus : bronchi ol i ti s a nd pneumoni a i n i nfa nts ; ri ba vi ri n, pa l i vi zuma b. • Pa ra i nfl uenza vi rus es : croup. • Rha bdovi rus : (ra bi es vi rus ): bul l et-s ha ped a ppea ra nce; ca us es ra bi es ; s kunks , ra ccoons , foxes , coyotes /dogs , a nd ba ts a re ma i n res ervoi rs i n the Uni ted Sta tes ; a ni ma l bi te tra ns mi s s i on through s a l i va ; control a ni ma l vectors ; Negri body—eos i nophi l i c i ntra cytopl a s mi c i ncl us i on body i n i nfected cel l s (bra i n, nucha l s ki n, a nd cornea ). • Orthomyxovi rus es : Infl uenza vi rus es A a nd B; s egmented genomes ; geneti c dri ft, mi nor a nti gen cha nges IA, IB; geneti c s hi ft, ma jor a nti gen cha nge to new hema ggl uti ni n (H) a nd/or neura mi ni da s e (N), IA onl y; os el ta mi vi r, za na mi vi r for trea tment; previ ous l y a ma nti di ne, ri ma nti di ne but mos t ci rcul a ti ng s tra i ns res i s ta nt. • Bunya vi rus es : La Cros s e vi rus , Ca l i forni a encepha l i ti s vi rus ; ha nta vi rus es . • Arena vi rus es : l ymphocyti c chori omeni ngi ti s vi rus ; vi rus es tha t ca us e hemorrha gi c fever (La s s a vi rus , Ta ca ri be vi rus ). dsRNA Viruses: Double-Shelled Capsids • Rota vi rus es : ca us e i nfa nti l e di a rrhea , l i ve a ttenua ted va cci ne. • Col ti vi rus : Col ora do ti ck fever.
BACTERIOLOGY • Gra m-pos i ti ve cocci : s ta phyl ococci ca ta l a s e +, s treptococci ca ta l a s e -. • Staphylococcus aureus: Ma nni tol -s a l t a ga r (s el ecti ve a nd di fferenti a l ), yel l ow col oni es , coagulase +, ma nni tol +, ca ta l a s e +; s ome a re methi ci l l i n res i s ta nt (MRSA), s ome ha ve va ncomyci n res i s ta nce emergi ng (VISA); protei n A bi nds IgG Fc i nhi bi ti ng pha gocytos i s , ca us es ra pi d-ons et food poi s oni ng (preformed enterotoxi n), toxi c s hock s yndrome, s ca l ded s ki n s yndrome, os teomyel i ti s , a cute ba cteri a l endoca rdi ti s (IV drug us ers ), a bs ces s es , a nd recurrent i nfecti on i n chroni c gra nul oma tous di s ea s e (CGD). • Staphylococcus saprophyticus: s econd l ea di ng ca us e of uri na ry tra ct i nfecti on (UTI) i n young s exua l l y a cti ve fema l es . • Streptococci : β-hemol yti c di vi ded i nto groups (13 groups : A-O) ba s ed on cel l wa l l ca rbohydra te a nti gens . Group A di vi ded i nto >50 types ba s ed on M protei ns (vi rul ence, s peci fi c i mmuni ty), ca ta l a s e nega ti ve. • Streptococcus pyogenes (group A): hya l uroni c a ci d ca ps ul e, ca rbohydra te a nti gen, M protei n, ba ci tra ci n s ens i ti ve, cel l ul i ti s , rheuma ti c fever, gl omerul onephri ti s , necroti zi ng fa s ci i ti s , erys i pel a s , a nd s ca rl et fever. • Vi ri da ns : i ncl ude S. mitis, a nd s o on. Norma l ora l fl ora , α-hemol yti c, s uba cute ba cteri a l endoca rdi ti s a fter denta l /ora l s urgery. • Enterococcus (us ed to be ca l l ed Streptococcus) faecalis (group D): norma l i ntes ti na l fl ora , s uba cute ba cteri a l endoca rdi ti s a fter pel vi c/a bdomi na l s urgery, UTIs , growth i n 6.5% Na Cl . • Streptococcus agalactiae (group B): s ometi mes norma l va gi na l fl ora ; i n da i ry products (ca ttl e pa thogen); neona ta l s eps i s ; (CAMP) tes t +. • Peptos treptococci : norma l ora l /va gi na l fl ora , endoca rdi ti s , a nd l ung a bs ces s . • Streptococcus pneumoniae: pneumoni a , meni ngi ti s , oti ti s medi a (chi l dren), optochi n s ens i ti ve, bi l e s ol ubl e, us e Quel l ung rea cti on (ca ps ul e Ags , hos t Abs ), a nd pneumococca l pol yva l ent va cci ne. • Di ck tes t: tes t s us cepti bi l i ty to s ca rl et fever. • Schul tz-Cha rl ton tes t: determi ne i f ra s h i s due to erythrogeni c toxi n of s ca rl et fever. • Gra m-nega ti ve cocci (Neisseria): oxi da s e +, di pl ococci , pol ys a ccha ri de ca ps ul e, endotoxi n, a s s oci a ted wi th C5, C6, V7, C8 compl ement defi ci ency; pa thogeni c forms : Tha yer-Ma rti n a ga r –, chocol a te a ga r +, nutri ent a ga r –, 37°C growth +, room tempera ture –; nonpa thogeni c forms : Tha yer-Ma rti n a ga r –, chocol a te a ga r +, nutri ent a ga r +, 37°C growth +, a nd room tempera ture +. • Neisseria meningitidis: ca ps ul e, endotoxi n, toxemi a , petechi a e, hemorrha ge, di s s emi na ted i ntra va s cul a r coa gul a ti on (DIC), a nd Wa terhous e– Fri deri chs en s yndrome. • Ba cteri a l meni ngi ti s : i n <40-yea r-ol d = S. pneumoniae; >40-yea r-ol d = S. pneumoniae; 2 to 6 months + neona tes = Group B s treptococci , Escherichia coli; a nd neona tes to 5-yea r-ol d chi l dren = N. meningitidis. • Neisseria gonorrhoeae: pi l i , endotoxi n, IgA protea s e, pha ryngi ti s , procti ti s , pel vi c i nfl a mma tory di s ea s e (PID), urethri ti s , a nd cervi ci ti s . • Gra m-pos i ti ve ba ci l l i : a erobi c (Bacillus); a na erobi c (Clostridium), ki l l ed by a utocl a ve. Al l a re s pore formers . • Bacillus anthracis: pol ypepti de ca ps ul e, exotoxi n, a nd a nthra x (Wool s orters di s ea s e). • Bacillus cereus: food poi s oni ng (food rehea ted once), enterotoxi n. • Clostridium: no cytochrome enzymes , no ca ta l a s e, a nd no s uperoxi de di s muta s e. • Clostridium tetani: noni nva s i ve, neurotoxi ns (prevents rel ea s e of neura l i nhi bi tory tra ns mi tters s uch a s γ-a mi nobutyri c a ci d [GABA] a nd gl yci ne), l ockja w, s pa s ti c pa ra l ys i s ; gi ve toxoi d/a nti toxi n. • Clostridium botulinum: noni nva s i ve, exotoxi ns (prevents a cetyl chol i ne rel ea s e), fl a cci d pa ra l ys i s , a nd a nti toxi n (honey i nges ti on i n i nfa ncy). • Clostridium perfringens: i nva s i ve, enterotoxi n, food poi s oni ng, myonecros i s , col l a gena s e, l eci thi na s e, a nd ga s ga ngrene. • Clostridium difficile: Ps eudomembra nous col i ti s ca n occur a fter broa d-s pectrum a nti bi oti c us a ge. • Corynebacterium diphtheriae: Gra m-pos i ti ve rod, meta chroma ti c gra nul es , exotoxi n (i nhi bi ts EF-2 a nd protei n s ynthes i s ). • Listeria monocytogenes: Gra m-pos i ti ve rod i n cerebros pi na l fl ui d (CSF), compromi s ed hos t, neona te, di a rrhea a fter ea ti ng ra w chees es , a nd tumbl i ng moti l i ty. • Salmonella: moti l e Gra m-nega ti ve rod, enteri c fever, food poi s oni ng; Salmonella typhi = huma n pa thogen; other s peci es = a ni ma l pa thogens ; moti l e; a nd nonl a ctos e fermenter.
• Shigella: nonmoti l e Gra m-nega ti ve rod, more vi rul ent tha n Salmonella, bl oody di a rrhea , s hi gel l os i s i s huma n di s ea s e, ora l –a na l route (fi ngers , fl i es , food, a nd feces ), toxi n i nhi bi ts protei n s ynthes i s . • Escherichia coli: Gra m-nega ti ve rod, mos t common UTI, s eps i s (s eri ous ); enterohemorrha gi c E. coli (EHEC) (col i ti s , hemol yti c uremi c s yndrome— verotoxi n, ha mburger, beef); enteroi nva s i ve E. coli (EIEC) (fever, bl oody s tool , a nd di a rrhea ); enterotoxi geni c E. coli (ETEC) (tra vel er di a rrhea ); enteropa thogeni c E. coli (EPEC) (i nfa nt fever a nd di a rrhea , nonbl oody s tool ).
• Pseudomonas aeruginosa: Gra m-nega ti ve rod, a nti bi oti c res i s ta nce, bl ue–green pi gments ; ca us es UTI, wounds , burns , greeni s h-yel l ow s putum. • Klebsiella: Gra m-nega ti ve, l a rge ca ps ul e; ca us es UTI, pneumoni a , es peci a l l y i n a l cohol i cs (curra nt jel l y s putum). • Haemophilus influenzae: Gra m-nega ti ve rod; ca us es meni ngi ti s , oti ti s , s i nus i ti s , a nd epi gl otti ti s . • Proteus: Gra m-nega ti ve rod, res ul t i n s wa rmi ng growth; produce urea s e (urea →, NH 3 ); a l s o produced by Helicobacter pylori a nd Ureaplasma urealyticum; ca us es UTI, wounds , rena l s tones , a nd l a rge s ta ghorn ca l cul i . • Gardnerella vaginalis: Gra m-nega ti ve, “cl ue cel l s ”; va gi ni ti s wi th di s cha rge (fi s hy s mel l , conduct Whi ff tes t). • Bordetella pertussis: Gra m-nega ti ve, ca ps ul e form, pi l i , ki l l ed va cci ne, ca us es whoopi ng cough. • Yersinia pestis: Gra m-nega ti ve, “s a fety pi n” (bi pol a r s ta i ni ng), ca us es pl a gue (buboni c/pneumoni c), s prea d by ra t fl ea . • Francisella tularensis: Gra m-nega ti ve, s prea d by s ki nni ng ra bbi ts (ja ck-ra bbi ts ), ca us es tul a remi a . • Pasteurella multocida: Gra m-nega ti ve, s prea d by ca t/dog bi tes ; ca us es cel l ul i ti s , “s hi ppi ng fever.” • Brucella: Gra m-nega ti ve, detected by dye s ens i ti vi ty tes t; ca us es undul a nt fever. • Mycobacterium tuberculosis: a ci d-fa s t, ca us es tubercul os i s , detected by a ci d-fa s t s ta i n, Lowens tei n–Jens en medi um, puri fi ed protei n deri va ti ve (PPD) tes ti ng. • Mycobacterium leprae: a ci d fa s t, ca us es l epros y, ca nnot be cul tured. • Haemophilus ducreyi: Gra m nega ti ve, ca us es pa i nful l es i on, cha ncroi d (s yphi l i s : pa i nl es s cha ncre). • Treponema pallidum: Gra m nega ti ve, detected by Venerea l Di s ea s e Res ea rch La bora tori es (VDRL) tes ts , fl uores cent treponema l a nti body a bs orpti on (FTA-ABS), a nd IgM a nti body; us e peni ci l l i n G for trea tment; ha s three s ta ges (1—i ni ti a l cha ncre, 2—whol e body ra s h, 3—chroni c i nfl a mma ti on ca us i ng ti s s ue des tructi on) s pi rochetes , da rk-fi el d mi cros copy. • Borrelia: Gra m nega ti ve, a ni l i ne dyes (Wri ght/Gi ems a ), Ixodes ti ck, rel a ps i ng fever, Lyme di s ea s e, a cute necroti zi ng ul cera ti ve gi ngi vi ti s , s pi rochete. • Legionella pneumophila: Legi onna i res di s ea s e, ful mi na ti ng pneumoni a , Gra m-nega ti ve rod, a i rborne through conta mi na ted wa ter (a i r-condi ti oner cool i ng s ys tem). • Exotoxi n: hea t l a bi l e. • Endotoxi n (LPS): hea t s ta bl e. • Di phtheri a /Pseudomonas exotoxi n: a ct vi a ADP-ri bos yl a ti on of EF-2, thus protei n s ynthes i s i nhi bi ted. • Escherichia coli, Vibrio cholerae, B. cereus hea t-l a bi l e enterotoxi n: ADP ri bos yl a ti on of G s protei n turns G s protei n on, thus a cti va ti ng a denyl a te cycl a s e, l ea di ng to ↑cAMP a nd di a rrhea . • Bordetella pertussis: Gra m nega ti ve, hea t-l a bi l e enterotoxi n: ADPri bos yl a ti on of G i protei n turns off G I protei n, thereby a cti va ti ng a denyl a te cycl a s e, l ea di ng to ↑ cAMP a nd na s a l di s cha rge. • Vibrio: oxi da s e pos i ti ve; one fl a gel l um; curved, “comma -s ha ped” Gra m-nega ti ve rod; ha l ophi l i c (except V cholerae). Al l a re Gra m nega ti ve. • Vibrio parahaemolyticus: s prea d by conta mi na ted s ea food, ca us es di a rrhea . • Vibrio vulnificus: s prea d by conta mi na ted ma ri ne a ni ma l s (oys ter i nges ti on), ca us es di a rrhea , s ki n l es i ons (ha ndl i ng). • Res i s ta nt nos ocomi a l i nfecti ons : va ncomyci n-res i s ta nt enterococci (VRE), trea t wi th qui nupri s ti n–da l fopri s ti n; methi ci l l i n-res i s ta nt S. aureus (MRSA), trea t wi th va ncomyci n; a nd va ncomyci n-i ndetermi na te S. aureus (VISA), cons i der new trea tment opti ons s uch a s l i nezol i d or qui nupri s ti n/da l fopri s ti n. • Mycobacterium tuberculosis ca us es i ni ti a l pri ma ry pul mona ry i nfecti on tha t ma y enter chroni c l a tent gra nul oma tos i s s ta ge or res ul t i n rea cti va ti on of di s ea s e cha ra cteri zed by hemoptys i s , l os s of wei ght, a nd fever. • Peni ci l l i n-res i s ta nt pneumococci (S. pneumoniae) Gra m pos i ti ve, ma y a ccount for up to 40% of i s ol a tes of S. pneumoniae. Thi rd- or fourth-genera ti on cepha l os pori ns ma y be us ed a s a l terna ti ve trea tment a s wel l a s va ncomyci n a nd ri fa mpi n. • Campylobacter (GE) a nd Helicobacter (PUD) a re both hel i ca l -s ha ped ba cteri a . Campylobacter ca us es a food-borne GI i l l nes s , mos t commonl y from undercooked mea t. Both ba cteri a a re s us cepti bl e to a nti bi oti cs s uch a s tetra cycl i ne. Helicobacter ma y be trea ted wi th Pepto-Bi s mol , metroni da zol e, a nd a moxi ci l l i n. Al l a re gra m nega ti ve. Media-Selective Examples • Bi l e es cul i n a ga r—us ed to i denti fy Enterococcus from non-Group D cocci . • Bordet-Gengou a ga r—us ed for i s ol a ti ng B. pertussis. • Chocol a te a ga r—us ed to i denti fy fa s ti di ous orga ni s ms (Neisseria a nd Haemophilus). • Tha yer-Ma rti n a ga r—us ed to i denti fy Neisseria. • Muel l er-Hi nton a ga r—us ed for s us cepti bi l i ty tes ti ng. • EMB a ga r a nd Ma cConkey a ga r—us ed to i denti fy enteroba cteri a cea e (enteri cs ). • Fl etcher medi um—us ed to i denti fy Listeria. • Loeffl er medi um—us ed to i denti fy C. diphtheriae. • Lowens tei n–Jens en medi um—us ed to i denti fy mycoba cteri a . • Mi ddl ebrook 7H10—us ed to i denti fy mycoba cteri a . • Ma nni tol s a l t a ga r—us ed to i denti fy s ta phyl ococci , s peci fi c for S. aureus.
• Sel eni te broth—us ed to i denti fy enri chment for Salmonella/Shigella.
RICKETTSIAE, CHLAMYDIAE, AND MYCOPLASMAS Rickettsiae • Rickettsia, Coxiella, Orientia, Anaplasma, a nd Ehrlichia—ma i n genera . Al l a re obl i ga te i ntra cel l ul a r pa ra s i tes due to l i mi ted a denos i ne tri phos pha te (ATP) producti on. Ins ect vectors i ncl ude ti cks , mi tes , a nd body l i ce. • Rocky Mounta i n s potted fever—caused by Rickettsia rickettsii, s prea d by ti cks , i nva des ca pi l l a ri es , ca us i ng va s cul i ti s . Ra s h commonl y progres s es from extremi ti es to trunk. Di a gnos i s i s us ua l l y s erol ogi c, us i ng cros s -rea cti ng a nti bodi es to Proteus vulgaris OX s tra i ns . • Trea t wi th tetra cycl i nes , doxycycl i ne. • Coxiella burnetii—res ervoi r i s l i ves tock; i nha l a ti on tra ns mi s s i on. Ca us es Q fever, a n a typi ca l pneumoni a . • Ehrlichia—i nfects monocytes , gra nul ocytes ; ti ck tra ns mi s s i on. • Anaplasma: A. phagocytophilum ca us es huma n gra nul ocyti c ehrl i chi os i s . • Orientia tsutsugamushi: ca us es s crub typhus . Chlamydiae • Obl i ga te i ntra cel l ul a r pa ra s i tes tha t requi re hos t ATP. Pos s es s a modi fi ed Gra m-nega ti ve cel l wa l l , a true ba cteri um. • Unus ua l l i fe cycl e—i nfecti ous el ementa ry bodi es bi nd to receptors a nd enter cel l s , formi ng a n i ntra cel l ul a r reti cul a te body. Di vi di ng reti cul a te bodi es form new el ementa ry bodi es . Reti cul a te bodi es form i ncl us i on bodi es i n the hos t cel l . • Chlamydia trachomatis i s s ens i ti ve to s ul fa drugs , a nd s ta i ns wi th i odi ne (gl ycogen s ta i ni ng). Serotypes A, B, a nd C ca us e tra choma , a chroni c fol l i cul a r kera toconjuncti vi ti s , often res ul ti ng i n bl i ndnes s (l ea di ng ca us e worl dwi de). • Serotypes D to K ca us e reproducti ve tra ct i nfecti ons , pneumoni a , a nd i ncl us i on conjuncti vi ti s . Chl a mydi a l geni ta l i nfecti ons a re wi des prea d a nd common. Neona ta l i nfecti ons often res ul t i n i ncl us i on conjuncti vi ti s . Trea t wi th erythromyci ns or tetra cycl i nes . • Serotypes L1, L2, a nd L3 ca us e l ymphogra nul oma venereum. • Identi fy geni ta l i nfecti ons wi th mol ecul a r probes , fl uores cent a nti body (FA) s ta i ni ng for ti s s ues , grow i n McCoy cel l cul tures . • Chlamydophila psittaci us es bi rds a s pri ma ry hos ts . Huma ns devel op a n a typi ca l pneumoni a from i nha l i ng the orga ni s m. Di a gnos i s i s us ua l l y s erol ogy, not i odi ne s ta i ni ng. • Chlamydophila pneumoniae (TWAR) ca us es huma n bronchi ti s , pneumoni a , a nd s i nus i ti s . Trea t wi th a zi thromyci n. Mycoplasma • Ba cteri a wi th no cel l wa l l . • Grown on l a bora tory medi a ; do not Gra m s ta i n a ccura tel y. • Mycoplasma pneumoniae—ca us es s ore throa t through a typi ca l pneumoni a (wa l ki ng pneumoni a ); trea t wi th tetra cycl i nes or erythromyci ns . • Ureaplasma urealyticum—urethri ti s , pros ta ti ti s ; forms ti ny col oni es , requi re urea for growth.
MYCOLOGY • Fungi (mol ds [moul ds ] a nd yea s ts ) a re euka ryoti c—cel l membra nes ha ve ergos terol (not chol es terol ) a nd the di fference i s a drug ta rget. • Funga l s tructures —hypha e (mol ds ) or yea s t cel l s . • Di morphi s m—a bi l i ty to grow i n two forms , for exa mpl e cha nge from hypha l to yea s t forms (or s pherul es of Coccidioides s pp.). • Hypha e a ma s s i nto a mycel i um; s epta te hypha e ha ve cros s -wa l l s ; nons epta te hypha e ha ve no or ra re cros s -wa l l s . • Yea s ts —ova l cel l s tha t repl i ca te by buddi ng or by fi s s i on (P. marneffii). • Spores a nd coni di a —reproducti ve s tructures ; bl a s toconi di a —yea s t buds ; coni di a —produced by hypha e (s ome s peci es produce both ma cro-a nd mi croforms ); endos pores —produced i n s pherul e by Coccidioides s pp.; a rthroconi di a —modi fi ed hypha l cel l s rel ea s ed by fra gmenta ti on. Spora ngi os pores produced wi thi n s pora ngi um, for exa mpl e Mucor s pp. • La bora tory tes t—Sa boura ud a ga r i s s ta nda rd funga l medi um. • Identi fi ca ti on—ma cros copi c (col ony) a nd mi cros copi c morphol ogy, bi ochemi ca l tes ts , i mmunol ogi c tes ts , or DNA probes . Antifungal Drugs • Drugs tha t ta rget ergos terol –ergos terol bi os ynthes i s : i nhi bi ti on of s qua l ene epoxi da s e (tol na fta te, a l l yl a mi nes ); i nhi bi ti on of P450 14-αdemethyl a s e (i mi da zol es a nd tri a zol es ); bi nd to ergos terol di s turbi ng membra ne s tructure (pol yenes ). • Anti meta bol i te: fl ucytos i ne i nhi bi ti on of RNA a nd DNA s ynthes i s . • Echi noca ndi ns : i nhi bi ti on bi os ynthes i s cel l wa l l gl uca n. • Drug res i s ta nce mecha ni s ms —upta ke a nd meta bol i s m (fl ucytos i ne); muta ti on s ubuni t β-1,3-gl uca n s yntha s e (echi noca ndi ns ); muta ti on a nd/or overexpres s i on of ta rget a nd/or effl ux pumps (a zol es ). Al tera ti on or decrea s e ergos terol content (pol yenes ). Superficial Skin, Cutaneous Dermatophyte, and Subcutaneous Infections • Malassezia s pp.—eti ol ogy of pi tyri a s i s (ti nea ) vers i col or, a s uperfi ci a l i nfecti on wi th hyper- or hypopi gmenta ti on of s ki n; mi cros copi c a na l ys i s s ki n s cra pi ng s hows “s pa ghetti a nd mea tba l l s ” a ppea ra nce. • Derma tophytes —three genera : Trichophyton s pp. a ffects s ki n, ha i r, a nd na i l s ; Microsporum s pp. a ffects ha i r a nd s ki n; Epidermophyton a ffects na i l a nd s ki n. • Ti nea s ca us e by derma tophytes —ri ngworm (T. capitis—s ca l p i nfecti on i nvol vi ng ha i r; T. corporis—i nfecti on gl a brous s ki n; T. cruris i nfecti on groi na ka jock i tch; T. pedis a ka a thl ete’s foot; T. unguim-na i l i nfecti on a ka onychomycos i s ca us ed by derma tophytes ); hya l i ne hypha e a nd a rthroconi di a i n ti s s ue. • Sporothrix schenckii—therma l l y di morphi c fungus found on pl a nts a nd i n s oi l (mol d form); s ubcuta neous i nocul a ti on of puncture wound, for exa mpl e from a thorn, or occa s i ona l l y s cra tch from i nfected ca t; devel op s ubcuta neous i nfecti on a t l oca ti on wi th s prea d a l ong dra i ni ng l ympha ti c (ros e ga rdener’s di s ea s e); yea s t form i n ti s s ue. Systemic Infections Due to Dimorphic Fungi
• Histoplasma capsulatum—mol d i n the envi ronment wi th tubercul a te ma croconi di a a nd s ma l l nondi s ti ncti on mi croconi di a ; s ma l l , ova l buddi ng yea s t i n cel l s of the reti cul oendothel i a l s ys tem (RES). • Ea s tern ha l f Uni ted Sta tes —Ohi o a nd Mi s s i s s i ppi ri ver va l l eys , es peci a l l y i mporta nt—bi rds a nd ba t ca ves . • Pri ma ry di s ea s e—a s ymptoma ti c to pneumoni a . • Di s s emi na ted di s ea s e—es peci a l l y i n i mmunos uppres s ed a nd AIDS pa ti ents . Ma y be a cute or s uba cute wi th mucocuta neous l es i ons common i n s uba cute. • La bora tory tes ts —hi s tory pl us bl ood s mea rs a nd cul ture, a nti gen detecti on. • Coccidioides s pp.—found i n a s a ndy envi ronment, es peci a l l y des erts (i n s outhwes tern USA, l ower pa rt of Ca l i forni a , Ari zona , New Mexi co, a nd Texa s ); dryi ng hypha e fra gment i nto a rthroconi di a ; i nha l ed a rthroconi di a devel op i nto s pherul es conta i ni ng endos pores . • Pri ma ry di s ea s e—va l l ey fever—a s ymptoma ti c to s el f-l i mi ted pneumoni a . • Di s s emi na ted form more often i n men tha n i n women, ri s k grea ter i mmunocompromi s ed i ndi vi dua l s a nd pregna nt women, ri s k a ppea rs i ncrea s ed a mong thos e of Afri ca n Ameri ca n or Fi l i pi no a nces try; a ffects s ki n, bone, joi nts , a nd meni nges . • La bora tory—cul ture i s ha za rdous a nd a proper techni que i s neces s a ry i f done; s putum, uri ne, a nd bronchi a l wa s hes ma y s how s pherul es . Detecti on of a nti bodi es i n s erum. • Blastomyces dermatitidis—envi ronment mol d, hypha e wi th coni di a on s ta l ks ; ti s s ue—l a rge yea s t cel l wi th broa d-ba s ed bud. • Sa me geogra phi ca l a rea a s Histoplasma, coni di a a re i nha l ed. • Pri ma ry di s ea s e—a s ymptoma ti c to pneumoni a . • Di s s emi na ted di s ea s e—s ki n mos t common ma ni fes ta ti on a nd ma y be pres enti ng compl a i nt. • La bora tory—cul ture a nd exa mi na ti on ti s s ue for l a rge yea s t cel l s , broa d-ba s ed buds . Opportunistic Mycoses • Aspergillus fumigatus—hypha e wi th bra nches a t a cute a ngl es a nd s ma l l coni di a ; ubi qui tous i n envi ronment. • Noni nva s i ve fungus ba l l s (a s pergi l l oma ) i n l ung ca vi ti es ; col oni za ti on i n ea rs a nd na s a l ca vi ty. • Opportuni s ti c (eg, i mmunos uppres s ed pa ti ent) i nva s i ve di s ea s e ma y be l oca l i zed i n l ungs or di s s emi na te to genera l i zed di s ea s e a nd ma y be l i fe threa teni ng. • Candida albicans—norma l fl ora of cuta neous a nd mucocuta neous s urfa ce us ua l l y i n yea s t form. Hypha e a nd ps eudohypha e a re genera l l y a ddi ti ona l l y pres ent i n i nfecti on. C. albicans mos t frequent i s ol a te i n mos t s tudi es ; other Candida s pp. i ncl ude C. glabrata a nd C. tropicalis. • Cuta neous or mucocuta neous i nfecti on a s s oci a ted morbi di ty. For exa mpl e, thrus h i n neona tes , AIDS; denture s toma ti ti s ; a nd va gi ni ti s . • Sys temi c—ca ndi demi a ; ma y hema togenous l y di s s emi na te a ny orga n, i ncl udi ng ki dney, bra i n, eye, a nd s ki n. Li fe threa teni ng. Ri s k fa ctors i ncl ude i mmunos uppres s i on a nd ca theters . • Cryptococcus neoformans—yea s t wi th l a rge ca ps ul e. • Envi ronment—s oi l wi th bi rd (es peci a l l y pi geons ) droppi ngs . • Pri ma ry di s ea s e—pri ma ry pul mona ry (often a s ymptoma ti c). • Di s s emi na ted i nfecti ons frequentl y ma ni fes t i n USA a s meni ngi ti s ; underl yi ng ri s k i ncl udes prol onged trea tment corti cos teroi ds , ma l i gna ncy, a nd AIDS. • La bora tory tes t—Indi a i nk mount body fl ui ds , ti s s ue s ta i ns hi ghl i ght ca ps ul e; cul ture; l a tex a ggl uti na ti on—CSF (ca ps ul a r a nti gen). • Cryptococcus gattii—geogra phi ca l l y l i mi ted, l es s frequentl y i s ol a ted a nd a s s oci a ted vegeta ti on (not gua no); ma y be more l i kel y to i nfect i mmunocompetent i ndi vi dua l s a nd mos t ca s es ma y ha ve pri ma ry pul mona ry s ymptoms . • Mucor, Rhizopus, a nd Absidia—nons epta te hypha e. • Envi ronment—common orga ni s ms . • Opportuni s t i nfecti ons —rhi nocerebra l i nfecti ons ; a ci dos i s , eg, di a beti cs . • La bora tory tes t—broa d, nons epta te hypha e wi th 90° a ngl es on bra nchi ng but often too few to s ee; cul ture. • Pneumocystis jiroveci—expos ure common—s el dom ca us es di s ea s e except i n i mmunocompromi s ed, es peci a l l y AIDS pa ti ents a nd debi l i ta ted i nfa nts ; ca us es i nters ti ti a l pneumoni a (ol d na me: P. carinii, i s ol a ted from ra ts , whi l e P. jiroveci from huma ns ). • La bora tory tes ts —orga ni s ms not cul tura bl e a nd rel y s ta i ns (eg, H&E, s i l ver, Gi ems a ) to detect a s ci (cys ts ), s pores , etc. • Trea tment—TMP-SMX, penta mi di ne (not a nti funga l s ; orga ni s m l a cks ergos terol ).
PARASITOLOGY • Protozoa a re s i ngl e-cel l ed a ni ma l s . Trophozoi tes a re moti l e (i nges ted RBC a re often s een i ns i de), whi l e cys ts (four nucl ei a nd chroma ti d body a re cha ra cteri s ti c) a re i nvol ved i n tra ns mi s s i on. • Amoeba s . • Entamoeba histolytica—di s ea s e of the l a rge i ntes ti ne; a mebi c dys entery—trophozoi tes feed on red bl ood cel l s (RBCs ), ca us i ng fl a s k-s ha ped ul cers . Al s o l i ver a nd l ung a bs ces s es pos s i bl e. • Naegleria—free-l i vi ng a moeba i n hot wa ter s ources ; ca us es pri ma ry a mebi c meni ngoencepha l i ti s (PAM); ra pi d ons et of s ymptoms , wi th dea th pos s i bl e i n da ys . • Acanthamoeba—free-l i vi ng a moeba s ; ca us e gra nul oma tous a moebi c encepha l i ti s (GAE); found i n ta p wa ter, fres hwa ter, s ea wa ter, a nd other s uch s ources . • Fl a gel l a tes . • Giardia lamblia—worl dwi de di s tri buti on, a ni ma l res ervoi rs ; cys ts i n wa ter s ources . Trophozoi tes a tta ch to i ntes ti ne, ca us i ng wa tery di a rrhea a nd ma l a bs orpti on (bea ver fever). Cra mpi ng, l i ght-col ored, fa tty s tool s ; a l s o a cqui red from da y-ca re centers or whi l e ca mpi ng. • Trichomonas vaginalis—trophozoi te wi th undul a ti ng membra ne a nd pol a r fl a gel l a ; pres ents wi th yel l ow di s cha rge tha t ha s a fi s hy odor; ma l es us ua l l y a s ymptoma ti c; s exua l l y tra ns mi tted. No cys t s ta ge. • Trypanosoma brucei—fl a gel l a tes tra ns mi tted by ts ets e fl y; ca us e Afri ca n s l eepi ng s i cknes s . Wi nterbottom s i gn (s wel l i ng of the pos teri or cervi ca l l ymph node i s cha ra cteri s ti c of di s ea s e). • Trypanosoma cruzi—Cha ga s di s ea s e tra ns mi tted by ki s s i ng bug; preva l ent mos tl y i n South a nd Centra l Ameri ca ; ca us es ca rdi omega l y, mega -col on. Roma na s i gn or cha goma (s wel l i ng a round the eye ca us ed by the entry of T. cruzi). • Lei s hma ni a —s a ndfl y vectors ; ca us e vi s cera l , cuta neous , a nd mucocuta neous l es i ons .
• Cryptosporidium parvum—found i n US wa ters ; ca us es a s el f-l i mi ted di a rrhea . Symptoms s evere i n i mmunocompromi s ed pa ti ents , es peci a l l y thos e wi th CD4 counts <200/µL. • Pl a s modi um s peci es ca us e ma l a ri a . Anopheles mos qui to vectors ; compl i ca ted l i fe cycl es ; P. vivax (Schuffner dots , enl a rged RBC), P. ovale (crena ted RBC), P. malariae (da i s y hea d s chi zont), P. falciparum (s i gnet ri ng, norma l -s i ze RBC, s a us a ge-s ha ped ga metocyte), a nd a n emergi ng s peci es P. knowlesi (s i mi l a r to P. malariae morphol ogi ca l l y). • Toxoplasma gondii—res ervoi r i s ca ts . Huma ns i nges t cys ts from ca t feces or undercooked mea ts ; es peci a l l y da ngerous to huma n fetus a s i t a ffects congeni ta l devel opment.
SUMMARY POINTS TO REMEMBER ABOUT PROTOZOAN PARASITES Transmission • Inges ti on (eg, Giardia, Entamoeba). • Di rect penetra ti on vi a i ns ect bi te (eg, Ma l a ri a , Trypanosoma). • Tra ns pl a centa l penetra ti on (eg, Toxoplasma). Diagnosis • Ma ny i nfecti ons ma y be di a gnos ed by mi cros copi c exa mi na ti on of the feces (eg, Giardia, Entamoeba), bl ood (eg, Ma l a ri a , Trypanosoma) or bone ma rrow (Leishmania). • Serol ogi c tes ts a re a va i l a bl e but cros s -rea cti vi ty wi th other pa ra s i tes ma y be a probl em. Clinical Manifestations • Ca n be nons peci fi c a nd cl i ni ca l l y unrema rka bl e a nd nons peci fi c (eg, di a rrhea a nd a bdomi na l di s comfort [i ntes ti na l pa ra s i tes ]) to very s peci es s peci fi c (eg, Cha ga s di s ea s e). Prevention and Treatment • Avoi da nce wi th the s ource of i nfecti ve s ta ge. • Pers ona l hygi ene. • Vector control . • Importa nt drugs to remember (metroni da zol e for i ntes ti na l protozoa ; qui ni ne deri va ti ves ; a tova quone–progua ni l ; a rtemi s i ni n deri va ti ves . • No va cci ne for a ny protozoa n pa ra s i te. Some va cci nes for ma l a ri a ha ve s hown promi s e i n cl i ni ca l tri a l s . • Fl ukes . • Fasciolopsis buski—a ffects i ntes ti nes ; cys ts on wa ter pl a nts i nges ted; ca us es di a rrhea . • Clonorchis sinensis—a ffects l i ver; tra ns mi tted from ra w or undercooked fi s h; bi l i a ry tree l oca l i za ti on a nd l i ver l oca ti on. • Fasciola hepatica—s heep l i ver fl uke; huma ns ca n become i nfected by i nges ti on of meta cerca ri a e on a qua ti c pl a nts . • Schistosoma—a l s o ca l l ed bl ood fl ukes ; porta l hypertens i on a nd hepa tos pl enomega l y (S. mansoni, S. japonicum). Cys ti ti s a nd urethri ti s (S. haematobium) wi th hema turi a , whi ch ca n progres s to bl a dder ca ncer. • Ces todes —s egmented fl a tworms wi th compl i ca ted l i fe cycl es . • Taenia solium (pork) a nd T. saginata (beef)—l a rva l forms (cys ti cercos i s ) found i n undercooked mea t. Adul t ta peworms devel op i n the i ntes ti ne. T. solium eggs when i nges ted by huma n ca n devel op i nto cys ti cercos i s . • Diphyllobothrium latum—fi s h ta peworm; fi s h i n fres hwa ter l a kes , under-cooked fi s h i nges ted; depl etes hos t of vi ta mi n B12. • Echinococcus granulosus—dog ta peworm. Huma ns a re i ntermedi a te hos ts a nd i nges t eggs from s heep or dog feces , hyda ti d cys ts of l i ver, anaphylaxis i f burs t. • Nema todes —roundworms . • Ascaris lumbricoides—ma y ca us e i ntes ti na l bl ocka ge. • Enterobius vermicularis (pi nworm)—eggs i n bedcl othes , detected i n s cotch ta pe tes t, etc; retroi nfecti on common; wi des prea d i n the Uni ted Sta tes . • Necator americanus—New Worl d hookworm. • Ancylostoma duodenale—Ol d Worl d hookworm; eggs found i n s oi l ; penetra te ba re feet. • Strongyloides stercoralis (threa dworm)—found i n tropi cs , s outhea s t Uni ted Sta tes ; i s s i mi l a r to hookworms ; no eggs , onl y l a rva l forms . Hyperi nfecti on ca n devel op i n pa ti ents on s teroi d thera py wi th hi gh morta l i ty. • Trichuris trichiura (whi pworm)—found i n tropi cs ; s prea ds when eggs a re i nges ted, or due to poor s a ni ta ti on; ca us es mucoi d or bl oody di a rrhea , a na l prol a ps e. • Trichinella spiralis (pork roundworm)—l a rva e i nges ted i n pork or wi l d ga me mea t. La rva e ma y ca l ci fy i n mus cl e of i ntermedi a te hos t. • Ti s s ue nema todes —fi l a ri a l worms . None a re s i gni fi ca nt i n the Uni ted Sta tes . • Onchocerca volvulus—a l s o ca l l ed ri ver bl i ndnes s . Bl a ckfl y i s the vector of di s ea s e. The preferred trea tment i s i vermecti n. • Loa loa—da y-bi ti ng fl y i s the vector. • Wuchereria bancrofti—mos qui to vectors ; ma y ca us e el epha nti a s i s by bl ocki ng l ympha ti cs .
SUMMARY POINTS TO REMEMBER ABOUT WORMS Transmission—Oral • Huma n feces . Feco-ora l tra ns mi s s i on i s i mporta nt i n s evera l worms . Soi l i ng by i nfected huma n feces i s res pons i bl e for i nfes ta ti on by Ascaris, Enterobius, Trichuris, a nd cys ti cercus l a rva e (l a rva l T. solium). • Ani ma l feces . Huma ns become i nfected wi th the eggs of Echinococcus granulosus (hyda ti d cys ts ) by ea ti ng products tha t ha ve been conta mi na ted by a ni ma l excreta . • Infected mea t. Ea ti ng ra w or i ns uffi ci entl y cooked mea t, whi ch conta i ns l a rva e, l ea ds to i nfecti on by a dul t Taenia. • Infected fi s h. Ea ti ng ra w or i ns uffi ci entl y cooked fi s h ma y l ea d to i nfecti on wi th trema todes s uch a s Clonorchis. • Infected cra bs a nd cra yfi s h. Ea ti ng l a rva l -i nfes ted, ra w, or i ns uffi ci entl y cooked cra bs ma y l ea d to pa ra goni mi a s i s (l ung fl uke). • Conta mi na ted pl a nts . Infecti on wi th the gi a nt i ntes ti na l fl uke (Fa s ci ol ops i a s i s ) occurs vi a the cons umpti on of s evera l ki nds of ra w pl a nts , for
exa mpl e wa ter nut a nd wa ter ches tnut, on whi ch l a rva e a re encys ted. • Conta mi na ted wa ter. Dri nki ng wa ter conta i ni ng cycl ops (s ma l l crus ta cea ns ) i nfected wi th Dracunculus, l ea ds to gui nea worm i nfecti on (a l mos t era di ca ted onl y 1000 i nfected peopl e). Transmission—Skin Penetration • La rva e of Strongyloides a nd hookworm enter through the s ki n from the s oi l . Schistosome cerca ri a e penetra te the s ki n when huma ns come i nto conta ct wi th i nfes ted wa ter. Clinical Manifestations • Ca n be nons peci fi c a nd cl i ni ca l l y unrema rka bl e a nd nons peci fi c (eg, di a rrhea , a bdomi na l di s comfort, na us ea , a nd a norexi a [i ntes ti na l nema todes ]) to very s peci es -s peci fi c (eg, cys ti cercos i s a nd hyda ti d cys t di s ea s e). Prevention and Treatment • Avoi da nce wi th the s ource of i nfecti ve s ta ge. Ins pecti on of mea t. Stora ge a nd proper cooki ng of mea t. • Anthel mi nti c trea tment—pra zi qua ntel , a l benda zol e, mebenda zol e, a nd i vermecti n a re the ba s i c drugs .
IMMUNOLOGY • Two types of i mmune res pons e: (1) a da pti ve or a cqui red (s peci fi c, s l ow pri ma ry res pons e, ra pi d s econda ry res pons e), a nd (2) i nna te (na ti ve or na tura l , ra pi d). • Inna te i mmuni ty: l i mi ted s peci fi ci ty, no i mmunol ogi ca l memory, fi rs t l i ne of defens e (epi thel i a l ), bi ochemi ca l defens es (s toma ch ↓pH, GI proteol yti c enzymes , a nd bi l e), pha gocytes (pol ymorphonucl ea r neutrophi l s [PMNs ] a nd monocytes , ma cropha ges ), na tura l ki l l er (NK) cel l s , s ol ubl e medi a tors (compl ement, a cute-pha s e protei ns s uch a s C-rea cti ve protei n, cytoki nes s uch a s ILs , IFNs , CSFs ), i nfl a mma ti on (C5a : chemota xi s , C3b: ops oni za ti on, neutrophi l s ). • Ada pti ve i mmuni ty: s peci fi c, a nti gen-dri ven, di s cri mi na tes s el f from non-s el f, pos s es s es memory, di vi ded i nto (1) humora l i mmuni ty (B cel l s , pl a s ma cel l s ) a nd (2) cel l -medi a ted i mmuni ty (T hel per cel l s , T cytotoxi c cel l s —CTLs ). • Anti bodi es (B l ymphocytes /pl a s ma cel l s ): ma i n functi ons a re (1) neutralize toxi ns /vi rus es , (2) opsonize ba cteri a , a nd (3) complement activation. • Anti bodi es (fi ve i s otypes ): IgG, IgA, IgM, IgD, a nd IgE (ba s ed on Fc hea vy-cha i n di fferences ), two l i ght cha i ns (ka ppa a nd l a mbda ) a nd two hea vy cha i ns hel d together by di s ul fi de bonds , the hi nge regi on i s pol yprol i ne, pa ra tope bi nds a nti gen a nd i s compos ed of hea vy a nd l i ght cha i ns . Peps i n yi el ds F(a b) 2 a nd pa pa i n yi el ds two Fa b fra gments a nd one Fc fra gment. • Anti body concentra ti ons (s erum): IgG > IgA > IgM > IgD > IgE. • IgG: cros s es the pl a centa (Rh i ncompa ti bi l i ty, hemol yti c di s ea s e of newborn), 80% of s erum a nti body, bi nds (a cti va tes ) compl ement, four s ubcl a s s es (IgG1, IgG2, IgG3, a nd IgG4), ma i n a nti body i n s econda ry (reca l l or memory) res pons e. • IgA: s ecretory a nti body, s erum (monomer), s ecreti ons (di mers ), two s ubcl a s s es , di mer (J cha i n), does not bi nd compl ement. • IgM: penta mer, bi nds compl ement, fi rs t to a ppea r a fter i nfecti on, el eva ted i n congeni ta l /peri na ta l i nfecti ons . • IgD: s us cepti bl e to proteol yti c degra da ti on, found wi th s urfa ce IgM on ma ture B l ymphocytes . • IgE: cytotropi c/rea gi ni c a nti body, a l l ergy a nti body, type I hypers ens i ti vi ty (ma s t cel l s /ba s ophi l s protecti ve i n worm i nfecti ons ), l owes t concentra ti on i n s erum. • Bence Jones protei ns : mul ti pl e myel oma —l a rge a mounts of κ/λ l i ght cha i ns i n uri ne excreti on. • Na tura l ki l l er cel l s : ma rker i s CD16 (IgG Fc receptor). • B cel l s : a nti body producers contri buti ng to a l l ergy (IgE), a utoi mmuni ty, hos t defens e (ops oni ze, neutra l i ze, compl ement a cti va te). • B-cel l ma rkers : Fc receptor, C3 receptor, CD21 (receptor for EB vi rus ), a nd CD10 (common a cute l ymphobl a s ti c l eukemi a a nti gen [CALLA]). • T cel l s : hos t defens e (fungi , vi rus es , M. tuberculosis), a l l ergy (type IV—del a yed hypers ens i ti vi ty), a nti body regul a ti on, gra ft/tumor rejecti on. • T-cel l ma rkers : CD2, TCRαβ-CD3, CD28, CD4 (a l s o receptor for HIV) or CD8, CD44 (mi gra ti on). • Compl ement defi ci enci es : (1) C1 es tera s e i nhi bi tor: a ngi oedema ; (2) deca y-a ccel era ti ng fa ctor (DAF): pa roxys ma l nocturna l hemogl obi nuri a ; (3) C3 defi ci ency: s evere, recurrent i nfecti ons (s i nus a nd res pi ra tory)—pneumonococci ; (4) C5 to C9 defi ci ency: di s s emi na ted gonococcemi a . • Ma jor hi s tocompa ti bi l i ty compl ex (MHC) Cl a s s I: exi s ts on a l l nucl ea ted cel l s —MHC I + pepti de = l i ga nd for CD8 T cel l s . • MHC Cl a s s II: exi s ts on a nti gen-pres enti ng cel l s (ma cropha ges /dendri ti c cel l s ), i mporta nt to orga n rejecti on—MHC II + pepti de = l i ga nd for CD4 T cel l s . • Cytoki nes : IFNα, β (a nti vi ra l ), TNF (i nfl a mma ti on, fever, a cute-pha s e rea cta nts , ca chexi a ), IL-1 (fever/pyrogen, a cute-pha s e protei ns ), IL-2 (T-cel l s ti mul a tor), IL-3 (bone ma rrow s ti mul a tor), IL-4 (IgE producti on), IL-5 (proeos i nophi l , a nti hel mi nths ), IL-6 (a cute-pha s e protei ns , B-cel l di fferenti a ti on), IL-8 (i nfl a mma ti on, chemota xi s ), IL-12 a nd IFN-γ NK cel l s ti mul a tor, TH 1 s ti mul a tor, a cti ve cytotoxi c l ymphocyte s ti mul a tor, promotes cel l -medi a ted i mmuni ty. • Acute-pha s e cytoki nes : IL-1, IL-6, a nd TNF-α. • Mi togens : B l ymphocytes (LPS), T l ymphocytes (phytohema ggl uti ni n [PHA] a nd Con A), both B a nd T cel l s (pokeweed mi togen [PWM]). • Enzyme-l i nked i mmunos orbent a s s a y (ELISA)-s ens i ti ve pres umpti ve di a gnos i s of HIV i nfecti on, wes tern bl ot s peci fi c, defi ni ti ve di a gnos i s of HIV i nfecti on → both detecti ng a nti -HIV a nti bodi es i n pa ti ent s era ; detecti on of HIV RNA by nucl ei c a ci d a mpl i fi ca ti on of vi ra l l oa d i s bes t predi ctor of “progres s i on to AIDS.” • Immunodefi ci enci es : (1) pri ma ry—ra re a nd cause di s ea s e; a nd (2) s econda ry—common a nd the result of di s ea s e. • Pri ma ry i mmunodefi ci enci es : Bruton a ga mma gl obul i nemi a —no B cel l s , l ow a nti bodi es , s ma l l tons i l s , onl y ma l es ; Di George s yndrome (congeni ta l thymi c a pl a s i a )—thi rd a nd fourth pha ryngea l pouches devel opment fa i l ure, no thymus , no T cel l s , no pa ra thyroi d (hypoca l cemi a ), a nd recurrent vi ra l , funga l , protozoa l i nfecti ons ; s evere combi ned i mmunodefi ci ency di s ea s e (SCID)—no T or B cel l s , defecti ve IL-2 receptor, defi ci ency a denos i ne enzyme, recurrent i nfecti ons (vi ra l , ba cteri a l , funga l , a nd protozoa l ); Wi s kott Al dri ch s yndrome—B- a nd T-cel l defi ci ency, l ow IgM, hi gh IgA, norma l IgE; a ta xi a tel a ngi ecta s i a —defecti ve DNA repa i r; Chèdi a k–Hi ga s hi di s ea s e—a utos oma l -reces s i ve defect i n pha gocytos i s ; CGD—NADPH oxi da s e defi ci ency, i ncrea s ed opportuni s ti c pa thogens , pha gocyti c defi ci ency; chroni c mucocuta neous ca ndi di a s i s — C. albicans T-cel l dys functi on. • Immunodefi ci ency cha ra cteri zed by unus ua l a nd recurrent i nfecti ons . • B-cel l (a nti body) defi ci ency—ba cteri a l i nfecti ons . • T-cel l defi ci ency—vi ra l , funga l , a nd protozoa l i nfecti ons .
• Pha gocyti c cel l s defi ci ency—pyogeni c i nfecti ons (ba cteri a l ), s ki n i nfecti ons , a nd s ys temi c ba cteri a l opportuni s ti c i nfecti ons . • Compl ement defi ci enci es —pyogeni c i nfecti ons (ba cteri a l ). • Hypers ens i ti vi ty: (1) type I (a na phyl a xi s , i mmedi a te-type hypers ens i ti vi ty, IgE); (2) type II (cytotoxi c hypers ens i ti vi ty); (3) type III (i mmune compl ex hypers ens i ti vi ty); a nd (4) type IV (cel l -medi a ted, del a yed-type hypers ens i ti vi ty). • Type I: ma s t cel l /ba s ophi l , IgE, va s oa cti ve a mi nes , a s thma , a na phyl a xi s , l oca l whea l , a nd fl a re. • Type II: IgM, IgG bi nd a nti gen a nd l ys e cel l , a utoi mmune hemol yti c a nemi a , Goodpa s ture s yndrome, a nd erythrobl a s tos i s feta l i s . • Type III: i mmune compl ex, s erum s i cknes s , Arthus rea cti on → a nti body–a nti gen compl exes . • Type IV: l ymphoki nes rel ea s ed from a cti va ted T l ymphocytes , TB s ki n tes t, conta ct derma ti ti s , tra ns pl a nt rejecti on, a nd l upus (SLE). • Autoa nti bodi es : s ys temi c l upus erythema tos us (a nti nucl ea r a nti bodi es , a nti -ds DNA, a nti -Smi th); drug-i nduced l upus (a nti hi s tone); rheuma toi d a rthri ti s (a nti -IgG); cel i a c di s ea s e (a nti gl i a di n), Goodpa s ture s yndrome (a nti ba s ement membra ne); Ha s hi moto thyroi di ti s (a nti mi cros oma l ); s cl eroderma Ca l ci nos i s Ra yna ud Es opha gus Scl eros i s Tel ea ngi ecta s i a e (CREST) (a nti centromere); a nd s cl eroderma di ffus e (a nti -s cl -70). • Acti ve i mmuni ty: i nduced a fter expos ure to forei gn a nti gens , memory es ta bl i s hed, s l ow pri ma ry res pons e, a nd ra pi d s econda ry (reca l l or memory) res pons e. • Va cci nes : (1) ca ps ul a r pol ys a ccha ri de va cci nes (Streptococcus, N. meningitidis, H. influenzae); (2) toxoi d va cci nes (C. diphtheriae, C. tetani, B. pertussis); (3) puri fi ed protei n va cci nes (B. pertussis, Borrelia burgdorferi, B. anthracis); (4) l i ve, a ttenua ted ba cteri a l va cci nes (M. bovis for tubercul os i s /BCG, F. tularensis); (5) ki l l ed ba cteri a l va cci nes (V. cholerae, Y. pestis, R. rickettsiae/typhus , C. burnetii/Q fever); (6) ki l l ed, l i ve, a ttenua ted, a nd pol ys a ccha ri de va cci nes (S. typhi). • Adjuva nts (huma n va cci nes ): a l umi num hydroxi de, l i pi d, or oi l -i n-wa ter emul s i on. • Pa s s i ve humora l i mmuni ty: a dmi ni s tra ti on of preformed a nti body i n i mmune gl obul i n prepa ra ti ons , no memory es ta bl i s hed, ra pi d ons et (eg, teta nus a nti toxi n, botul i num a nti toxi n, di phtheri a a nti toxi n), a nti toxi n = i mmune gl obul i ns . • Pa s s i ve cel l ul a r i mmuni ty: a dmi ni s tra ti on of s peci fi c l ymphocytes (NK cel l s , T cel l s ), s hort l i ved, ma y not res ul t i n memory, a da pti ve cel l thera py (ACT).
Physiology and Molecular Microbiology Questions 1. A 28-yea r-ol d fema l e wi th fol l i cul i ti s i s not res pons i ve to a 10-da y trea tment cours e wi th peni ci l l i n. An enzyme produced by the eti ol ogi c a gent i s mos t l i kel y res pons i bl e for thi s trea tment fa i l ure. At whi ch s i te on the mol ecul e s hown does thi s enzyme a ct to des troy peni ci l l i n?
a. 1 b. 2 c. 3 d. 4 e. 5 2. A 35-yea r-ol d ma l e wa s trea ted wi th a n a mi nogl ycos i de for a n i nfecti on wi th a gra m-nega ti ve rod. Whi ch of the fol l owi ng ba cteri a l proces s es i s i nvol ved i n tra ns port of thi s a nti bi oti c i nto the cel l ? a . Fa ci l i ta ted di ffus i on b. Fermenta ti on c. Group tra ns l oca ti on d. Oxi da ti ve phos phoryl a ti on e. Tra ns pepti da ti on 3. A 36-yea r-ol d ma l e devel oped a pa i nful purul ent urethra l di s cha rge fol l owi ng a 2-week va ca ti on to Tha i l a nd. A Gra m s ta i n revea l s gra mnega ti ve di pl ococci . Iron, whi ch i t obta i ns through s urfa ce receptors , i s es s enti a l for the expres s i on of the mi croorga ni s m’s vi rul ence fa ctors . From whi ch of the fol l owi ng mol ecul es does i t obta i n i ron? a . Ferri c oxi de b. La ctoferri n c. Li popol ys a ccha ri de (LPS) d. Pyocya ni n e. Si derophores 4. A fema l e medi ca l s tudent i s a dmi tted to the emergency depa rtment wi th s ymptoms of s evere uri na ry tra ct i nfecti on (UTI). The Escherichia coli s tra i n i s ol a ted from uri ne produced extended-s pectrum β-l a cta ma s e. In whi ch a na tomi c a rea of the cel l woul d thi s enzyme be l oca ted?
Structure of gra m-nega ti ve ba cteri um. a. A b. B c. C d. D e. E Questions 5 and 6 A 52-yea r-ol d ma l e devel ops a bs ces s es fol l owi ng s urgery to repa i r a n a bdomi na l guns hot wound. Gra m s ta i n of the foul -s mel l i ng exuda te from hi s a bs ces s revea l s numerous pol ymorphonucl ea r l eukocytes (PMNs or neutrophi l s ) a nd s evera l gra m-nega ti ve rods tha t di d not grow on bl ood pl a tes i n the pres ence of O2 . Meta bol i s m of O2 res ul ts i n toxi c rea cti ve oxygen s peci es . 5. Whi ch of the fol l owi ng enzymes i na cti va tes s uperoxi de free ra di ca l s a . ATPa s e b. Ca ta l a s e c. Permea s e d. Peroxi da s e e. Superoxi de di s muta s e 6. Whi ch of the fol l owi ng a nti bi oti cs woul d be the bes t choi ce for trea ti ng thi s pa ti ent’s i nfecti on? a . Ampi ci l l i n b. Chl ora mpheni col c. Ci profl oxa ci n d. Genta mi ci n e. Metroni da zol e 7. A teena ged boy s uffered a foot l a cera ti on whi l e s wi mmi ng i n a pol l uted wa ter a rea i n a ri ver. He di d not s eek medi ca l trea tment, a nd the wound devel oped a foul -s mel l i ng exuda te. One of the ba cteri a i s ol a ted from the a bs ces s exuda te wa s mi s s i ng s uperoxi de di s muta s e, ca ta l a s e, a nd a peroxi da s e. Whi ch of the fol l owi ng s ta tements bes t des cri bes thi s mi croorga ni s m? a . It i s a ca pnophi l e b. It i s a fa cul ta ti ve a na erobe c. It i s a mi croa erophi l e
d. It i s a n a na erobe e. It i s a n obl i ga te a erobe Questions 8 and 9 A 20-yea r-ol d pregna nt fema l e pa ti ent pres ents to the emergency room wi th a 4-da y hi s tory of fever, chi l l s , a nd mya l gi a . Two da ys pri or to thi s , s he ha d noted pa i nful geni ta l l es i ons tha t ha d begun a s ves i cl es . Pel vi c exa mi na ti on revea l ed extens i ve ves i cul a r a nd ul cera ti ve l es i ons on the l eft l a bi a mi nora a nd ma jora wi th ma rked edema , a nd i ngui na l l ympha denopa thy. 8. Whi ch of the mi croorga ni s ms ca us i ng geni ta l ul cers ca n be demons tra ted by da rk fi el d mi cros copy? a . Chlamydia trachomatis LGV s erova rs b. Haemophilus ducreyi c. Herpes s i mpl ex vi rus type 2 d. Klebsiella granulomatis e. Treponema pallidum 9. Whi ch of the fol l owi ng tes ts woul d prove tha t the pa ti ent i s i nfecti ous for herpes s i mpl ex vi rus (HSV) type 2? a . Cul ture b. Detecti on of HSV2-s peci fi c IgM c. Di rect i mmunofl uores cent a s s a y d. Nucl ei c a ci d a mpl i fi ca ti on tes ti ng e. Tza nck s mea r 10. Gra m-nega ti ve di pl ococci were demons tra ted i n a Gra m s ta i n of urethra l dra i na ge from a n 18-yea r-ol d ma l e who pres ented wi th s ymptoms of urethri ti s . Conti nuous pa s s a ge of thi s s tra i n on l a bora tory medi um res ul ted i n the revers i on of a fi mbri a ted to a nonfi mbri a ted s tra i n. Whi ch of the fol l owi ng i s the mos t l i kel y i mpl i ca ti on of thi s phenomenon?
Gra m-s ta i ned photomi crogra ph s howi ng i ntra cel l ul a r gra m-nega ti ve di pl ococci a nd numerous PMNs . (Courtesy of Bill Schwartz; Public Health Image Library, Centers for Disease Control and Prevention, 1971.) a . A nega ti ve ca ps ul e s tra i n b. Dea th of the orga ni s m c. Ina bi l i ty to col oni ze the mucos a l epi thel i um d. Los s of s erol ogi c s peci fi ci ty e. Revers i on to a gra m-pos i ti ve s ta i n 11. Twenty-ei ght hours a fter ea ti ng undercooked chi cken, a 50-yea r-ol d fa rmer pres ents to the emergency room wi th a bdomi na l pa i n, cra mpi ng, bl oody di a rrhea , a nd na us ea . An i s ol a te from the s tool i s bi ochemi ca l l y i denti fi ed a s Salmonella enterica; however, the i s ol a te ca nnot be s erotyped. Whi ch of the fol l owi ng ha s thi s orga ni s m l os t? a . Ca ps ul e b. Fl a gel l a c. Ma nnos e receptor
d. Pi l i e. O-s peci fi c pol ys a ccha ri de 12. A 2-yea r-ol d i nfa nt i s di a gnos ed wi th meni ngi ti s . A l umba r puncture revea l s numerous neutrophi l s a nd gra m-pos i ti ve cocci i n pa i rs tha t a ppea r enca ps ul a ted. She i s a dmi tted to the hos pi ta l a nd s ta rted on i ntra venous (IV) β-l a cta ms . Whi ch of the fol l owi ng ta rgets woul d mos t l i kel y pl a y a rol e i n the devel opment of res i s ta nce to thi s a nti bi oti c i n the mos t l i kel y eti ol ogi c a gent of thi s chi l d’s meni ngi ti s ? a . Ba ctoprenol b. DNA gyra s e c. Peni ci l l i n-bi ndi ng protei n d. Revers e tra ns cri pta s e e. RNA pol ymera s e 13. A ca ttl e fa rmer devel ops necroti c l es i ons on hi s a rms a nd fa ce fol l owi ng a tra uma ti c encounter wi th a bul l . Sel ecti ve i nhi bi ti on of s ynthes i s of di pi col i ni c a ci d by the eti ol ogi c a gent of the i nfecti on woul d mos t l i kel y i nhi bi t the forma ti on of the i nfecti ve s tructure. Whi ch of the fol l owi ng woul d be i nhi bi ted?
(Courtesy of Public Health Image Library, Centers for Disease Control and Prevention.) a . Ba cteri a l s pore forma ti on b. Ba cteri a l vegeta ti ve cel l s c. Funga l a rthros pores d. Funga l mi croconi di a e. Mycoba cteri a l vegeta ti ve cel l s Questions 14 and 15
A 30-yea r-ol d ma l e pres ents to the emergency room wi th hi gh fever a nd ma l a i s e, whi ch he reports tha t i t bega n 4 da ys a go a nd got progres s i vel y wors e ea ch da y. He a ppea rs underwei ght a nd very i l l . Phys i ca l exa mi na ti on revea l s needl e ma rks i n both a ntecubi ta l fos s a e. Upon l i s teni ng for hea rt s ounds , you hea r a di s ti ncti ve s ys tol i c hea rt murmur. You order bl ood cul tures a nd ma ke a pres umpti ve di a gnos i s of a cute ba cteri a l endoca rdi ti s . Fol l owi ng i s the growth curve of the orga ni s m growi ng i n a nutri ent medi um a t 35°C wi th both O2 a nd a dded CO2 pres ent.
14. In whi ch of the fol l owi ng growth pha s es woul d the orga ni s m mos t l i kel y be res i s ta nt to β-l a cta m a nti bi oti cs ? a . La g pha s e b. Log pha s e c. Sta ti ona ry pha s e d. Dea th pha s e 15. On whi ch of the fol l owi ng growth pha s es woul d trea tment wi th genta mi ci n ha ve a ma xi ma l effect? a . La g pha s e b. Log pha s e c. Sta ti ona ry pha s e d. Dea th pha s e 16. An outbrea k of di a rrhea i s thought to be rel a ted to a group of vendors who were s el l i ng hot dogs a t the county fa i r. Stool cul tures a re pos i ti ve for Shigella i n a l mos t a l l i ndi vi dua l s who a te the hot dogs . Growth of the i s ol a ted col oni es i n nutri ent l i qui d medi um wi thout the tra ns fer to fres h medi um wi l l eventua l l y i nduce the dea th pha s e of the orga ni s m. Whi ch of the fol l owi ng i s a l i mi ti ng fa ctor i n mi crobi a l growth under l a bora tory condi ti ons ? a . Accumul a ti on of oxygen-free ra di ca l s b. Accumul a ti on of peroxi de c. Accumul a ti on of toxi c products i n the growth medi um d. Los s of s uperoxi de di s muta s e e. Oxygen 17. A 62-yea r-ol d woma n wi th di a gnos ed type 2 di a betes l i ved a l one a nd di d es s enti a l l y nothi ng to ma na ge her i l l nes s , i ncl udi ng di s rega rdi ng her phys i ci a n’s i ns tructi ons . She wa s ta ken to her l oca l emergency room (ER) wi th s evere, mul ti pl e i nfected foot l es i ons , whi ch yi el ded a va ri ety of opportuni s ti c mi crobes wi th a mi xture of a nti bi oti c s us cepti bi l i ti es . The phys i ci a n deci ded to trea t wi th s ys temi c a nd topi ca l a nti mi crobi a l s . Whi ch of the fol l owi ng a nti mi crobi a l a gents mus t onl y be us ed topi ca l l y? a . Ba ci tra ci n b. Genta mi ci n c. Itra cona zol e d. Peni ci l l i n e. Va ncomyci n 18. A 42-yea r-ol d a l cohol i c ma n pres ents wi th fever, chi l l s , cough, a nd ches t x-ra y s ugges ti ve of pneumoni a . The Gra m-s ta i ned s mea r of s putum s hows ma ny PMNs a nd gra m-pos i ti ve cocci i n pa i rs a nd cha i ns . Whi ch of the fol l owi ng i s the correct order of the procedura l s teps when performi ng
the Gra m s ta i n? a . Fi xa ti on, crys ta l vi ol et, a l cohol /a cetone decol ori za ti on, s a fra ni n b. Fi xa ti on, crys ta l vi ol et, i odi ne trea tment, a l cohol /a cetone decol ori za ti on, s a fra ni n c. Fi xa ti on, crys ta l vi ol et, i odi ne trea tment, s a fra ni n d. Fi xa ti on, crys ta l vi ol et, s a fra ni n e. Fi xa ti on, s a fra ni n, i odi ne trea tment, a l cohol /a cetone decol ori za ti on, crys ta l vi ol et 19. A 78-yea r-ol d ma n pres ents to the l oca l emergency depa rtment wi th a s evere hea da che a nd s ti ff neck. The cerebros pi na l fl ui d (CSF) s peci men i s cl oudy. Ana l ys i s revea l s 400 whi te bl ood cel l s per cubi c mi l l i meter (95% PMNs ), a protei n concentra ti on of 75 mg/dL, a nd a gl ucos e concentra ti on of 20 mg/dL. Whi l e i n the ER, a res i dent does a Gra m s ta i n of the CSF but mi s ta kenl y forgets the i odi ne trea tment s tep. If the meni ngi ti s i s ca us ed by Streptococcus pneumoniae, how wi l l the ba cteri a s een on the res i dent’s s l i de a ppea r? a . Al l the cel l s wi l l be bl ue b. Al l the cel l s wi l l be decol ori zed c. Al l the cel l s wi l l be purpl e d. Al l the cel l s wi l l be red e. Al l the cel l s wi l l l ys e; thus , no Gra m s ta i n res ul ts wi l l be obta i ned f. Ha l f of the cel l s wi l l be red a nd the other ha l f wi l l be bl ue 20. A 28-yea r-ol d fema l e jus t returned from a 1-week crui s e wi th s tops a l ong the coa s t of Mexi co. Forty-ei ght hours a fter her return s he i s reported to ha ve hea da che, fever, a bdomi na l cra mps , a nd cons ti pa ti on. Over the next 5 da ys , her fever i ncrea s es wi th conti nued compl a i nts of mya l gi a s , ma l a i s e, a nd a norexi a . A bl ood cul ture i s pos i ti ve for S. enterica s er. Typhi . Her condi ti on i mproves wi th a trea tment cours e of a ci profl oxa ci n. Whi ch of the fol l owi ng i s the functi on of pori ns tha t woul d prevent the effecti ve us e of thi s a nti mi crobi a l ? a . Hydrol ys i s of hydrophi l i c a nti mi crobi a l s b. Meta bol i s m of phos phoryl a ted i ntermedi a tes c. Serol ogi c s ta bi l i za ti on of the O a nti gen d. Ina cti va ti on of hydrophobi c a nti mi crobi a l s e. Tra ns fer of mol ecul es through the outer membra ne 21. A 21-yea r-ol d ma n wa s bi tten by a ti ck whi l e hi ki ng i n Mi chi ga n. Four months l a ter, he pres ented to hi s doctor compl a i ni ng of s wel l i ng a nd pa i n i n hi s l eft knee. A s creeni ng tes t for Lyme di s ea s e wa s equi voca l . An IgG wes tern bl ot wa s performed us i ng the pa ti ent’s s erum a ga i ns t protei ns of Borrelia burgdorferi a nd Borrelia turicatae i s s hown bel ow. Whi ch of the fol l owi ng i s a n a ccura te i nterpreta ti on of the tes t?
Wes tern bl ot for Borrelia burgdorferi-s peci fi c IgG a nti bodi es . Fi ve of 10 s peci fi c ba nds for B. burgdorferi mus t be pres ent for tes t to be cons i dered
pos i ti ve. (18, 21 [Os pC], 28, 30, 39 [BmpA], 41 [Fl a ], 45, 58 [not GroEL], 66, a nd 93 kDa .) a . The pa ti ent ha s ea rl y Lyme di s ea s e b. The pa ti ent ha s ea rl y di s s emi na ted Lyme di s ea s e c. The pa ti ent l a te di s s emi na ted Lyme di s ea s e d. The pa ttern mos t l i kel y repres ents nons peci fi c rea cti vi ty e. The s creeni ng tes t s houl d be repea ted Questions 22 and 23 Over 30 i ndi vi dua l s , a ttendees of a home i mprovement conference a nd thei r fa mi l y members , a re hos pi ta l i zed wi th bl oody di a rrhea . Severa l chi l dren of the a ttendees devel op fever, a bdomi na l pa i n, a nd s evere hema tol ogi ca l a bnorma l i ti es . An i nves ti ga ti on es ta bl i s hes tha t a l l of thes e i ndi vi dua l s devel oped s ymptoms fol l owi ng cons umpti on of ha mburgers from the s a me fa s t-food res ta ura nt cha i n. Al though other i ndi vi dua l s a te the s a me ha mburgers , they di d not report a ny s ymptoms . 22. Whi ch of the fol l owi ng tes ts i s the bes t to detect the mos t l i kel y eti o-l ogi c a gent of thi s outbrea k? a . Gra m s ta i n of s tool s peci mens b. Immunoa s s a y for Shi ga toxi n-produci ng Escherichia coli c. Pol ymera s e cha i n rea cti on (PCR) for Campylobacter d. Serol ogi c tes ti ng for Salmonella enterica a nti bodi es e. Stool cul ture 23. The cl i ni ca l l a bora tory i s tryi ng to devel op a mol ecul a r a s s a y to detect the s us pected a gent. Nucl eoti de pri mers a re a va i l a bl e for the vi rul ence gene. Whi ch of the fol l owi ng mol ecul a r methods i s bes t a nd the mos t ra pi d for detecti ng thi s gene i n the s tool s a mpl e? a . DNA s equenci ng b. Dot bl ot hybri di za ti on c. PCR d. Rea l -ti me PCR e. Southern bl ot hybri di za ti on 24. An outbrea k of a di a rrhea i s s us pected to be rel a ted to ha mburgers tha t were s erved a t a fa s t food res ta ura nt. Stool cul tures from the pa trons a nd the food ha ndl ers were pos i ti ve for Salmonella. To a s s es s i f the outbrea k wa s ca us ed by a s peci fi c Salmonella s tra i n, i nves ti ga tors obta i ned chromos oma l DNA from the i s ol a ted s tra i ns , puri fi ed the DNA s a mpl es , a nd di ges ted the s a mpl es wi th XbaI, a res tri cti on enzyme tha t produces l a rge DNA fra gments . The res ul ts a re s hown i n the bel ow fi gure. Wha t mol ecul a r techni que wa s us ed to produce thes e res ul ts ?
(Modified from Egorova S, Timinouni M, Demartin M, et al. Ceftriaxone-resistant Sa l monel l a enteri ca serotype Newport, France. Emerg Infect Dis 2008. http://wwwnc.cdc.gov/eid/article/14/6/07-1168.htm; accessed 01-09-2013.) a . Cl oni ng
b. PCR c. Pul s ed-fi el d gel el ectrophores i s d. Sodi um dodecyl s ul fa te pol ya cryl a mi de gel el ectrophores i s e. Southern bl ot hybri di za ti on 25. Some of the E. coli ba cteri a tha t were ori gi na l l y i s ol a ted from a conta mi na ted s a l a d were tetra cycl i ne res i s ta nt whi l e the others were s us cepti bl e. However, when tetra cycl i ne-res i s ta nt a nd -s us cepti bl e s tra i ns were grown together, a l l of them beca me tetra cycl i ne res i s ta nt. Thi s effi ci ent tra ns fer of res i s ta nce depends on whi ch of the fol l owi ng? a . Cel l l ys i s a nd the rel ea s e of DNA from donor ba cteri a b. Competent cel l s c. Conjuga ti ve pl a s mi ds d. Recombi na s e enzymes e. Tra ns pos ons 26. A hi gh s chool -a ged young woma n pres ented to her fa mi l y phys i ci a n wi th wha t a ppea red to be a n a cute uncompl i ca ted UTI. She wa s trea ted wi th a β-l a cta m a nti mi crobi a l , but her s ymptoms pers i s ted. E. coli wa s i s ol a ted from the i nfecti on, but ma ny of the orga ni s ms a ppea red Gra m-s ta i n va ri a bl e a nd rounded. The rounded forms were i denti fi ed a s s pheropl a s ts . Whi ch of the fol l owi ng s ta tements a bout the E. coli cel l s s hown i n the mi crophotogra ph bel ow i s mos t cha ra cteri s ti c of the orga ni s m obs erved i n thi s i nfecti on?
a . They a re commonl y referred to a s endos pores b. They a re os moti ca l l y s ta bl e c. They res ul ted from trea tment wi th the β-l a cta m d. They ha ve formed cel l wa l l s 27. A 3-yea r-ol d gi rl from a fa mi l y tha t does not bel i eve i n i mmuni za ti on pres ents to the emergency room wi th a s ore throa t, fever, ma l a i s e, a nd di ffi cul ty brea thi ng. A gra y membra ne coveri ng the pha rynx i s obs erved on phys i ca l exa mi na ti on. Corynebacterium diphtheriae i s confi rmed a s the eti ol ogi c a gent of thi s i nfecti on. Whi ch of the fol l owi ng i s requi red to prove tha t C. diphtheriae i s the eti ol ogi c a gent of thi s chi l d’s i nfecti on? a . Demons tra ti on of cys tei na s e producti on b. Is ol a ti on of C. diphtheriae from throa t cul ture c. Meta chroma ti c gra nul es s een on methyl ene bl ue s ta i n d. Pl eomorphi c gra m-pos i ti ve ba ci l l i s een on Gra m s ta i n e. Toxi geni ci ty demons tra ted by the El ek tes t 28. A 3-yea r-ol d gi rl from a da y ca re center i s brought to the l oca l publ i c hea l th cl i ni c beca us e of a s evere, i ntra cta bl e cough. Duri ng the previ ous 10 da ys , s he ha d a pers i s tent col d tha t ha d wors ened. The cough devel oped the previ ous da y a nd wa s s o s evere tha t vomi ti ng frequentl y fol l owed i t. The chi l d a ppea rs exha us ted from the coughi ng epi s odes . A bl ood cel l count s hows a ma rked l eukocytos i s wi th a predomi na nce of l ymphocytes . Whi ch of the fol l owi ng i s mos t a ppropri a te for di a gnos i s of thi s chi l d’s i l l nes s ? a . Cul ture a l one b. Cul ture pl us PCR c. Di rect fl uores cence a s s a y (DFA) a l one d. DFA pl us cul ture e. PCR a l one 29. A 55-yea r-ol d ma l e pres ents wi th s evere bi l a tera l pul mona ry i nfi l tra te, el eva ted tempera ture, l eucocytos i s , el eva ted enzymes , a nd el eva ted crea ti ne ki na s e. He a nd s i x of hi s fri ends ha d recentl y vi s i ted thei r fa vori te res ta ura nt, whi ch ha d a l a rge wa ter founta i n tha t wa s mi s ty on the da y
of hi s vi s i t. Whi ch of the fol l owi ng woul d be expected on a Gra m s ta i n tha t wa s counters ta i ned wi th s a fra ni n for 3 mi nutes (prol onged counters ta i n)? a . Strongl y s ta i ni ng gra m-pos i ti ve ba ci l l i b. Wea kl y s ta i ni ng gra m-pos i ti ve ba ci l l i c. Strongl y s ta i ni ng gra m-nega ti ve ba ci l l i d. Wea kl y s ta i ni ng gra m-nega ti ve ba ci l l i e. Strongl y s ta i ni ng gra m-nega ti ve cocci f. Wea kl y s ta i ni ng gra m-nega ti ve cocci Questions 30 to 33 The fol l owi ng fi ve growth curves a re l ettered (A to E) corres pondi ng to a n expected growth curve i f certa i n a nti bi oti cs were a dded to a n exponenti a l l y growi ng cul ture of E. coli. The a rrow i ndi ca tes when a nti bi oti cs were a dded to the growi ng cul ture.
Growth curves i n the pres ence or a bs ence of a nti bi oti cs . 30. Peni ci l l i n trea tment woul d be expected to produce whi ch one of the fol l owi ng growth curves ? a. A b. B c. C d. D e. E 31. Chl ora mpheni col woul d be expected to produce whi ch one of the fol l owi ng growth curves ? a. A b. B c. C d. D e. E 32. Sul fona mi de woul d be expected to produce whi ch one of the fol l owi ng growth curves ? a. A b. B c. C d. D e. E
33. If no a nti bi oti cs were a dded to the exponenti a l l y growi ng cul ture, whi ch one of the fol l owi ng growth curves woul d res ul t? a. A b. B c. C d. D e. E 34. Severa l s tra i ns of S. pneumoniae a re i s ol a ted from va ri ous pa ti ents . Some demons tra te hi gh vi rul ence whi l e others a ppea r to be nonvi rul ent. Mi xi ng thes e cul tures i n the l a bora tory ca us es the nonvi rul ent s tra i ns to become pa thogeni c i n l a bora tory a ni ma l experi ments . Upta ke by a reci pi ent cel l of s ol ubl e DNA rel ea s ed from a donor cel l i s defi ned a s whi ch of the fol l owi ng? a . Conjuga ti on b. Fra mes hi ft muta ti on c. Homol ogous recombi na ti on d. Tra ns ducti on e. Tra ns forma ti on 35. A nons pore-formi ng, gra m-pos i ti ve ba ci l l us wa s i s ol a ted from a throa t s peci men from a pri ma ry s chool -a ged chi l d who ha d not been va cci na ted wi th the DTa P va cci ne. The s tra i n i s ol a ted ca rri ed a ba cteri opha ge on whi ch the gene for toxi n wa s encoded. How di d thi s s tra i n become toxi geni c? a . Conjuga ti on b. Fra mes hi ft muta ti on c. Homol ogous recombi na ti on d. Tra ns ducti on e. Tra ns forma ti on 36. An i ncrea s e i n a nti bi oti c res i s ta nce ha s been obs erved i n Staphylococcus aureus, Pseudomonas aeruginosa, a nd E. coli s tra i ns i s ol a ted from pa ti ents i n medi ca l centers . Di rect tra ns fer of a pl a s mi d between two ba cteri a i s defi ned a s whi ch of the fol l owi ng? a . Conjuga ti on b. Fra mes hi ft muta ti on c. Homol ogous recombi na ti on d. Tra ns ducti on e. Tra ns forma ti on 37. E. coli ha s a doubl i ng ti me of 30 mi nutes i n huma n uri ne a t room tempera ture. A pa ti ent ha d 1000 ba cteri a per mL of uri ne when a uri ne s peci men wa s col l ected. How ma ny ba cteri a woul d be pres ent i f the s peci men s a t a t room tempera ture for 4 hours before bei ng pl a ted for cul ture i n the l a bora tory? a . 4000 b. 16,000 c. 64,000 d. 256,000 e. 512,000 38. A 24-yea r-ol d fema l e pres ented wi th pa i n duri ng uri na ti on. Gra m s ta i n of the uncentri fuged uri ne revea l ed the pres ence of gra m-nega ti ve rods . Wha t vi rul ence fa ctor i s es s enti a l for the s urvi va l of thes e uropa thogeni c ba cteri a i n the uri na ry tra ct? a . Pi l i b. LPS (endotoxi n) c. Hea t l a bi l e toxi n d. Fl a gel l a e. Ca ps ul e 39. A 30-yea r-ol d hos pi ta l i zed pa ti ent wi th a n i ntra venous (IV) ca theter devel oped fever a nd s ys temi c i nfecti on. The s ource of the i nfecti on wa s ba cteri a tha t conta mi na ted the ca theter duri ng i ts i ns erti on. The IV ca theter ha d to be removed beca us e the ba cteri a grew wi thi n the ca theter formi ng a bi ofi l m. Bi ofi l m devel opment depends on the a bi l i ty of the ba cteri a to produce whi ch of the fol l owi ng? a . Endotoxi n b. Peri pl a s m c. Pol ys a ccha ri des d. Pori ns e. Tei choi c a ci d 40. A 55-yea r-ol d Bri ti s h tea cher pres ents wi th wei ght l os s , wea knes s , mus cl e a trophy, a nd decl i ni ng cogni ti ve functi on. Her hi s tory revea l s tha t her fa vori te mea l i s s oup ma de wi th cow bra i n, whi ch s he ha s ea ten a l mos t every week s i nce s he wa s 10 yea rs ol d. Whi ch of the fol l owi ng bes t des cri bes the mos t l i kel y eti ol ogi c a gent of her s ymptoms ? a . Abnorma l l y fol ded protei n b. Ca ps i d conta i ni ng DNA c. Envel oped ca ps i d conta i ni ng RNA d. Mul ti cel l ul a r cys t-formi ng orga ni s m e. Uni cel l ul a r orga ni s m wi th one chromos ome 41. Over 200 i s oni a zi d-res i s ta nt s tra i ns of Mycobacterium tuberculosis i s ol a ted from di fferent pa ti ents i n the northwes tern regi on of Rus s i a a re s creened by a PCR-res tri cti on fra gment l ength pol ymorphi s m a s s a y. Thi s a na l ys i s revea l s a 93.6% preva l ence of a s peci fi c G to C muta ti on i n the
katG i n s tra i ns from pa ti ents wi th both newl y a nd previ ous l y di a gnos ed ca s es of tubercul os i s . Whi ch of the fol l owi ng bes t des cri bes the type of muta ti on tha t res ul ted i n i s oni a zi d res i s ta nce i n thes e s tra i ns ? a . Del eti on b. Invers i on c. Mi s s ens e d. Nons ens e e. Tra ns vers i on repl a cement 42. Seven cl os el y rel a ted i s ol a tes of Candida albicans exhi bi ted progres s i ve decrea s es i n s us cepti bi l i ty to pos a cona zol e. Sequenci ng of the gene i nvol ved i n a zol e res i s ta nce i n thes e s tra i ns revea l ed predi cted protei ns wi th s i ngl e a mi no a ci d cha nges . Whi ch of the fol l owi ng bes t des cri bes the type of muta ti on tha t ha s res ul ted i n decrea s ed s us cepti bi l i ty to pos a cona zol e i n thes e s tra i ns ? a . Del eti on b. Invers i on c. Mi s s ens e d. Nons ens e e. Tra ns vers i on repl a cement 43. A 25-yea r-ol d ma n pres ents to the emergency room wi th s evera l red, s wol l en, tender bi te wounds on both a rms tha t he s ta ted occurred yes terda y when he res cued hi s dog from a dogfi ght i nvol vi ng three other dogs , whos e owner(s ) i s unknown. Hi s ri ght wri s t a nd l eft el bow a re a l s o s wol l en a nd there i s a xi l l a ry l ympha denopa thy on the l eft s i de. Gra m s ta i n of purul ent ma teri a l from the wors t wound s hows s ma l l gra m-nega ti ve pl eomorphi c coccoba ci l l i . The pa ti ent reports hi s l a s t teta nus va cci na ti on wa s 2 yea rs a go. In a ddi ti on to a nti bi oti cs , whi ch of the fol l owi ng s houl d be i ncl uded i n thi s pa ti ent’s trea tment? a . Hepa ti ti s B vi rus prophyl a xi s b. IV i mmunogl obul i ns (nons peci fi c) c. Ra bi es prophyl a xi s d. Teta nus prophyl a xi s e. Va ri cel l a -zos ter prophyl a xi s 44. A pa ti ent pres ents to the emergency room wi th vomi ti ng, di a rrhea , hi gh fever, a nd del i ri um. Upon phys i ca l exa mi na ti on, you noti ce l a rge buboes , whi ch a re pa i nful on pa l pa ti on, a nd purpura a nd ecchymos es s ugges ti ve of di s s emi na ted i ntra va s cul a r coa gul a ti on. Gra m s ta i n on a s pi ra te of a bubo revea l s gra m-nega ti ve rods wi th bi pol a r s ta i ni ng. Whi ch of the fol l owi ng a nti bi oti cs i s the drug of choi ce for empi ri c thera py? a . Cefta zi di me b. Chl ora mpheni col c. Peni ci l l i n d. Streptomyci n e. Va ncomyci n 45. A 3-yea r-ol d gi rl who ha s mi s s ed s evera l s chedul ed i mmuni za ti ons pres ents to the emergency room wi th a hi gh fever. She i s i rri ta bl e a nd ha s a s ti ff neck. Fl ui d from a s pi na l ta p revea l s 20,000 whi te bl ood cel l s per mi l l i l i ter wi th 85% pol ymorphonucl ea r cel l s . Whi ch of the fol l owi ng i s the drug of choi ce for empi ri c thera py a ga i ns t orga ni s ms of chi l dhood meni ngi ti s ? a . Ceftri a xone b. Erythromyci n c. Genta mi ci n d. Peni ci l l i n e. Va ncomyci n 46. Duri ng the cours e of hi s hos pi ta l s ta y, a s everel y burned 60-yea r-ol d ma l e devel ops a ra pi dl y di s s emi na ti ng ba cteri a l i nfecti on. Sma l l gra mnega ti ve rods tha t a re oxi da s e pos i ti ve a re cul tured from green pus ta ken from the burn ti s s ue. Whi ch combi na ti on of a nti bi oti cs i s the bes t choi ce for empi ri c thera py a ga i ns t thi s eti ol ogi c a gent? a . Cefta zi di me pl us va ncomyci n b. Erythromyci n pl us i mi penem c. Peni ci l l i n pl us genta mi ci n d. Pi pera ci l l i n/ta zoba cta m pl us cepha l othi n e. Ti ca rci l l i n/cl a vul a na te pl us tobra myci n 47. La bora tory res ul ts of a cl i ni ca l s peci men from a pa ti ent wi th hos pi ta l -a cqui red pneumoni a revea l the pres ence of methi ci l l i n-res i s ta nt Staphylococcus aureus (MRSA). Whi ch of the fol l owi ng drugs i s the bes t empi ri c trea tment? a . Cefta zi di me b. Di cl oxa ci l l i n c. Peni ci l l i n d. Tobra myci n e. Va ncomyci n 48. A young, es s enti a l l y hea l thy woma n wa s concerned a bout her l os s of job ti me due to recurrent UTIs . Her phys i ci a n pres cri bed a n a nti bi oti c, whi ch woul d control mi crobi a l nucl eoti de s ynthes i s by i nhi bi ti ng di hydrofol i c a ci d reducta s e i n ba cteri a up to 50,000 ti mes more tha n i n ma mma l i a n cel l s . Whi ch of the fol l owi ng a gents work by thi s mecha ni s m? a . Ampi ci l l i n b. Amphoteri ci n c. Chl ora mpheni col
d. Levofl oxa ci n e. Tri methopri m 49. A 52-yea r-ol d woma n pres ents wi th fever of 103°F, hea da che, ri ght fl a nk pa i n, na us ea a nd vomi ti ng, a nd uri na ry frequency wi th hema turi a a nd dys uri a . Rena l ul tra s ound demons tra tes a ri ght uri na ry s tone wi th ri ght hydronephros i s . Whi ch of the fol l owi ng a nti bi oti cs i s the mos t a ppropri a te trea tment opti on? a . Ampi ci l l i n b. Amphoteri ci n c. Chl ora mpheni col d. Peni ci l l i n e. Tri methopri m/s ul fa methoxa zol e 50. A 75-yea r-ol d Afri ca n Ameri ca n ma l e wi th neurogeni c bl a dder pres ents to the emergency room wi th hypertens i on, fever up to 104.6°F, a nd na us ea a nd vomi ti ng. The uri ne from hi s fol ey ca theter gi ves a pos i ti ve cul ture for a n a nti bi oti c-res i s ta nt s tra i n of Enterococcus faecalis. He ha d previ ous l y been gi ven a n a nti bi oti c tha t bi nds to D-a l a ni ne-D-a l a ni ne. To whi ch of the fol l owi ng a nti bi oti cs i s thi s i s ol a te mos t l i kel y res i s ta nt? a . Ampi ci l l i n b. Amphoteri ci n c. Chl ora mpheni col d. Levofl oxa ci n e. Va ncomyci n 51. A pa ti ent wi th l eukemi a ha s a ches t CT fi ndi ng tha t s ugges ts a s pergi l l os i s . Whi ch of the fol l owi ng a nti mi crobi a l s a ffects ergos terol s ynthes i s a nd woul d mos t l i kel y be us ed i n thi s pa ti ent’s trea tment? a . Amphoteri ci n B b. Ca s pofungi n c. Gri s eoful vi n d. Mi ca fungi n e. Vori cona zol e 52. A 6-yea r-ol d gi rl i s di a gnos ed wi th meni ngi ti s . A l umba r puncture revea l s numerous neutrophi l s a nd gra m-nega ti ve di pl ococci . She i s a dmi tted to the hos pi ta l for a nti bi oti c trea tment, whi ch i s compl i ca ted by the fa ct tha t s he i s known to be a l l ergi c to β-l a cta ms . Wha t i s the mecha ni s m of a cti on of the a l terna ti ve drug of choi ce to trea t thi s i nfa nt’s meni ngi ti s ? a . Bl ocks tRNA bi ndi ng to the A s i te b. Ca us es mi s rea di ng of mRNA c. Inhi bi ts forma ti on of the pepti de bond d. Prevents tra ns l oca ti on e. Res ul ts i n prema ture termi na ti on 53. A cl i ni ca l l a bora tory performs rea l -ti me PCR for detecti on of MRSA i n the a rea where s peci mens a re pl a ted. The s upervi s or di s covers tha t the l a s t 50 s peci mens tes ted were pos i ti ve. However, compa ni on cul tures were pos i ti ve for onl y 15 of the s peci mens . Wha t i s the mos t l i kel y rea s on for thi s di s crepa ncy? a . Rea l -ti me PCR i s more s ens i ti ve tha n cul ture b. Rea l -ti me PCR i s more s peci fi c tha n cul ture c. The PCR i ns trument needs to be ca l i bra ted d. The PCR works ta ti on ha s been conta mi na ted wi th MRSA DNA 54. Gues ts a t a pa rty cons umed beef broth tha t wa s boi l ed ea rl i er i n the da y but l eft a t room tempera ture for s evera l hours . The i ndi vi dua l s pres ented wi th s ymptoms of food poi s oni ng, i ncl udi ng wa tery di a rrhea a nd a bdomi na l cra mps , 8 to 10 hours l a ter. The s ymptoms l a s ted 24 hours . The a gent tha t ca us ed the s ymptoms i s mos t l i kel y whi ch of the fol l owi ng? a . Spore-formi ng gra m-pos i ti ve ba ci l l i b. Gra m-pos i ti ve cocci c. Gra m-nega ti ve ba ci l l i d. An opportuni s ti c fungus e. An enteri c vi rus 55. A 25-yea r-ol d ma l e pres ented wi th s evere urethri ti s . Over the pa s t 2 da ys , he ha d devel oped fever a nd chi l l s . Gra m s ta i n of the urethra l di s cha rge revea l ed the pres ence of gra m-nega ti ve di pl ococci . The fever a nd chi l l s a re mos t l i kel y due to the rel ea s e of exces s i ve a mounts of whi ch ba cteri a l component? a . Ca ps ul e b. Exotoxi n c. Li pool i gos a ccha ri de (LOS) d. Opa ci ty protei n e. Pi l i 56. A 2-yea r-ol d ha d been trea ted three ti mes wi th a mpi ci l l i n for a cute oti ti s medi a . Fl ui d a s pi ra ted from hi s mi ddl e ea r duri ng pl a cement of tympa nos tomy tubes grows Moraxella catarrhalis, whi ch i s res i s ta nt to a mpi ci l l i n. Whi ch enzyme i s res pons i bl e for thi s res i s ta nce? a . Acetyl tra ns fera s e b. β-La cta ma s e c. Ca ta l a s e d. DNa s e
e. Phos photra ns fera s e 57. A pa ti ent a dmi tted to s urgi ca l i ntens i ve ca re for dehi s cence of her s urgi ca l i nci s i on wa s s creened for MRSA by PCR for the mecA gene. Na s a l , recta l , a nd wound s wa bs were s ubmi tted for tes ti ng. The na s a l a nd wound s a mpl es were pos i ti ve for MRSA by PCR; however, the wound cul ture grew Staphylococcus epidermidis but no MRSA. Wha t i s the mos t l i kel y rea s on for the di s crepa ncy i n the res ul ts of tes ti ng on the wound s a mpl es ? a . The cul ture wa s performed i mproperl y b. The PCR wa s conta mi na ted c. The S. epidermidis i s ol a te ca rri es the mecA gene d. The wrong pri mers were us ed i n the PCR 58. Neisseria meningitidis, group B, i s i denti fi ed a s the ca us e of a l oca l meni ngi ti s outbrea k i n a mi l i ta ry tra i ni ng ca mp. Whi ch of the fol l owi ng protects thi s orga ni s m from compl ement-medi a ted pha gocytos i s by neutrophi l s ? a . Opa ci ty protei ns b. Pol ys a ccha ri de ca ps ul e c. Pi l i d. Li pool i gos a ccha ri de e. Ca ta l a s e 59. A chi l d a ttendi ng cl a s s es i n a pres chool i s noted by hi s tea cher to ha ve s evera l s ki n l es i ons on hi s a rms . The l es i ons a re pus tul a r i n a ppea ra nce a nd s ome ha ve broken down a nd a re covered wi th a yel l ow crus t. Whi ch of the fol l owi ng protects the mos t l i kel y eti ol ogi c a gent of thi s chi l d’s i nfecti on from pha gocytos i s a nd provi des s erol ogi c s peci fi ci ty? a . Erythrogeni c toxi n b. Hya l uroni c a ci d c. Li potei choi c a ci d d. M protei n e. Streptol ys i n O 60. A pha rma col ogi c compound i ntended for i njecti on wa s conta mi na ted wi th gra m-nega ti ve ba ci l l i duri ng producti on. The product wa s fi l tered before pa cka gi ng. Qua l i ty control cul tures were s teri l e s o the product wa s s hi pped for us e. However, numerous pers ons who recei ved the product devel oped fever a nd s evera l devel oped hypotens i on. Whi ch of the fol l owi ng wa s mos t l i kel y res pons i bl e for the rea cti on obs erved i n thes e pa ti ents ? a . Ba cteri a l pol ys a ccha ri des b. Hya l uroni c a ci d c. Li popol ys a ccha ri de d. Protei n toxi n e. Tei choi c a ci d 61. A 64-yea r ol d fema l e wi th a hi s tory of COPD vi s i ted her phys i ci a n beca us e of recent poor hea l th s ymptoms , i ncl udi ng cough, fever a nd ni ght s wea ts , wea knes s , a nd 20-pound wei ght l os s . Ches t x-ra y demons tra ted a nodul a r i nfi l tra te i n the upper l obe. La bora tory s ta i ni ng of s putum revea l ed a ci d-fa s t orga ni s ms . Whi ch cha ra cteri s ti c of the mos t l i kel y orga ni s m i s res pons i bl e for thi s s ta i ni ng res ul t? a . Ergos terol b. Gl ycol i pi ds c. Hya l uroni c a ci d d. Pepti dogl yca n e. Tei choi c a ci d 62. In 2001, a number of governmenta l offi ces recei ved ma i l ed envel opes tha t conta i ned a n unknown whi te powder. Severa l empl oyees were conta mi na ted a nd devel oped cuta neous a nd/or i nha l a ti ona l a nthra x. Whi ch of the fol l owi ng i s res pons i bl e for the a nti pha gocyti c properti es of thi s orga ni s m? a . D-gl uta mi c a ci d ca ps ul e b. Hya l uroni c a ci d c. Letha l fa ctor d. M protei n e. Protecti ve a nti gen 63. Twel ve el derl y res i dents l i vi ng i n a n a s s i s ted ca re fa ci l i ty s uffered from s i nus i ti s , oti ti s medi a , a nd mi l d pneumoni a s duri ng mi dwi nter. Des pi te the fa ct tha t they ha d a l l recei ved the 13-va l ent pneumococca l conjuga te va cci ne recentl y l i cens ed for a dul ts , S. pneumoniae wa s i s ol a ted from 10 of the pa ti ents . Whi ch of the fol l owi ng i s the bes t expl a na ti on for the pneumococca l i nfecti ons ? a . El derl y pa ti ents do not mount good i mmune res pons es to va cci nes b. Some pa ti ents wi l l not res pond to the va cci ne c. The ca ps ul a r type res pons i bl e wa s not pres ent i n the va cci ne d. The va cci ne wa s defecti ve
Answers 1. The answer is d. (Katzung, Ch 43. Murray, Ch 17. Ryan, Ch 23.) The s tructura l i ntegri ty of the β-l a cta m ri ng i n peni ci l l i ns i s es s enti a l for thei r a nti mi crobi a l a cti vi ty. Ma ny res i s ta nt s tra i ns of s ta phyl ococci produce a β-l a cta ma s e (peni ci l l i na s e) tha t cl ea ves the β-l a cta m ri ng of peni ci l l i n a t the ca rbon-ni trogen bond (4 i n di a gra m). Other orga ni s ms , i ncl udi ng col i form ba cteri a a nd Pseudomonas, produce cepha l os pori na s es , meta l l o-βl a cta ma s es , a nd ca rba pena ma s es tha t cl ea ve the β-l a cta m ri ngs of cepha l os pori ns a nd/or ca rba penems , a s wel l a s peni ci l l i ns , a t the s a me s i te. Peni ci l l i n a mi da s e i na cti va tes peni ci l l i n by di s rupti ng the bond between the ra di ca l a nd ni trogen i n the free a mi no group (1 i n di a gra m). Bonds 2, 3, a nd 5 a re not commonl y broken by ba cteri a l enzymes . 2. The answer is d. (Katzung, Ch 45. Murray, Ch 13. Ryan, Ch 21, 23.) Ami nogl ycos i des pa s s i vel y di ffus e a cros s the outer membra ne of gra m-nega ti ve ba cteri a through pori ns . The pa s s a ge of a mi nogl ycos i des i nto the cytopl a s m i s a n a cti ve proces s dependent on oxi da ti ve phos phoryl a ti on (d). Fa ci l i ta ted di ffus i on (a ) i nvol ves s peci fi c protei n ca rri ers . Group tra ns l oca ti on (c) occurs i n the a bs ence of oxygen. Fermenta ti on (b) i s a mecha ni s m for producti on of energy. Tra ns pepti da ti on (e) i s a rea cti on i nvol vi ng the tra ns fer of one or more a mi no a ci ds from one pepti de cha i n to a nother, or i n the a ddi ti on of a mi no a ci ds to the growi ng pepti de cha i n duri ng tra ns l a ti on. 3. The answer is b. (Murray, Ch 12, 26. Ryan, Ch 21, 30.) Unl i ke E. coli, Salmonella, Pseudomonas, a nd other gra m-nega ti ve ba ci l l i , Neisseria gonorrhoeae does not produce s i derophores (e). Ins tea d the pa thogeni c Neisseria obta i n i ron through s urfa ce receptors tha t i ntera ct wi th l a ctoferri n (b) a nd tra ns ferri n, hos t mol ecul es tha t s eques ter i ron. Ferri c oxi de (a ) i s produced by s ome envi ronmenta l ba cteri a . LPS (c) does not pl a y a rol e i n the i ron upta ke or meta bol i s m of the ba cteri a . Pyocya ni n (d) i s a bl ue redox pi gment produced by P. aeruginosa tha t ca n genera te rea cti ve oxygen i ntermedi a tes a nd a ffect the el ectron tra ns port cha i n a nd ves i cul a r tra ns port of euka ryoti c cel l s . 4. The answer is c. (Murray, Ch 12. Ryan, Ch 21.) The peri pl a s m i s the s pa ce between the outer membra ne a nd the cytopl a s mi c membra ne of gra mnega ti ve ba cteri a . The peri pl a s mi c s pa ce (c) i n E. coli ha s been s hown to conta i n enzymes i nvol ved i n tra ns port, degra da ti on, a nd s ynthes i s , i ncl udi ng β-l a cta ma s e. The other s tructures a re l a bel ed i n the di a gra m a bove (ca ps ul e—A; outer membra ne—B; cytopl a s mi c membra ne—D; cytopl a s m). The chromos ome a nd other s tructures found wi thi n or on the cel l s urfa ce, s uch a s the fl a gel l um a nd pi l us pres ent i n the di a gra m, were not i ndi ca ted a mong the choi ces .
5. The answer is e. (Murray, Ch 13. Ryan, Ch 21.) Toxi c oxygen ra di ca l s , s uperoxi de a nd hydrogen peroxi de, a re genera ted duri ng a erobi c meta bol i s m.
Superoxi de di s muta s e (e) ca ta l yzes the rea cti on tha t detoxi fi es s uperoxi de . Both ca ta l a s e (b) a nd peroxi da s e (d) detoxi fy hydrogen peroxi de, but peroxi da s es a l s o a ct on l i pi d peroxi des . The rea cti on ca ta l yzed by ca ta l a s e i s . ATPa s e (a ) converts ATP i nto ADP pl us a free phos pha te i on. Permea s es (d) a re membra ne tra ns port protei ns tha t fa ci l i ta te the pa s s a ge of s peci fi c mol ecul es a cros s i nto or out of the cel l . 6. The answer is e. (Katzung, Ch 44-46. Murray, Ch 13, 38. Ryan, Ch 21, 29.) The eti ol ogi c a gent of thi s ma n’s i nfecti on i s a n a na erobe, mos t l i kel y Bacteroides fragilis. Ampi ci l l i n (a ) i s unl i kel y to be s ucces s ful a s mos t i s ol a tes of B. fragilis produce β-l a cta ma s e. Chl ora mpheni col (b) i s ra rel y us ed i n the Uni ted Sta tes beca us e of i ts toxi ci ty, a l though i t i s us ed for trea tment of s eri ous ri cketts i a l i nfecti on s uch a s Rocky Mounta i n s potted fever a nd a s a n a l terna ti ve for trea tment of ba cteri a l meni ngi ti s i n pa ti ents who ha ve hypers ens i ti vi ty to peni ci l l i ns a nd cepha l os pori ns . Ci profl oxa ci n (c), a fl uoroqui nol one a nti bi oti c, ha s no s pectrum of a cti vi ty a ga i ns t a na erobes . Oxygen i s neces s a ry for tra ns port of a mi nogl ycos i des l i ke genta mi ci n (d) i nto the ba cteri a l cel l ; thus , they ha ve no s pectrum of a cti vi ty a ga i ns t a na erobes . Of the drugs l i s ted, metroni da zol e (e) i s the bes t choi ce for i nfecti ons wi th a na erobi c gra m-nega ti ve ba ci l l i . Addi ti ona l a nti bi oti cs wi th a cti vi ty a ga i ns t a na erobi c gra m-nega ti ve ba ci l l i a re ca rba penems a nd β-l a cta m/β-l a cta ma s e i nhi bi tor combi na ti ons . Bacteroides ha s become i ncrea s i ngl y res i s ta nt to cl i nda myci n, whi ch us ed to be a good a l terna ti ve, wi th up to 25% of i s ol a tes now res i s ta nt. 7. The answer is d. (Murray, Ch 13. Ryan, Ch 21.) Superoxi de di s muta s e i s a n enzyme found i n both proka ryoti c a nd euka ryoti c cel l s tha t ca n s urvi ve i n a n envi ronment of O2 . La ck of thi s enzyme, a s wel l a s peroxi da s e a nd ca ta l a s e, ens ures tha t a ba cteri um wi l l not grow i n the pres ence of O2 , ma ki ng i t a n a na erobe (d). Ca pnophi l es (a ) prefer a n a tmos phere wi th i ncrea s ed CO2 a nd a mbi ent O2 ; Haemophilus ducreyi i s ca pnophi l i c. Mi croa erophi l es (c) s uch a s Campylobacter jejuni prefer i ncrea s ed CO2 a nd reduced O2 . Fa cul ta ti ve a na erobes (b) ca n grow i n the pres ence or a bs ence of O2 . Obl i ga te a erobes (e), s uch a s Mycobacterium tuberculosis, requi re O2 for growth unl es s they ca n uti l i ze a n a l terna ti ve termi na l el ectron a cceptor. 8. The answer is e. (Murray, Ch 15. Ryan, Ch 64. Workowski & Berman, sections on diagnosis.) The mi crobes tha t ca us e geni ta l ul cers a re Chlamydia trachomatis LGV s erova rs 1 to 3, Haemophilus ducreyi, herpes s i mpl ex vi rus types 1 a nd 2, Klebsiella granulomatis, a nd Treponema pallidum. The va ri ous methods for di a gnos i s a re outl i ned i n the bel ow ta bl e. Treponema pallidum (e) ca n be demons tra ted by da rkfi el d mi cros copy i n pri ma ry a nd s econda ry s yphi l i ti c l es i ons .
9. The answer is a. (Murray, Ch 15. Ryan, Ch 64. Workowski & Berman, sections on diagnosis.) See the ta bl e a bove. Cul ture (a ) i s the bes t method to prove infectivity. However, vi ra l cul ture decrea s es i n s ens i ti vi ty a s the l es i ons begi n to hea l , s o nucl ei c a ci d a mpl i fi ca ti on tes ti ng or PCR (d) i s i ncrea s i ngl y us ed. PCR detects vi ra l DNA, whi ch ma y be pres ent i n non-i nfecti ve pa rti cl es . Beca us e herpes s i mpl ex i s s hed i ntermi ttentl y upon rea cti va ti on, nega ti ve cul ture or PCR does not rul e out l a tent i nfecti on. Vi ra l a nti gens , detected by di rect i mmunofl uores cent a s s a y (c) (or enzyme i mmunoa s s a y), ma y be pres ent a fter i nfecti ous pa rti cl es ha ve been neutra l i zed or di s rupted by a nti vi ra l s . Cytol ogi c detecti on by Tza nck s mea r (e) of geni ta l l es i ons or cervi ca l Pa p s mea r i s i ns ens i ti ve a nd nons peci fi c a nd s houl d not be rel i ed upon. Serol ogi c detecti on (b) us i ng tes ts tha t a re type-s peci fi c ma y be us ed i n ca s es or recurrent geni ta l s ymptoms or a typi ca l s ymptoms wi th nega ti ve cul ture; cl i ni ca l di a gnos i s of geni ta l herpes wi thout l a bora tory confi rma ti on, or a pa rtner wi th geni ta l herpes . Screeni ng of the genera l popul a ti on s houl d not be done. 10. The answer is c. (Murray, Ch 12, 14, 26. Ryan, Ch 21, 22, 30.) The vi gnette a nd fi gure deta i l a typi ca l ca s e of Neisseria gonorrhoeae. Ba cteri a ma y s hi ft ra pi dl y between the fi mbri a ted (fi m +) a nd the nonfi mbri a ted (fi m–) s ta tes . Fi mbri a e functi on a s a dhes i ons to s peci fi c s urfa ces a nd, cons equentl y, pl a y a ma jor rol e i n pa thogenes i s . La ck of fi mbri a e prevents col oni za ti on of the mucos a l s urfa ce by the ba cteri um (c). Pi l i (fi mbri a e) a re ha i rl i ke a ppenda ges tha t extend s evera l mi l l i meters from the gonococca l s urfa ce. Fi m cha nges woul d ha ve no effect on ca ps ul e pres ence (a ) or l os s of s erol ogi c s peci fi ci ty (d). Such cha nges woul d not ca us e the dea th of the orga ni s m (b), a nd Neisseria orga ni s ms never revert to a gra m-
pos i ti ve s ta i ni ng res ul t (e) due to the ma jor di fferences found i n the s tructures of gra m-pos i ti ve a nd gra m-nega ti ve cel l wa l l s . 11. The answer is e. (Levinson, Ch 2. Murray, Ch 12, 27. Ryan, Ch 21, 33.) LPS, a component of the outer membra ne of gra m-nega ti ve mi croorga ni s ms cons i s ts of three regi ons : l i pi d A, whi ch forms the outer l ea fl et of the l i pi d bi l a yer outer membra ne; the core pol ys a ccha ri de; a nd the O-a nti gen pol ys a ccha ri de (e) s i de cha i n tha t confers s eros peci fi ci ty or s erotype for the Enterba cteri a cea e. Stra i ns tha t ha ve l os t the O a nti gen ca nnot be s erotpyed. Fl a gel l a (b) confer the H a nti gens , whi ch a re a l s o us ed i n the typi ng of Salmonella s tra i ns a fter the O typi ng; s tra i ns tha t ha ve l os t fl a gel l a ca nnot be H-typed. The ca ps ul e (a ) confers the K a nti gen; pi l i (d) ca n be conjuga ti ve or be i nvol ved i n moti l i ty or a dhes i on (us ua l l y ca l l ed fi mbri a e). Nei ther the K a nti gens nor the pi l us - nor fi mbri a -rel a ted a nti gens a re uti l i zed i n the s erotypi ng of Salmonella for epi demi ol ogi c purpos es . The ma nnos e receptor (c) i s found on ma cropha ges a nd us ed by them to cha ra cteri ze pa thogeni c mi crobes i n the hos t i nna te res pons e.
12. The answer is c. (Levinson, Ch 10, 11. Murray, Ch 17. Ryan, Ch 23.) Tra ns pepti da s es , or peni ci l l i n-bi ndi ng protei ns (PBPs ) (c), a re i na cti va ted when bound to peni ci l l i n. Al tered PBPs no l onger bi nd the β-l a cta m a nti bi oti c. The a cqui s i ti on of a new PBP or modi fi ca ti on of the exi s ti ng one i s the mecha ni s m by whi ch S. pneumoniae, the mos t l i kel y eti ol ogi c of thi s chi l d’s meni ngi ti s , become res i s ta nt to β-l a cta ms . Al tered PBPs a re a l s o s een i n N. gonorrhoeae, S. aureus, a nd other ba cteri a . Ba ctoprenol (a ) i s not known to be i nvol ved i n a nti bi oti c res i s ta nce. Fl uoroqui nol ones ta rget the DNA gyra s e (b), whi l e ri fa myci ns ta rget the ba cteri a l RNA pol ymera s e (e). Ba cteri a do not uti l i ze revers e tra ns cri pta s e (d). 13. The answer is a. (Murray, Ch 12, 21. Ryan, Ch 21, 26.) The vi gnette pres ents a ca s e of cuta neous a nthra x. Anthra x i s a cqui red by cuta neous i ntroducti on, i nges ti on, or i nha l a ti on of endos pores from conta mi na ted a ni ma l s s uch a s ca ttl e, s heep, a nd goa ts . Inhi bi ti on of di pi col i ni c a ci d s ynthes i s woul d prevent forma ti on of ba cteri a l s pores (a ), but woul d not a ffect vegeta ti ve cel l s (b, e). Mycoba cteri a do not form s pores . Di pi col i ni c a ci d i s not found i n funga l a rthros pores (c) or mi croconi di a (d). 14. The answer is a. (Levinson, Ch 3, 10. Murray, 13, 17. Ryan, 21, 23.) The ba cteri a l growth cycl e i s cha ra cteri zed by four pha s es a s s hown i n the fi gure for thi s ques ti on. In the l a g pha s e (a ), the ba cteri a a re not di vi di ng but exhi bi t dyna mi c meta bol i c a cti vi ty a s they a djus t to the new envi ronment. Dependi ng on the s peci es a nd the tempera ture, pH, a nd nutri ents a va i l a bl e, the ba cteri a begi n di vi di ng wi thi n a few hours a nd enter the l og pha s e (b) where they grow exponenti a l l y for 12 to 18 hours . As nutri ents become depl eted a nd/or toxi c wa s te products a ccumul a te i n the cul ture, growth s l ows s o tha t the number of new cel l s a nd cel l s tha t di e a re ba l a nced; thi s i s the s ta ti ona ry pha s e (c). When nutri ents a re exha us ted or the cul ture medi um becomes too toxi c, the number of vi a bl e cel l s decrea s es dra ma ti ca l l y; thi s i s the dea th pha s e (d). Si mi l a r pha s es occur when the ba cteri a a re i ntroduced i nto the hos t, a l though the ti mi ng ma y va ry due to the s peci fi c hos t envi ronment a nd the hos t defens es encountered. Anti bi oti cs tha t a ffect the cel l wa l l , s uch a s β-l a cta ms , a re not effecti ve i n the l a g pha s e (a ). 15. The answer is b. (Levinson, Ch 3, 10. Murray, Ch 13, 17. Ryan, Ch 21, 23.) Ami nogl ycos i des exert three effects on protei n s ynthes i s : (1) bl ock i ni ti a ti on of tra ns l a ti on, (2) ca us e i ncorpora ti on of i ncorrect a mi no a ci ds i nto the growi ng pepti de cha i n, a nd (3) el i ci t prema ture termi na ti on of tra ns l a ti on. Protei n s ynthes i s occurs throughout the growth cycl e, but opti mum effecti venes s of a mi nogl ycos i des i s s een i n the l og pha s e (b). 16. The answer is c. (Levinson, Ch 18. Murray, Ch 18. Ryan, Ch 33.) Di fferenti a ti on of the gra m-nega ti ve ba ci l l i tha t ca us e ga s troenteri ti s begi ns wi th a erobi c (Enteroba cteri a cea e a nd Vibrio) vers us mi croa erophi l i c (b) (Campylobacter) growth. Morphol ogy on a l a ctos e-conta i ni ng s el ecti ve a ga r s uch
a s Ma cConkey a ga r s epa ra tes Salmonella a nd Shigella, whi ch do not ferment l a ctos e (a ), wherea s E. coli a nd Vibrio do. Shigella ca n be di fferenti a ted from Salmonella on a ga r conta i ni ng i ron; Shigella do not produce H 2 S (c) whi l e Salmonella do. Vibrio s peci es a re oxi da s e pos i ti ve (d); the Enteroba cteri a cea e a re not. Urea s e producti on (e) di s ti ngui s hes Proteus s pp. from Salmonella. 17. The answer is a. (Katzung, Ch 43, 45, 48.) Peni ci l l i n (d) i s wel l -tol era ted a s i s i tra cona zol e (c). Va ncomyci n (e) i s i rri ta ti ng a nd ca n res ul t i n phl ebi ti s a t the s i te of i njecti on; nephrotoxi ci ty of a mi nogl ycos i des i s exa cerba ted by concomi ta nt us e of va ncomyci n, but ca n be control l ed by ca reful dos a ge. Genta mi ci n (b) a nd other a mi nogl ycos i des a re ototoxi c a nd nephrotoxi c, but thes e a dvers e effects ca n us ua l l y be control l ed by moni tori ng of s erum concentra ti on a nd ca reful dos a ge. Ba ci tra ci n (a ) i s hi ghl y nephrotoxi c, s o much s o tha t i t ca nnot be a dmi ni s tered s ys temi ca l l y. Beca us e ba ci tra ci n i s poorl y a bs orbed, i t ca n be us ed topi ca l l y, provi di ng l oca l a nti ba cteri a l a cti vi ty but no s ys temi c toxi ci ty. 18. The answer is b. (Levinson, Ch 2. Murray, Ch 4. Ryan, Ch 4.) Fi rs t des cri bed i n 1884 by a Da ni s h phys i ci a n, Ha ns Chri s ti a n Gra m, the Gra m s ta i n ha s proved to be one of the mos t us eful di a gnos ti c l a bora tory procedures i n mi crobi ol ogy a nd medi ci ne. The Gra m s ta i n procedure i s cha ra cteri zed by the fol l owi ng s teps : (1) fixation of the ba cteri a to the s l i de, (2) crys ta l vi ol et (a cri di ne dye) trea tment, (3) i odi ne trea tment, (4) decolorization us i ng a l cohol /a cetone wa s h, a nd (4) counterstaining us i ng s a fra ni n. Gra m-pos i ti ve ba cteri a ha ve thi ck outer wa l l s wi th no l i pi ds , wherea s gra m-nega ti ve ba cteri a ha ve a thi n wa l l a nd a n outer membra ne. The di fference between gra m-pos i ti ve a nd gra m-nega ti ve orga ni s ms i s i n the cel l -wa l l permea bi l i ty to thes e compl exes on trea tment wi th mi xtures of a cetone a nd a l cohol s ol vents . Thus , gra m-pos i ti ve ba cteri a reta i n purpl e i odi nedye compl exes , wherea s gra m-nega ti ve ba cteri a do not reta i n thes e compl exes when decol ori zed us i ng a n a l cohol /a cetone wa s h. 19. The answer is d. (Levinson, Ch 2. Murray, Ch 4. Ryan, Ch 4.) If the i odi ne trea tment s tep i s omi tted duri ng the Gra m s ta i n proces s , the purpl e i odi nedye compl exes wi l l not form. The crys ta l vi ol et wi l l wa s h a wa y duri ng the a l cohol /a cetone decol ori za ti on wa s hi ng s tep a nd a l l cel l s wi l l a ppea r red (d). Gra m s ta i ni ng of pus or fl ui ds a l ong wi th cl i ni ca l fi ndi ngs ca n gui de the ma na gement of a n i nfecti on before cul ture res ul ts a re a va i l a bl e i n the cl i ni ca l s etti ng. 20. The answer is e. (Levinson, Ch 11. Ryan, Ch 21.) Pori ns a re protei n tri mers tha t functi on i n outer-membra ne (OM) permea bi l i ty. Pori ns permi t the tra ns fer of mol ecul es a cros s the OM (e) i ncl udi ng the pa s s a ge of ma ny a nti mi crobi a l drugs s uch a s the fl uoroqui nol ones . Pori ns pa rti ci pa te i n mul ti drug-res i s ta nce effl ux pumps tha t export drugs l i ke ci profl oxa ci n from the cel l . Pori ns pl a y no rol e i n the meta bol i s m requi red for hydrol ys i s of a nti mi crobi a l s (a ), meta bol i s m of meta bol i c i ntermedi a tes (b), s erol ogi c s ta bi l i za ti on of the O a nti gen (c), or i na cti va ti on of hydrophobi c a nti mi crobi a l s (d). 21. The answer is d. (Levinson, Ch 24. Murray, Ch 39. Ryan, Ch 37.) The di a gnos i s of Lyme di s ea s e i s compl i ca ted. Ea rl y Lyme di s ea s e (a ) (3-30 da ys pos tti ck bi te) i s us ua l l y di a gnos ed cl i ni ca l l y. IgM s peci fi c for Borrelia burgdorferi a ppea rs between 2 a nd 4 weeks a fter the l es i ons , pea ks a t 4 to 6 weeks , a nd di s a ppea rs (returns to ba s el i ne) by 4 to 6 months . Speci fi c IgG us ua l l y a ppea rs a fter 30 da ys a nd l a s ts a s l ong a s di s ea s e pers i s ts . Ea rl y di s s emi na ted Lyme (b) (da ys to weeks pos t-ti ck bi te) i s di a gnos ed by cl i ni ca l s us pi ci on, l i kel i hood of expos ure, a nd s erol ogy. A pos i ti ve s creeni ng EIA (enzyme i mmunoa s s a y) or IFA (i mmunofl uores cence a s s a y) for s peci fi c IgM a nd/or IgG, dependi ng on ti mi ng, fol l owed by a pos i ti ve wes tern bl ot i s di a gnos ti c. La te di s s emi na ted Lyme di s ea s e (c) ca n a l s o be di a gnos ed s erol ogi ca l l y by detecti on of hi gh l evel s of s peci fi c IgG on s creeni ng a nd pos i ti ve IgG wes tern bl ot. Pa ti ents wi th neuroborrel i os i s us ua l l y ha ve s peci fi c IgG i n the CSF. A pos i ti ve wes tern bl ot for Lyme di s ea s e requi res the pres ence of a t l ea s t 5 of 10 s peci fi c ba nds for B. burgdorferi: 18, 21 (Os pC), 28, 30, 39 (BmpA), 41 (Fl a ), 45, 58 (not GroEL), 66, a nd 93 kDa . The pa ttern s hown i n the fi gure s hows onl y one a nti body-pos i ti ve ba nd, whi ch i s a l s o pres ent wi th the B. turicatae protei ns . Thi s i ndi ca tes nons peci fi c rea cti vi ty (d). There i s no need to repea t the s creeni ng tes t (e); other di a gnos es for the pa ti ent’s a rthri ti s s houl d be cons i dered. http://www.cdc.gov/l yme/di a gnos i s trea tment/La bTes t/TwoStep/Wes ternBl ot/ 22. The answer is b. (Levinson, Ch 9, 18. Murray, Ch 5, 27. Ryan, Ch 4, 33.) The vi gnette s trongl y s ugges ts tha t the pa ti ents were i nfected wi th a Shi ga toxi n-produci ng s tra i n of E. coli (STEC). Whi l e cul ture on s el ecti ve a nd di fferenti a l a ga r ca n detect the pres ence of O157 STEC, a s wel l a s Salmonella a nd Shigella, s tool s s houl d s i mul ta neous l y be a s s a yed for non-O157 STEC wi th a tes t tha t detects the Shi ga toxi n or the genes encodi ng thes e toxi ns (recommenda ti on for i denti fi ca ti on of STEC by cl i ni ca l l a bora tori es ). Cul ture (e) wi l l not detect non-O157 STEC s tra i ns . Gra m s ta i n (a ) woul d s how the pres ence of feca l l eukocytes , but ca nnot be us ed to determi ne the pres ence or a bs ence of a pa rti cul a r s peci es of gra m-nega ti ve ba ci l l i . PCR for Campylobacter (c) a nd s erol ogi c tes ti ng for Salmonella enterica a nti bodi es (d) a re not rel eva nt to the ca s e pres enta ti on. The i mmunoa s s a y (EIA) for Shi ga toxi n-produci ng E. coli (b) i s the tes t tha t wi l l detect a l l s tra i ns . Beca us e the a mount of free feca l Shi ga toxi n i n s tool s i s often l ow, EIA tes ti ng of enri chment broth cul tures i ncuba ted overni ght i s recommended ra ther tha n di rect tes ti ng of s tool s peci mens , a l though tes ti ng of both s peci mens ca n be done. 23. The answer is d. (Murray, Ch 5.) Us i ng a DNA s equence a s a templ a te, pol ymera s e cha i n rea cti on (PCR) (c) converts few copi es of the DNA templ a te i nto a mi l l i on copi es . Among the di fferent a ppl i ca ti ons of PCR i s the di a gnos i s of i nfecti ous di s ea s es . Us i ng a hea t s ta bl e DNA pol ymera s e a nd s hort DNA s egments tha t a re compl ementa ry to the ta rget DNA (pri mers ), the rea cti on a mpl i fi es the ta rget DNA through s eri es of mel ti ng, a nnea l i ng, a nd extens i on s teps i n whi ch the compl ementa ry DNA s tra nds a re s ynthes i zed. The hi gh s ens i ti vi ty of PCR permi ts the detecti on of extremel y s ma l l a mount DNA wi thi n the s a mpl e. Bes i des i ts s ens i ti vi ty, the a s s a y i s ra pi d a nd ma y detect vi ra l DNA before the ons et of the di s ea s e. The fi na l s tep, whi ch i ncl udes runni ng the a mpl i fi ed product on a ga ros e gel to vi s ua l i ze i t, i s ti me-cons umi ng a nd not very pra cti ca l for cl i ni ca l s etti ngs . Thi s di s a dva nta ge wa s el i mi na ted by rea l -ti me PCR (d) i n whi ch the s ynthes i zed DNA i s detected a nd qua nti fi ed a s the PCR rea cti on progres s es i n rea l ti me. The techni que us es a reporter s i gna l , a fl uores cence l a bel ed probe. The i ntens i ty of the detected fl uores cence s i gna l , whi ch correl a tes wi th the a mount of the a mpl i fi ed DNA ta rget, a l l ows detecti on of the PCR product ea rl i er a nd el i mi na tes the need for runni ng the fi na l product on a ga ros e gel . Compa red wi th rea l -ti me PCR, Southern bl ot hybri di za ti on (e) a nd dot bl ot hybri di za ti on (b) a re ti mecons umi ng, requi re l a rger a mount of DNA, a nd a re not pra cti ca l for cl i ni ca l s etti ngs . DNA s equenci ng (a ) a na l ys i s i s a n a ddi ti ona l s tep tha t ma y be us ed to confi rm the i denti ty of the DNA a mpl i fi ed by PCR. It wi l l not hel p i n the i ni ti a l di a gnos i s . PCR a s s a ys to detect the stx1 a nd stx2 genes a re us ed by ma ny publ i c hea l th l a bora tori es for di a gnos i s a nd confi rma ti on of STEC i nfecti on. Dependi ng on the pri mers us ed, thes e a s s a ys ca n di s ti ngui s h between stx1 a nd stx2. Mos t of thes e PCR a s s a ys a re des i gned a nd va l i da ted for tes ti ng i s ol a ted col oni es ta ken from pl a ted medi a ; s ome a s s a ys ha ve been va l i da ted for tes ti ng on s tool s peci mens s ubcul tured to a n enri chment broth a nd i ncuba ted for 18 to 24 hours . Currentl y, Shi ga toxi n PCR a s s a ys on DNA extra cted from whol e s tool s peci mens a re not recommended beca us e the s ens i ti vi ty i s l ow. DNA-ba s ed Shi ga toxi n gene detecti on i s not a pproved by FDA for di a gnos i s of huma n STEC i nfecti ons by cl i ni ca l l a bora tori es . 24. The answer is c. (Murray, Ch 5.) Conventi ona l a ga ros e gel el ectrophores i s , i n whi ch the current runs i n onl y one di recti on, i s ca pa bl e of s epa ra ti ng a nd res ol vi ng DNA fra gments no l a rger tha n 30 kbp i n s i ze. In contra s t, pul s ed-fi el d gel el ectrophores i s (PFGE) (c) extends the s i ze ra nge of the res ol ved DNA mol ecul es up to 5 Mbp. In PFGE, chromos oma l DNA i s extra cted wi thout s hea ri ng. The DNA i s then di ges ted wi th res tri cti on enzymes tha t cut onl y i n few pl a ces , thereby genera ti ng l a rge DNA fra gments . The fra gments a re s epa ra ted on a ga ros e gel s by el ectrophores i s i n whi ch the di recti on of the vol ta ge i s peri odi ca l l y s wi tched (pul s ed). Ea ch pul s e conti nues for s evera l hours a l l owi ng the s epa ra ti on of the l a rge DNA
fra gments . PFGE i s frequentl y us ed i n epi demi ol ogi ca l s tudi es of ba cteri a l pa thogens to i denti fy the s peci fi c s tra i n (s ubtype) tha t ca us ed the outbrea k of food poi s oni ng. PCR (b) a nd Southern bl ot hybri di za ti on (e) a re ca pa bl e of i denti fyi ng a s tra i n, s uch a s Listeria or Salmonella, by determi ni ng s peci fi c genes wi thi n the s tra i n but a re not ca pa bl e of i denti fyi ng the s ubtype. Sodi um dodecyl s ul fa te pol ya cryl a mi de gel el ectrophores i s i s (d) des i gned to s epa ra te protei ns produced by the ba cteri a . The s ubtypes a re unl i kel y to produce di fferent protei ns . Cl oni ng (a ) i s i ns erti ng a DNA fra gment i n a cl oni ng vector for further a na l ys i s of the gene ca rri ed on tha t fra gment. It wi l l not defi ne the ba cteri a l s ubtypes . 25. The answer is c. (Murray, Ch 13. Hartwell, Ch 14.) Ma ny a nti bi oti c res i s ta nce genes i n ba cteri a a re ca rri ed on conjuga ti ve pl a s mi ds (c) a l s o known a s R fa ctors . Thes e pl a s mi ds a re tra ns ferred from one ba cteri um to a nother, of the s a me or rel a ted s peci es , by conjuga ti on. Conjuga ti on i s a proces s by whi ch the donor ba cteri um (ma l e cel l ) i s brought i n di rect conta ct wi th the reci pi ent ba cteri um (fema l e cel l ) through the conjuga ti ve pi l us . In E. coli, the conjuga ti ve pi l us i s referred to a s a s ex pi l us or F pi l us . The conjuga ti ve pl a s mi d ca rri es genes neces s a ry for i ts tra ns fer i ncl udi ng the pi l us genes . The pl a s mi d i s tra ns ferred i nto the reci pi ent cel l a s a s tra nd of s s DNA, whi ch reci rcul a ri zes wi thi n the reci pi ent cel l . The compl ementa ry DNA s tra nd i s then s ynthes i zed i n the reci pi ent cel l . The s s DNA i n the donor cel l i s a l s o repl i ca ted; thus , both the donor a nd the reci pi ent now ca rry a copy of the pl a s mi d. Due to the di rect conta ct between ba cteri a through the pi l us , conjuga ti on i s a n effi ci ent proces s of DNA tra ns fer. A tra ns pos on (e) i s a mobi l e geneti c el ement tha t i s ca pa bl e of movi ng from one repl i con (a chromos ome or a pl a s mi d) to a nother but i s i nca pa bl e of i ni ti a ti ng DNA tra ns fer. Recombi na s e enzymes (d) a re requi red for the recombi na ti on proces s tha t occurs between homol ogous regi ons of DNA (a s i n i ntegra ti on of a DNA i n a repl i con). Competent cel l s (b) a re pa rt of the ba cteri a l popul a ti on tha t i s ca pa bl e of ta ki ng up DNA from a s ol uti on (na ked DNA). Thi s ma y occur na tura l l y or a rti fi ci a l l y (i n the l a bora tory). E. coli competent cel l s a re onl y genera ted i n the l a bora tory through trea tment wi th certa i n chemi ca l s . Cel l l ys i s a nd rel ea s e of donor DNA (a ) ma y be pa rt of a mecha ni s m through whi ch na tura l l y competent ba cteri a s uch a s Neisseria ta ke up na ked DNA duri ng i nfecti on. 26. The answer is c. (Brooks, pp 30, 161, 348. Levinson, pp 8-9, 89. Ryan, p 19.) The orga ni s ms i l l us tra ted i n the ques ti on a re s pheropl a s ts of E. coli. Lys ozyme cl ea ves the β-1-4-gl ycos i di c bond between N-a cetyl mura mi c a ci d a nd N-a cetyl gl ucos a mi ne. Spheropl a s ts a re ba cteri a wi th cel l wa l l s tha t ha ve been pa rti a l l y removed by the a cti on of l ys ozyme or peni ci l l i n. Ordi na ri l y, wi th di s i ntegra ti on of the wa l l s , the cel l s undergo l ys i s ; however, i n a hypertoni c medi um, the cel l s pers i s t a nd a s s ume a s pheri ca l confi gura ti on. Endos pores a re formed by gra m-pos i ti ve ba cteri a i n the genera Bacillus a nd Clostridium. It ha s a l s o been s hown tha t for E. coli a nd other gra m-nega ti ve rods , expos ure to mi ni ma l concentra ti ons of a nti bi oti cs does not rupture the cel l wa l l but promotes el onga ti on of the cel l by i nhi bi ti ng the di vi s i on cycl e. 27. The answer is e. (Levinson, Ch 17. Murray, Ch 14, 23. Ryan, Ch 26.) The vi gnette des cri bes a chi l d wi th di phtheri a . The fi ndi ng of pl eomorphi c gra mpos i ti ve ba ci l l i on Gra m s ta i n (d) or demons tra ti on of meta chroma ti c gra nul es by methyl ene bl ue s ta i n (c) a re s ugges ti ve tha t C. diphtheriae mi ght be pres ent. Cul ture for C. diphtheriae requi res a s peci a l medi um conta i ni ng tel l uri te, s uch a s Ti ns da l e a ga r. C. diphtheriae ca n be di fferenti a ted from other s peci es of Corynebacterium by producti on of cys tei na s e (a ), whi ch ca us es the orga ni s m to produce col oni es s urrounded by a brown ha l o on thi s a ga r. However, i s ol a ti on a l one (b) i s i ns uffi ci ent to prove tha t the s tra i n ca us ed di phtheri a . Onl y toxi geni c s tra i ns of C. diphtheriae ca us e di phtheri a , s o a ny i s ol a te i denti fi ed a s C. diphtheriae mus t be tes ted for toxi n producti on (e) us i ng the El ek tes t. The toxi n genes a re ca rri ed on a l ys ogeni c ba cteri opha ge, a nd not a l l s tra i ns ca rry thi s pha ge. PCR ca n a l s o be performed for the di phtheri a toxi n genes , but even thi s i s not concl us i ve a s thes e genes ma y not be expres s ed. 28. The answer is b. (Levinson, Ch 19. Murray, Ch 32. Ryan, Ch 31.) The vi gnette des cri bes a chi l d wi th pertus s i s ca us ed by Bordetella pertussis. Cul ture of B. pertussis requi res pl a ti ng of a na s opha ryngea l s wa b on s peci a l medi um conta i ni ng cha rcoa l a nd bl ood wi th a nd wi thout cepha l exi n for bes t res ul t. The s peci men mus t be col l ected before a ny a nti bi oti cs a re gi ven a nd the cl os er to ons et of s ymptoms the better the res ul t. However, cul ture a l one (a ) i s not s uffi ci entl y s ens i ti ve. DFA i s no l onger recommended by the Centers for Di s ea s e Preventi on a nd Control (CDC) due probl ems wi th both fa l s e pos i ti ve a nd fa l s e nega ti ve tes ts , whether us ed a l one (c) or wi th cul ture (d). PCR (e), whi ch a ppea red a t fi rs t to be more s ens i ti ve tha n cul ture, ha s been s hown over the cours e of ti me to ha ve a bout the s a me s ens i ti vi ty a s cul ture. Therefore, the bes t a pproa ch i s to col l ect two s wa bs a nd us e one for cul ture a nd one for PCR (b). Be a wa re there i s grea t i ncons i s tency i n textbooks a nd revi ews rega rdi ng the bes t methods for di a gnos i s of pertus s i s . The CDC i s the bes t gui de i n thi s ca s e. 29. The answer is d. (Levinson, Ch 19. Murray, Ch 34. Ryan, Ch 34.) The vi gnette des cri bes a pa ti ent wi th l egi onel l os i s (a l s o ca l l ed Legi onna i res di s ea s e). Legionella s pp. a re gra m-nega ti ve ba ci l l i tha t s ta i n poorl y i f a t a l l by tra di ti ona l Gra m s ta i n. However, the orga ni s ms ca n be demons tra ted by prol onged counters ta i ni ng wi th s a fra ni n for a t l ea s t 3 mi nutes . Even wi th prol onged counters ta i n, the orga ni s ms s ti l l a ppea r a s wea kl y s ta i ni ng (very pa l e pi nk) gra m-nega ti ve ba ci l l i (d). The ba cteri a ma y a ppea r coccoi d, but s houl d not be mi s ta ken for gra m-nega ti ve cocci (e, f). Legionella s houl d not a ppea r gra m-pos i ti ve (a , b) i n a correctl y performed Gra m s ta i n. 30. The answer is e. (Katzung, Ch 43, 44, 46. Murray, Ch 13, 17. Ryan, Ch 21, 23.) Peni ci l l i n ca us es l ys i s of growi ng ba cteri a l cel l s . Beca us e peni ci l l i n i s ba cteri ci da l , the number of vi a bl e cel l s s houl d fa l l i mmedi a tel y a fter i ntroducti on of the drug i nto the medi um of a n exponenti a l l y growi ng s us cepti bl e ba cteri a l cul ture. Thi s i s repres ented by curve E (e). 31. The answer is d. (Katzung, Ch 43, 44, 46. Murray, Ch 13, 17. Ryan, Ch 21, 23.) Chl ora mpheni col i s ba cteri os ta ti c; i t ca us es a n i mmedi a te, revers i bl e i nhi bi ti on of protei n s ynthes i s . Thus , chl ora mpheni col reta rds cel l growth wi thout ca us i ng cel l dea th, a s repres ented by curve D (d). 32. The answer is c. (Katzung, Ch 43, 44, 46. Murray, Ch 13, 17. Ryan, Ch 21, 23.) Sul fona mi des a re a l s o ba cteri os ta ti c. However, s ul fona mi des a ct by competi ng wi th para-a mi nobenzoi c a ci d i n the s ynthes i s of fol a te. Thei r effect i s not a ppa rent unti l i ntra cel l ul a r s tores of fol a te a re depl eted, s o the i nhi bi ti on i s not a ppa rent a s qui ckl y. Thi s i s repres ented by curve C (c). 33. The answer is b. (Katzung, Ch 43, 44, 46. Murray, Ch 13, 17. Ryan, Ch 21, 23.) The number of vi a bl e cel l s i n a cul ture eventua l l y wi l l l evel off (rea ch s ta ti ona ry pha s e) even i f no a nti bi oti c i s a dded to the envi ronment. A key fa ctor i n thi s phenomenon i s the l i mi ted a va i l a bi l i ty of nutri ents . Thi s i s repres ented by curve B (b). Curve A (a ) i s not phys i ol ogi ca l l y pos s i bl e for ba cteri a , whi ch doubl e thei r number a t a cons ta nt (l oga ri thmi c) ra te. 34. The answer is e. (Levinson, Ch 4. Murray, Ch 13. Ryan, Ch 21.) Tra ns forma ti on (e) i s the term for upta ke of exogenous or forei gn DNA, whi ch ma y be rel ea s ed from l ys ed cel l s or provi ded a rti fi ci a l l y i n the l a bora tory. Conjuga ti on (a ) i nvol ves the di rect pa s s a ge of DNA from one ba cteri um (donor) to a nother (reci pi ent) through a conjuga ti ve pi l us (s ex pi l us ). Tra ns ducti on (d) i s the tra ns fer of DNA medi a ted by ba cteri opha ges . Homol ogous recombi na ti on (c) ma y ta ke pl a ce once DNA ha s entered the cel l by conjuga ti on or tra ns forma ti on i f the cl os el y rel a ted s equences exi s t on the chromos ome a nd the exogenous DNA. A fra mes hi ft muta ti on (b) occurs when a s ma l l del eti on or i ns erti on (not i n mul ti pl es of three) i s ma de i n a gene. 35. The answer is d. (Levinson, Ch 4. Murray, Ch 13. Ryan, Ch 21.) Tra ns ducti on (d) i s the tra ns fer of DNA medi a ted by ba cteri opha ges . In genera l i zed tra ns ducti on, the pha ge vi rus ca n ca rry a ny s egment of the donor chromos ome; i n s peci a l i zed tra ns ducti on, the pha ge ca rri es onl y s peci fi c genes , genera l l y thos e i mmedi a tel y a dja cent to the s i te of propha ge i ns erti on.
36. The answer is a. (Levinson, Ch 4. Murray, Ch 13. Ryan, Ch 21.) Conjuga ti on (a ) i nvol ves the di rect pa s s a ge of DNA from one ba cteri um (donor) to a nother (reci pi ent) through a conjuga ti ve pi l us (s ex pi l us ). Tra ns ducti on (d) i s the tra ns fer of DNA medi a ted by ba cteri opha ges . 37. The answer is d. (Levinson, Ch 3. Murray, Ch 13. Ryan, Ch 21.) Ba cteri a reproduce by bi na ry fi s s i on a nd thus undergo exponenti a l (l oga ri thmi c) growth. In thi s ques ti on, a doubl i ng ti me for E. coli wa s gi ven a t 30 mi nutes i n uri ne. Therefore, a fter 4 hours there wi l l be ei ght doubl i ng ti mes . Si nce there were 1000 ba cteri a per mL a t the ti me of col l ecti on, the number of E. coli pres ent a fter 4 hours ca n be ca l cul a ted us i ng the formul a : N × 2n , where N equa l s the number a t the s ta rt a nd n equa l s the number of genera ti ons . 1000 × 28 = 256,000. In thi s exa mpl e, wha t bega n a s a potenti a l l y i ns i gni fi ca nt number of ba cteri a (dependi ng on the cl i ni ca l s i tua ti on) ha s mul ti pl i ed to a s i gni fi ca nt number. If the l a bora tory or the cl i ni ci a n wa s una wa re of the del a y, the pa ti ent mi ght ha ve been di a gnos ed wi th a UTI when no i nfecti on wa s pres ent. The fi gure s hows the doubl i ng of one ba cteri um over four doubl i ng ti mes .
(Reproduced, with permission, from Brooks GF, et al. Ja wetz’s Medi ca l Mi crobi ol ogy. 24th ed. New York, NY: McGraw-Hill; 2007:53.) 38. The answer is a. (Murray, Ch 1, 27.) Pi l i (a ) or fi mbri a e a re ha i rl i ke s tructures tha t a re found on the s urfa ce of ma ny ba cteri a . They a re compos ed of repea ted s ubuni ts of the pi l i n protei n. They promote ba cteri a l a dherence to ea ch other a nd ba cteri a l a dherence to di fferent hos t ti s s ues . Uropa thogeni c E. coli col oni ze the uri na ry tra ct a nd res i s t the wa s hi ng a cti on of uri ne through thei r pi l i . The ti p of the pi l us conta i ns a s peci fi c protei n tha t recogni zes a receptor on the hos t cel l . The other choi ces a re not i nvol ved i n E. coli uropa thogenes i s . Ca ps ul es (e) a re l oos e pol ys a ccha ri de or protei n l a yers tha t s urround the gra m-nega ti ve or gra m-pos i ti ve ba cteri a . Ca ps ul es a re a nti pha gocyti c, protect the ba cteri a from hydrophobi c mol ecul es , a nd promote a dhere of certa i n ba cteri a s uch a s Streptococcus mutans to hos t ti s s ues . Fl a gel l a (d), whi ch a re a nchored on the ba cteri a l s urfa ce, a re es s enti a l for ba cteri a l moti l i ty. The hea t-l a bi l e (c) a nd hea t-s ta bi l e toxi ns a re enterotoxi ns s ecreted by the enterotoxi geni c E. coli. Thes e toxi ns produce wa tery di a rrhea by s ti mul a ti ng hypers ecreti on of fl ui ds . LPS (b) compos es the outer l ea fl et of the outer membra ne i n gra m-nega ti ve ba cteri a a nd i s a n endotoxi n, whi ch s ti mul a tes i nna te i mmune res pons es . 39. The answer is c. (Murray, Ch 12, 14.) Pa thogeni c ba cteri a s uch a s the gra m-nega ti ve ba ci l l us Pseudomonas aeruginosa a nd the gra m-pos i ti ve coccus Staphylococcus aureus col oni ze the s urfa ce of certa i n s urgi ca l a ppl i a nces s uch a s a rti fi ci a l hea rt va l ves a nd ca theters . Mul ti pl e l a yers of the col oni zi ng ba cteri a s urround thems el ves wi th a pol ys a ccha ri de (c) ma tri x, whi ch protects them from the effect of a nti bi oti cs a nd hos t i mmune defens es . The rema i ni ng choi ces do not contri bute to bi ofi l m devel opment. Pori ns (d), protei ns tha t a re l oca ted wi thi n the outer membra ne of gra m-nega ti ve ba cteri a , fa ci l i ta te the tra ns fer of hydrophi l i c mol ecul es through the membra ne. Tei choi c a ci ds (e) found wi thi n the cel l wa l l of gra m-pos i ti ve ba cteri a a re a ni oni c pol ymers of pol ygl yca n tha t provi de ri gi di ty to the cel l wa l l . In gra m-nega ti ve ba cteri a , the peri pl a s mi c s pa ce occupi es the a rea between the externa l s urfa ce of the cytopl a s mi c membra ne a nd the i nterna l s urfa ce of the outer membra ne. The peri pl a s m (b) conta i ns hydrol yti c enzymes , vi rul ence protei ns , a nd components of the s uga r tra ns port s ys tems . Endotoxi n (LPS), a component of the outer membra ne of gra m-nega ti ve ba cteri a , i s recogni zed by the hos t defens es a nd s ti mul a tes ma cropha ges to produce cytoki nes . 40. The answer is a. (Levinson, Ch 44. Murray, Ch 64. Ryan, Ch 20.) The vi gnette pres ents a ca s e of i nfecti ous pri on di s ea s e or new-va ri a nt Creutzfel dtJa kob di s ea s e a cqui red by the i nges ti on of the bovi ne s pongi -form encepha l opa thy (BSE) pri on. Pri ons a re i nfecti ous pa rti cl es tha t a re currentl y thought to be compos ed s ol el y of protei n (i e, they conta i n no detecta bl e nucl ei c a ci d). Norma l hos t pri ons do not ca us e di s ea s e, but pri ons s ynthes i zed from muta ted genes (i nheri ted CJD, s pora di c CJD), BSE pri ons , a nd pri ons found i n other tra ns mi s s i bl e s pongi form encepha l opa thi es a re a bnorma l l y fol ded protei ns (a ). Thes e a bnorma l l y fol ded protei ns ca ta l yze the refol di ng of norma l pri ons i nto the CJD form l ea di ng to di s ea s e. Vi rus es ha ve nucl ei c a ci d, ei ther RNA or DNA, pres ent i n protei n ca ps i ds (b); s ome vi rus es a re envel oped (b) i n l i pi d bi l a yer membra nes pi ra ted
from thei r hos t. Vi rus es , ba cteri a (e), a nd pa ra s i tes (d) ca n a l l ca us e CNS di s ea s e, but none a re a s s oci a ted wi th the cl i ni ca l pi cture/hi s tory of the vi gnette. 41. The answer is e. (Murray, Ch 13. Ryan, Ch 21. Mokrousov, pp 1417-1424.) Muta ti ons res ul t from three types of mol ecul a r cha nges , na mel y, ba s e s ubs ti tuti on muta ti on, fra mes hi ft muta ti on, a nd tra ns pos on or i ns erti on s equences ca us i ng muta ti ons . Invers i on muta ti ons (b) a re ca us ed by i ns erti on s equences (ISs ) or IS-l i ke el ements . Mi s s ens e muta ti on (c) refers to ba s e s ubs ti tuti on res ul ti ng i n a codon tha t ca us es a di fferent a mi no a ci d to be i ns erted. Nons ens e muta ti on (d) refers to ba s e s ubs ti tuti on genera ti ng a termi na ti on codon tha t prema turel y s tops protei n s ynthes i s . Repl a cement muta ti ons (e) a re tra ns i ti on or tra ns vers i on dependi ng on the s ubs ti tuti on. Tra ns i ti on muta ti ons a re the repl a cement of a pyri mi di ne (C, T) by a pyri mi di ne or a puri ne (A, G) by a puri ne. Tra ns vers i ons (e) a re the repl a cement of a puri ne by a pyri mi di ne or pyri mi di ne by a puri ne. 42. The answer is b. (Murray, Ch 13. Ryan, Ch 21. Li, pp 74-80.) The muta ti on des cri bed here i s a mi s s ens e muta ti on (c), or one i n whi ch ba s e s ubs ti tuti on res ul ti ng i n a codon tha t ca us es a di fferent a mi no a ci d to be i ns erted. See the a ns wer to 41 for other res pons es . 43. The answer is c. (Levinson, Ch 11. Murray, Ch 58. Ryan, Ch 17.) The pa ti ent ha s bi te wounds mos t l i kel y i nfected wi th Pasteurella multocida. Si nce the wounds were ca us ed by dogs whos e owners were unknown, the pa ti ent s houl d a l s o begi n ra bi es prophyl a xi s (c). There i s no need for va ri cel l a zos ter prophyl a xi s (e) s i nce there i s no hi s tory of s hi ngl es a t thi s ti me. The pa ti ent i s up to da te on hi s teta nus i mmuni za ti on, s o teta nus prophyl a xi s i s not needed ei ther (d). IV i mmunogl obul i ns (nons peci fi c) (b) a re us ed to trea t pa ti ents wi th IgG defi ci ency. Hepa ti ti s B vi rus (HBV) prophyl a xi s i s not needed unl es s the bi tes were i nfl i cted by a huma n whos e HBV s ta tus wa s unknown a nd coul d not be determi ned. 44. The answer is d. (Katzung, Ch 51. Levinson, Ch 10. Murray, Ch 17. Ryan, Ch 23.) The pa ti ent i s i nfected wi th Yersinia pestis a nd ha s buboni c pl a gue. The drug of choi ce for pl a gue i s s treptomyci n (d). Genta mi ci n or a nother a mi nogl ycos i de ca n be s ubs ti tuted. Cefta zi di me, chl ora mpheni col , peni ci l l i n, a nd va ncomyci n a re not us ed to trea t pl a gue. 45. The answer is a. (Katzung, Ch 51. Levinson, Ch 10. Murray, Ch 17. Ryan, Ch 23.) The chi l d i n the ques ti on ha s ba cteri a l meni ngi ti s . The mos t l i kel y eti ol ogi c a gents a re Haemophilus influenzae, N. meningitidis, a nd S. pneumoniae. Ceftri a xone (a ) a nd cefota xi me ha ve the hi ghes t a cti vi ty a ga i ns t thes e a gents . Cefta zi di me, a nother thi rd-genera ti on cepha l os pori n, ha s l i mi ted a cti vi ty a ga i ns t H. influenzae a nd i s not recommended unl es s the s peci fi c i denti fi ca ti on a nd s us cepti bi l i ty of the mi croorga ni s m i s known. Erythromyci n, genta mi ci n, peni ci l l i n, a nd va ncomyci n do not cros s the bl ood-bra i n ba rri er a s wel l a s the thi rd-genera ti on cepha l os pori ns . 46. The answer is e. (Katzung, Ch 51. Levinson, Ch 10. Murray, Ch 17. Ryan, Ch 23.) The pa ti ent mos t l i kel y ha s a n i nfecti on wi th P. aeruginosa. The bes t combi na ti on for thi s pa ti ent i s ti ca rci l l i n/cl a vul a na te pl us tobra myci n (e). P aeruginosa i s frequentl y res i s ta nt to mul ti pl e a nti bi oti cs , a nd s tra i ns a cqui red i n hos pi ta l i ntens i ve ca re uni ts a nd burn uni ts ca n be res i s ta nt to a l l commonl y us ed a nti mi crobi a l s . Unti l the s peci fi c s us cepti bi l i ty for the pa ti ent’s i s ol a te i s a va i l a bl e, the bes t choi ce i s a n a nti ps eudomona l peni ci l l i n (pi pera ci l l i n (d) or ti ca rci l l i n) pl us a β-l a cta ms e i nhi bi tor a nd a n a mi nogl ycos i de. Cefta zi di me (a ) i s cons i s tentl y a cti ve a ga i ns t ma ny P. aeruginosa s tra i ns but hos pi ta l -a cqui red s tra i ns ma y be res i s ta nt. Erythromyci n (b), peni ci l l i n (c), cepha l othi n (d), a nd va ncomyci n (a ) ha ve no a cti vi ty a ga i ns t P. aeruginosa. Fl uoroqui nol ones ma ke a good a l terna ti ve trea tment wi th a mi nogl ycos i des , but i mi penem (b) mus t a l wa ys be gi ven wi th ci l a s ta ti n. 47. The answer is e. (Katzung, Ch 51. Levinson, Ch 10. Murray, Ch 17. Ryan, Ch 23.) Thi s pa ti ent ha s a hos pi ta l -a cqui red methi ci l l i n-res i s ta nt S. aureus (HAMRSA) i nfecti on, for whi ch the drug of choi ce i s va ncomyci n (e). HA-MRSA a re frequentl y res i s ta nt to mul ti pl e a nti bi oti cs , wherea s communi tya cqui red methi ci l l i n-res i s ta nt S. aureus (CA-MRSA) a re more s us cepti bl e. For CA-MRSA, cl i nda myci n ma y be a better choi ce. Di cl oxa ci l l i n (b) a nd cefta zi di me (a ) a re us ed to trea t methi ci l l i n-s us cepti bl e S. aureus s tra i ns . Al mos t a l l s tra i ns of S. aureus i n the Uni ted Sta tes produce peni ci l l i na s e, s o peni ci l l i n (c) s houl d not be us ed. Tobra myci n (d) i s us ed ma i nl y for s eri ous gra m-nega ti ve i nfecti ons a nd ma y be effecti ve. However, S. aureus s tra i ns a re emergi ng wi th decrea s ed s us cepti bi l i ty to va ncomyci n. 48. The answer is e. (Katzung, Ch 43, 44, 46, 48. Levinson, Ch 10. Murray, Ch 17. Ryan, Ch 23.) The mecha ni s m of a cti on des cri bed i s tha t of tri m-ethopri m (TMP) (e), a di a mi nopyri mi di ne tha t i s a fol i c a ci d a nta goni s t. Al though TMP i s commonl y us ed i n combi na ti on wi th s ul fa drugs , i ts mode of a cti on i s di s ti nct. TMP i s s tructura l l y s i mi l a r to the pteri di ne porti on of di hydrofol a te a nd prevents the convers i on of fol i c a ci d to tetra hydrofol i c a ci d by i nhi bi ti on of di hydrofol a te reducta s e. Fortuna tel y, thi s enzyme i n huma ns i s rel a ti vel y i ns ens i ti ve to TMP. Ampi ci l l i n (a ), a s tructura l a na l og of the na tura l D-Al a -D-Al a s ubs tra te for peni ci l l i n-bi ndi ng protei n (PBP), prevents the tra ns pepti da s e functi on of PBP tha t cros s l i nks the devel opi ng pepti dogl yca n cel l wel l . Amphoteri ci n (b) i s a n a nti funga l drug tha t bi nds ergos terol i n the funga l membra ne. Chl ora mpheni col (c) bi nds revers i bl y to the 50S ri bos oma l s ubuni t a nd i nhi bi ts forma ti on of pepti de bond by i nhi bi ti ng the tra ns pepti da s e functi on. Levofl oxa ci n (d) bl ocks ba cteri a l DNA s ynthes i s by i nhi bi ti ng ba cteri a l topoi s omera s e II (DNA gyra s e) a nd topoi s omera s e IV (s epa ra ti on of repl i ca ted chromos oma l DNA). 49. The answer is e. (Katzung, Ch 51. Levinson, Ch 18. Murray, Ch 27. Ryan, Ch 33.) The drug of choi ce for compl i ca ted UTIs wi thout s eps i s i s tri methopri m/s ul fa methoxa zol e (e). Ampi ci l l i n (a ) i s no l onger s uffi ci entl y effecti ve a ga i ns t E. coli, Proteus s pp., a nd other gra m-nega ti ve ba ci l l i a s s oci a ted wi th UTI wi th ki dney s tone forma ti on. Chl ora mpheni col (c) i s not us ed to trea t UTI, a nd i s ra rel y us ed i n the Uni ted Sta tes for a ny i nfecti on except ri cketts i a l i nfecti ons a nd s ome ca s es of chi l dhood meni ngi ti s . Peni ci l l i n (d) i s not a cti ve a ga i ns t enteri c gra m-nega ti ve ba ci l l i . Amphoteri ci n (b) i s a n a nti funga l drug. 50. The answer is e. (Katzung, Ch 43. Murray, Ch 20. Ryan, Ch 25.) Enterococcus faecalis a nd other enterococci a re i nherentl y res i s ta nt to oxa ci l l i n a nd cepha l os pori ns a nd ma y a cqui re res i s ta nce to a mi nogl ycos i des a nd va ncomyci n; yet they ha ve rema i ned s us cepti bl e to peni ci l l i ns , es peci a l l y a mpi ci l l i n (a ). Trea tment wi th va ncomyci n (e), whi ch bi nds to D-Al a -D-Al a of pepti dogl yca n, ca n s el ect va ncomyci n-res i s ta nt s tra i ns (VRE) from the popul a ti on of enterocci i n the col on. Thes e VRE ca n then ca us e i nfecti on. Trea tment of choi ce for VRE UTI i s a mpi ci l l i n pl us a n a mi nogl yco-s i de. Da ptomyci n ma y be s ubs ti tuted for ei ther drug i n ca s e of res i s ta nce. Amphoteri ci n (b) i s a n a nti funga l . Chl ora mpheni col (c) i s not us ed to trea t UTI. Levofl oxa ci n (d) ha s no a cti vi ty a ga i ns t VRE. 51. The answer is e. (Katzung, Ch 48. Murray, Ch 69. Ryan, Ch 43.) Vori cona zol e (e), a n a nti funga l a zol e, i s the drug of choi ce for trea ti ng a s pergi l l os i s i n i mmunocompromi s ed i ndi vi dua l s s uch a s the pa ti ent i n the vi gnette who ha s l eukemi a . It i s l es s toxi c tha n a mphoteri ci n B (a ), a n a l terna ti ve trea tment. Anti funga l a zol es a ffect ergos terol s ynthes i s by a cti ng on the demethyl a s e enzyme i n the s yntheti c pa thwa y. Amphoteri ci n B bi nds to ergos terol a nd a l ters the permea bi l i ty of the cel l by formi ng pores i n the cel l membra ne. The pores a l l ow the l ea ka ge of i ntra cel l ul a r i ons a nd ma cromol ecul es , l ea di ng to cel l dea th. Bi ndi ng to huma n membra ne s terol s a l s o occurs , whi ch l i kel y a ccounts for the s evere toxi ci ty of the drug. Ca s pofungi n (b), pri ma ri l y us ed to trea t i nva s i ve ca ndi di a s i s , ca n a l s o be us ed to trea t i nva s i ve a s pergi l l os i s , but i t works by bl ocki ng s ynthes i s of the gl uca n component of the cel l wa l l . Ni kkomyci n Z (d), a drug i n devel opment, bl ocks chi ti n s ynthes i s a nd ha s a cti vi ty a ga i ns t Coccidioides a nd Blastomyces but not Aspergillus. Gri s eoful vi n (c) i s a topi ca l or s ys temi c a nti funga l us ed to trea t derma tophytos i s . It functi ons by di s rupti ng the mi crotubul es .
52. The answer is c. (Katzung, Ch 51. Levinson, Ch 18. Murray, Ch 27. Ryan, Ch 33.) The gi rl i n the vi gnette mos t l i kel y ha s Neisseria meningitidis meni ngi ti s . The drug of choi ce i s ceftri a xone, whi ch i s contra i ndi ca ted by the chi l d’s known β-l a cta m a l l ergy due to cros s -hypers ens i ti vi ty. The a l terna ti ve drug of choi ce i s chl ora mpheni col , whi ch i nhi bi ts forma ti on of the pepti de bond (c) through i nhi bi ti on of the tra ns pepti da s e rea cti on. Meropenem, a s econd a l terna ti ve, i s a l s o a β-l a cta m wi th cros s -hyper-s ens i ti vi ty. Tetra cycl i ne, whi ch bl ocks tRNA bi ndi ng to the A s i te (a ), i s not us ed to trea t meni ngi ti s a nd s houl d not be us ed i n chi l dren under 10. Ami nogl ycos i des , whi ch ca us e mi s rea di ng of mRNA (b) a nd res ul t i n prema ture termi na ti on (e) of tra ns l a ti on, a s wel l a s bl ocki ng i ni ti a ti on of protei n s ynthes i s , a re not genera l l y us ed to trea t meni ngi ti s except i n ca s es ca us ed by Listeria. Ma crol i des prevent tra ns l oca ti on (d) a nd a re not us ed to trea t meni ngi ti s . 53. The answer is d. (Murray, Ch 5, 18. Ryan, Ch 4, 24.) In genera l , rea l -ti me PCR i s more s ens i ti ve tha n cul ture (a ), due to the a bi l i ty of the a s s a y to detect very few copi es of ba cteri a l DNA pres ent i n the s peci men. Recentl y, ma ny cl i ni ca l l a bora tori es ha ve begun us i ng rea l -ti me PCR for the mecA gene or the SCC mec ca s s ette tha t ca rri es mecA to detect the pres ence of MRSA i n na s a l s peci mens col l ected from pa ti ents upon a dmi s s i on to the hos pi ta l . Numerous s tudi es ha ve s hown tha t the s ens i ti vi ty of rea l -ti me PCR i s s l i ghtl y hi gher tha n tha t of opti ma l l y performed chromogeni c cul ture for MRSA. However, even a t 85% s ens i ti vi ty, i f the 50 pos i ti ve s a mpl es were true pos i ti ves , one woul d expect to ha ve recovered 42 to 43 i s ol a tes i n the compa ni on cul tures ra ther tha n 15. Rea l -ti me PCR wa s thought to be more s peci fi c tha n cul ture (b), but the a ppea ra nce of i ncrea s i ng numbers of mecA gene va ri a ti ons ha s l ed to fa l s e-nega ti ve res ul ts due to pri mer mi s ma tch a nd fa i l ure to a mpl i fy the gene even when pres ent. Detecti ng SCC mec wa s thought to be the s ol uti on to thi s probl em, onl y to come under fi re beca us e the s a me SCC mec ca s s ette found i n communi ty-a cqui red MRSA i s pres ent i n methi ci l l i n-res i s ta nt S. epidermidis, l ea di ng to mi s cl a s s i fi ca ti on of pa ti ents wi th MRSE. Thi s fi ndi ng ha s l ed to the devel opment of mul ti pl ex PCR tes ts tha t detect genes s peci fi c for S. aureus i n a ddi ti on to the mecA gene. Unfortuna tel y, ma ny l a bora tori es ha ve i mpl emented nucl ei c a ci d tes ti ng wi thout ha vi ng a cces s to dedi ca ted s pa ce for s a mpl e prepa ra ti on a nd the PCR i ns trument, a s des cri bed i n the vi gnette. Thi s frequentl y l ea ds to conta mi na ti on of the PCR works ta ti on wi th MRSA DNA (d), whi ch i s then a mpl i fi ed i n the rea cti on produci ng a fa l s e-pos i ti ve res ul t. Fa i l ure of the thermocycl er, the PCR i ns trument, beca us e i t needs to be ca l i bra ted (c), i s a pos s i bi l i ty, but s houl d ha ve been a ddres s ed through requi red i ns trument ma i ntena nce a nd runni ng of a ppropri a te control s . 54. The answer is a. (Murray, Ch 12, 36. Diagnosis and management of foodborne illness, pp 1-33.) Under ha rs h envi ronmenta l condi ti ons , certa i n gra mpos i ti ve ba cteri a convert from the vegeta ti ve s ta te i nto a dorma nt s ta te or s pore. The s pores , whi ch a re dehydra ted s tructures , protect ba cteri a l DNA a nd other contents from the effect of the i ntens e hea t, ra di a ti on, a nd s ta nda rd di s i nfecta nts . If s pores pres ent i n the food a re not ki l l ed duri ng prepa ra ti on, a nd i f the cooked food i s l eft for s evera l hours a t room tempera ture, the s pores wi l l germi na te a l l owi ng vegeta ti ve ba cteri a to produce the enterotoxi n. The s pore-formi ng gra m-pos i ti ve ba cteri a (a ), Clostridium perfringens a nd Bacillus cereus, produce enterotoxi ns tha t ca us e wa tery di a rrhea a nd a bdomi na l cra mps but no fever. Whi l e very s i mi l a r, the vi gnette s ugges ts C. perfringens a s the eti ol ogi c a gent. Ons et i s more ra pi d tha n wi th B. cereus di a rrhea l toxi n, a nd whi l e the types of food overl a p, tempera ture-a bus ed food i s frequentl y a s s oci a ted wi th C. perfringens. Among the gra m-pos i ti ve cocci (b), Staphylococcus aureus produces enterotoxi n, but the ons et i s more a brupt (1-6 hours ) a nd fever ma y be pres ent. The gra m-nega ti ve ba ci l l i (a ) mus t fi rs t col oni ze the i ntes ti ne a nd grow, even i f a n enterotoxi n i s a t the root of the di a rrhea . Thus , ons et of s ymptoms occurs from 24 hours to s evera l da ys a fter i nges ti on of the food. Opportuni s ti c fungi (d) a re not known to be i nvol ved i n food poi s oni ng. Enteri c vi rus es (e) s uch a s norovi rus a nd rota vi rus requi re 12 to 48 hours a nd 1 to 3 da ys , res pecti vel y, for s ymptoms to a ppea r. They a re more commonl y a s s oci a ted wi th foods conta mi na ted by food workers duri ng prepa ra ti on (s a l a ds , s a ndwi ches , a nd frui t), or food prepa red wi th conta mi na ted wa ter (s a l a ds , frui t, a nd i ce). 55. The answer is c. (Murray, Ch 12, 26.) In Neisseria, the equi va l ent to LPS i s l i pool i gos a ccha ri de (LOS) (c), whi ch cons i s ts of l i pi d A a nd core ol i gos a ccha ri de but l a cks the O a nti gen. By tri ggeri ng a n i nfl a mma tory res pons e, LOS ca us es mos t of the s ymptoms duri ng Neisseria gonorrhoeae i nfecti on. It a cti va tes the compl ement a nd s ti mul a tes the i nfl ux of pha gocytes l ea di ng to the purul ent di s cha rge. LOS a l s o contri butes to s erum res i s ta nce, whi ch i s a n i mporta nt fea ture of s tra i ns tha t ca us es s ys temi c i nfecti on. Ra pi dl y growi ng Neisseria rel ea s es outer membra ne bl ebs , whi ch conta i n LOS. Pi l i (e) medi a te the i ni ti a l a tta chment of N. gonorrhoeae to the s urfa ce of cervi ca l or urethra l epi thel i a l cel l s . Pi l i a re a tta ched to the cel l s urfa ce a nd a re not rel ea s ed. The opa ci ty protei n (d), whi ch provi des N. gonorrhoeae col oni es wi th thei r opa que a ppea ra nce, i s a n outer membra ne protei n. It medi a tes bi ndi ng of N. gonorrhoeae to epi thel i a l cel l s a nd pl a ys a rol e i n cel l -to-cel l s i gna l i ng. Si mi l a r to the pi l i , the opa ci ty protei n i s a cel l -a s s oci a ted fa ctor. The ca ps ul e (a ) s urrounds pa thogeni c ba cteri a a nd provi des them wi th a nti pha gocyti c properti es . However, N. gonorrhoeae i s not enca ps ul a ted. Exotoxi ns (b), whi ch a re produced by s ome gra m-nega ti ve a nd gra m-pos i ti ve ba cteri a , bi nd to s peci fi c receptors on the hos t cel l s a nd ei ther a l ter the functi on of the hos t cel l or des troy i t. N. gonorrhoeae does not produce exotoxi n. 56. The answer is b. (Murray, Ch 30. Ryan, Ch 35.) Mos t i s ol a tes of Moraxella catarrhalis, a common ca us e of a cute oti ti s medi a , produce β-l a cta ma s e (b) ma ki ng them res i s ta nt to the peni ci l l i ns . They a re a l mos t a l l s us cepti bl e to thi rd-genera ti on cepha l os pori ns , ma crol i des , tetra cycl i ne (contra i ndi ca ted i n a 2-yea r-ol d), tri methopri m/s ul fa methoxa zol e, a nd a mpi ci l l i n/s ul ba cta m. Chl ora mpheni col a cetyl tra ns fera s e (a ) i s res pons i bl e for na tura l l y occurri ng chl ora mpheni col res i s ta nce i n ba cteri a . Ami nogl ycos i de phos photra ns fera s es (e) confer res i s ta nce to a mi nogl ycos i de a nti bi oti cs . Ca ta l a s e (c) i s a n enzyme i nvol ved i n the detoxi fi ca ti on of the rea cti ve oxygen s peci es H 2 O2 ; DNa s e (d) i s a n enzyme tha t des troys DNA. Both a re produced by M. catarrhalis, but nei ther i s i nvol ved i n a nti bi oti c res i s ta nce. 57. The answer is c. (Murray, Ch 5, 18. Ryan, Ch 4, 24.) Due to va ri a ti ons i n the mecA gene whi ch confers methi ci l l i n (oxa ci l l i n) res i s ta nt, s evera l of the rea l -ti me PCR a s s a ys us ed by cl i ni ca l l a bora tori es now a mpl i fy the SCC mec ca s s ette tha t ca rri es mecA i n order to determi ne whether pa ti ents a re col oni zed wi th MRSA upon a dmi s s i on. Any s peci men tes ti ng pos i ti ve i s cons i dered to ha rbor MRSA. However, the s a me SCC mec ca s s ette found i n communi ty-a cqui red MRSA i s pres ent i n methi ci l l i n-res i s ta nt S. epidermidis (c). Unl es s a ddi ti ona l ta rgets s peci fi c for S. aureus a re a mpl i fi ed, the a ctua l s ource of the a mpl i con coul d ha ve been S. epidermidis, or other s peci es of Staphylococcus. It i s enti rel y pos s i bl e for a pers on to ca rry MRSA i n the na s a l pa s s a ges a nd be i nfected wi th a di fferent s tra i n of S. aureus tha t i s methi ci l l i n-s us cepti bl e or wi th a di fferent s peci es of Staphylococcus. There i s no rea s on to bel i eve the PCR wa s conta mi na ted (b) or tha t the wrong pri mers were us ed i n the PCR (d). S. epidermidis i s a common ca us e of s urgi ca l wound i nfecti ons , ga i ni ng entry di rectl y i nto the i nci s i on from the s urroundi ng s ki n. There i s no rea s on to s us pect tha t the cul ture wa s performed i mproperl y (a ). 58 to 62. (Levinson, Ch 7. Murray, Ch 14. Ryan, Ch 22.) Thi s s eri es of ques ti ons revi ews vi rul ence fa ctors a nd components of va ri ous pa thogeni c ba cteri a —Neisseria meningitidis (58), Streptococcus pyogenes (59), Mycobacterium tuberculosis (61), a nd Bacillus anthracis (62), a s wel l a s the rol e of LPS a s endogenous pyrogen (60). Vi rul ence fa ctors i n genera l a re di s cus s ed i n the cha pters l i s ted a bove, a nd i ncl ude ca ps ul es , pi l i , endotoxi n (LPS, LOS), tei choi c a ci d, ca ta l a s e, a nd exotoxi ns . Ba cteri a l (a nd funga l ) cel l wa l l components i ncl ude pepti dogl yca n, tei choi c a ci d, gl ycol i pi ds or wa xes , a nd ergos terol (fungi ). 58. The answer is b. (Levinson, Ch 16. Murray, Ch 26. Ryan, Ch 30.) At l ea s t 13 s erogroups of N. meningitidis ha ve been i denti fi ed by i mmuno-l ogi c s peci fi ci ty of ca ps ul a r a nti gens . Fi ve, A, B, C, Y, a nd W-135, a re the mos t i mporta nt s tra i ns a s s oci a ted wi th di s ea s e. Vi rul ence fa ctors a s s oci a ted wi th N. meningitidis a re the pol ys a ccha ri de ca ps ul e (b), pi l i (c) tha t medi a te a tta chment, a n IgA protea s e, a nd l i pool i gos a ccha ri de (d) or endotoxi n tha t medi a tes the cl i ni ca l ma ni fes ta ti ons . The pol ys a ccha ri de ca ps ul e (b) bi nds s erum fa ctor H to i ts s urfa ce, protecti ng the mi crobe from
compl ement-medi a ted pha gocytos i s by neutrophi l s unl es s the ca ps ul es a re ops oni zed wi th a nti body. Thi s i s the functi on of the pol ys a ccha ri de N. meningitidis va cci ne. The orga ni s m i s oxi da s e a nd ca ta l a s e (e) pos i ti ve, but thes e a re tra i ts us ed to i denti fy the ba cteri um. Opa ci ty protei ns (a ) a re found i n N. gonorrhoeae where they medi a te fi rm a tta chment to hos t cel l s . 59. The answer is d. (Levinson, Ch 15. Murray, Ch 19. Ryan, Ch 25.) Streptococcus pyogenes, or Group A Streptococcus (GAS), produces a number of vi rul ence fa ctors . The M protei n (d) i s the orga ni s m’s mos t i mporta nt a nti pha gocyti c fa ctor, a nd i t conveys s erol ogi c s peci fi ci ty—over 100 s erotypes a re now known. In the ea rl y s ta ges of growth, the ba cteri a ha ve hya l uroni c a ci d (b) ca ps ul es . Thi s ca ps ul e (s i mi l a r to huma n hya l uroni c a ci d s tructure) i s ra pi dl y des troyed by the orga ni s m’s own hya l uroni da s e. Al s o known a s s prea di ng fa ctor, hya l uroni da s e pl a ys a rol e i n GAS cel l ul i ti s . Erythrogeni c toxi n (a ) i s a s upera nti gen produced by s ome s tra i n of GAS l ys ogeni zed by a ba cteri opha ge ca rryi ng the toxi n gene; i t ca us es the ra s h of s ca rl et fever. A s econd s upera nti gen, s treptococca l pyrogeni c toxi n, ca us es s treptococca l toxi c s hock s yndrome. Streptol ys i n O (e) a n oxygen-l a bi l e hemol ys i n i s us eful for i denti fi ca ti on of the orga ni s m a nd i s a nti geni c s o a nti s treptol ys i n a nti bodi es ca n be us ed to di a gnos i s rheuma ti c fever, a s equel a e of GAS i nfecti on. Li potei choi c a ci d (c) i s a component of the cel l wa l l tha t i s i nvol ved i n bi ndi ng of the ba cteri um to hos t fi bronecti n. 60. The answer is c. (Levinson, Ch 57. Murray, Ch 7. Ryan, Ch 2.) Li popol ys a ccha ri de (LPS or endotoxi n) (c) cons i s ts of three regi ons : l i pi d A, whi ch forms the outer l ea fl et of the l i pi d bi l a yer outer membra ne; the core pol ys a ccha ri de; a nd the O-a nti gen pol ys a ccha ri de s i de cha i n. Endotoxi n i s recogni zed by ma cropha ges through thei r LPS receptors CD14 a nd Tol l -l i ke receptor 4. Upon thi s recogni ti on, the ma cropha ge s ecretes i nterl euki n (IL)-1, IL-6, a nd tumor necros i s fa ctor-α (TNF-α), whi ch s ti mul a te i nfl a mma tory res pons es i ncl udi ng fever. Thi s occurs whether the i nta ct mi crobe i s pres ent or not. Overproducti on of TNF-α ca n l ea d to hypotens i on. Tei choi c a ci d (e) i s a l s o recogni zed by ma cropha ges through tol l -l i ke receptors , but thi s s ubs ta nce i s not pres ent i n gra m-nega ti ve ba cteri a . Ba cteri a l pol ys a ccha ri des (a ) a nd hya l uroni c a ci d (b) do not el i ci t thi s type of i nfl a mma tory res pons e. Protei n toxi ns (d) woul d produce s ymptoms i n keepi ng wi th the type of toxi n a nd rel y on the a ppropri a te receptor bei ng pres ent, whi ch ma y not be the ca s e i n event of s ys temi c a dmi ni s tra ti on (i ntra venous ) or i njecti on i ntra mus cul a rl y. 61. The answer is b. (Levinson, Ch 21. Murray, Ch 25. Ryan, Ch 26.) The vi gnette des cri bes Mycobacterium tuberculosis i nfecti on. Mycoba cteri a a re rods ha ped, a erobi c ba cteri a tha t do not form s pores . Whi l e mycoba cteri a ha ve pepti dogl yca n (d), i t i s hi ghl y decora ted wi th ma ny bra nched-cha i n pol ys a ccha ri des , protei ns , a nd l i pi ds . The cel l wa l l a l s o conta i ns mycol i c a ci ds a nd l i poa ra bi noma nna n, a s tructure functi ona l l y a na l ogous to LPS. Thes e gl ycol i pi ds (b) ma ke the l i pi d content of the cel l wa l l a pproxi ma tel y 60%. The a ci d-fa s t na ture of mycoba cteri a i s due to thi s wa xy coa t; onl y extreme condi ti ons a l l ow the s ta i n to penetra te, a nd once i ns i de, the s ta i n ca nnot be removed by a ci d a nd a l cohol . Ergos terol (a ) i s found i n funga l cel l membra nes . Hya l uroni c a ci d (b) compri s es the ca ps ul e of S. pyogenes a nd i s found on huma n cel l s . Mycoba cteri a do not conta i n tei choi c a ci d (e); thi s i s a component of gra m-pos i ti ve ba cteri a l cel l wa l l s . 62. The answer is a. (Levinson, Ch 21. Murray, Ch 21. Ryan, Ch 26.) Bacillus anthracis produces a n unus ua l ca ps ul e compos ed of pol y-D-gl uta mi c a ci d (a ). The ca ps ul e prevents pha gocytos i s of the orga ni s ms by PMNs a nd i s a n i mporta nt vi rul ence fa ctor. Stra i ns tha t do not produce ca ps ul es a re nonvi rul ent. Letha l fa ctor (c) combi nes wi th protecti ve a nti gen (e) to form the l etha l toxi n, whi ch cl ea ves mi togen-a cti va ted protei n ki na s e res ul ti ng i n cel l dea th. Protecti ve a nti gen (e) a l s o combi nes wi th edema fa ctor to form edema toxi n, a ca l modul i n-dependent a denyl a te cycl a s e whos e a cti on i ncrea s es i ntra cel l ul a r cAMP res ul ti ng i n s evere edema . Hya l uroni c a ci d (b) compos es the often s hort-l i ved ca ps ul e of S. pyogenes. M protei n (d) of S. pyogenes i s a nti pha gocyti c. 63. The answer is c. (Levinson, Ch 15. Murray, Ch 19. Ryan, Ch 25.) There a re more tha n 90 ca ps ul a r i mmunotypes of Streptococcus pneumoniae. Immuni ty to S. pneumoniae i s conveyed by a nti bodi es a ga i ns t the s peci fi c ca ps ul a r type. Va cci nes ha ve been formul a ted to conta i n the mos t commonl y i s ol a ted ca ps ul a r types . Ori gi na l l y, the S. pneumoniae conjuga ted va cci ne conta i ned s even s erotypes . Unfortuna tel y, the s erotype repl a cement phenomenon occurred i n whi ch a nonva cci ne s tra i n bega n to ca us e di s ea s e a mong the va cci na ted popul a ti on. Over ti me thi s l ea d to the l i cens i ng of a 13-va l ent pneumococca l conjuga ted va cci ne (PCV-13), whi ch wa s recommended for chi l dren. A 23-va l ent nonconjuga ted va cci ne (PV-23) wa s devel oped for chi l dren over a ge 2 a nd a dul ts who a re a t ri s k for the di s ea s e. Recent res ea rch s howed tha t ol der a dul ts va cci na ted wi th PCV-13 el a bora ted hi gher protecti ve a nti body ti ters tha n thos e i mmuni zed wi th PV-23. PCV-13 ha s now been l i cens ed for a dul ts 50 a nd ol der. The fa i l ure of the va cci ne to protect thes e i ndi vi dua l s i s mos t l i kel y due to the repl a cement phenomenon—the ca ps ul a r type res pons i bl e wa s not pres ent i n the va cci ne (c). El derl y pa ti ent do mount good i mmune res pons es to va cci nes s o (a ) i s not the l i kel y ca us e. Some pa ti ents wi l l not res pond to the va cci ne (b), but the effecti venes s of the va cci ne i s hi gher tha n 17% (10/12, the number of pa ti ents who beca me i nfected). In fa ct, recent a na l ys es of s tra i ns ca us i ng i l l nes s i n thos e over 65 s ugges t tha t over 70% of the ca s es of i nva s i ve pneumococca l di s ea s e a re covered by PCV-13. It i s unl i kel y tha t the va cci ne wa s defecti ve (d), a l though thi s ca n occur.
Virology Questions 64. A 27-yea r-ol d ma n pres ents to hi s pri ma ry ca re phys i ci a n wi th compl a i nts of a fever, hea da che, mus cl e a ches , a nd s wol l en gl a nds . The phys i ci a n obs erves di s s emi na ted l ympha denopa thy, pha ryngi ti s , a nd a ra s h on the ma n’s upper ches t. The pa ti ent s ta tes tha t he ha d been to a pa rty 2 weeks a go where he experi mented wi th i njecti ng drugs to get hi gh. Needl es were s ha red a mong the pa rty-goers . A ra pi d l a tex tes t for huma n i mmunodefi ci ency vi rus (HIV) a nti bodi es performed i n the phys i ci a n’s offi ce i s nega ti ve. The doctor ha s a s trong s us pi ci on tha t thi s ma n ha s a cute retrovi ra l s yndrome. Whi ch of the fol l owi ng tes ts i s mos t l i kel y to s upport a di a gnos i s of HIV i nfecti on a t thi s ti me? a . CD4 l ymphocyte count b. HIV a nti body tes t by enzyme-l i nked i mmunos orbent a s s a y (EIA) c. HIV p24 a nti gen d. Revers e tra ns cri pta s e pol ymera s e cha i n rea cti on (PCR) for HIV RNA e. Wes tern bl ot for HIV a nti bodi es 65. A 9-yea r-ol d ma l e wi th a hi s tory of fever a nd nons peci fi c s ymptoms pres ents wi th a bri ght red cheeks a nd a ma cul a r l a cy ra s h over hi s body. Whi ch of the fol l owi ng vi rus es i s the mos t l i kel y ca us e of thi s di s ea s e? a . Herpes s i mpl ex vi rus (HSV) type 1 b. Pa rvovi rus B19 c. Rubel l a vi rus d. Rubeol a (mea s l es ) vi rus e. Va ri cel l a -zos ter vi rus (VZV) 66. A 24-yea r-ol d pregna nt woma n pres ents nea r term wi th l es i ons s us pi ci ous for pri ma ry geni ta l herpes . Cul ture i denti fi es the pres ence of HSV type 2. At the ti me of del i very, s he s ti l l ha s a cti ve geni ta l l es i ons . Whi ch of the fol l owi ng s houl d be done to a voi d tra ns mi tti ng the vi rus to the ba by? a . Ces a rea n del i very b. Interna l feta l moni tori ng c. Rupture of the membra nes to s peed del i very d. Va gi na l del i very 67. A 24-yea r-ol d s treet pers on, who i s known to be HIV-pos i ti ve, enters the communi ty hea l th cl i ni c compl a i ni ng of s ores i n hi s mouth. He s a ys he ha s been ha vi ng fevers a nd ni ght s wea ts a nd thi nks he ha s l os t wei ght recentl y. Exa mi na ti on of hi s mouth revea l s the l es i ons s hown i n the i ma ge. Scra pi ng of the whi te pa tches s hows buddi ng yea s t a nd ma s s es of ps eudo-hypha e. Hi s CD4 T-cel l count i s 280/µL a nd vi ra l l oa d i s 75,000 copi es /→L. The doctor a nd pa ti ent a gree i t i s ti me to begi n a nti retrovi ra l thera py. Whi ch of the fol l owi ng regi mens i s bes t for thi s trea tment-na ïve pa ti ent?
(Courtesy of CDC/Sol Silverman Jr, DDS, University of California, San Francisco 1987; ID #6066.) a . Aba ca vi r a l one b. Efa vi renz pl us tenofovi r pl us emtri ci ta bi ne c. Da runa vi r boos ted wi th ri tona vi r
d. Ma ra vi roc pl us enfuvi rti de pl us ra l tegra vi r e. Nevi ra pi ne a l one 68. An HIV-pos i ti ve pa ti ent, a fter trea tment wi th tenofovi r/emtri ci ta bi ne pl us ri tona vi r-boos ted a ta za na vi r, ha s a CD4 T-cel l count of 325/µL a nd a vi ra l l oa d of l es s tha n 50 copi es of HIV RNA/mL. Previ ous l y her CD4+ T-cel l count wa s 280/µL a nd vi ra l l oa d wa s 100,000 copi es /mL. Whi ch of the fol l owi ng bes t des cri bes thi s pa ti ent? a . Thi s pa ti ent i s no l onger i n da nger of opportuni s ti c i nfecti on b. The 5-yea r prognos i s i s excel l ent c. The pa ti ent’s HIV s creeni ng tes t i s mos t l i kel y nega ti ve d. The pa ti ent i s not i nfecti ous e. The a nti retrovi ra l thera py ha s been effecti ve 69. An HIV-pos i ti ve pa ti ent wi th a vi ra l l oa d of 100,000 copi es /mL of HIV RNA a nd a drop i n hi s CD4 T-cel l count from 240 to 50/µL ha s been di a gnos ed wi th Pneumocystis jiroveci pneumoni a . Whi ch of the fol l owi ng i s the bes t des cri pti on of the s ta ge of thi s pa ti ent’s HIV di s ea s e? a . HIV i nfecti on, s ta ge 1 b. HIV i nfecti on, s ta ge 2 c. HIV i nfecti on, s ta ge 3 (AIDS) d. HIV i nfecti on, s ta ge unknown 70. A 19-yea r-ol d col l ege s tudent pres ents to the s tudent hea l th cl i ni c compl a i ni ng of s ore throa t, fever, s wol l en neck l ymph nodes , a nd ma l a i s e of s evera l da ys . Hi s compl ete bl ood count s hows WBC count 22,000/µL wi th 10% neutrophi l s , 28% l ymphocytes , 47% rea cti ve l ymphocytes , a nd 15% monocytes . Hi s monos pot tes t i s pos i ti ve. Whi ch of the fol l owi ng i s ca us i ng thi s s tudent’s i nfecti on? a . Adenovi rus b. Cytomega l ovi rus c. Echovi rus d. Eps tei n–Ba rr vi rus e. Huma n meta pneumovi rus 71. Duri ng a medi ca l checkup for a new i ns ura nce pol i cy, a 60-yea r-ol d gra ndmother i s found to be pos i ti ve by a conventi ona l EIA s creeni ng tes t for a nti bodi es a ga i ns t HIV-1. She ha s no known ri s k fa ctors for expos ure to the vi rus . Whi ch of the fol l owi ng i s the mos t a ppropri a te next s tep? a . Immedi a tel y begi n a nti retrovi ra l thera py b. Perform the EIA s creeni ng tes t a s econd ti me c. Reques t tha t a vi ra l bl ood cul ture be done by the l a bora tory d. Tel l the pa ti ent tha t s he i s l i kel y to devel op AIDS e. Tes t the pa ti ent for Pneumocystis jiroveci i nfecti on 72. A 74-yea r-ol d ma n who l i ved i n Il l i noi s devel oped ma l a i s e, fever, cough, a nd s ore throa t i n Augus t. Two da ys l a ter, he vi s i ted hi s doctor beca us e of s evere hea da che, na us ea a nd vomi ti ng, a nd conti nued fever. He tol d hi s doctor tha t the mos qui toes ha d been fi erce i n the l a s t 2 weeks a nd tha t he ha d been bi tten numerous ti mes . The doctor noted tremors i n the ma n’s ha nds a s wel l a s fever of 104°F, a nd a dmi tted hi m to the hos pi ta l for tes ts . Exa mi na ti on of CSF revea l ed norma l gl ucos e a nd protei n wi th 150 l ymphocytes /µL; PCR a s s a ys for HSV a nd Wes t Ni l e vi rus (WNV) on the CSF were nega ti ve. Des pi te s upporti ve ca re, the ma n s l i pped i nto a coma a nd di ed. Whi ch of the fol l owi ng vi rus es wa s mos t l i kel y res pons i bl e for thi s ma n’s i l l nes s ? a . Coltivirus b. Dengue vi rus c. Erythrovirus (pa rvovi rus B19) d. La Cros s e vi rus e. St. Loui s encepha l i ti s vi rus 73. A 64-yea r-ol d ma n compl a i ned of poor memory a nd di ffi cul ty wi th vi s i on tha t wa s progres s i ng ra pi dl y a nd myocl oni c jerks . Cerebros pi na l fl ui d exa mi na ti on a t a reference l a bora tory revea l ed the pres ence of 14-3-3 protei n. Over the next 6 months hi s cogni ti ve deteri ora ti on beca me s evere a nd he di ed 2 months l a ter. At a utops y, s pongi form encepha l opa thy wa s noted. Whi ch of the fol l owi ng i s the mos t a ppropri a te di a gnos i s for thi s ma n? a . Spora di c Creutzfel dt–Ja kob di s ea s e (CJD) b. Fa mi l i a l CJD c. Ia trogeni c CJD d. Va ri a nt CJD 74. In 2003, the zoonoti c s evere a cute res pi ra tory s yndrome (SARS) corona vi rus ca us ed a pa ndemi c i n whi ch over 8000 peopl e were i nfected a nd the morta l i ty ra te wa s 10%. In 2012, a novel corona vi rus wa s i s ol a ted from 12 pers ons i n Sa udi Ara bi a , Qa ta r, a nd Bri ta i n wi th s evere res pi ra tory i l l nes s ; s o fa r, 50% ha ve di ed. Whi ch of the fol l owi ng s yndromes i s more commonl y ca us ed by other known types of huma n corona vi rus es ? a . Common col d b. Herpa ngi na c. Meni ngi ti s d. Pneumoni a e. Ves i cul a r l es i ons 75. A 35-yea r-ol d i ntra venous (IV) drug a bus er wi th known chroni c hepa ti ti s B vi rus (HBV) s ta tus s uddenl y pres ents wi th a n a cute hepa ti ti s epi s ode. He devel ops ma s s i ve hepa ti c necros i s a nd di es . Whi ch of the fol l owi ng i s mos t l i kel y res pons i bl e for the cha nge i n hi s condi ti on? a . A hepa ti ti s B muta nt ha s devel oped b. He ha s contra cted hepa ti ti s D vi rus (HDV)
c. He ha s devel oped ci rrhos i s d. Hi s food conta i ned hepa ti ti s A vi rus (HAV) e. Hi s food conta i ned hepa ti ti s E vi rus (HEV) 76. Whi ch of the fol l owi ng a nti vi ra l compounds i nhi bi ts a cti vi ty of the pyrophos pha te-bi ndi ng s i te of vi ra l DNA pol ymera s es a nd i s us ed to trea t s eri ous i nfecti ons wi th cytomega l ovi rus ? a . Ama nta di ne b. Fos ca rnet c. Ga nci cl ovi r d. Ri ba vi ri n e. Zi dovudi ne 77. A cl i ni c a s s oci a ted wi th a medi ca l s chool a nd l oca ted i n a l ower i ncome ci ty di s tri ct documents a s eri es of ca s es i nvol vi ng echovi rus es i n s chool -a ge chi l dren. Mos t ca s es experi enced common col d s ymptoms pl us mi l d fever a nd ma cul opa pul a r ra s h; s ome were hos pi ta l i zed wi th a cute ons et of fever, hea da che, nucha l ri gi di ty, a nd petechi a l ra s h. Al l experi enced compl ete recovery wi thi n 1 week wi thout s peci fi c a nti vi ra l thera py. Whi ch of the fol l owi ng body s ys tems i s the ma i n ta rget of echovi rus es ? a . Bl oods trea m b. Centra l nervous s ys tem (CNS) c. Intes ti na l tra ct d. Lymphoi d ti s s ues e. Upper res pi ra tory tra ct 78. A newborn i nfa nt pres ents wi th ves i cul a r s ki n l es i ons . He a l s o ha d genera l i zed s ymptoms s ugges ti ve of CNS a nd l i ver i nvol vement. Hi s mother ha d devel oped pa i nful ves i cul a r l es i ons on her geni ta l i a s evera l da ys pri or to the bi rth of her s on. She ha d not s ought medi ca l hel p unti l s he wa s i n hea vy l a bor. At a dmi s s i on to l a bor a nd del i very, i nterna l l es i ons were s een on her cervi x a nd va gi na l wa l l s , but the bi rth wa s emi nent, precl udi ng C-s ecti on. Whi ch of the fol l owi ng i s the mos t ra pi d tes t for defi ni ti ve i denti fi ca ti on of the mos t l i kel y eti ol ogi c a gent?
Ves i cul a r l es i ons of congeni ta l herpes . (Courtesy of CDC.) a . Detecti on of s peci fi c HSV IgG a nti bodi es b. Di rect i mmunofl uores cence for HSV on cel l s from l es i ons c. HSV PCR on cerebros pi na l fl ui d d. Tza nck s mea r e. Vi ra l cul ture of fl ui d from l es i ons 79. Severa l chi l dren i n a da y ca re center for pres chool ers devel oped fever, i rri ta bi l i ty, l a ck of a ppeti te, a nd a ves i cul a r ra s h found on thei r ha nds , feet, a nd mouths . Wi th whi ch vi rus were thes e chi l dren mos t l i kel y i nfected?
(A: Courtesy of James Heilman, MD, Creative Attribution-Share Alike 3.0 Unported license; B: Courtesy of Ngufra, 2102-07-06, GNU Free Documentation License; C: Courtesy of DJ Midgley, May 2008, Creative Commons Attribution-Share Alike 3.0 Unported license.) a . Corona vi rus b. Coxs a cki evi rus A c. Orthoreovi rus d. Res pi ra tory s yncyti a l vi rus e. Rhi novi rus 80. A 15-yea r-ol d boy i s ta ken to hi s pedi a tri ci a n a fter experi enci ng fever, ma l a i s e, a nd a norexi a fol l owed by tender s wel l i ng of hi s pa roti d gl a nds . Whi ch of the fol l owi ng i s the mos t l i kel y compl i ca ti on to occur i n thi s pa ti ent? a . Gui l l a i n–Ba rré s yndrome b. Hemorrha ge c. Myoca rdi ti s d. Oophori ti s e. Orchi ti s 81. An otherwi s e hea l thy 65-yea r-ol d ma l e wa s i n a ca r a cci dent a nd broke s evera l ri bs on the l eft s i de. Approxi ma tel y 12 da ys l a ter, he devel oped a pa i nful , wel l -ci rcums cri bed ves i cul a r ra s h over the l eft ri b ca ge tha t pers i s ts for s evera l weeks . The ra s h i s mos t l i kel y due to whi ch of the fol l owi ng?
(Courtesy of CDC, 1995, ID#6886.) a . Pri ma ry i nfecti on wi th HSV type 1 b. Rea cti va ti on of l a tent HSV type 1 c. Pri ma ry i nfecti on wi th Eps tei n–Ba rr vi rus d. Rea cti va ti on of l a tent Eps tei n–Ba rr vi rus e. Pri ma ry i nfecti on wi th VZV f. Rea cti va ti on of l a tent VZV 82. A 3-yea r-ol d chi l d who ha d not been i mmuni zed pres ents a t the phys i ci a n’s offi ce wi th s ymptoms of coryza , cough, conjuncti vi ti s , a nd photophobi a . He ha s a l ow-gra de fever, a nd s ma l l , bl ui s h-whi te ul cera ti ons a re s een on the bucca l mucos a oppos i te the l ower mol a rs . Wha t i s the ca us a ti ve a gent of thi s chi l d’s s ymptoms ? a . Adenovi rus b. HSV c. Infl uenza vi rus d. Mea s l es vi rus e. Rubel l a vi rus 83. A s exua l l y a cti ve woma n wa s s een for a routi ne gynecol ogi c exa m tha t i ncl uded a Pa p s mea r. The report i ndi ca ted cervi ca l i ntra epi thel i a l neopl a s i a . In s i tu hybri di za ti on s howed the pres ence of huma n pa pi l l oma vi rus (HPV) type 16 genomes wi thi n the neopl a s ti c cel l s . Whi ch of the fol l owi ng proces s es i s requi red for HPV to l ea d to the devel opment of ca ncer? a . Integra ti on of the vi ra l genome b. Los s of HPV E6 a nd E7 genes c. Muta ti on of the vi rus d. Vi ra l repl i ca ti on 84. Two s i bl i ngs , a ges 2 a nd 4, experi ence fever, rhi ni ti s , a nd pha ryngi ti s tha t res ul t i n l a ryngotra cheobronchi ti s . Both ha ve a ha rs h, ba rk-l i ke cough a nd hoa rs enes s . Whi ch of the fol l owi ng vi rus es i s the l ea di ng ca us e of thei r s yndrome? a . Adenovi rus b. Coxs a cki evi rus B c. Pa ra i nfl uenza vi rus d. Rhi novi rus e. Rota vi rus 85. An outbrea k of hepa ti ti s occurred i n a n a rea of Indi a wi th poor s a ni ta ti on. Mos t of the pa ti ents reported fever, na us ea wi th vomi ti ng, a nd wei ght l os s occurri ng over s evera l da ys fol l owed by ja undi ce a nd pruri tus . Tes ti ng qui ckl y rul ed out HAV. A number of women i n the a rea a re pregna nt. For whi ch of the fol l owi ng a re thes e women a t ri s k? a . Chroni c hepa ti ti s b. Feta l hydrops c. Ful mi na nt hepa ti c fa i l ure d. Gui l l a i n–Ba rré s yndrome e. Reye s yndrome 86. An 18-yea r-ol d ma n wa s ta ken to a n emergency medi ci ne depa rtment beca us e of fever a nd hea da che for 36 hours a nd now compl a i nt of a s ti ff neck. No ba cteri a l a gents a ppea red to be i nvol ved a nd a n i ni ti a l di a gnos i s of a s epti c meni ngi ti s wa s ma de. Whi ch of the fol l owi ng l a bora tory fi ndi ngs i n the exa mi na ti on of hi s cerebros pi na l fl ui d l ed to thi s di a gnos i s ?
a . Decrea s ed protei n content b. El eva ted gl ucos e concentra ti on c. Eos i nophi l i c pl eocytos i s d. Lymphocyti c pl eocytos i s e. Neutrophi l i c pl eocytos i s 87. A s treet pers on wel l known to the l oca l publ i c hea l th cl i ni c a ppea rs to ha ve a cute s ymptoms of hepa ti ti s a nd tes ts pos i ti ve for HDV a nti gen. Knowi ng tha t HDV requi res HBV, whi ch of the fol l owi ng s ets of tes t res ul ts s hows thi s pa ti ent ha d chroni c HBV i nfecti on a nd wa s s uperi nfected wi th HDV? a . HBs Ag +, HBeAg +, Anti -HBcAg IgM +, Anti -HBcAg IgG -, Anti -HBs Ag b. HBs Ag +, HBeAg +, Anti -HBcAg IgM -, Anti -HBcAg IgG +, Anti -HBs Ag c. HBs Ag -, HBeAg -, Anti -HBcAg IgM -, Anti -HBcAg IgG +, Anti -HBs Ag + d. HBs Ag -, HBeAg -, Anti -HBcAg IgM -, Anti -HBcAg IgG -, Anti -HBs Ag + 88. A nurs e devel ops cl i ni ca l s ymptoms cons i s tent wi th hepa ti ti s . She reca l l s s ti cki ng hers el f wi th a needl e a pproxi ma tel y 5 months before, a fter dra wi ng bl ood from a pa ti ent. Serol ogi c tes ts for HBs Ag, a nd a nti bodi es to HBs Ag a nd HAV a re a l l nega ti ve; however, s he i s pos i ti ve for HBcAg IgM a nti body. Whi ch of the fol l owi ng cha ra cteri zes the current hea l th s ta te of the nurs e? a . Does not ha ve hepa ti ti s B b. Ha s res ol ved hepa ti ti s B c. Ha s chroni c hepa ti ti s B d. Is i n wi ndow peri od of a cute hepa ti ti s B e. Wa s i mmuni zed wi th HBs Ag 89. A 65-yea r-ol d Fl ori da fi s herma n forgot hi s i ns ect repel l ent on a recent s porti ng tri p. A week l a ter, he devel oped fever, chi l l s , hea da che, a nd fl ul i ke s ymptoms . He wa s brought to the Emergency Depa rtment by hi s wi fe wi th photophobi a , extreme l etha rgy, a nd s evere hea da che. CNS exa mi na ti on revea l ed cra ni a l nerve defi ci ts a nd hemi pa res i s . The pa ti ent wa s a dmi tted to i ntens i ve ca re wi th a gra ve prognos i s . Whi ch of the fol l owi ng i s the vector tha t tra ns mi tted the i nfecti on from whi ch thi s ma n i s s ufferi ng? a . Bi rd b. Fl ea c. Mos qui to d. Sa nd fl y e. Ti ck 90. A l oca l s chool di s tri ct fi nds a l a rge number of s tudent a bs ences , wi th the chi l dren pres enti ng wi th rhi norrhea , na s a l obs tructi on, hea da che, a nd ma l a i s e, but no fever. A s tra i n of rhi novi rus i s the mos t l i kel y eti ol ogi c a gent of thes e i nfecti ons . By whi ch method i s thi s vi rus mos t frequentl y s prea d? a . Feca l –ora l route b. Ha nd-to-ha nd conta ct c. Res pi ra tory dropl ets d. Sexua l conta ct e. Verti ca l tra ns mi s s i on 91. A 10-month-ol d i nfa nt who wa s born 4 weeks prema ture wa s brought to the Emergency Depa rtment wi th hi gh fever, rhi norrhea , cough, a nd di ffi cul ty brea thi ng. On exa mi na ti on, the ba by ha d dys pnea a nd ta chypnea ; ra l es a nd wheezi ng were hea rd over both l ungs . The ba by wa s a dmi tted to Pedi a tri c Intens i ve Ca re where s he s uffered res pi ra tory fa i l ure a nd wa s pl a ced on mecha ni ca l venti l a ti on. Two di fferent types of tes ts for res pi ra tory s yncyti a l vi rus (RSV or Pneumovirus) were nega ti ve, a s were tes ts for pa ra i nfl uenza vi rus , i nfl uenza A a nd B vi rus es , a nd a denovi rus . Whi ch of the fol l owi ng vi rus es i s the mos t l i kel y eti ol ogi c a gent? a . Cytomega l ovi rus b. HSV type 1 c. Huma n meta pneumovi rus d. Pa rvovi rus B19 e. Rhi novi rus 92. A 32-yea r-ol d woma n wa s bi tten on the fi ngers by a fera l ki tten tha t s he wa s tryi ng to feed. She cl ea ned the wounds , a nd a fter a week, the s i tes hea l ed wi thout ba cteri a l i nfecti on. Si xty da ys l a ter, s he noti ced pa i n, i tchi ng, a nd numbnes s a t the s i tes of the bi te wounds . Al a rmed, s he ma de a n a ppoi ntment to s ee her doctor the next da y. By the ti me of the a ppoi ntment, her a rm wa s pa ra l yzed, a nd s he wa s febri l e, ha d a hea da che, a nd wa s very a nxi ous . Her doctor s ent her to the hos pi ta l for a nucha l s ki n bi ops y, whi ch wa s s ent to a reference l a bora tory for workup. The H&E s ta i n s howed vi ra l i ncl us i on bodi es (A, a rrows ) a nd DFA (di rect fl uores cent a nti body tes t) wi th vi rus -s peci fi c a nti s erum wa s pos i ti ve (B). Wi th whi ch vi rus wa s thi s woma n i nfected?
(A: Courtesy of CDC/Dr Daniel P. Perl, 1971, ID#1958; B: Courtesy of CDC/Dr. Tierkel, ID#6455.) a . Cytomega l ovi rus b. Ea s tern equi ne encepha l i ti s vi rus (EEEV) c. Echovi rus d. HSV type 1 e. Ra bi es vi rus 93. Kuru wa s a fa ta l di s ea s e of certa i n New Gui nea na ti ves a nd wa s cha ra cteri zed by tremors a nd a ta xi a ; Creutzfel dt–Ja kob di s ea s e (CJD) i s cha ra cteri zed by both a ta xi a a nd dementi a . CJD ha s been a cci denta l l y tra ns ferred to others by conta mi na ted growth hormone from huma n pi tui ta ry gl a nds , cornea l tra ns pl a nts , a nd conta mi na ted s urgi ca l i ns truments . Thes e di s ea s es a re thought to be ca us ed by whi ch of the fol l owi ng? a . Cel l wa l l -defi ci ent ba cteri a b. Envi ronmenta l toxi ns c. Fl a gel l a tes d. Pri ons e. Sl ow vi rus es 94. Recentl y, a recombi na nt va cci ne ba i t to prevent ra bi es i n ra ccoons ha d been us ed i n wooded s uburba n communi ti es . Thi s ba i t us es a l a rge doubl e-s tra nded DNA vi rus tha t repl i ca tes i n the cytopl a s m a s the ca rri er of the ra bi es gl ycoprotei n gene. A woma n who wa s i mmunocompromi s ed found a ba i t tha t ha d broken open a nd pi cked i t up to di s pos e of i t. She s ubs equentl y devel oped l es i ons on her ha nds 11 da ys a fter s he ha ndl ed the ba i t. Wha t ca us ed thes e l es i ons ?
(Courtesy of CDC; MMWR 2009;58:1204-1207.) a . Adenovi rus type 5 b. Echovi rus 11 c. Ra bi es vi rus d. Va cci ni a vi rus e. Va ri ol a (s ma l l pox) vi rus 95. A 35-yea r-ol d ma n devel oped hea da che, na us ea , vomi ti ng, a nd s ore throa t 8 weeks a fter returni ng from a tri p a broa d. He eventua l l y refus ed to dri nk wa ter a nd ha d epi s odes of profus e s a l i va ti on, di ffi cul ty i n brea thi ng, a nd ha l l uci na ti ons . Two da ys a fter the pa ti ent di ed of ca rdi a c a rres t, i t wa s l ea rned tha t he ha d been bi tten by a dog whi l e on hi s tri p. Whi ch of the fol l owi ng trea tments , i f gi ven i mmedi a tel y a fter the dog bi te, coul d ha ve hel ped prevent thi s di s ea s e? a . Broa d-s pectrum a nti bi oti cs
b. Hi gh-dos e a cycl ovi r c. IV ri ba vi ri n d. Ra bi es i mmune gl obul i n pl us ra bi es va cci ne e. Teta nus i mmune gl obul i n a nd teta nus toxoi d va cci ne 96. A pa ti ent who works i n a n i ndus tri a l s etti ng pres ents to hi s ophtha l mol ogi s t wi th promi nent s ubconjuncti va l hemorrha ge, peri orbi ta l s wel l i ng, a nd cornea l cha nges cons i s tent wi th kera ti ti s . The pa ti ent reported s evere photophobi a a nd the s ens a ti on tha t s omethi ng wa s i n hi s eye. Ni ne other workers devel oped s i mi l a r s ymptoms 7 da ys l a ter. The di fferenti a l di a gnos i s s houl d i ncl ude i nfecti on wi th whi ch of the fol l owi ng vi rus es ? a . Adenovi rus b. Eps tei n–Ba rr vi rus c. Pa rvovi rus d. Res pi ra tory s yncyti a l vi rus e. VZV 97. A hos pi ta l worker i s found to be pos i ti ve for hepa ti ti s B s urfa ce a nti gen. Subs equent tes ts revea l the pres ence of HBeAg a s wel l . Whi ch of the fol l owi ng bes t des cri bes the worker? a . Ha s a bi ol ogi c fa l s e-pos i ti ve tes t for hepa ti ti s b. Is hi ghl y conta gi ous c. Is l es s conta gi ous d. Is not conta gi ous e. Ha s res ol ved hepa ti ti s B 98. An extended fa mi l y met for a fa mi l y reuni on i n a rura l a rea of Texa s . Al l reported numerous mos qui to bi tes . One week l a ter s evera l fa mi l y members ha d hea da che, na us ea , fever, a nd ma l a i s e. Two devel oped s ti ff neck a nd s evere hea da che tha t res ol ved over the next 5 da ys , a nd a n 8month-ol d wa s hos pi ta l i zed wi th di ffus e encepha l i ti s . Al l fa mi l y members recovered compl etel y except the i nfa nt who wa s l eft wi th a s ei zure di s order. An a rbovi rus wa s confi rmed a s the eti ol ogi c a gent by s erol ogi c tes ti ng of the effected pers ons . Whi ch of the fol l owi ng i s the mos t l i kel y eti ol ogi c a gent? a . Dengue vi rus b. Lymphocyti c chori omeni ngi ti s vi rus c. Rubel l a vi rus d. Wes tern equi ne encepha l i ti s vi rus e. WNV 99. A 2-month-ol d i nfa nt wa s a dmi tted to the medi ca l center i n Februa ry for trea tment of bronchi ol i ti s . An i mmunofl uores cent a s s a y wa s pos i ti ve for a res pi ra tory vi rus . As the i nfa nt wa s s truggl i ng to brea the, ri ba vi ri n trea tment wa s s ta rted i mmedi a tel y. Wi th whi ch vi rus wa s thi s i nfa nt i nfected? a . Coxs a cki evi rus A b. HBV c. HSV d. Pa rvovi rus e. Res pi ra tory s yncyti a l vi rus 100. In Ja nua ry, a 74-yea r-ol d woma n from Iowa i s brought to the emergency depa rtment by her hus ba nd. He s ta tes tha t s he ha d recent ons et of hi gh fever a nd hea da che. Duri ng the l a s t 2 da ys , s he ha s been confus ed a nd ca nnot perform da i l y chores . Shortl y a fter a rri va l s he s uffers a s ei zure. Her phys i ca l exa mi na ti on i ndi ca tes s ome wea knes s es i n her l eft s i de a nd neck s ti ffnes s . Ma gneti c res ona nce i ma gi ng i ma ges s how encepha l i ti s l oca l i zed to the ri ght tempora l l obe. Wha t i s the mos t l i kel y ca us a ti ve a gent? a . Adenovi rus b. Coxs a cki evi rus B c. HSV type 1 d. Listeria monocytogenes e. WNV 101. An 8-month-ol d gi rl s uddenl y devel oped a hi gh fever (103°F). Her pedi a tri ci a n exa mi ned her a nd found no s i gns of upper res pi ra tory tra ct i nfecti on, meni ngi ti s , or encepha l i ti s . Two da ys l a ter, the gi rl ’s fever rea ched 105°F a nd s he s uffered a febri l e s ei zure. By the ti me the chi l d wa s brought to the pedi a tri ci a n’s offi ce, her tempera ture ha d dropped. The doctor noted a genera l i zed pa pul a r ra s h. Wha t wa s the doctor’s mos t l i kel y di a gnos i s for thi s chi l d? a . Erythema i nfecti os um ca us ed by pa rvovi rus B19 b. Ha nd-foot-a nd-mouth di s ea s e ca us ed by Coxs a cki evi rus A c. Mea s l es ca us ed by Morbillivirus d. Ros eol a i nfa ntum ca us ed by huma n herpes vi rus 6 e. Rubel l a ca us ed by rubel l a vi rus 102. A 5-month-ol d i nfa nt, s een i n the emergency room i n wi nter, pres ents wi th fever a nd pers i s tent cough wi th wheezi ng. Her mother s ta tes tha t the ba by’s ol der brother, a ge 3, ha d recentl y ha d a runny nos e, s ore throa t, a nd fever. Phys i ca l exa mi na ti on of the i nfa nt revea l ed ta chypnea a nd ta chyca rdi a ; expi ra tory wheezes were hea rd over both l ungs . The ba by wa s cya noti c a nd retra cti ons were obs erved a nd a ches t x-ra y s howed hyperi nfl a ted l ung fi el ds . Whi ch of the fol l owi ng i s mos t l i kel y the ca us e of thi s i nfecti on? a . Adenovi rus b. Coxs a cki evi rus c. Pa ra i nfl uenza vi rus d. Res pi ra tory s yncyti a l vi rus
e. Rhi novi rus 103. Whi ch one of the fol l owi ng groups of peopl e i s mos t l i kel y to be a t i ncrea s ed ri s k for HIV i nfecti on? a . Sexua l pa rtners of IV drug a bus ers who s ha re needl es b. Recepti oni s ts a t a hos pi ta l c. Pers ons who recei ved bl ood tra ns fus i ons i n 2013 d. Members of a hous ehol d i n whi ch there i s a pers on who i s HIV-pos i ti ve e. Fa ctory workers whos e coworkers a re HIV-pos i ti ve 104. An obs tetri ci a n s ees a pregna nt pa ti ent who wa s expos ed to rubel l a vi rus i n the 18th week of pregna ncy. She does not remember getti ng a rubel l a va cci na ti on. Whi ch of the fol l owi ng i s the bes t i mmedi a te cours e of a cti on? a . Admi ni s ter rubel l a i mmune gl obul i n b. Admi ni s ter rubel l a va cci ne c. Order a rubel l a a nti body ti ter to determi ne i mmune s ta tus d. Rea s s ure the pa ti ent beca us e rubel l a i s not a probl em unti l a fter the 30th week e. Termi na te the pregna ncy 105. Two vi ra l va cci nes a re expected to reduce the i nci dence of ca ncers . Whi ch va cci nes a re thes e? a . Adenovi rus a nd mumps vi rus va cci nes b. HAV a nd pol i ovi rus va cci nes c. HPV 16/18 a nd hepa ti ti s B va cci nes d. Mea s l es vi rus a nd rubel l a vi rus va cci nes e. Rota vi rus a nd VZV va cci nes 106. A group of hea l thca re workers from the Uni ted Sta tes s ta ffi ng a cl i ni c i n Indi a were worki ng wi th chi l dren a dmi tted wi th a cute fl a cci d pa ra l ys i s . The i l l nes s bega n wi th fever, na us ea , vomi ti ng, a nd s evere hea da che fol l owed by neck s ti ffnes s , mus cl e pa i n a nd wea knes s , a nd cons ti pa ti on. None of the workers beca me i l l beca us e they ha d been va cci na ted a ga i ns t thi s di s ea s e. Whi ch vi ra l va cci ne protected thes e workers ? a . HAV b. Mea s l es vi rus c. Pol i ovi rus d. Rubel l a vi rus e. Yel l ow fever vi rus 107. A 70-yea r-ol d nurs i ng home pa ti ent refus ed the i nfl uenza va cci ne a nd s ubs equentl y devel oped i nfl uenza , whi ch ra pi dl y progres s ed to vi ra l pneumoni a , for whi ch s he wa s hos pi ta l i zed. Two da ys l a ter, s he beca me profoundl y wors e, wa s hypoxemi c on oxygen, a nd ha d a WBC count of 22,000/µL wi th 80% neutrophi l s . She di ed of a cute pneumoni a 1 week a fter contra cti ng the fl u. Whi ch of the fol l owi ng mi croorga ni s ms wa s mos t l i kel y res pons i bl e for her fa ta l i l l nes s ? a . Escherichia coli b. Klebsiella pneumoniae c. Legionella pneumophila d. Listeria monocytogenes e. Staphylococcus aureus 108. Al ong wi th s evera l chi l dren a t hi s el ementa ry s chool who ha d s i mi l a r s ymptoms , a 6-yea r-ol d boy wa s s ent home from s chool beca us e hi s eyes were red wi th a wa tery, nonpurul ent di s cha rge. He ha d a fever of 102°F a nd compl a i ned of s ore throa t. A ra pi d tes t for Group A Streptococcus wa s nega ti ve a nd hi s doctor tol d the boy’s mother tha t her chi l d woul d recover wi thi n a week. Whi ch of the fol l owi ng orga ni s ms wa s the mos t l i kel y ca us e of hi s i nfecti on? a . Adenovi rus b. Chlamydia trachomatis c. Haemophilus aegyptius d. HSV type 1 e. Staphylococcus aureus 109. A hus ba nd a nd wi fe performed the yea rl y s pri ng cl ea ni ng of thei r mounta i n ca bi n, l oca ted i n the s outhwes tern pa rt of the Uni ted Sta tes . The woma n pres ented to her phys i ci a n 2 weeks l a ter wi th fever, mya l gi a , hea da che, a nd na us ea , fol l owed by progres s i ve pul mona ry edema a nd res pi ra tory fa i l ure. How di d s he a cqui re thi s vi ra l i nfecti on? a . Conta ct wi th her hus ba nd b. Dri nki ng wa ter i n the ca bi n c. Inha l i ng a eros ol i zed rodent excreta d. Mos qui to bi te e. Ti ck bi te 110. A 35-yea r-ol d profes s i ona l bus i nes s woma n noti ces the a ppea ra nce of s evera l hyperkera toti c, wel l -dema rca ted growths on the pa l m s i de of her i ndex fi nger a nd on her toe. They do not cha nge i n s i ze a nd ca us e her onl y mi ni ma l di s comfort. Bi ops y of one of the l es i ons i s s hown a t 40x. Whi ch of the fol l owi ng vi rus es i s the mos t l i kel y eti ol ogi c a gent?
(A: File in public domain; obtained from Wikimedia Commons; B: H&E s ta i n (40×) of s ki n bi ops y. By Nephron; permission through GNU Free Documentation License.) a . Adenovi rus b. HPV c. Mol l us ci poxvi rus d. Echovi rus e. VZV 111. A 32-yea r-ol d ga y ma l e went to hi s communi ty STD cl i ni c, where i t wa s found tha t he ha d peri a na l condyl oma a ccumi na tum. Phys i ca l remova l wa s recommended due to the s i ze of the s es s i ons a l ong wi th i mmunomodul a tory thera py. Whi ch of the fol l owi ng drugs wa s mos t l i kel y s el ected? a . Acycl ovi r b. 5-Fl uoroura ci l c. Imi qui mod d. Podophyl l i n e. Tri chl oroa ceti c a ci d 112. A 7-yea r-ol d gi rl wi th s i ckl e cel l a nemi a wa s brought to her phys i ci a n by her pa rents who reported tha t s he s eemed to be extremel y fa ti gued a nd pa l e-l ooki ng. They s ta ted tha t s evera l of her cl a s s ma tes ha d recentl y ha d ra s hes a nd bri ght red cheeks . On exa mi na ti on, the doctor di d not s ee a ra s h, but obs erved tha t her conjuncti va , gums , a nd na i l beds were pa l e a nd tha t s he ha d ta chyca rdi a . A CBC revea l ed tha t her hemogl obi n l evel ha d fa l l en by 2 g/dL from her l a s t res ul t 3 months a go; her reti cul ocyte count wa s 0.05%. From whi ch of the fol l owi ng i s thi s chi l d s ufferi ng? a . Apl a s ti c cri s i s from pa rvovi rus B19 i nfecti on b. Peri ca rdi ti s ca us ed by Coxs a cki evi rus B c. Ga s troenteri ti s wi th bl eedi ng ca us ed by Norovirus d. Exa cerba ted a nemi a from Coltivirus i nfecti on e. Hemorrha gi c cys ti ti s ca us ed by BK pol yoma vi rus 113. An i nfa nt who a ppea red hea l thy a t bi rth devel oped s ens ori neura l hea ri ng l os s wi thi n the fi rs t yea r of l i fe. Vi ra l cul ture on uri ne from thi s chi l d i s pos i ti ve for a rel a ti vel y s l ow-growi ng vi rus (3 weeks ). Wi th whi ch vi rus wa s thi s i nfa nt mos t l i kel y i nfected a t bi rth? a . Cytomega l ovi rus b. HSV type 2 c. Rubel l a vi rus d. Mea s l es vi rus e. VZV 114. A 6-month-ol d i nfa nt ha s ha d wa tery di a rrhea for 5 da ys ; he vomi ted a coupl e of ti mes . The s tool s ha ve no bl ood or pus . He i s dehydra ted. He ha s not been outs i de of Ci nci nna ti , but two other toddl ers who vi s i ted for a da y a re a l s o s i ck. Wha t i s the mos t l i kel y ca us e of thi s chi l d’s di a rrhea ?
a . Enterovi rus b. Norovi rus c. Rota vi rus d. Salmonella enterica e. Staphylococcus aureus enterotoxi n 115. Suba cute s cl eros i ng pa nencepha l i ti s (SSPE) begi ns wi th mi l d cha nges i n pers ona l i ty, beha vi or a nd memory, a nd s ei zures . The proces s i s progres s i ve a nd ends wi th dementi a a nd dea th. Infecti on wi th whi ch vi rus precedes SSPE? a . Eps tei n–Ba rr vi rus b. HIV c. JC pol yoma vi rus d. Mea s l es vi rus e. Mumps vi rus 116. A coupl e who ha d been hi ki ng i n Uta h i n Ma y devel oped fever, mya l gi a s , hea da che, a nd pa i n behi nd thei r eyes . The fever wa s pres ent for 3 da ys , s ubs i ded, a nd then recurred, l a s ti ng 3 da ys . Thei r doctor recommended a nti pyreti c thera py a nd tol d them they s houl d not dona te bl ood for 6 months . Wi th whi ch vi rus wa s thi s coupl e mos t l i kel y i nfected? a . Coltivirus b. Coxs a cki evi rus B c. Dengue vi rus d. Si n Nombre ha nta vi rus e. Wes tern equi ne encepha l i ti s vi rus 117. An outbrea k of di s ea s e ca us ed by a vi rus occurred i n Uga nda , Afri ca . Cl i ni ca l ma ni fes ta ti ons i ncl uded hemoptys i s a nd bl eedi ng from the eyes , s ki n, a nd ga s troi ntes ti na l (GI) tra ct. The morta l i ty ra te exceeded 70%. The vi rus a ppea red to be tra ns mi tted i n the vi l l a ge by conta ct wi th the bl ood a nd bodi l y s ecreti ons of effected i ndi vi dua l s ; thus , i nfecti ons ra tes were hi gher a mong thos e ca ri ng for the s i ck. Whi ch vi ra l di s ea s e occurred i n thi s outbrea k? a . Dengue hemorrha gi c fever b. Ebol a hemorrha gi c fever c. Ha nta vi rus pul mona ry s yndrome d. Wes t Ni l e encepha l i ti s e. Yel l ow fever 118. A tra ns pl a nt pa ti ent who ha d s erol ogi c evi dence of previ ous Eps tei n–Ba rr vi rus i nfecti on wa s ta ki ng hi gh l evel s of i mmunos uppres s i ve medi ca ti ons . He pres ents wi th genera l i zed l ympha denopa thy, fever, ni ght s wea ts , wei ght l os s , a bdomi na l pa i n, a nd tons i l l i ti s . The dos a ge of i mmunos uppres s i ve drugs gi ven to the pa ti ent i s decrea s ed, a nd the l ympha denopa thy regres s es . Whi ch of the fol l owi ng i s the bes t di a gnos i s for thi s pa ti ent? a . Burki tt l ymphoma b. Hodgki n l ymphoma c. Infecti ous mononucl eos i s d. Lymphoprol i fera ti ve di s order e. Na s opha ryngea l ca rci noma (NPC) 119. An i nfa nt i s born to a n HIV-pos i ti ve mother who di d not recei ve a nti -retrovi ra l thera py duri ng her pregna ncy. The mother’s HIV vi ra l l oa d, tes ted jus t before del i very, wa s 15,000 copi es /mL. Both mother a nd ba by tes ted pos i ti ve for HIV a nti bodi es by ra pi d tes ti ng. Si nce thi s i nfa nt i s a t ri s k of verti ca l tra ns mi s s i on of HIV from her mother, the pedi a tri ci a n deci ded to trea t her prophyl a cti ca l l y wi th a revers e tra ns cri pta s e i nhi bi tor. Whi ch of the fol l owi ng i s the mos t a ppropri a te choi ce for prophyl a xi s ? a . Aba ca vi r b. Lopi na vi r c. Nevi ra pi ne d. Ra l tegra vi r e. Zi dovudi ne 120. A 25-yea r-ol d woma n from Ea s t Texa s dona ted bl ood i n l a te Jul y. The next da y, s he ca l l ed the Bl ood Center reporti ng s udden ons et of fever, ma l a i s e, mya l gi a , a nd ba cka che. The s ta ff a t the Bl ood Center noti fi ed the woma n 3 da ys l a ter tha t her bl ood ha d tes ted pos i ti ve for a n a rthropodborne vi rus . Wi th whi ch vi rus wa s thi s young woma n i nfected? a . WNV b. St. Loui s encepha l i ti s vi rus c. Dengue vi rus d. HSV e. Coltivirus 121. A 25-yea r-ol d gra dua te s tudent pres ents to the l oca l cl i ni c wi th fever, ma l a i s e, l ympha denopa thy, a nd pha ryngi ti s . Hi s s pl een i s not enl a rged a nd a l though there i s a predomi na nce of l ymphocytes reported i n hi s peri phera l s mea r, the heterophi l e a nti body tes t i s nega ti ve. Wha t i s the mos t l i kel y eti ol ogy of thi s s tudent’s i nfecti on? a . Adenovi rus b. Cytomega l ovi rus c. Eps tei n–Ba rr vi rus d. Pa rvovi rus B19 e. Hepa ti ti s C vi rus (HCV)
122. A mi ddl e-a ged ma n wi th a l ong hi s tory of mul ti pl e opera ti ons a nd bl ood tra ns fus i ons wa s di a gnos ed wi th chroni c hepa ti ti s C. He wa s then trea ted wi th pegyl a ted i nterferon-α (IFN-α) a nd wei ght-dos ed ri ba vi ri n. How does IFN-α a ffect HCV? a . Bl ocks vi ra l envel ope fus i on wi th hos t cel l membra ne b. Di rectl y i nhi bi ts the vi ra l RNA pol ymera s e c. Induces the a nti vi ra l s ta te i n hos t cel l s to prevent HCV repl i ca ti on d. Inhi bi ts the vi ra l protea s e e. Interferes wi th gua nos i ne-dependent proces s es wi thi n the cel l 123. A 35-yea r-ol d ma n pres ents wi th s ymptoms of ja undi ce, ri ght upper qua dra nt pa i n, a nd vomi ti ng. Hi s ALT i s el eva ted. He i s di a gnos ed wi th HAV i nfecti on a fter ea ti ng a t a res ta ura nt where others were a l s o i nfected. Whi ch of the fol l owi ng s houl d be done to protect hi s 68-yea r-ol d fa ther a nd hi s 6-month-ol d s on? a . Admi ni s ter IFN-α to both b. Gi ve ea ch one dos e of γ-gl obul i n c. Immuni ze both wi th one dos e of hepa ti ti s A va cci ne d. Qua ra nti ne hous ehol d conta cts a nd obs erve e. No trea tment i s neces s a ry 124. A 42-yea r-ol d ma l e AIDS pa ti ent pres ented to the derma tol ogy cl i ni c for eva l ua ti on of s ki n l es i ons . He ha d numerous pl a que-l i ke l es i ons over hi s a rms , ches t, a nd neck. Ora l exa mi na ti on revea l ed the l es i on s hown i n the i ma ge on hi s pa l a te. Wha t i s the mos t l i kel y eti ol ogi c a gent of thes e l es i ons ?
(Courtesy of CDC/Sol Silverman Jr, DDS, University of California, San Francisco 1987; ID#6070.) a . Bartonella henselae b. Huma n herpes vi rus 8 c. HPV d. Huma n T-cel l l eukemi a vi rus e. Staphylococcus aureus 125. La tent i nfecti on of neurons occurs wi th whi ch of the fol l owi ng vi rus es ? a . Adenovi rus b. Eps tei n–Ba rr vi rus c. HSV d. Mea s l es vi rus e. Ra bi es vi rus 126. On November 6, a pa ti ent ha d the ons et of a n i l l nes s cha ra cteri zed by fever, chi l l s , hea da che, cough, a nd ches t pa i n. The i l l nes s l a s ted 1 week. On December 5, s he ha d a nother i l l nes s very s i mi l a r to the fi rs t, whi ch l a s ted 6 da ys . She ha d no i nfl uenza i mmuni za ti on duri ng thi s peri od. Her hema ggl uti na ti on i nhi bi ti on a nti body ti ters to nH1N1 i nfl uenza vi rus were a s fol l ows : November 6: 10
November 30: 10
December 20: 160
There wa s no l a bora tory error. Whi ch of the fol l owi ng i s the bes t concl us i on from thes e da ta ? a . The pa ti ent wa s i l l wi th i nfl uenza on November 6 b. The pa ti ent wa s i l l wi th i nfl uenza on December 5 c. The pa ti ent wa s i l l wi th i nfl uenza on December 20 d. It i s i mpos s i bl e to rel a te ei ther i l l nes s wi th the nH1N1 i nfl uenza vi rus 127. Recentl y, a new ds DNA nonenvel oped vi rus ha s been a s s oci a ted wi th a huma n ca ncer. The vi ra l genome wa s found to be i ntegra ted i nto the hos t chromos ome of cel l s i n a n a ggres s i ve s ki n ca ncer, Merkel cel l ca rci noma . To whi ch genus does thi s new vi rus bel ong?
a . Alphavirus b. Erythrovirus c. Orthohepadnavirus d. Polyomavirus e. Rotavirus 128. A touri s t who recentl y returned from a Ca ri bbea n crui s e s uddenl y devel ops fever, hea da che, pa i n behi nd her eyes , s evere joi nt, bone, a nd mus cl e pa i n, a nd a ma cul opa pul a r ra s h. The s hi p ha d ma de numerous s tops a t va ri ous i s l a nds to a l l ow expl ora tory tri ps . The touri s t reported s i gni fi ca nt encounter wi th mos qui toes a t one of the s tops . Whi ch of the fol l owi ng i s the mos t l i kel y di a gnos i s ? a . Dengue b. Hemorrha gi c fever wi th rena l s yndrome c. Hepa ti ti s C d. Rubel l a e. Yel l ow fever 129. A 30-yea r-ol d fema l e who ha d a hi s tory of s eri ous i l l nes s requi ri ng s urgery a nd i nfus i on of mul ti pl e bl ood products devel oped fever, na us ea , a nd ja undi ce. Her condi ti on ha s conti nued for 2 yea rs a s a cl i ni ca l l y mi l d di s ea s e wi th fl uctua ti ng l evel s of bi l i rubi n a nd l i ver enzymes . Recent bl ood chemi s try tes ti ng s howed her s erum a s pa rta te a mi notra ns fera s e (AST) to be 352 U/L, ALT 512 U/L, a nd tota l bi l i rubi n 4.5 mg/dL. Whi ch of the fol l owi ng bes t cha ra cteri zes the vi rus mos t l i kel y ca us i ng her i l l nes s ? a . DNA vi rus bel ongi ng to the Hepadnaviridae b. s s (+)RNA vi rus bel ongi ng to the Hepeviridae c. s s (+)RNA vi rus bel ongi ng to the Picornaviridae d. s s (+)RNA vi rus bel ongi ng to the Flaviviridae e. s s (-)RNA vi rus known a s Deltavirus 130. An IV-drug us er di s covered tha t a fri end wi th whom he s ha red needl es for i njecti ons wa s di a gnos ed wi th vi ra l hepa ti ti s . He ha d hi s bl ood dra wn a t the l oca l publ i c hea l th cl i ni c a nd tes ted for HBV. Whi ch of the fol l owi ng ma rkers i s us ua l l y the fi rs t vi ra l ma rker detected a fter i nfecti on wi th HBV? a . HBcAg b. HBeAg c. HBs Ag d. HBeAg IgG e. HBcAg IGM 131. A 55-yea r-ol d woma n who ha d i mmi gra ted 30 yea rs a go to the Uni ted Sta tes from Domi ni ca i n the Ca ri bbea n pres ented wi th cuta neous l es i ons a nd hepa tos pl enomega l y. She wa s hyperca l cemi c, ha d l ymphocytos i s , a nd bone l es i ons were demons tra ted on x-ra y. Peri phera l s mea r s howed cl overl ea f l ymphocytes , cons i s tent wi th a cute T-cel l l eukemi a (CD4+ l ymphocytes ), i n whi ch a provi rus wa s found. Whi ch vi rus i s mos t l i kel y res pons i bl e for her di s ea s e? a . HIV-1 b. HIV-2 c. HTLV-1 d. HTLV-2 132. A 19-yea r-ol d ma l e pres ented to hi s fa mi l y phys i ci a n compl a i ni ng of s evere pa i n i n hi s eye a nd i ntol era nce to l i ght. Hi s eye wa s red a nd tea ri ng. Ophtha l mi c vi s ua l i za ti on revea l ed coa l es ci ng dendri ti c ul cers i n hi s ri ght eye tha t were ea s i l y s een wi th fl uores cei n s ta i ni ng of the cornea . The pa ti ent s ta ted tha t he does not wea r conta ct l ens es , a nd tha t he ha d never ha d fever bl i s ters ; hi s mother to corrobora ted thi s . Wha t i s the mos t l i kel y eti ol ogi c a gent of hi s ul cer?
(Courtesy of HK Yang et al, Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea, 30 August 2012. Permission licensed under the Creative Commons Attribution 2.5 Generic license.)
a . Acanthamoeba b. Forei gn body c. Fusarium d. HSV type 1 e. Severe a l l ergy 133. Rea cti va ti on of VZV i s known to occur i n pers ons recei vi ng i mmunos uppres s i ve thera py. Whi ch of the fol l owi ng i s the bes t a nti vi ra l for trea ti ng thi s i nfecti on? a . Ama nta di ne b. Boceprevi r c. Ri ba vi ri n d. Va l a cycl ovi r e. Zi dovudi ne 134. An i nfa nt wi th mi crocepha l y, ja undi ce, a nd hepa tos pl enomega l y wa s a l s o s ma l l for ges ta ti on, a nd ha d thrombocytopeni a . Ra di ol ogy of the neona te’s hea d revea l ed i ntra cra ni a l ca l ci fi ca ti ons . Whi ch one of the fol l owi ng vi rus es mos t l i kel y ca us ed thes e congeni ta l ma l forma ti ons ? a . Rubel l a vi rus b. Res pi ra tory s yncyti a l vi rus c. HIV d. Mumps vi rus e. Cytomega l ovi rus 135. A 32-yea r-ol d woma n who ha d not recei ved the us ua l pedi a tri c va cci na ti ons devel oped fever, hea da che, ma l a i s e, a nd ea r pa i n a ccompa ni ed by s wel l i ng of the pa roti d gl a nds . One week l a ter, her fever s ubs i ded but s he devel oped pel vi c pa i n a nd tendernes s . Wi th whi ch vi rus wa s s he i nfected? a . Cytomega l ovi rus b. Mumps vi rus c. Ra bi es vi rus d. Res pi ra tory s yncyti a l vi rus e. Rubel l a vi rus 136. Worl dwi de 3 to 5 mi l l i on ca s es of s evere i nfl uenza i l l nes s es a nd 250,000 to 500,000 dea ths occur a nnua l l y. Grea t effort i s ma de a nnua l l y to prepa re i nfl uenza va cci nes a ga i ns t ci rcul a ti ng s tra i ns of Influenzavirus A a nd B. Yet, i n s ome yea rs , the va cci ne i s l es s effecti ve i n neutra l i zi ng the vi rus even though the ci rcul a ti ng s tra i ns a re the s a me type a s tha t from the previ ous yea r; tha t i s , both a re H1N1 or both a re H2N3. Whi ch of the fol l owi ng mecha ni s ms i s res pons i bl e for thi s probl em? a . Anti geni c dri ft b. Anti geni c s hi ft c. Compl ementa ti on d. Intra mol ecul a r recombi na ti on e. Phenotypi c mi xi ng 137. A vi s i tor from rura l Mexi co vi s i ted the Uni ted Sta tes a nd wa s a dmi tted to a hos pi ta l a fter bei ng di a gnos ed wi th proba bl e ra bi es . Whi ch of the fol l owi ng i s the bes t repres enta ti on of hi s prognos i s ? a . He s houl d s urvi ve wi thout compl i ca ti ons b. He s houl d s urvi ve but ha ve s ei zures for l i fe c. He ha s a 50% cha nce of s urvi va l i f a ggres s i ve thera py i s i ns ti tuted d. Ra bi es i s a l mos t i nva ri a bl y fa ta l 138. Al though va cci na ti on wi th l i ve, a ttenua ted, or ki l l ed vi ra l va cci nes ha s been the mos t effecti ve wa y of control l i ng vi ra l di s ea s e i n the popul a ti on, common col ds rema i n wi des prea d beca us e of the mul ti pl e s erotypes i denti fi ed. Whi ch of the fol l owi ng vi rus es repres ents thi s probl em? a . Cytomega l ovi rus b. Mumps vi rus c. Ra bi es vi rus d. Res pi ra tory s yncyti a l vi rus e. Rhi novi rus 139. A 3-yea r-ol d gi rl who wa s i n da y ca re pres ented wi th s udden ons et of fever, na us ea , vomi ti ng, a nd a norexi a . Her s cl era were yel l ow a nd her a bdomen wa s tender to pa l pa ti on. Bl ood chemi s tri es s howed a n AST of 640 U/L a nd ALT wa s 520 U/L. Previ ous l y, two other chi l dren ha d ha d s i mi l a r s ymptoms . Whi ch of the fol l owi ng tes ts woul d be mos t l i kel y to revea l the eti ol ogy of her hepa ti ti s ? a . Vi ra l cul ture of s tool b. Tes t for hepa ti ti s B s urfa ce a nti gen c. El ectron mi cros copy on s tool s peci men d. Detecti on of rota vi rus a nti gen e. Anti -HAV IgM 140. In Ja nua ry, two s chool di s tri cts s a w a s udden i ncrea s e i n a bs ences . At the s a me ti me, s a l es of over-the-counter medi ca ti ons for fever, cough, a nd col d s ymptoms i ncrea s ed dra ma ti ca l l y. To determi ne the eti ol ogy of thi s outbrea k of res pi ra tory i l l nes s , the publ i c hea l th depa rtment conducted a s urvey of l oca l phys i ci a ns to s ee wha t types of pa ti ents they were currentl y s eei ng mos t. The doctors a l l reported i ncrea s ed numbers of pa ti ents compl a i ni ng of a brupt ons et of hi gh fever, s evere hea da che, a nd mya l gi a fol l owed by s ore throa t, dry cough, wea knes s , a nd s evere
fa ti gue. The pa ti ents were i l l for 3 to 5 da ys , but ma ny reported pers i s tent ma l a i s e. Wha t i s the mos t l i kel y di a gnos i s for thi s outbrea k? a . Common col d b. Ha nd-foot-a nd-mouth di s ea s e c. Infl uenza d. Pha ryngi ti s e. Pneumoni a 141. A va cci ne a ga i ns t Morbillivirus (mea s l es vi rus ), i ntroduced i n 1963, ha s decrea s ed the i nci dence of mea s l es from a n expected event i n the l i fe of every chi l d to 50 to 200 ca s es per yea r i n the Uni ted Sta tes . Whi ch of the fol l owi ng bes t cha ra cteri zes the va cci ne tha t ha s dra ma ti ca l l y reduced the i nci dence of thi s di s ea s e i n the Uni ted Sta tes ? a . Ina cti va ted vi rus b. Li ve a ttenua ted vi rus c. Recombi na nt vi ra l protei n d. Vi rus -s peci fi c i mmunogl obul i n e. Wi l d-type l i ve vi rus 142. A newl ywed coupl e wa s s urpri s ed to fi nd tha t both experi enced geni ta l herpes l es i ons i n thei r fi rs t yea r of ma rri a ge. Both were gi ven a n a nti vi ra l tha t i s a cti va ted onl y i n i nfected cel l s . Whi ch of the fol l owi ng i s the vi ra l enzyme res pons i bl e for a cti va ti on of the drug of choi ce for thi s i nfecti on? a . DNA-dependent DNA pol ymera s e b. Integra s e c. Protea s e d. RNA-dependent RNA pol ymera s e e. Thymi di ne ki na s e 143. A neona te born to a woma n wi th chroni c hepa ti ti s B i nfecti on i s a t grea t ri s k of contra cti ng the vi rus a nd s ubs equentl y becomi ng a chroni c ca rri er of HBV. Whi ch of the fol l owi ng i s the bes t a pproa ch to preventi ng the neona te becomi ng i nfected? a . Gi ve hepa ti ti s B i mmunogl obul i n (HBIg) a t bi rth b. Gi ve HBIg a t 6 months , when ma terna l a nti bodi es ha ve di mi ni s hed c. Immuni ze wi th recombi na nt HBV va cci ne (rHBV) a t bi rth d. Immuni ze wi th rHBV a t 1 yea r e. Gi ve HBIg a nd i mmuni ze wi th rHBV va cci ne a t bi rth 144. Twenty da ys a fter conta ct wi th a n i ndi vi dua l wi th a n a cute di s ea s e pres enta ti on, a 12-yea r-ol d gi rl ha s fever (l ow gra de), ma l a i s e, a nd a ra s h compos ed of crops of ves i cl es tha t l a s ts 5 da ys . Thi s common chi l dhood di s ea s e i s ca us ed by whi ch of the fol l owi ng vi rus es ? a . Adenovi rus b. Cytomega l ovi rus c. HPV d. Mea s l es vi rus e. VZV 145. Over 400 mi l i ta ry recrui ts undergoi ng ba s i c tra i ni ng experi enced a n a cute res pi ra tory di s ea s e outbrea k i n thei r s econd month of ca mp. Mos t ha d hi gh fever a nd s ore throa ts wi th coughi ng; 27 devel oped pneumoni a , fi ve s evere enough to requi re i ntens i ve ca re, a nd one di ed. Whi ch of the fol l owi ng a gents i s the mos t l i kel y ca us e of thi s outbrea k? a . VZV b. Rota vi rus c. Pa pi l l oma vi rus d. Cytomega l ovi rus e. Adenovi rus 146. Whi ch of the fol l owi ng geneti c di s orders predi s pos es pa ti ents to wi des prea d HPV i nfecti on a nd cuta neous s qua mous cel l ca rci noma ? a . Epi dermodys pl a s i a verruci formi s b. Fa mi l i a l a denoma tous pol ypos i s c. Li –Fra umeni s yndrome d. NPC e. Xeroderma pi gmentos um 147. A 9-month-ol d gi rl , who ha s never been va cci na ted, pres ents wi th a 3-da y hi s tory of fever a nd wa tery, nonbl oody di a rrhea . On phys i ca l exa mi na ti on, s he a ppea rs dehydra ted. Whi ch of the fol l owi ng des cri bes the genome of the mos t l i kel y i nfecti ng orga ni s m? a . Doubl e-s tra nded DNA b. Si ngl e-s tra nded DNA c. Segmented s i ngl e-s tra nded mi nus -s ens e RNA d. Nons egmented s i ngl e-s tra nded pl us -s ens e RNA e. Segmented doubl e-s tra nded RNA 148. A 20-yea r-ol d col l ege footba l l pl a yer pres ented hi ms el f to the l oca l emergency medi ci ne depa rtment compl a i ni ng of hea da che, fever, a nd ma l a i s e for 2 weeks a nd now a s ore throa t. The phys i ci a n noted enl a rged l ymph nodes a nd hepa tos pl enomega l y. La bora tory tes ts found i ncrea s ed number of a typi ca l l ymphocytes a nd a rea cti ve heterophi l e a nti body tes t. The phys i ci a n a dvi s ed hi m not to pl a y footba l l unti l hi s s ymptoms ha d res ol ved. Wha t i s the bes t expl a na ti on for thi s a dvi ce?
a . To a vert hea t exha us ti on b. To a voi d rupture of hi s s pl een c. To prevent ma l nutri ti on d. To s ta ve off a n a pl a s ti c cri s i s 149. A huma ni ta ri a n hea l thca re worker depl oyed i n emergency to Da rfur, Suda n, forgot to us e i ns ect repel l a nt. Four da ys a fter bei ng bi tten s evera l ti mes by mos qui toes , he devel oped fever, chi l l s , hea da che, ba ck a che, a nd mus cl e a ches . Two da ys l a ter, he s uffered a nos ebl eed a nd noti ced hi s s tool s were bl a ck. The next da y, he wa s ja undi ced a nd vomi ted bl a ck ma teri a l . Des pi te s upporti ve ca re, he devel oped orga n fa i l ure a nd di ed. Wha t wa s the ca us e of thi s pa ti ent’s dea th? a . Dengue hemorrha gi c s hock b. Ha nta vi rus ca rdi opul mona ry s yndrome c. Hemorrha gi c fever wi th rena l s yndrome d. SARS e. Yel l ow fever 150. A pa ti ent who ha d not been va cci na ted a ga i ns t i nfl uenza ha s hem-a ggl uti na ti on i nhi bi ti on ti ters a ga i ns t i nfl uenza vi rus A a s fol l ows : a cute = 10, conva l es cent = 80. Whi ch of the fol l owi ng i s the correct concl us i on concerni ng thi s pa ti ent? a . No i nfecti on b. Pri ma ry i nfecti on c. Ana mnes ti c res pons e d. Pa s t i nfecti on 151. A 10-yea r-ol d boy i n a ma l a ri a l a rea of Afri ca wa s di a gnos ed wi th a poorl y di fferenti a ted B-cel l tumor of the ja w tha t wa s cha ra cteri zed by a tra ns l oca ti on of the c-myc oncogene, t(8:14). The boy a l s o ha s a n el eva ted a nti body ti ter to a s peci fi c vi ra l ea rl y a nti gen wi th a res tri cted pa ttern of fl uores cence. Thi s di s ea s e i s ca us ed by whi ch of the fol l owi ng? a . Borrelia burgdorferi b. Chlamydia trachomatis c. Cytomegalovirus d. Eps tei n–Ba rr vi rus e. HSV 152. A 55-yea r-ol d Chi nes e ma n i n s outhern Chi na s ought medi ca l hel p due to a s eri ous oti ti s medi a , whi ch wa s rel a ted to obs tructi on of hi s Eus ta chi a n tubes . Medi ca l exa mi na ti on a nd l a bora tory tes ti ng res ul ted i n a di a gnos i s of NPC. Whi ch of the fol l owi ng vi rus es ma y be detected by the PCR i n a va ri ety of cel l s of pa ti ents wi th thi s type of ca rci noma ? a . Eps tei n–Ba rr vi rus b. Mea s l es vi rus c. Mumps vi rus d. Pa rvovi rus B19 e. Rubel l a vi rus 153. A pa ti ent wi th HIV i nfecti on tha t ha s progres s ed to AIDS ha d been trea ted previ ous l y for cytomega l ovi rus pneumoni a . For whi ch a ddi ti ona l CMV di s ea s e woul d thi s pa ti ent a l s o be a t ri s k? a . Apl a s ti c cri s i s b. Ki dney fa i l ure c. Reti ni ti s d. Reye s yndrome e. SSPE 154. An es ti ma ted 6.2 mi l l i on new HPV i nfecti ons occur a nnua l l y i n the Uni ted Sta tes . The pea k i nci dence occurs i n a dol es cents a nd young a dul ts under 25 yea rs of a ge. Whi ch of the fol l owi ng s peci mens i s bes t for s creeni ng for the pres ence of HPV i nfecti on of the cervi x? a . DNA mol ecul a r probe for HPV genomes b. HPV-s peci fi c a nti bodi es c. Pa p s mea r on cel l s from cervi x for koi l ocytes d. PCR for HPV DNA e. Vi ra l cul ture for HPV 155. A bus i nes s ma n who contra cted dengue i n the Phi l i ppi nes duri ng a bus i nes s tri p i n 2011 took hi s fa mi l y to the Ca ri bbea n for a va ca ti on i n 2012. The enti re fa mi l y wa s pl a gued wi th mos qui to bi tes whi l e wa l ki ng ea rl y one morni ng. Four da ys l a ter, the ma n, hi s wi fe, a nd thei r 17-ol dda ughter experi enced s udden ons et of fever of 103 to 104°F, chi l l s a nd s evere hea d, ba ck, a nd mus cl e a ches . He ha d pa i n behi nd hi s eyes . Thei r 12-yea r-ol d s on ha d s i mi l a r s ymptoms but l es s ened i n i ntens i ty, whi l e thei r 6-yea r-ol d da ughter ha d fever tha t broke a nd returned a nd a ra s h. Thei r fevers l a s ted 3 to 4 da ys wi th ons et of ra s h i n a l l . Shortl y a fter thei r fevers s ubs i ded, the ma n a nd the 6-yea r-ol d devel oped a bdomi na l pa i n, petechi a e, a nd bl eedi ng gums . Wha t compl i ca ti on di d thi s ma n a nd chi l d devel op? a . Acute res pi ra tory di s tres s s yndrome b. Dengue hemorrha gi c fever c. Encepha l i ti s d. Gui l l a i n–Ba rré s yndrome e. Seconda ry ba cteri a l i nfecti on 156. A 16-yea r-ol d ma l e devel oped ches t pa i n a nd dys pnea , whi ch gra dua l l y wors ened. He wa s exa mi ned i n the Emergency Depa rtment where ta chyca rdi a a nd s i gns of hea rt fa i l ure were noted. El ectroca rdi ogra phi c cha nges were s een a nd ches t x-ra y revea l ed ca rdi omega l y. An enterovi rus
wa s i s ol a ted from a s tool s peci men. Whi ch of the fol l owi ng wa s the a gent mos t l i kel y i s ol a ted? a . Coxs a cki evi rus A b. Coxs a cki evi rus B c. Echovi rus 11 d. Enterovi rus 70 e. Pol i ovi rus 3 157. A 38-yea r-ol d woma n ha s devel oped crops of ves i cul a r l es i ons . After 3 da ys , s he devel oped pneumoni a a nd wa s hos pi ta l i zed. Whi ch of the fol l owi ng woul d be mos t l i kel y to be pres ent i n l ung cel l s obta i ned by bronchoa l veol a r bi ops y? a . Cowdry A i ncl us i on bodi es b. Gua rni eri bodi es c. Koi l ocytes d. Negri bodi es e. Owl ’s eye cel l s 158. A pa ti ent di a gnos ed wi th i nfl uenza reported ons et of s ymptoms 18 hours a go. Whi ch of the fol l owi ng i s the mos t a ppropri a te trea tment for thi s pa ti ent? a . Ama nta di ne b. Fos ca rnet c. Os el ta mi vi r d. Ri ba vi ri n e. Zi dovudi ne 159. A group of 15 young col l ege s tudents ha rves ted oys ters from a ba y nea r Ga l ves ton des pi te a wa rni ng s i gn tha t the a rea wa s conta mi na ted wi th s ewa ge. Ten a te the oys ters ra w. Twenty-fi ve da ys l a ter, s i x of them pres ented to thei r phys i ci a ns wi th s udden ons et of a cute ja undi ce a nd l i ver functi on a bnorma l i ti es . Whi ch of the fol l owi ng i s the mos t l i kel y ca us e of thei r i nfecti ons ? a . HAV b. HBV c. HCV d. HDV e. HEV 160. An 18-month ol d devel oped a cute ga s troenteri ti s wi th fever a nd wa tery di a rrhea tha t l a s ted 10 da ys . She ha d been va cci na ted a ga i ns t rota vi rus a t 2 a nd 4 months of a ge a s recommended. Ei ght da ys l a ter, both of her brothers , a ges 3 a nd 6, devel oped a cute ga s troenteri ti s . Whi ch of the fol l owi ng tes ts woul d mos t l i kel y revea l the eti ol ogi c a gent of thei r ga s troenteri ti s ? a . Cul ture for Norovirus b. DFA for enterovi rus on i ntes ti na l bi ops y c. EIA for a denovi rus 40/41 d. EM exa mi na ti on of s tool for a s trovi rus e. Serol ogy for Rotavirus 161. An outbrea k of di a rrhea i n a da y ca re center i s s us pected to be of rota vi ra l ori gi n. Whi ch tes t i s mos t a ppropri a te to di a gnos e thi s outbrea k? a . Cul ture b. EIA c. El ectron mi cros copy d. Hi s tol ogi c exa mi na ti on of bi ops y e. Serol ogy 162. Adul ts a nd chi l dren experi enced a n outbrea k of di a rrhea wi th na us ea a nd vomi ti ng whi l e a boa rd a crui s e s hi p i n the Ca ri bbea n. The ca us a ti ve a gent wa s detected by EIA tes ti ng. Whi ch vi rus l i s ted bel ow wa s mos t l i kel y res pons i bl e for thi s outbrea k? a . Adenovi rus 40/41 b. Astrovirus c. HAV d. Norovirus e. Rotavirus 163. An outbrea k of di a rrhea occurred a mong el derl y pa ti ents i n a n a s s i s ted ca re fa ci l i ty, whi ch ha d been repea tedl y ci ted by the publ i c hea l th depa rtment for poor hygi ene pra cti ces . The a gent tha t ca us ed the i nfecti ons ha d a s ta rl i ke morphol ogy i n el ectron mi crogra phs . EIA tes ts for s evera l a gents of vi ra l ga s troenteri ti s were nega ti ve. Whi ch vi rus wa s mos t l i kel y res pons i bl e for thi s outbrea k? a . Adenovi rus 40/41 b. Astrovirus c. HAV d. Norovirus e. Rotavirus 164. A young refugee from Afgha ni s ta n devel oped mi l d fever, cervi ca l l ympha denopa thy, a nd a ra s h tha t bega n on her fa ce a nd s prea d downwa rd over her trunk. After 3 da ys , the ra s h di s a ppea red. She ha d not been i mmuni zed a ga i ns t a ny i nfecti ons except di phtheri a a nd teta nus . Wha t i s the bes t di a gnos i s for thi s chi l d? a . Chi ckenpox
b. Erythema i nfecti os um c. Mea s l es d. Ha nd-foot-a nd-mouth di s ea s e e. Rubel l a 165. A 57-yea r-ol d ma n di a gnos ed previ ous l y wi th chroni c hepa ti ti s C i s bei ng trea ted for hi s i nfecti on. Whi ch of the fol l owi ng tes ts i s the bes t to eva l ua te hi s thera py for a n ea rl y vi rol ogi c res pons e? a . HCV IgG b. HCV IgM c. HCV RNA l evel d. Li ver bi ops y e. Serum ALT l evel s 166. A 45-yea r-ol d ma n wi th a cti ve chroni c hepa ti ti s B i nfecti on i s bei ng trea ted to reduce l i ver i nfl a mma ti on a nd fi bros i s a nd to prevent progres s i on to ci rrhos i s . He i s HBeAg-pos i ti ve a nd ha d begun a 48-week cours e of pegyl a ted IFN-α, but he wa s una bl e to tol era te the s i de effects . Whi ch of the fol l owi ng woul d be the bes t a nti vi ra l to trea t thi s pa ti ent? a . Acycl ovi r b. Fos ca rnet c. Ri ba vi ri n d. Tenofovi r e. Zi dovudi ne 167. Two weeks a fter a s eri es of mi d-Jul y thunders torms res ul ted i n a n expl os i on of the mos qui to popul a ti on, a 10-yea r-ol d boy l i vi ng on a fa rm i n s outhern Mi nnes ota wa s brought to the emergency room by hi s pa rents . He ha s a 2-da y hi s tory of fever, hea da che, a nd vomi ti ng, but toda y he a ppea red confus ed. Hi s cerebros pi na l fl ui d wa s cl ea r wi th 100 WBC (75% l ymphocytes ) a nd a hea d CT wa s norma l . Enterovi rus i nfecti on wa s qui ckl y rul ed out by PCR tes ti ng. Whi ch of the fol l owi ng i s the mos t l i kel y ca us e of hi s s ymptoms ? a . La Cros s e vi rus b. Pol i ovi rus c. Ra bi es vi rus d. St. Loui s encepha l i ti s vi rus e. Venezuel a n equi ne encepha l i ti s vi rus 168. Whi ch of the fol l owi ng woul d be pres ent i n a neona te wi th congeni ta l rubel l a s yndrome (CRS) but not i n a neona te wi th cytomega l i c i ncl us i on di s ea s e (congeni ta l CMV i nfecti on)? a . Intra uteri ne growth reta rda ti on b. Hepa tos pl enomega l y c. Menta l reta rda ti on d. Pa tent ductus a rteri os us e. Sens ori neura l hea ri ng l os s 169. Vi rus es ha ve va ri ous wa ys of enteri ng the huma n body a nd produci ng di s ea s e. Whi ch of the fol l owi ng des cri pti ons a ccura tel y des cri bes the route of tra ns mi s s i on a nd ta rget di s ea s e for the vi rus i ndi ca ted? a . Corona vi rus : feca l –ora l ; pepti c ul cers b. Echovi rus : feca l –ora l ; a s epti c meni ngi ti s c. HIV: res pi ra tory dropl et; a nemi a d. Infl uenza vi rus : bl ood-borne; ma cul opa pul a r ra s h e. Ra bi es vi rus : rodent-borne; pneumoni a 170. A 68-yea r-ol d ma n from centra l Ca l i forni a who l i ked to s i t i n the pa rk a nd doze devel oped fever, hea da che, mus cl e wea knes s , a nd na us ea a nd vomi ti ng. Hi s mus cl e wea knes s progres s ed, a nd he wa s a dmi tted to the hos pi ta l wi th a cute fl a cci d pa ra l ys i s . No foca l l es i ons were s een on MRI. After a prol onged hos pi ta l s ta y, he wa s di s cha rged to a reha bi l i ta ti on center where he rega i ned functi on. Wi th whi ch vi rus wa s thi s ma n mos t l i kel y i nfected? a . WNV b. St. Loui s encepha l i ti s vi rus c. Pol i ovi rus d. HSV e. Coltivirus 171. An i mmunocompromi s ed pa ti ent pres ented wi th a progres s i ve cerebra l deteri ora ti on evi denced by di ffi cul ty s pea ki ng, memory l os s , a nd l os s of coordi na ti on tha t l ed to pa ra l ys i s . An MRI revea l ed l es i ons i n the whi te ma tter; bra i n bi ops y revea l ed foci of demyel i na ti on, a s trocytos i s , a nd nucl ea r i ncl us i on bodi es wi thi n ol i godendrocytes . Norma l CSF fi ndi ngs (cel l count, gl ucos e, protei n) were pres ent, but vi ra l DNA wa s found i n the CSF by PCR. Whi ch of the fol l owi ng vi rus es ca us es i s the eti ol ogi c a gent of thi s pa ti ent’s di s ea s e? a . HPV b. JC pol yoma vi rus c. Pri on va ri a nt CJD d. Mea s l es vi rus e. WNV 172. An i rri ta bl e 18-month-ol d toddl er wi th fever a nd bl i s ter-l i ke ul cera ti ons on mucous membra nes of the ora l ca vi ty refus es to ea t (repres enta ti ve i ma ge, l eft). The s ymptoms wors en a nd then s l owl y res ol ve over a peri od of 2 weeks . Si x months l a ter, the chi l d devel ops a s i ngl e
ves i cul a r l es i on tha t res ol ves i n 6 da ys (repres enta ti ve i ma ge, ri ght); s he does not ha ve fever. Whi ch of the fol l owi ng s cena ri os i s mos t l i kel y?
(A: Courtesy of CDC/Robert E. Sumpter, 1987, ID#12616; B: Courtesy of CDC/Dr. Herrmann, 1964, ID#5434.) a . The vi rus wi l l rema i n l a tent i n the tri gemi na l ga ngl i a b. The ves i cul a r l es i ons wi l l not recur c. The chi l d wi l l devel op Gui l l a i n–Ba rré s yndrome d. The chi l d wi l l devel op hepa tocel l ul a r ca rci noma l a ter i n l i fe e. The chi l d wi l l devel op SSPE 173. A s exua l l y a cti ve 17-yea r-ol d ma n pres ents to the l oca l free cl i ni c to check s ome s ma l l pa pul es tha t a ppea red on hi s peni s . The pa pul es a re s ma l l , whi te l es i ons wi th a centra l depres s i on. There i s no di s cha rge or pa i n on uri na ti on. Wha t i s the vi rus mos t l i kel y ca us i ng thes e l es i ons ? a . Adenovi rus b. Coxs a cki evi rus A c. HPV type 6 d. Molluscipoxvirus e. Orf vi rus 174. A 3-month-ol d i nfa nt born a t prema turel y a t 30 weeks of ges ta ti on i s i n the neona ta l i ntens i ve ca re uni t i n November. The fi rs t ca s es of res pi ra tory s yncyti a l vi rus ha ve been di a gnos ed i n the ci ty. Whi ch of the fol l owi ng ma y be gi ven to thi s i nfa nt a s prophyl a xi s to prevent res pi ra tory s yncyti a l vi rus (RSV) i nfecti on? a . IFN-α b. Pa l i vi zuma b c. Pool ed i mmunogl obul i n d. Ri ba vi ri n e. Ri tuxi ma b 175. Ma l nouri s hed chi l dren a re a t ri s k for compl i ca ti ons of mea s l es , l ea di ng to grea ter morbi di ty a nd morta l i ty. Whi ch of the fol l owi ng s houl d be gi ven to chi l dren to reduce thes e ri s ks ?
a . Vi ta mi n A b. Vi ta mi n B c. Vi ta mi n C d. Vi ta mi n D e. Vi ta mi n E 176. Whi ch of the fol l owi ng i mmune res pons es i s requi red to prevent ta rget i nfecti on by pol i ovi rus , EEEV, a nd La Cros s e vi rus ? a . Compl ement a cti va ti on b. Cytotoxi c T cel l s s peci fi c for the vi rus c. Na tura l ki l l er cel l s d. Neutra l i zi ng IgG s peci fi c for the vi rus e. Neutrophi l s 177. A 45-yea r-ol d woma n l i vi ng i n Wa s hi ngton, DC, ha d been compl a i ni ng to her l a ndl ord a bout mi ce i n her a pa rtment. A week a go, s he s uffered fl u-l i ke s ymptoms a ccompa ni ed by s wol l en l ymph nodes a nd a ra s h, whi ch ha d res ol ved over 5 da ys . Four da ys l a ter, s he devel oped a s evere hea da che a nd other s i gns of vi ra l encepha l i ti s . She reported no conta ct wi th mos qui toes . Wi th whi ch vi rus wa s s he mos t l i kel y i nfected? a . La Cros s e vi rus b. La s s a fever vi rus c. Lymphocyti c chori omeni ngi ti s vi rus d. Si n Nombre ha nta vi rus e. Wes tern equi ne encepha l i ti s vi rus 178. An el derl y ma n ha d been i n s evera l mi l i ta ry confl i cts duri ng the ea rl y 1980s a nd recei ved bl ood tra ns fus i ons for i njuri es . He recentl y cons ul ted hi s phys i ci a n for wha t wa s di a gnos ed a s cryogl obul i nemi a a nd gl omerul onephri ti s . Addi ti ona l tes ti ng revea l ed tha t he wa s i nfected by a fl a vi vi rus whos e tra ns mi s s i on wa s bl oodborne. Whi ch of the fol l owi ng vi rus es wa s i nvol ved i n thi s i nfecti on? a . HAV b. HBV c. HCV d. HDV e. HEV 179. An outbrea k of i nfl uenza occurred i n a rura l communi ty. Si nce i nfl uenza ca n be trea ted i f thera py i s begun wi thi n 48 hours of ons et of s ymptoms , s peci fi c detecti on of the vi rus i s i mporta nt. Whi ch of the fol l owi ng tes ts l i s ted i s the mos t ra pi d for detecti on of i nfl uenza vi rus es ? a . Col d a ggl uti ni n tes t b. Cul ture of res pi ra tory s ecreti ons on monkey ki dney cel l s c. Detecti on of i nfl uenza a nti gen i n res pi ra tory s ecreti ons d. El ectron mi cros copy of s putum e. Pa i red s era for s peci fi c a nti body res pons e
Answers 64. The answer is d. (Levinson, Ch 39, 43, 45. Murray, Ch 62. Ryan, Ch 18.) Revers e tra ns cri pta s e (RT) PCR for HIV RNA (d) ha s recentl y been s hown to be the mos t va l ua bl e tes t for di a gnos i s of a cute HIV i nfecti on (a cute retrovi ra l s yndrome) duri ng the wi ndow peri od before a nti bodi es ca n be detected. Thi s qua l i ta ti ve tes t for detecti on of HIV vi ri ons i s pos i ti ve a t the ti me s ymptoms of a cute i nfecti on a ppea r, a s ea rl y a s 7 da ys pos ti nfecti on; the tes t i s a l s o pos i ti ve i n a s ymptoma ti c i ndi vi dua l s a nd i s us ed to s creen dona ted bl ood. The tes t for HIV p24 a nti gen (c) i s the next to become pos i ti ve, 17 to 38 da ys a fter i nfecti on. Anti bodi es a ppea r l a s t a t 21 to 42 da ys (3 to 6 weeks ) pos ti nfecti on. Whi l e there i s s ome di fference i n the ti me to pos i ti vi ty of the va ri ous types of HIV a nti body tes ts , the HIV a nti body tes t by ELISA (b) woul d be no more l i kel y to be pos i ti ve thi s ea rl y tha n the l a tex a ggrega ti on tes t. The wes tern bl ot for HIV a nti bodi es (e) i s us ed to confi rm pos i ti ve s creeni ng tes ts for a nti bodi es . The CD4 T-cel l count (a ) i s us ed to a s s es s s ta tus of the i mmune s ys tem, determi ne the ti mi ng for trea tment, s ugges t the l i kel i hood of ons et of va ri ous opportuni s ti c i nfecti ons , a nd moni tor progres s res pons e of the i mmune s ys tem to trea tment. The count i s unl i kel y to be decrea s ed a t 2 weeks pos ti nfecti on a l though a drop does coi nci de wi th the pea k of vi remi a . 65. The answer is b. (Levinson, Ch 38. Murray, Ch 53. Ryan, Ch 10.) Pa rvovi rus B19 (b) i s the ca us a ti ve a gent of erythema i nfecti os um (fi fth di s ea s e). The i nfecti on occurs i n two pha s es . Fi rs t i s the l yti c, i nfecti ous pha s e cha ra cteri zed by nons peci fi c fl ul i ke s ymptoms (fever, chi l l s , hea da che, a nd mya l gi a ) tha t l a s ts a bout a week. Thi s a ccompa ni ed by a decrea s e i n reti cul ocyte count a nd hemogl obi n, whi ch i s not us ua l l y noti ced i n hea l thy chi l dren a nd a dul ts . The s econd pha s e begi ns a week l a ter when vi rus -s peci fi c IgG a nti body a ppea rs a nd i ncl udes the cha ra cteri s ti c “s l a pped cheek” a ppea ra nce a nd l a cy reti cul a r ra s h. Adul ts often devel op pol ya rthropa thy or a rthra l gi a . The ra s h a nd a rthropa thy a re due to ci rcul a ti ng a nti gen–a nti body compl exes . The ra s hes of rubel l a vi rus (c) a nd rubeol a vi rus (mea s l es vi rus ) (d) occur i n conjuncti on wi th fever. The l es i ons produced by HSV1 (a ) a nd VZV (e) a re ves i cul a r i n na ture. 66. The answer is a. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Thi s pa ti ent ha s ei ther pri ma ry or recurrent HSV-2. Pri ma ry i nfecti ons a re a s ymptoma ti c i n 75% of pa ti ents ma ki ng thes e i nfecti ons res pons i bl e for the ma jori ty of the neona ta l HSV i nfecti ons . Women wi th recurrent i nfecti ons who ha ve a nti bodi es to HSV-2 a re l es s l i kel y to tra ns mi t HSV to thei r neona tes duri ng bi rth. Currentl y (2007), the Ameri ca n Col l ege of Obs tetri ci a ns a nd Gynecol ogi s ts recommend tha t ces a rea n del i very (a ) i s i ndi ca ted i n women wi th a cti ve geni ta l l es i ons a t ons et of l a bor (pa rturi ti on). Addi ti ona l l y, s uch women s houl d be offered a nti vi ra l thera py a t 36 weeks of ges ta ti on or beyond. Interna l feta l moni tori ng (b) a nd rupture of the membra nes to s peed del i very (c) s houl d not be done when a cti ve HSV l es i ons a re pres ent; a nd i f pos s i bl e, va gi na l del i very (d) s houl d be a voi ded. If thi s i s not pos s i bl e, the pedi a tri ci a n s houl d be noti fi ed rega rdi ng the mother’s a cti ve HSV. 67. The answer is b. (Guidelines for the Use of Antiretroviral Agents in HIV-1 Infected Adults and Adolescents. Katzung, Ch 49. Levinson, Ch 39, 43, 45. Murray, Ch 62. Ryan, Ch 18. Schneider E et al.) The i ma ge s hows a cute ora l ps eudomembra nous ca ndi di a s i s or thrus h, one of the opportuni s ti c i nfecti ons tha t occur i n pers ons wi th CD4 T-cel l counts between 200 a nd 500/µL. At CD4 counts l ower tha n 200/µL, Candida becomes chroni c a nd more i nva s i ve, extendi ng i nto the es opha gus . The Centers for Di s ea s e Preventi on a nd Control s trongl y recommends tha t a l l HIV-pos i ti ve i ndi vi dua l s be trea ted wi th hi ghl y a cti ve a nti vi ra l thera py (HAART), es peci a l l y when thei r CD4 T-cel l counts fa l l bel ow 350/mµL (http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5710a2.htm) or i f the pa ti ent i s pregna nt or ha s certa i n other concomi ta nt condi ti ons . The recommended regi mens for trea tmentna ïve i ndi vi dua l s i ncl udes two nucl eos i de revers e tra ns cri pta s e i nhi bi tors (NRTI) pl us one nonnucl eos i de RTI; or two NRTI pl us a ri tona vi r-boos ted protea s e i nhi bi tor (PI); or two NRTI pl us one i ntegra s e i nhi bi tor; a fi fth regi men cons i s ts of three NRTI. The combi na ti on of drugs works together to fores ta l l a ppea ra nce of res i s ta nce. The combi na ti on of efa vi renz pl us tenofovi r pl us emtri ci ta bi ne (b), one NNRTI pl us two NRTI, res pecti vel y, meets the recommenda ti ons . Aba ca vi r (a ), a NRTI tha t requi res HLA-B*5701 tes ti ng pri or to us e i f a t a l l pos s i bl e; nevi ra pi ne (e), a NNRTI; a nd da runa vi r boos ted wi th ri tona vi r (c), both PI, s houl d never be us ed a l one. Ma ra vi roc pl us enfuvi rti de pl us ra l tegra vi r (d), the CCR5 i nhi bi tor, fus i on i nhi bi tor, a nd i ntegra s e i nhi bi tor, res pecti vel y, a re us ed for s a l va ge thera py fol l owi ng vi rol ogi c fa i l ure or when res i s ta nce i s pres ent to ma ny NRTI, NNRTI, a nd PI; a l though not neces s a ri l y together. The di a gra m s hows the s i te of a cti on of the a va i l a bl e a nti retrovi ra l s .
Si tes of a cti on of a nti retrovi ra l drugs a nd the cl a s s es to whi ch they bel ong. (Prepared by Jane Colmer-Hamood in Microsoft PowerPoint.) 68. The answer is e. (Beckwith. Levinson, Ch 39, 43, 45. Murray, Ch 62. Ryan, Ch 18.) Pa ti ents often i mprove ra pi dl y on a ppropri a te HAART; thei r CD4 l ymphocyte counts i ncrea s e a nd thei r HIV vi ra l l oa ds a re dra s ti ca l l y reduced, often to l es s tha n 50 copi es per mi l l i l i ter. Thes e two cha nges a re i ndi ca ti ve of the fa ct tha t the a nti retrovi ra l thera py ha s been effecti ve (e). Whi l e her ri s k of contra cti ng s ome opportuni s ti c i nfecti ons , s uch a s es opha gi ti s ca us ed by Candida albicans or cytomega l ovi rus , Cryptococcus neofor-mans meni ngi ti s , Toxoplasma gondii encepha l i ti s , or Cryptosporidium parvum di a rrhea , ha s l es s ened, s he i s s ti l l a t ri s k for other opportuni s ti c i nfecti ons . Thes e i ncl ude pol yderma toma l VZV (s hi ngl es ), a cqui s i ti on or rea cti va ti on of Mycobacterium tuberculosis, ora l ha i ry l eukopl a ki a ca us ed by Eps tei n–Ba rr vi rus , a nd C. albicans pha ryngi ti s (thrus h), a s wel l a s recurrent ba cteri a l pneumoni a . Thus , choi ce (a ), the pa ti ent i s no l onger i n da nger of opportuni s ti c i nfecti ons , i s i ncorrect. Whi l e s he ma y ha ve a n excel l ent 5-yea r prognos i s (b), tha t ca nnot be s ta ted a t thi s ti me. The pa ti ent’s HIV s creeni ng tes t (c) s houl d rema i n pos i ti ve unti l l a te i n AIDS, when a nti body l evel s do drop off. The pa ti ent s ti l l ha s vi ra l RNA pres ent a nd mus t be cons i dered i nfecti ous , s o choi ce (d) i s i ncorrect; even i f her HIV RNA drops to undetecta bl e l evel s , s he coul d s ti l l ha rbor the vi rus wi thi n ma cropha ges , dendri ti c cel l s , or other cel l s wi thi n her body. 69. The answer is c. (Beckwith. Levinson, Ch 39, 43, 45. Murray, Ch 62. Ryan, Ch 18. Schneider.) Current cri teri a for HIV i nfecti on requi re a pos i ti ve res ul t from a n HIV a nti body s creeni ng tes t confi rmed by a pos i ti ve res ul t from a wes tern bl ot or i ndi rect i mmunofl uores cence a s s a y for HIV a nti bodi es ; or a pos i ti ve res ul t or report of a detecta bl e qua nti ty of HIV nucl ei c a ci d, HIV p24 a nti gen, or HIV i s ol a ti on (http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5710a1.htm). Then, a s s ta ted i n the revi s ed ca s e defi ni ti ons : “A confi rmed ca s e meets the l a bora tory cri teri a for di a gnos i s of HIV i nfecti on a nd one of the four HIV i nfecti on s ta ges (s ta ge 1, s ta ge 2, s ta ge 3, or s ta ge unknown).” The s ta ges a re outl i ned i n the ta bl e bel ow.
70. The answer is d. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) The pa ti ent ha s i nfecti ous mononucl eos i s (IM) ca us ed by Eps tei n–Ba rr vi rus (d); the key bei ng the pos i ti ve monos pot tes t (heterophi l e a nti body tes t). CMV (b) ca n a l s o ca us e a mononucl eos i s s yndrome, but the mono-s pot woul d be nega ti ve. In the ca s e of heterophi l e (monos pot)-nega ti ve IM, tes ts for a nti bodi es for CMV a nd for s peci fi c EBV protei ns (vi ra l ca ps i d a nti gen, ea rl y a nti gen, a nd nucl ea r a nti gen) s houl d be done. Not a l l pers ons devel op heterophi l e a nti bodi es , es peci a l l y chi l dren a nd ol der a dul ts ; a nd thes e a nti bodi es a re tra ns i ent. Adenovi rus (a ) i s more frequentl y a s s oci a ted wi th pha ryngoconjuncti vi ti s or pneumoni a ; echovi rus (c) wi th a s epti c meni ngi ti s ; a nd huma n meta pneumovi rus (e) wi th res pi ra tory i nfecti ons . The ma jori ty of i nfecti ons ca us ed by thes e three vi rus es occur i n chi l dren. 71. The answer is b. (Beckwith. Levinson, Ch 39, 43, 45. Murray, Ch 62. Ryan, Ch 18. Schneider.) Numerous tes ts a re now a va i l a bl e for screening pa ti ents for a nti bodi es to HIV i ncl udi ng ra pi d tes ts performed on bl ood, ora l s ecreti ons , a nd uri ne. The ra pi d tes ts a re EIAs a nd l a tex a ggrega ti on tes ts tha t do not ha ve to be repea ted, but tha t requi re a confi rma tory wes tern bl ot or i mmunofl uores cence a s s a y. Conventi ona l EIAs requi re repea t tes ti ng by the s a me tes t (b) fol l owed by a confi rma tory tes t i f the EIA i s repea tedl y rea cti ve. As s creeni ng tes ts , thes e a s s a ys ha ve a hi gh s ens i ti vi ty, whi ch mea ns tha t fa l s e-pos i ti ve res ul ts ma y occur. The wes tern bl ot a nd IFA ha ve hi gh s peci fi ci ti es a nd l ow fa l s e-pos i ti ve ra tes . Key here i s screening; di a gnos ti c tes ti ng i s di fferent beca us e the i ndex of s us pi ci on for HIV i s hi gh. In thi s s etti ng, a nega ti ve EIA s houl d be repea ted i n 3 months a nd/or a nucl ei c a ci d tes t be performed. The pa ti ent s houl d not be tol d s he i s even HIV-pos i ti ve, much l es s tha t s he i s l i kel y to devel op AIDS (d) unti l her pos i ti ve tes t i s confi rmed. There i s no rea s on to begi n a nti retrovi ra l thera py (a ) or to tes t the pa ti ent for Pneumocystis jiroveci i nfecti on (e); thi s i nfecti on a ppea rs i n HIV-i nfected pers ons when thei r CD4 T-cel l count drops bel ow 200/µL. 72. The answer is e. (Levinson, Ch 42, 43. Murray, Ch 60. Ryan, Ch 16.) The mos t common a rthropod-borne encepha l i ti s vi rus es ca us i ng neuroi nva s i ve di s ea s e i n the Uni ted Sta tes a re WNV (hundreds to thous a nds of ca s es of neuroi nva s i ve di s ea s e per yea r), La Cros s e vi rus (55-137 per yea r), St. Loui s encepha l i ti s vi rus (5-13 per yea r), a nd EEEV (4-12 ca s es per yea r). Whi l e La Cros s e vi rus i s a more common ca us e of neuroi nva s i ve di s ea s e tha n St. Loui s encepha l i ti s vi rus (e), SLEV (e) i s the mos t l i kel y to ha ve been res pons i bl e. La CV (d) ca us es neuroi nva s i ve di s ea s e a l mos t excl us i vel y i n chi l dren younger tha n 16 yea rs of a ge. See the bel ow ta bl e for more i nforma ti on.
73. The answer is a. (Levinson, Ch 44. Murray, Ch 64. Ryan, Ch 20.) Ra pi dl y progres s i ve dementi a a nd myocl onus a s s oci a ted wi th pres ence of 14-3-3 protei n i s s trongl y s ugges ti ve of Creutzfel dt–Ja kob di s ea s e, whi ch wa s confi rmed by the pres ence of s pongi form encepha l opa thy a t a utops y. CJD occurs i n four forms . Spora di c CJD (a ) ha s a medi a n a ge of ons et of 62 yea rs (60-74 for mos t, a l though ca s es a s young a s 17 ha ve been s een) a nd res ul ts from s ponta neous convers i on of norma l PrPC to PrPSC or s ponta neous muta ti on of the PRNP gene l ea di ng to producti on of PrPSC, the a bnorma l form; myocl onus i s a n i mporta nt component of s ymptoms ; dea th us ua l l y occurs wi thi n 8 months a fter ons et of s ymptoms . Fa mi l i a l CJD (b), a s s oci a ted wi th a n a utos oma l domi na nt i nheri ta nce of muta ti ons i n the PRNP gene, ons ets between 45 a nd 49 yea rs of a ge; progres s i on i s s l ower a nd dea th occurs i n a bout 2 yea rs . Va ri a nt CJD (d) i s a cqui red through ea ti ng mea t from ca ttl e wi th bovi ne s pongi form encepha l opa thy; the ma jori ty of reported ca s es ha ve been l i nked to expos ure i n the Uni ted Ki ngdom; a ge of ons et va ri es , but medi a n i s 28 yea rs of a ge; ps ychi a tri c a bnorma l i ti es a nd s ens ory s ymptoms a re predomi na nt i n va ri a nt CJD; dea th occurs i n a pproxi ma tel y 14 months . Ia trogeni c CJD (c) ha s occurred fol l owi ng cornea l tra ns pl a nts , dura gra fts , a dmi ni s tra ti on of huma n pi tui ta ry-deri ved gona dotropi ns , a nd us e of conta mi na ted s urgi ca l i ns truments a nd EEG el ectrodes ; i a trogeni c va ri a nt CJD ha s a l s o been documented from bl ood tra ns fus i on.
74. The answer is b. (Levinson, Ch 40. Murray, Ch 55. Ryan, Ch 15.) Whi l e rhi novi rus es a re the ma jor ca us e of the common col d (50%-80% of ca s es ), huma n corona vi rus es ca us e up to 15% of ca s es of common col d (b), es peci a l l y i n ol der chi l dren a nd a dul ts . The corona vi rus es ca us i ng s evere res pi ra tory i l l nes s ha ve been zoonoti c i n ori gi n; huma n corona vi rus es ra rel y ca us e pneumoni a (d). Corona vi rus -l i ke pa rti cl es ha ve been demons tra ted by EM i n s tool s of chi l dren a nd a dul ts wi th di a rrhea a nd neona tes wi th necroti zi ng enterocol i ti s . Huma n corona vi rus es ha ve not been a s s oci a ted wi th ves i cul a r l es i ons (e) or meni ngi ti s (c). Coxs a cki evi rus A ca us es herpa ngi na (b). 75. The answer is b. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) HDV, previ ous l y known a s the del ta a gent, wa s fi rs t des cri bed i n 1977 a nd ha s been s hown to be a s a tel l i te RNA vi rus tha t requi res HBs Ag for enca ps i da ti on. Thus , i t requi res the pres ence of repl i ca ti ng HBV. It i s found mos t often i n IV drug a bus ers a nd pers ons who ha ve recei ved mul ti pl e bl ood tra ns fus i ons . HDV ca n be a cqui red a s a coi nfecti on wi th HBV a nd fol l ows the progres s of the HBV i nfecti on. If HBV i s res ol ved, HDV i s a l s o res ol ved; i f HBV becomes chroni c, HDV a l s o pers i s ts . HDV ca n a l s o be a cqui red a s a s uperi nfecti on i n a pers on wi th chroni c HBV. In thes e i ndi vi dua l s , a n a cute hepa ti ti s epi s ode occurs tha t ma y progres s to ful mi na nt hepa ti ti s des cri bed i n the vi gnette. Thi s s i tua ti on s trongl y s ugges ts tha t the pa ti ent contra cted HDV (b). It i s unl i kel y tha t a HBV muta nt woul d devel op (a ). Ci rrhos i s (c) devel ops over yea rs a nd i s a chroni c proces s i nvol vi ng fi broti c cha nges i n the l i ver. It i s pos s i bl e tha t the pers on a cqui red HAV from food (d), but ful mi na nt hepa ti ti s i s not us ua l l y s een i n the Uni ted Sta tes except i n thos e over 50; even then, i t i s ra re (2% or l es s of a l l ca s es of HAV i nfecti on res ul t i n dea th). HEV i s found i n Mexi co, Indi a , pa rts of Chi na a nd s outhea s t As i a , a nd North Afri ca . Food i n the Uni ted Sta tes woul d be unl i kel y to conta i n HEV (e). 76. The answer is b. (Katzung, 49. Levinson, Ch 35. Murray, Ch 48. Ryan, Ch 8.) Both fos ca rnet (b) a nd ga nci cl ovi r (c) a re us ed to trea t cytomega l o-vi rus i nfecti on, but fos ca rnet i nhi bi ts pyrophos pha te bi ndi ng a cti vi ty of vi ra l DNA pol ymera s e whi l e ga nci cl ovi r i s a nucl eos i de a na l og tha t prevents el onga ti on of the DNA cha i n. Zi dovudi ne (e) i s a nucl eos i de a na l og tha t i nhi bi ts vi ra l revers e tra ns cri pta s es . Ama nta di ne (a ) bl ocks the M2 cha nnel of i nfl uenza vi rus A preventi ng rel ea s e of the nucl eoca ps i d i nto the cel l . Ri ba vi ri n (d) ta rgets the RNA-dependent RNA pol ymera s es of s evera l mi nus s ens e s s RNA vi rus es , es peci a l l y res pi ra tory s yncyti a l vi rus a nd La s s a fever vi rus . 77. The answer is b. (Levinson, Ch 40. Murray, Ch 54. Ryan, Ch 9, 12.) Echovi rus es were di s covered a cci denta l l y duri ng s tudi es on pol i omyel i ti s . On entry vi a i nges ti on or i nha l a ti on, echovi rus es (a nd other members of the Enterovirus genus ) repl i ca te i n the i ntes ti na l (c) a nd upper res pi ra tory (e) tra cts (pri ma ry repl i ca ti on s i tes ). They s prea d to the l ymphoi d ti s s ues (d) a nd repl i ca te there a s wel l (s econda ry repl i ca ti on s i te). From the pri ma ry a nd s econda ry repl i ca ti on s i tes , echovi rus es enter the bl oods trea m (a ) a nd a re di s s emi na ted to the CNS (b), the TARGET ti s s ue/orga n. Infecti on i n the i ntes ti na l tra ct i s us ua l l y s i l ent; vi ri ons a re s hed wi thout s ymptoms ; repl i ca ti on i n the upper res pi ra tory tra ct ma y produce s ymptoms of common col d. The TARGET di s ea s e i s a s epti c meni ngi ti s , des cri bed for thos e hos pi ta l i zed. The pres ence of s peci fi c IgA a nti body wi l l prevent i nfecti on or modul a te i t by reduci ng the numbers of vi rus es tha t ca n repl i ca te. The pres ence of s peci fi c IgG, ei ther a t the ti me of i nfecti on or pri or to di s s emi na ti on i n the bl oods trea m prevents i nfecti on of ta rget ti s s ue/orga n. 78. The answer is b. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) The pres enta ti on of ves i cul a r l es i ons i n mother a nd s evere di s ea s e i n the ba by s ugges ts congeni ta l herpes a cqui red i n utero. Ra pi d di a gnos i s a nd i ni ti a ti on of a nti vi ra l thera py wi th IV a cycl ovi r i s cri ti ca l for s urvi va l of the i nfa nt. Neona ta l herpes i s more frequentl y a cqui red duri ng or s hortl y a fter bi rth a nd ca n be ca tegori zed a s s ki n, eye, a nd mucous membra ne (SEM) di s ea s e a ppea ri ng 10 to 12 da ys a fter bi rth, di s s emi na ted i nfecti on a ppa rent wi thi n the fi rs t few da ys of l i fe, or CNS i nfecti on occurri ng a t 2 to 3 weeks of a ge. Recogni ti on a nd trea tment of neona ta l herpes s i mpl ex SEM i s i mporta nt a s wi thout trea tment, ma ny wi l l progres s to di s s emi na ted di s ea s e. When l es i ons a re pres ent, the mos t ra pi d tes t tha t a l l ows definitive i denti fi ca ti on i s the di rect i mmunofl uores cence a s s a y on cel l s from the l es i ons (b) i n whi ch s peci fi c a nti s era a ga i ns t HSV-1 a nd HSV-2 a re a ppl i ed to the cel l s ; the tes t ta kes a s l i ttl e a s 30 mi nutes . Vi ra l cul ture of the l es i ons (e) woul d a l s o be pos i ti ve, but ta kes 18 to 14 hours . Tza nck s mea r woul d l i kel y be pos i ti ve a s wel l , but the tes t onl y detects the pres ence of mul ti nucl ea ted gi a nt cel l s s ugges ti ve of huma n herpes vi rus i nfecti on. As the mother mos t l i kel y ha s a pri ma ry i nfecti on wi th HSV, s he i s unl i kel y to ha ve HSV-s peci fi c IgG a nti bodi es (a ); HSV-s peci fi c IgM a nti bodi es woul d not be tra ns ferred to the neona te. HSV PCR on cerebros pi na l fl ui d (c), whi ch ta kes s evera l hours , i s us ed to di a gnos i s s us pected HSV meni ngi ti s or encepha l i ti s a nd i s often referred to s peci a l ty l a bora tori es for tes ti ng. See bel ow for compa ri s on of di rect IFA for HSV (i n thi s ca s e HSV2, A) a nd the Tza nck s mea r (B).
Sta i ns for herpes s i mpl ex vi rus . (A) Di rect fl uores cence a s s a y on cel l s obta i ned from l es i on us i ng a nti body s peci fi c for HSV type 2. A compa ni on tes t wi th a nti -HSV type 1 wa s nega ti ve. (B) Tza nck s mea r on cel l s from l es i on s howi ng mul ti nucl ea te gi a nt cel l s typi ca l of s ome huma n herpes vi rus es (HSV1, HSV2, a nd VZV). (Courtesy of CDC and (A) Dr. Craig Lyerla, 1977, ID#3644 and (B) Joe Miller, 1975, ID#6508.) 79. The answer is b. (Levinson, Ch 40. Murray, Ch 54. Ryan, Ch 9, 12.) Coxs a cki evi rus A (b), a member of the Enterovirus genus , ca us es ha nd–foot–mouth di s ea s e i n young chi l dren, frequentl y i n outbrea ks a s s oci a ted wi th da y ca re centers or s chool s . Rhi novi rus es (e) a nd corona vi rus (a ) s tra i ns endemi c i n the Uni ted Sta tes ca us e common col ds ; orthoreovi rus es (c) a re res pons i bl e for a cute res pi ra tory a nd ga s troenteri ti s i nfecti ons . RSV (d) ca us es upper res pi ra tory tra ct i nfecti on i n chi l dren a nd s eri ous l ower res pi ra tory tra ct i nfecti on i n i nfa nts . 80. The answer is e. (Levinson, Ch 39, 46. Murray, Ch 56. Ryan, Ch 9, 10.) The mos t common compl i ca ti on of mumps vi rus i nfecti on i n pos tpuberta l ma l es i s orchi ti s (e), occurri ng i n a bout 33% to 50% of ca s es . Other compl i ca ti ons occur a t l ower frequenci es i ncl udi ng myoca rdi ti s (c), meni ngoencepha l i ti s , Gui l l a i n–Ba rré s yndrome (a ), ma s ti ti s , pneumoni a , thyroi di ti s , pa ncrea ti ti s , hea ri ng l os s , a nd i mmune thrombocytopeni a purpura , whi ch ma y be a s s oci a ted wi th hemorrha ge (b). Oophori ti s occurs i n a pproxi ma tel y 7% of pos tpuberta l fema l es . 81. The answer is f. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Thi s i s a cl a s s i c des cri pti on for a rea cti va ti on of va ri cel l a -zos ter vi ra l l a tent i nfecti on (f), known a s herpes zos ter or zos ter. The geogra phy of the l es i ons refl ects the pa rti cul a r derma tome fed by the i nfected ga ngl i on. Ma ny pri ma ry i nfecti ons wi th VZV a re s ubcl i ni ca l , yet s ti l l res ul t i n l a tent i nfecti ons i n s ens ory ga ngl i on nerve ti s s ue. Pri ma ry VZV i nfecti on (va ri cel l a or chi ckenpox) (e) i s us ua l l y mi l d, a nd ma ni fes ts a s crops of l es i ons a ppea ri ng fi rs t on the trunk a nd s prea di ng to fa ce a nd extremi ti es . HSV1 pri ma ry
i nfecti ons (a ) a re mos t often s ubcl i ni ca l but us ua l l y ma ni fes t a s s ca ttered l es i ons on l i ps a nd ora l mucos a when l es i ons a re pres ent. HSV1 rea cti va ti on (b) produces fewer l es i ons tha n on pri ma ry i nfecti on i n i mmuno-competent pers ons . EBV i nfecti on, whether pri ma ry (c) or rea cti va ti on (d), does not produce ves i cul a r l es i ons . Coxs a cki e A vi rus es a nd orthopoxvi rus es (va cci ni a vi rus , va ri ol a vi rus , a nd monkeypox vi rus ) ca us e ves i cul a r exa nthems but thes e woul d a ppea r more s i mi l a r to pri ma ry i nfecti on wi th HSV1 a nd VZV, res pecti vel y. 82. The answer is d. (Levinson, Ch 39, 46. Murray, Ch 56. Ryan, Ch 9, 10.) Mea s l es or rubeol a cha ra cteri zed by the prodrome of cough, coryza , conjuncti vi ti s , a nd photophobi a pl us the pa thognomoni c Kopl i k s pots i s ca us ed by mea s l es vi rus (Morbillivirus) (d). In i ndus tri a l i zed countri es , va cci na ti on ha s reduced the i mporta nce of thi s chi l dhood i nfecti on. The number of mea s l es ca s es occurri ng a nnua l l y ra nges from 50 to 200, wi th mos t a s s oci a ted wi th outbrea ks a mong groups tha t do not i mmuni ze thei r chi l dren. Adenovi rus (a ) ma y ca us e pha ryngoconjuncti vi ti s , a n upper res pi ra tory i nfecti on s i mi l a r to the mea s l es prodrome, but Kopl i k s pots a re not pres ent. HSV (b), i nfl uenza vi rus (c), a nd rubel l a vi rus (e) a re not a s s oci a ted wi th the des cri bed prodrome nor wi th Kopl i k s pots . 83. The answer is a. (Levinson, Ch 38, 43. Murray, Ch 49. Ryan, Ch 19.) HPVs ca us e nongeni ta l cuta neous a nd a nogeni ta l or mucos a l s yndromes . Mucos a l a nd a nogeni ta l s yndromes i ncl ude cervi ca l i ntra epi thel i a l neopl a s i a (CIN) a nd ca ncer; conjuncti va l , ora l , a nd l a ryngea l pa pi l l oma s , a nd a nogeni ta l wa rts or condyl oma a ccumi na tum. HPV types 16, 18, 31, a nd 45 a re hi gh-ri s k s tra i ns a s s oci a ted wi th CIN a nd ca ncer, a l though a ddi ti ona l types ha ve a l s o been found i n s uch l es i ons . HPV types 6 a nd 11 ca us e the ma jori ty of pa pi l l oma s a nd condyl oma a ccumi na tum. HPV i nfect the ba s a l kera ti nocytes of the epi thel i a l l a yer of s ki n a nd mucous membra nes . Expres s i on of vi ra l protei ns E5, E6, a nd E7 s ti mul a tes cel l growth a nd res ul ts i n thi ckeni ng of the l a yers . As the cel l s ma ture, genome repl i ca ti on ta kes pl a ce a nd ma ture vi ri ons a re rel ea s ed a t the epi thel i a l s urfa ce. The oncogeni c mecha ni s m of HPV i nvol ves i ntegra ti on of the vi ra l genome (a ) i nto the hos t chromos ome. Thi s res ul ts i n i na cti va ti on of genes requi red for vi ra l repl i ca ti on (d), whi ch does not occur i n thes e cel l s , a nd overexpres s i on of HPV E6 a nd E7 protei ns , whi ch bi nd p53 a nd p105RB cel l ul a r growth s uppres s or protei ns , a producti on of a cl one of repl i ca ti ng cel l s wi th pos s i bl e progres s i on to neopl a s i a . Los s of HPV E6 a nd E7 (b) woul d fores ta l l oncogeni c cha nges ; muta ti on of the vi rus (c) i s not pa rt of the proces s . 84. The answer is c. (Levinson, Ch 39, 44, 46. Murray, Ch 56. Ryan, Ch 9, 10.) Pa ra i nfl uenza vi rus es (genus Respirovirus) (c) a re i mporta nt ca us es of res pi ra tory di s ea s es i n i nfa nts a nd young chi l dren. The s pectrum of di s ea s e ca us ed by thes e vi rus es ra nges from a mi l d febri l e col d to l a ryngotra cheo-bronchi ti s (croup), a nd bronchi ti s i n young chi l dren a nd a dul ts to more s eri ous bronchi ol i ti s or pneumoni a i n i nfa nts . Adenovi rus (a ), Coxs a cki evi rus B (b), a nd rhi novi rus (d) ca us e upper res pi ra tory tra ct i nfecti ons tha t ra nge from mi l d (common col d) to s eri ous (pneumoni a , ARDS), but they do not ca us e croup. Rota vi rus (e) i s a ma jor ca us e of di a rrhea l i l l nes s i n i nfa nts . 85. The answer is c. (Andary. Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13. Weiner.) Recogni zed i n the 1980s , HEV, Hepevirus, i s a s s (+)RNA nonenvel oped vi rus pl a ced i n a new fa mi l y—Hepeviridae. The vi rus i s found i n Southea s t a nd Centra l As i a , Afri ca , North Ameri ca (Mexi co), South Ameri ca , a nd Aus tra l i a . Epi demi cs ha ve been obs erved i n As i a , Afri ca , Indi a , a nd Mexi co. Li ke HAV, i t i s enteri ca l l y tra ns mi tted, often by wa ter conta mi na ted wi th huma n feces . Epi demi cs frequentl y a ffect young a dul ts more tha n thos e of other a ges . The overa l l fa ta l i ty ra te i s 4%, but pregna nt women more frequentl y devel op ful mi na nt hepa ti c fa i l ure (c) a nd 20% di e from compl i ca ti ons . Chroni c hepa ti ti s (a ) does not occur i n norma l i ndi vi dua l s i n whom the i nfecti on res ol ves ; there i s a s s oci a ti on of HEV wi th chroni c hepa ti ti s i n pers ons who a l rea dy ha ve hepa ti ti s , l i ver tra ns pl a nta ti on, or who a re i mmunocompromi s ed i n humora l i mmune res pons es . Feta l hydrops (b) ma y occur i n women who a cqui re pa rvovi rus B19 i nfecti on duri ng pregna ncy; Gui l l a i n–Ba rré s yndrome (d) i s a cl us ter of cl i ni ca l s yndromes tha t i ncl ude a cute i nfl a mma tory demyel i na ti ng pol yra di cul oneuropa thy, a cute motor a xona l neuropa thy, a nd a cute motor-s ens ory a xona l neuropa thy tha t a re a s s oci a ted wi th a number of mi croorga ni s ms : Campylobacter jejuni, CMV, EBV, Mycoplasma pneumoniae, VZV, a nd HIV (http://emedicine.medscape.com/article/315632-overview#a0101; a cces s ed 02-08-2013). Reye s yndrome (e), a cute noni nfl a mma tory encepha l opa thy a nd fa tty degenera ti ve l i ver fa i l ure, occurs pri ma ri l y i n chi l dren a fter i l l nes s wi th i nfl uenza A or B vi rus or VZV, es peci a l l y i n conjuncti on wi th us e of a s pi ri n to reduce fever. Numerous other vi rus es a nd s ome ba cteri a ha ve a l s o been i mpl i ca ted. However, the i nci dence of Reye s yndrome ha s decl i ned wi th the decrea s e i n a s pi ri n us a ge i n chi l dren (http://emedicine.medscape.com/article/803683-overview#a0101; a cces s ed 02-08-2013). 86. The answer is d. (Levinson, Ch 40. Murray, Ch 54. Ryan, Ch 9, 12.) As epti c meni ngi ti s i s cha ra cteri zed by a pl eocytos i s of mononucl ea r cel l s , us ua l l y l ymphocytes , i n the CSF (d). Al though neutrophi l s ma y predomi na te duri ng the fi rs t 12 to 24 hours , a s hi ft to l ymphocytes occurs therea fter. The cel l count i n a s epti c meni ngi ti s i s us ua l l y between 50 a nd 1000/µL, i n contra s t to the neutrophi l i c pl eocytos i s (e) of ba cteri a l meni ngi ti s , whi ch i s us ua l l y grea ter tha n 1000/µL. The CSF pers ons wi th a s epti c i s free of cul tura bl e ba cteri a a nd conta i ns norma l gl ucos e (b) a nd norma l to s l i ghtl y el eva ted protei n l evel s (a ). Peri phera l whi te bl ood cel l counts us ua l l y a re norma l . Al though vi rus es a re the mos t common ca us e of a s epti c meni ngi ti s , s pi rochetes , chl a mydi a e, a nd other mi croorga ni s ms a l s o ca n produce the di s ea s e. Eos i nophi l i c pl eocytos i s (c) i s s een i n s ome pa ra s i ti c di s ea s es , s uch a s cys ti cercos i s , a nd i n di s s emi na ted Coccidioides immitis i nfecti on.
87. The answer is b. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) HDV ca n be a cqui red a s a coi nfecti on—HBV a nd HDV a cqui red a t the s a me ti me; or, a s a s uperi nfecti on—HDV a cqui red by a pers on wi th chroni c HBV i nfecti on. Di a gnos i s of HDV i nfecti on ma y be ma de by detecti on of del ta a nti gen, a nti -HDV IgM a nd/or IgG, or HDV RNA. Acute, chroni c, res ol ved, or i mmuni zed HBV s ta tus i s determi ned by a ba ttery of s erol ogi c tes ts . Superi nfecti on wi th HDV i s i ndi ca ted by pos i ti ve tes ts for HDV a nd the pres ence of a nti -HBcAg IgG but not IgM (b). Coi nfecti on wi th HDV woul d be
i ndi ca ted by the pres ence of a nti -HBcAg IgM but not IgG (a ).
88. The answer is d. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) HBs Ag i s pres ent i n mos t pa ti ents before s ymptoms a ppea r a nd rema i ns pos i ti ve duri ng the ea rl y a cute, a cute, a nd l a te a cute s ta ges of di s ea s e. Nea r, or s hortl y a fter, the ti me cl i ni ca l s ymptoms end HBs Ag ca n no l onger be detected i n pa ti ents who a re res ol vi ng thei r HBV i nfecti ons . However, a nti -HBs Ag ca nnot be detected i n thes e pa ti ents unti l a l mos t a month l a ter. The ti me (a fter the di s a ppea ra nce of HBs Ag a nd before the a ppea ra nce of a nti -HBs Ag) i s known a s the wi ndow peri od (d). Duri ng thi s ti me, di a gnos i s of a cute hepa ti ti s B i s ma de by detecti on of a nti -HBcAg IgM. The s ubs equent a ppea ra nce of a nti -HBs Ag i ndi ca tes res ol uti on of i nfecti on. Res ol ved hepa ti ti s B i nfecti on (b) i s i ndi ca ted by HBs Ag –, HBeAg –, Anti -HBcAg IgM –, Anti -HBcAg IgG +, Anti -HBs Ag +; chroni c hepa ti ti s B i nfecti on (c) i s i ndi ca ted by HBs Ag +, HBeAg +, Anti -HBcAg IgM -, Anti -HBcAg IgG +, Anti -HBs Ag; pers ons i mmuni zed a ga i ns t HBV (e) ha ve onl y a nti HBs Ag IgG. Hepa ti ti s s ymptoms i n the fa ce of nega ti ve tes ts for vi ra l eti ol ogy i ndi ca te a nother i nfecti ous a gent, toxi c i njury to the l i ver, or pos s i bl e di s ea s e of the bi l i a ry tra ct.
Gra phs compa ri ng s ymptoms , a nti gens , a nd a nti bodi es pres ent i n a cute hepa ti ti s B a nd chroni c hepa ti ti s B. 89. The answer is c. (Levinson, Ch 39, 42, 46. Murray, Ch 60. Ryan, Ch 10, 16.) Thi s pa ti ent ha s encepha l i ti s mos t l i kel y ca us ed by the EEEV. EEEV i s tra ns mi tted by mos qui toes (c) a nd i s us ua l l y s een i n the s ummer months . The vi rus i s found ma i nl y i n s ta tes on the Atl a nti c a nd Gul f coa s ts , wi th Fl ori da a nd Georgi a recordi ng the grea tes t number of ca s es . Whi l e the ma jori ty of thos e who contra ct EEEV a re a s ymptoma ti c, thos e over 60 a nd younger tha n 15 yea rs of a ge a re a t ri s k of devel opi ng Ea s tern equi ne encepha l i ti s , a s eri ous , ra pi dl y progres s i ng encepha l i ti s wi th a poor prognos i s . Bi rds (a ) a re the res ervoi r for EEEV. Fl ea s (b), s a nd fl i es (d), a nd ti cks (e) a re not vectors of EEEV. See the a ns wer to ques ti on 72 for a ddi ti ona l i nforma ti on. 90. The answer is b. (Levinson, Ch 40. Murray, Ch 54. Ryan, Ch 9, 12.) Rhi novi rus i s a ma jor ca us e of the common col d. The pri ma ry mode of tra ns mi s s i on i s di rect ha nd-to-ha nd conta ct (b), fol l owed by tra ns mi s s i on vi a fomi tes s uch a s ti s s ues , cl othi ng or utens i l s , fol l owed by res pi ra tory dropl et tra ns mi s s i on (c). Thes e nonenvel oped vi rus es ca n s urvi ve on unwa s hed ha nds a nd objects for ma ny hours . Tra ns mi s s i on by the feca l –ora l route (a ), s exua l conta ct (d), or verti ca l tra ns mi s s i on (e) do not occur wi th rhi novi rus es . 91. The answer is c. (Levinson, Ch 39, 44, 46. Murray, Ch 56. Ryan, Ch 9, 10.) The mos t l i kel y eti ol ogi c a gent of thi s i nfa nt’s pneumoni a i s the huma n meta pneumovi rus (c), a member of the Paramyxoviridae cl os el y rel a ted to but di s ti nct from res pi ra tory s yncyti a l vi rus . Di s covered i n 2001, thi s vi rus i s now known to be res pons i bl e for 5% to 15% of s eri ous l ower res pi ra tory tra ct i nfecti ons i n young chi l dren. As wi th RSV, i nfa nts born prema turel y a nd thos e wi th preexi s ti ng l ung or hea rt di s ea s e or i mmunocompromi s a ti on a re a t grea ter ri s k for s eri ous i nfecti on wi th hMPV. Cytomega l ovi rus (a ) a nd HSV type 1 (b) ma y ca us e pneumoni a i n i mmunocompromi s ed i nfa nts , but the pres enta ti on woul d be di fferent. Pa rvovi rus B19 (d) does not ca us e pneumoni a , a nd onl y occa s i ona l s tra i ns of rhi novi rus (e) ma y ca us e pneumoni a a s mos t s tra i ns prefer to grow a t the much l ower tempera tures found i n the na s a l pa s s a ges . 92. The answer is e. (Levinson, Ch 46. Murray, Ch 58. Ryan, Ch 16.) The bes t s peci men for di a gnos i s of ra bi es i n the l i vi ng pa ti ent i s a bi ops y of s ki n a t
the ba ck of the neck (nucha l bi ops y). The fi ndi ng of Negri bodi es on H&E s ta i n i s pa thognomoni c for ra bi es vi rus (e); a pos i ti ve s ta i ni ng rea cti on wi th ra bi es -s peci fi c a nti bodi es confi rms the di a gnos i s . Negri bodi es a re eos i nophi l i c cytopl a s mi c i ncl us i on bodi es found wi thi n i nfected neurons i n the hi ppoca mpus a nd cerebra l cortex or i n s ki n cel l s . The vi gnette des cri bes the fi rs t pha s e of ra bi es , or entry i nto the CNS, whi ch l a s ts from 2 to 10 da ys . Thi s i s fol l owed by a cute ra bi es , whi ch ca n be pa ra l yti c or furi ous , a nd a l mos t i nva ri a bl y l ea ds to dea th. EEEV (b) a nd echovi rus (c) do not produce s peci fi c i ncl us i on bodi es . HSV type 1 (d) produces eos i nophi l i c Cowdry A i ncl us i on bodi es wi thi n the nucl eus of i nfected cel l s . Cytomega l ovi rus (a ) produces ba s ophi l i c nucl ea r i ncl us i on bodi es tha t res embl e owl eyes . Negri bodi es of ra bi es vi rus (A), Cowdry A i ncl us i on of HSV (B), a nd owl eye i ncl us i on of CMV (C) a re compa red bel ow.
Compa ri s on of vi ra l i ncl us i on bodi es . Cytopl a s mi c Negri bodi es of ra bi es vi rus (A), nucl ea r Cowdry A i ncl us i ons of HSV (B), a nd nucl ea r owl -eye i ncl us i ons of CMV (C). 93. The answer is d. (Levinson, Ch 44. Murray, Ch 64. Ryan, Ch 20.) Kuru a nd CJD a re s i mi l a r but not i denti ca l di s ea s es wi th very di fferent epi demi ol ogy. Kuru wa s preva l ent a mong certa i n tri bes i n New Gui nea who pra cti ced ri tua l ca nni ba l i s m by ea ti ng the bra i ns of the depa rted. CJD i s found worl dwi de i n fa mi l i a l a nd s pora di c forms a nd ha s been tra ns mi tted by cornea l tra ns pl a nts a nd i n pi tui ta ry hormone prepa ra ti ons (i a trogeni c CJD). An i nfecti ous form—va ri a nt CJD—i s a s s oci a ted wi th ea ti ng ca ttl e wi th bovi ne s pongi form encepha l opa thy; ca s es ha ve occurred pri ma ri l y i n Engl a nd. Pri ons a re unconventi ona l s el f-repl i ca ti ng protei ns , s ometi mes ca l l ed amyloid. It i s now thought tha t CJD, Kuru, a nd a ni ma l di s ea s es s uch a s s cra pi e, vi s na , a nd bovi ne s pongi form encepha l opa thy (ma d cow di s ea s e) a re ca us ed by pri ons . Pri ons do not conta i n DNA or RNA. Ba cteri a , fl a gel l a tes (pa ra s i tes ), a nd vi rus es a l l conta i n nucl ei c a ci d genomes . No a ppa rent evi dence of envi ronmenta l toxi ns a bl e to ca us e Kuru/CJD ha ve been reported. 94. The answer is d. (Levinson, Ch 37. Murray, Ch 52. Ryan, Ch 11.) The des cri pti on of the vi rus genome (ds DNA) a nd s i te of repl i ca ti on (cytopl a s m) a re cha ra cteri s ti c of poxvi rus es ; va cci ni a vi rus (d) i s the i mmuni zi ng a gent a ga i ns t va ri ol a vi rus (e). Adenovi rus type 5 (a ) i s a ds DNA vi rus tha t repl i ca tes i n the nucl eus ; i t ca us es res pi ra tory i nfecti ons . Ra bi es vi rus (c) a nd echovi rus 11 (b) a re s s (-)RNA a nd s s (+)RNA vi rus es , res pecti vel y; they do repl i ca te i n the cytopl a s m. None of thes e l a tter three vi rus es ca us e s ki n l es i ons l i ke thos e s hown i n the i ma ge for ques ti on 94. Routi ne va cci na ti on of the genera l publ i c wi th va cci ni a vi rus to prevent s ma l l pox ha s been di s conti nued i n the Uni ted Sta tes , a s the ri s k of contra cti ng the di s ea s e i s ni l (va ri ol a vi rus i s exti nct i n the worl d) a nd beca us e the compl i ca ti ons of i mmuni za ti on wi th va cci ni a vi rus , i ncl udi ng genera l i zed va cci ni a , va cci ni a necros um (progres s i ve i nfecti on), a nd encepha l i ti s , a re s eri ous a nd ca n be fa ta l . The va cci ne i s s ti l l us ed wi thi n the mi l i ta ry due to concerns over the us e of va ri ol a vi rus (ma i nta i ned a s frozen s tocks i n the Uni ted Sta tes a nd other countri es ) a s a bi owea pon. Va cci na ti on of mi l i ta ry pers onnel a nd fi rs t res ponders i n 2001 s howed tha t the ri s k of compl i ca ti ons from va cci ni a vi rus i mmuni za ti on s ti l l exi s ts , a nd tha t the vi rus ca n be s prea d from the reci pi ent to members of the hous ehol d. However, the us e of va cci ni a vi rus a s a vector to ca rry the gene for the ra bi es gl ycoprotei n ha s become common. The vector i s pa cka ged i n ba i ts des i gned to be ea ten by ra ccoons a nd other s ma l l ma mma l s tha t a re known tra ns mi t ra bi es vi rus . Expos ure to the va cci ni a vi rus wi thi n the ba i t ca n l ea d to i nfecti on i n huma ns , es peci a l l y i n i mmunocompromi s ed i ndi vi dua l s . 95. The answer is d. (Levinson, Ch 46. Murray, Ch 58. Ryan, Ch 16.) Ra bi es i s ca us ed by a rha bdovi rus , a mi nus -s ens e, s i ngl e-s tra nded, nons egmented RNA vi rus wi th a n envel oped, bul l et-s ha ped vi ri on). The vi rus i nfects a wi de ra nge of wa rm-bl ooded a ni ma l s , i ncl udi ng huma ns . The vi rus i s wi del y di s s emi na ted wi thi n the i nfected a ni ma l s , wi th hi gh l evel s i n s a l i va . If the a ni ma l i s ca ptured or ki l l ed, exa mi na ti on of i ts bra i n for ra bi es vi rus ca n be done i n ti me to determi ne whether ra bi es prophyl a xi s i s neces s a ry. The bes t mea ns to prevent ra bi es begi ns wi th s crupul ous wound ca re, i ncl udi ng wa s hi ng a nd probi ng for a ny forei gn bodi es (eg, broken teeth) i n the wound. If the a ni ma l i s not a va i l a bl e, or tes ts pos i ti ve for ra bi es , a nd i f the pers on ha s not been i mmuni zed wi th ra bi es va cci ne, the trea tment of choi ce i s to gi ve huma n ra bi es i mmunogl obul i n (HRIg) pl us ra bi es va cci ne a t s epa ra te s i tes (d). The HRIg s houl d be i nfus ed i nto the wound a nd the rema i nder gi ven a s a deep IM i njecti on. After ons et of s ymptoms , nei ther of thes e s houl d be gi ven. Broa d-s pectrum a nti bi oti cs (a ) ma y be gi ven a s pa rt of wound ca re to prevent ba cteri a l i nfecti on, but they wi l l not prevent ra bi es . Acycl ovi r (b) a nd ri ba vi ri n (c), rega rdl es s of dos a ge or route of a dmi ni s tra ti on, ha ve no rol e i n ra bi es prophyl a xi s . Teta nus i mmune gl obul i n a nd/or teta nus toxoi d va cci ne (e) ma y a l s o be pa rt of the wound ca re regi men, but a re gi ven to prevent teta nus , not ra bi es . 96. The answer is a. (Levinson, Ch 38. Murray, Ch 50. Ryan, Ch 9, 15.) Mi l d ocul a r i nvol vement often occurs a s pa rt of the res pi ra tory s yndromes ca us ed by a denovi rus es . Adenovi rus (a ) a l s o ca n ca us e s evere kera ti ti s tha t ca n l ea d to perma nent eye da ma ge. Thes e i nfecti ons ma y occur i n outbrea ks i n i ndus tri a l , hos pi ta l , or cl i ni c s etti ngs through expos ure of groups of workers /pa ti ents to conta mi na ted fomi tes . The workers i nvol ved i n thi s cl us ter of i nfecti ons ha d s ha red eye drops due to the dus ty envi ronment i n whi ch they were worki ng. EBV (b), pa rvovi rus (c), RSV (d), a nd VZV (e) a re not routi nel y reported a s ca us i ng thi s type of i l l nes s . HSV-1, whi ch wa s not a mong the choi ces , ca n ca us e kera toconjuncti vi ti s a nd kera ti ti s . Dendri ti c or coa l es ci ng (geogra phi c) ul cers ca n be vi s ua l i zed i n HSV-1 kera ti ti s . 97. The answer is b. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) As ca n be s een i n the fi gure found i n the a ns wer to Ques ti on 88, HBs Ag a nd i nfecti ous vi ri ons a re s hed over the s a me cours e of ti me, wi th HBeAg a ppea ri ng i n the bl oods trea m a t the hei ght of vi ra l repl i ca ti on. Thus , the pres ence of HBeAg i ndi ca tes the i ndi vi dua l i s hi ghl y conta gi ous (b). Al though HBs Ag ca n be s hed a fter i nfecti ous vi ri ons a re no l onger bei ng produced, the
pa ti ent i s s ti l l cons i dered conta gi ous , but to a l es s er degree (c) tha n when HBeAg i s pres ent. The pers on i s cons i dered i nfecti ous a s l ong a s HBs Ag pers i s ts , s o a ns wers d (not conta gi ous ) a nd e (res ol ved) a re i ncorrect. The i nci dence of fa l s e-pos i ti ve res ul ts for HBeAg i s l ow (a ), wi th s peci fi ci ti es ra ngi ng from 98.6% to 99% reported, dependi ng on the product us ed. 98. The answer is d. (Levinson, Ch 39, 42, 46. Murray, Ch 60. Ryan, Ch 10, 16.) Wes tern equi ne encepha l i ti s vi rus (d) i s the onl y vi rus on the l i s t l i kel y to ca us e encepha l i ti s i n a n i nfa nt. It i s a l s o found ma i nl y wes t of the Mi s s i s s i ppi Ri ver; s ta tes wi th the hi ghes t number of reported ca s es i ncl ude Col ora do, Texa s , North Da kota , a nd Ca l i forni a . Rubel l a vi rus (c) ca n ca us e encepha l i ti s , but thi s vi rus i s extremel y uncommon i n the Uni ted Sta tes beca us e of the s ucces s ful va cci ne devel oped to prevent rubel l a . WNV (e) i s more l i kel y to ca us e meni ngi ti s i n a chi l d a nd encepha l i ti s i n a pers on over 60. Dengue vi rus (a ) i nfecti on ra rel y l ea ds to encepha l i ti s . Lymphocyti c chori omeni ngi ti s vi rus (b) i s rodent-borne ra ther tha n a rthropod-borne. See the ta bl e a ccompa nyi ng the a ns wer to ques ti on 72. Note, a ccordi ng to the Centers for Di s ea s e Preventi on a nd Control , WEEV a cti vi ty ha s been a bs ent from the Uni ted Sta tes for the pa s t 5 yea rs . 99. The answer is e. (Levinson, Ch 39, 44, 46. Murray, Ch 56. Ryan, Ch 9, 10.) Ri ba vi ri n, a gua nos i ne a na l og, i s a pproved for a eros ol trea tment of res pi ra tory s yncyti a l vi rus i nfecti ons (e) i n prema ture or i mmunocom-promi s ed i nfa nts who a re l i kel y to ha ve a more s evere cl i ni ca l cours e. Currentl y, a eros ol trea tment of chi l dren i s no l onger s ta nda rd trea tment. Ri ba vi ri n i s a pproved for ora l trea tment of HCV i nfecti on (i n combi na ti on wi th IFN-α) a nd for IV trea tment of La s s a fever a nd other vi ra l hemorrha gi c fevers . It i s not us ed for trea tment of Coxs a cki evi rus A (a ), HBV (b), HSV (c), or pa rvovi rus (d) i nfecti ons . 100. The answer is c. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) HSV type 1 (c) encepha l i ti s (HSE), whi ch us ua l l y i nvol ves the tempora l l obe, i s the mos t common ca us e of s pora di c (nonepi demi c) encepha l i ti s a nd i s often l etha l . Severe neurol ogi c s equel a e a re s een i n s urvi vi ng pa ti ents . Mos t HSE ca s es occur i n a dul ts over 50, but a fi rs t pea k of i nfecti ons occurs i n thos e younger tha n 20 yea rs of a ge. PCR a mpl i fi ca ti on of vi ra l DNA from CSF ha s repl a ced vi ra l i s ol a ti on. Coxs a cki evi rus B (a nd A) s tra i ns (b) ca us e a s epti c meni ngi ti s , a s wel l a s other condi ti ons . Adenovi rus es (a ) a re pri ma ri l y known for ca us i ng pha ryngoconjuncti vi ti s i n chi l dren; they ra rel y ca us e encepha l i ti s . Listeria monocytogenes i s a ba cteri um tha t ca n ca us e meni ngoencepha l i ti s pri ma ri l y i n i mmunocompromi s ed pa ti ents ; i t i nfects the bra i n pa renchyma , es peci a l l y the bra i ns tem. WNV (e) ca us es encepha l i ti s a s s oci a ted wi th mos qui to tra ns mi s s i on, s o i t i s more common i n s ummer a nd ea rl y fa l l . Loca l i zed l es i ons a re not s een wi th Wes t Ni l e encepha l i ti s . 101. The answer is d. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Ros eol a i nfa ntum ca us ed by huma n herpes vi rus 6 (d) l ea ds to s ei zures i n 15% of s ymptoma ti c i nfa nts . In hea l thy i nfa nts , the i nfecti on i s a s ymptoma ti c or fol l ows the cours e des cri bed i n the vi gnette. In i mmunocompromi s ed chi l dren, the a brupt ons et i ncl udes CNS a nd other orga n s ys tem i nvol vement. Fol l owi ng i nfecti on, the vi rus rema i ns l a tent i n l ymphocytes a nd monocytes . Infecti on i n a dul ts or rea cti va ti on i n a dul thood ma y produce a mononucl eos i s -l i ke s yndrome wi th l ympha denopa thy a nd hepa ti ti s . In i mmunocompromi s ed pa ti ents s uch a s bone ma rrow, ki dney, a nd l i ver tra ns pl a nt pa ti ents , much more s eri ous i nfecti ons /rea cti va ti ons occur tha t ma y l ea d to orga n rejecti on a nd dea th. Erythema i nfecti os um (a ), ha nd-food-a nd-mouth di s ea s e (b), mea s l es (c), a nd rubel l a (d) (ca us ed by the vi rus es i ndi ca ted i n the choi ces ) ea ch pres ent di fferentl y: “s l a pped cheek” reti cul a r ra s h 7 to 10 da ys fol l owi ng a nons peci fi c prodrome; ves i cl es a ppea ri ng on the ha nds , a nd di s s emi na ted ma cul opa pul a r ra s hes begi nni ng on the neck, res pecti vel y. 102. The answer is d. (Levinson, Ch 39, 44, 46. Murray, Ch 56. Ryan, Ch 9, 10.) The vi gnette des cri bes a n i nfa nt wi th s evere bronchi ol i ti s ca us ed by res pi ra tory s yncyti a l vi rus (Pneumovirus) (d). RSV i s the mos t common ca us e of bronchi ol i ti s a nd pneumoni a i n i nfa nts l es s tha n 1 yea r of a ge. The i nfecti on i s l oca l i zed to the res pi ra tory tra ct. The vi rus ca n be detected ra pi dl y by i mmunofl uores cence on res pi ra tory epi thel i a cel l s obta i ned by na s opha ryngea l s ucti on. In ol der chi l dren, the i nfecti on res embl es the common col d. Adenovi rus (a ) a nd cytomega l ovi rus (b) ca n ca us e pneumoni a i n i nfa nts , but the pres enta ti on does not us ua l l y i ncl ude bronchi ol i ti s . Pa ra i nfl uenza vi rus (Respirovirus) (c) i nfecti on ma y pres ent a s bronchi ol i ti s , but i t i s l es s common tha n RSV, es peci a l l y i n wi nter. Rhi novi rus (e) ra rel y ca us es pneumoni a a s mos t s tra i ns ca nnot repl i ca te a t core body tempera ture. 103. The answer is a. (Levinson, Ch 39, 43, 45. Murray, Ch 62. Ryan, Ch 18.) The ri s k of a cqui ri ng HIV i nfecti on i s i ncrea s ed i n pers ons who ha ve mul ti pl e s exua l pa rtners , es peci a l l y s exua l pa rtners who i nject drugs us i ng s ha red needl es (a ). Hos pi ta l recepti oni s ts (b), members of a hous ehol d i n whi ch there i s a pers on who i s HIV-pos i ti ve (d), a nd fa ctory workers wi th HIV-pos i ti ve coworkers (e) ha ve l i ttl e to no ri s k for contra cti ng HIV i n thei r norma l a nd us ua l i ntera cti ons wi th peopl e a round them. The ri s k of HIV a cqui red through bl ood products bega n droppi ng i n 1985 wi th the devel opment of tes ts for HIV p24 a nti gen a nd HIV a nti bodi es . Si nce the a dvent of nucl ei c a ci d a mpl i fi ca ti on tes ti ng for HIV, the ri s k for a cqui ri ng HIV through bl ood or bl ood products (i n the Uni ted Sta tes ) ha s dropped further to 1/1,000,000 uni ts . Pers ons who recei ve bl ood now (2013) (c) a re a t l i ttl e ri s k. Ri s ks a s s oci a ted wi th HIV tra ns mi s s i on a re s hown i n the ta bl e from the Centers for Di s ea s e Preventi on a nd Control .
104. The answer is c. (Levinson, Ch 39, 42, 46. Murray, Ch 60. Ryan, Ch 10, 16.) The hi ghes t ri s k of tera togeni c effects from feta l i nfecti on wi th rubel l a occurs duri ng the fi rs t 20 weeks of ges ta ti on; therefore, a ns wer d, whi ch s ta tes rubel l a i s not a probl em unti l the 30th week, i s i ncorrect. In s eronega ti ve pa ti ents , the ri s k of i nfecti on exceeds 90%. However, before other mea s ures (s uch a s termi na ti on of pregna ncy [e]) a re cons i dered, a rubel l a a nti body ti ter to determi ne i mmune s ta tus (c) mus t be performed. Rubel l a i mmune gl obul i n (a ) i s not a va i l a bl e, a nd IV pool ed i mmune gl obul i n i njected i nto the mother woul d be unl i kel y to protect the fetus a ga i ns t rubel l a beca us e vi remi a occurs a t the ti me s ymptoms a ppea r. Immuni zi ng the mother a ga i ns t rubel l a (b) woul d not protect the fetus for the s a me rea s on—a nti bodi es tha t devel op woul d be too l a te to prevent tra ns pl a centa l s prea d. And, whi l e i na dvertent a dmi ni s tra ti on of rubel l a va cci ne to pregna nt women di d not res ul t i n neona tes wi th congeni ta l s yndrome, i t i s genera l l y unwi s e to gi ve a l i ve a ttenua ted va cci ne to a pregna nt woma n. 105. The answer is c. (Levinson, Ch 36. Murray, Ch 11, 49-51, 54, 56, 59, 60, 63.) HPV 16/18 a nd HBV (c) a re i mpl i ca ted i n cervi ca l (a nd other geni ta l ) ca ncer a nd hepa tocel l ul a r ca rci noma , res pecti vel y. Thus , the va cci nes a ga i ns t thes e a gents a re expected to reduce the i nci dence of thes e ca ncers . Thi s ha s been s een i n regi ons of the worl d where routi ne HBV va cci ne i s us ed a t bi rth or s hortl y therea fter. The other vi rus es —a denovi rus /mumps vi rus (a ), HAV/pol i ovi rus (b), mea s l es vi rus /rubel l a vi rus (d), a nd rota vi rus /VZV (e)—a re not a s s oci a ted wi th ca ncers i n huma ns , a l though a denovi rus es ca us e ca ncer i n s ome a ni ma l s . 106. The answer is c. (Levinson, Ch 40. Murray, Ch 54. Ryan, Ch 9, 12.) The di s ea s e des cri bed i n the vi gnette i s pol i omyel i ti s (or pol i o), whi ch i s s ti l l pres ent i n Indi a , Pa ki s ta n, Afgha ni s ta n, a nd s evera l countri es i n Afri ca . The workers from the Uni ted Sta tes ha d recei ved ei ther the Sa l k ki l l ed pol i ovi rus va cci ne or the Sa bi n l i ve a ttenua ted pol i ovi rus va cci ne (c) dependi ng on thei r a ges . Beca us e the pol i ovi rus es ha ve been era di ca ted from the Northern Hemi s phere a nd the l i ve a ttenua ted pol i ovi rus va cci ne s tra i ns ha ve been a s s oci a ted wi th CNS i nfecti on i n s ome reci pi ents , the ki l l ed va cci ne i s the onl y one us ed i n the Uni ted Sta tes toda y. The workers mos t l i kel y ha d a l s o recei ved the mea s l es (b), mumps , a nd rubel l a (d) vi rus va cci nes a nd the HAV (a ) va cci ne, but thos e woul d not protect them from pol i o. The yel l ow fever vi rus (e) va cci ne i s genera l l y gi ven onl y to thos e tra vel i ng to a n endemi c a rea . 107. The answer is e. (Levinson, Ch 39. Murray, Ch 57. Ryan, Ch 9.) Staphylococcus aureus (e) i s one of the mos t common ca us es of s econda ry ba cteri a l pneumoni a fol l owi ng i nfl uenza . The others a re Streptococcus pneumoniae a nd Haemophilus influenzae. Escherichia coli (a ) a nd Klebsiella pneumoniae (b) ma y a l s o ca us e pos ti nfl uenza s econda ry ba cteri a l pneumoni a , but the numbers of ca s es a re much l ower. Pri ma ry i nfl uenza pneumoni a i s a s eri ous compl i ca ti on of i nfl uenza i n i ts own ri ght, mos t often a ffecti ng el derl y pers ons i n nurs i ng homes , pers ons wi th ca rdi ova s cul a r di s ea s e, a nd pregna nt women i n thei r thi rd tri mes ter. S. aureus s econda ry ba cteri a l pneumoni a devel ops ra pi dl y, wi thi n 2 to 3 da ys of pri ma ry i nfl uenza pneumoni a ; s econda ry ba cteri a l pneumoni a ca us ed by S. pneumoniae or H. influenzae occurs 2 to 3 weeks a fter the i ni ti a l s ymptoms of i nfl uenza . Legionella pneumophila i s us ua l l y the pri ma ry ca us e of l ung di s ea s e. Listeria monocytogenes (d) i s a cqui red vi a i nges ti on of conta mi na ted food, s prea di ng from the GI tra ct to the joi nts or CNS i n i mmunocompromi s ed i ndi vi dua l s or to the pl a centa i n pregna nt women. 108. The answer is a. (Levinson, Ch 38. Murray, Ch 50. Ryan, Ch 9, 15.) Conjuncti vi ti s i s s een i n ma ny chi l dhood i nfecti ons . When a ccompa ni ed by fever a nd s ore throa t, pha ryngoconjuncti va l fever i s mos t often ca us ed by a denovi rus (a ). HSV type 1 (d) eye i nfecti ons us ua l l y pres ent a s kera ti ti s (cornea l ul cer). The rema i ni ng choi ces a re ba cteri a , whi ch us ua l l y ca us e purul ent dra i na ge ra ther tha n wa tery. Chlamydia trachomatis (b) i s
a s s oci a ted wi th eye i nfecti ons i n neona tes born to mothers wi th geni ta l i nfecti ons . C. trachomatis a l s o ca us es tra choma , a s l owl y progres s i ve di s ea s e tha t begi ns a s fol l i cul a r i nfl a mma ti on of the eyel i d a nd ca n l ea d to s ca rri ng a nd bl i ndnes s ; tra choma occurs pri ma ri l y i n Afri ca , the Mi ddl e Ea s t, a nd northern Indi a . Haemophilus aegyptius (c) ca us es epi demi c purul ent conjuncti vi ti s , often known a s “pi nk-eye.” Thi s s peci es of Haemophilus i s found more frequentl y i n tropi ca l cl i ma tes a nd i s now uncommon i n the Uni ted Sta tes where Haemophilus influenzae i s encountered more frequentl y. Staphylococcus aureus (e) us ua l l y ca us es bl epha ri ti s , or i nfl a mma ti on of the eyel i ds . 109. The answer is b. (Levinson, Ch 39, 42, 46. Murray, Ch 61. Ryan, Ch 16.) The vi gnette des cri bes ha nta vi rus pul mona ry s yndrome (HPS) (a l s o known a s ha nta vi rus ca rdi opul mona ry s yndrome), whi ch i s a cqui red by i nha l i ng a eros ol i zed rodent excreta (c). The fi rs t ca s es of HPS recogni zed i n the modern era occurred i n 1993, when a n outbrea k of a fa ta l res pi ra tory di s ea s e occurred i n the s outhwes tern Uni ted Sta tes . Deer mi ce were the vectors i n tha t outbrea k ca us ed by a Hantavirus gi ven the na me “Si n Nombre.” At l ea s t 24 di fferent types of New Worl d ha nta vi rus es , di s tri buted throughout the Ameri ca s , a re now known; ea ch ha s a di fferent rodent vector a nd a l l ca us e HPS. The morta l i ty ra te for HPS i s hi gh, 80% i n the 1993 outbrea k, but wi th devel opment of a ggres s i ve i nterventi ons , i t i s now 30% to 40%. Members of the Bunyavirus genus , a l s o of the Bunyaviridae, a re a rthropod-borne, wi th the s peci es found i n the Ameri ca s tra ns mi tted by mos qui toes (d) a nd the Afri ca n s peci es tra ns mi tted by ti cks (e) or fl i es . Huma n-to-huma n tra ns mi s s i on by conta ct (a ) occurs wi th s ome South Ameri ca n s tra i ns of Hantavirus, but i s not common. Dri nki ng wa ter (b) i s not i mpl i ca ted i n the s prea d of Hantavirus i nfecti ons . 110. The answer is b. (Levinson, Ch 38, 43. Murray, Ch 49. Ryan, Ch 19.) The vi gnette des cri bes common wa rts ca us ed by HPV (b) a nd the a ccompa nyi ng i ma ge s hows koi l ocytes i n hyperpl a s ti c s ki n, whi ch a re pa thognomoni c for HPV i nfecti on. HPVs ca us e nongeni ta l cuta neous a nd a nogeni ta l or mucos a l s yndromes . Nongeni ta l cuta neous s yndromes i ncl ude common wa rts , fl a t wa rts , pl a nta r wa rts , a nd epi dermodys pl a s i a verruci formi s . The HPV types a s s oci a ted wi th thes e l es i ons a re di fferent from the types tha t ca us e mucos a l s yndromes (6, 11, 16, 18, 31, a nd 45) except for type 2 tha t ca n ca us e common wa rts , pl a nta r wa rts , a nd ora l pa pi l l oma s . Adenovi rus (a ) does not ca us e s ki n l es i ons ; Molluscipoxvirus (c) ca us es pea rl y l es i ons wi th di mpl ed centers from whi ch whi te ma teri a l ca n be extruded. When i t ca us es s ki n l es i ons , echovi rus (d) i s a s s oci a ted wi th a ma cul opa pul a r ra s h. VZV (e) ca us es ves i cul a r l es i ons . 111. The answer is c. (Levinson, Ch 38, 43. Murray, Ch 49. Ryan, Ch 19.) Of the choi ces l i s ted, onl y i mi qui mod (c) i s a n i mmunomodul a tory a gent. It i s a n i nducer of cytoki nes of i nna te i mmuni ty, s ti mul a ti ng producti on of IFN-α, tumor necros i s fa ctor, i nterl euki n-1, a nd i nterl euki n-8. It ca n be us ed i n conjuncti on wi th phys i ca l remova l of HPV outgrowths to prevent vi ra l repl i ca ti on i n a ny rema i ni ng i nfected cel l s . Acycl ovi r (a ) i s a n a nti vi ra l s peci fi c for HSVs a nd VZVs , whi ch ha ve vi ra l thymi di ne ki na s es to a cti va te the drug. 5-Fl uoroura ci l (b) i s a cytotoxi c a gent tha t i nterferes wi th RNA a nd DNA s ynthes i s , podophyl l i n (d) i s a cytotoxi c a gent tha t i s a nti mi toti c, a nd tri chl oroa ceti c a ci d (e) i s a kera tol yti c a gent tha t chemi ca l l y ca uteri zes s ki n, kera ti n, a nd other ti s s ues . The l a tter three a gents ca n a l l be us ed i n trea ti ng condyl oma a ccumi na tum, but they a re not i mmunomodul a tory. 112. The answer is a. (Levinson, Ch 38. Murray, Ch 53. Ryan, Ch 10.) Pa rvovi rus B19 ca us es erythema i nfecti os um i n previ ous l y wel l chi l dren a nd a dul ts tha t often res ul ts i n a drop i n hemogl obi n l evel tha t i s not noti ced. In chi l dren wi th chroni c hemol yti c a nemi a s , s uch a s s i ckl e cel l di s ea s e, pa rvovi rus B19 i nfecti on ca n res ul t i n a pl a s ti c cri s i s (a ) a s s oci a ted wi th a drop i n the hemogl obi n l evel of 2 g/dL or more. Thi s ca n neces s i ta te hos pi ta l i za ti on i n thes e chi l dren. The vi rus preferenti a l l y i nfects erythroi d precurs ors . The chi l d ha s ta chyca rdi a from the a nemi a . There i s nothi ng i n the hi s tory to s ugges t Coxs a cki evi rus B peri ca rdi ti s (b), Norovirus ga s troenteri ti s (c), or BK pol yoma vi rus hemorrha gi c cys ti ti s (e); nor i s there a ny rea s on to s us pect Coltivirus i nfecti on (d), whi ch woul d be a s s oci a ted wi th l oca ti on, s ea s on, a nd ti ck bi te. Norovirus ga s troenteri ti s i s not a s s oci a ted wi th bl eedi ng. Addi ti ona l compl i ca ti ons of pa rvovi rus B19 i nfecti on i ncl ude ma terna l tra ns pl a centa l i nfecti on of the fetus wi th res ul ta nt feta l hydrops rel a ted to a nemi a i n the fetus , unremi ttent a nemi a i n i mmuno-s uppres s ed pers ons s uch a s tra ns pl a nt reci pi ents , a nd pol ya rthropa thy/a rthri ti s i n a dul ts . 113. The answer is a. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Approxi ma tel y 40,000 i nfa nts (out of 4 mi l l i on bi rths ) a re born wi th congeni ta l CMV i nfecti ons . Of thes e, 10% wi l l be s ymptoma ti c a nd cons i dered to ha ve cytomega l i c i ncl us i on di s ea s e; a nd 90% of thes e i nfa nts wi l l s uffer neurol ogi c s equel a e s uch a s hea ri ng l os s a t bi rth, mi crocepha l y, menta l reta rda ti on, a nd devel opmenta l di s a bi l i ti es . The rema i ni ng 36,000 wi l l ha ve a s ymptoma ti c CMV (a ) i nfecti on a nd a pproxi ma tel y 15% wi l l devel op neurol ogi ca l s equel a e, i ncl udi ng s ens ori neura l hea ri ng l os s . HSV type 2 (b) congeni ta l i nfecti on pres ents a s ves i cul a r l es i ons or a s di s s emi na ted i nfecti on or CNS di s ea s e, both of whi ch ca n be l etha l . Congeni ta l va ri cel l a s yndrome ca us ed by VZV (e) i s a s s oci a ted wi th mi crocepha l y, s ki n l es i ons , a nd l i mb a nd eye defects . Rubeol a vi rus (mea s l es vi rus ) (d) i nfecti on i n the mother l ea ds to s ponta neous a borti on or preterm bi rth of the fetus . CRS ca us ed by rubel l a vi rus (d) l ed to a borti on, s ti l l bi rth, a nd s eri ous defects i ncl udi ng s ens ori neura l hea ri ng l os s , ocul a r a bnorma l i ti es , a nd congeni ta l hea rt defects . CRS ha s been vi rtua l l y el i mi na ted i n the Uni ted Sta tes by the us e of the l i ve a ttenua ted rubel l a va cci ne s i nce 1969. 114. The answer is c. (Levinson, Ch 40. Murray, Ch 59. Ryan, Ch 9, 15.) The s ymptoms of rota vi rus (c) i nfecti on l a s t l onger tha n thos e of norovi rus (b), whi ch genera l l y runs i ts cours e i n 72 hours or l es s . The rota vi rus va cci ne ha s grea tl y reduced the numbers of ca s es of rota vi rus i nfecti on a nd the morbi di ty a s s oci a ted wi th i t i n thos e who devel op the i nfecti on des pi te va cci na ti on. However, no va cci ne i s 100% effecti ve a nd s ome i nfa nts wi l l s ti l l devel op ful l -bl own rota vi rus enteri ti s . Enterovi rus es (a ) do not ca us e ga s troenteri ti s . Salmonella enterica (a ) i n di a rrhea i s cha ra cteri zed by the pres ence of WBC i n the s tool a nd s ometi mes bl ood. Staphylococcus aureus enterotoxi n (e) woul d be unl i kel y i n a n i nfa nt 6 months ol d, but woul d pres ent wi thi n 1 to 6 hours of i nges ti on wi th na us ea a nd vomi ti ng the ma jor s ymptoms . A number of vi rus es tha t ca us e ga s troenteri ti s ha ve been recogni zed. The fol l owi ng ta bl e s umma ri zes the cha ra cteri s ti cs of thes e vi rus es .
115. The answer is d. (Levinson, Ch 39, 44, 46. Murray, Ch 56, 64. Ryan, Ch 9, 10, 20.) SSPE, a very l a te a nd ra re s equel a of i nfecti on wi th Morbillivirus (mea s l es vi rus ) (d), occurs a pproxi ma tel y 10 yea rs a fter mea s l es . It i s a degenera ti ve CNS i nfecti on res ul ti ng from a pers i s tent i nfecti on ca us ed by
a defecti ve vi rus tha t s prea ds cel l to cel l but does not produce cel l -free ma ture vi ri ons . Mea s l es ca n a l s o res ul t i n a cute encepha l i ti s i n 1/1000 ca s es , often res ul ti ng i n perma nent bra i n da ma ge a nd 10% fa ta l i ty; del a yed a cute encepha l i ti s tha t occurs 1 to 6 months l a ter a nd i s i nva ri a bl y fa ta l ; or a cute di s s emi na ted encepha l omyel i ti s (pos ti nfecti ous encepha l i ti s ), a demyel i na ti ng condi ti on a ffecti ng the bra i n a nd s pi na l cord. Eps tei n–Ba rr vi rus (a ) ca n ca us e neurol ogi c compl i ca ti ons i n 1% of i nfecti ons , i ncl udi ng a cute encepha l i ti s or meni ngi ti s , Gui l l a i n–Ba rré s yndrome, Bel l pa l s y, a nd tra ns vers e myel i ti s . HIV (b) ca n ca us e HIV dementi a , whi l e the JC pol yoma vi rus ca us es progres s i ve mul ti foca l l eukoencepha l opa thy i n pers ons who a re profoundl y i mmunos uppres s ed, i ncl udi ng thos e wi th AIDS a nd thos e on i mmunos uppres s i ve thera py. The mumps vi rus (Rubulavirus) (e) i nvol ves the CNS i n 50% of ca s es , 10% of whom devel op a s epti c meni ngi ti s ; 1 i n 200 of thes e pa ti ents devel op encepha l i ti s a s wel l . Mumps ca n a l s o res ul t i n hea ri ng l os s . 116. The answer is a. (Levinson, Ch 40. Murray, Ch 59. Ryan, Ch 9, 16.) Coltivirus (a ), a member of the Reovi ri da e, i s a doubl e-s tra nded RNA vi rus wi th a s egmented genome. It ca us es Col ora do ti ck fever a s des cri bed i n the vi gnette. The vi rus ci rcul a tes i n red bl ood cel l s , whi ch ha ve a n a vera ge l i fe s pa n of 120 da ys ; thus , the recommenda ti on to a voi d dona ti ng bl ood for 6 months . CTF i s us ua l l y a mi l d di s ea s e wi th epi s odes of fever i nters pers ed wi th a febri l e peri ods , the “s a ddl e-ba ck” fever pa ttern. The vi rus i s l i mi ted to the mounta i nous regi ons of the Northwes t Uni ted Sta tes a nd Ca na da a nd i s found a t el eva ti ons of 4000 feet or hi gher, the ra nge of the rodent res ervoi r a nd the Dermacentor andersoni ti ck vector. The i nfecti on i s common; s evera l hundred ca s es occur ea ch yea r. Wes tern equi ne encepha l i ti s vi rus (e) us ua l l y pres ents a s encepha l i ti s ; no ca s es ha ve been recorded i n the Uni ted Sta tes for the pa s t 5 yea rs . Dengue vi rus (c) ma y begi n wi th a s i mi l a r pres enta ti on but woul d be a s s oci a ted wi th tra vel i n s ubtropi ca l or tropi ca l regi ons . Coxs a cki evi rus B (b) ca us es nons peci fi c s ymptoms tha t a re mi l d fol l owed by ta rget orga n di s ea s e s uch a s myos i ti s or pl eurodyni a . The pres enta ti on of Si n Nombre ha nta vi rus (d), whi ch overl a ps the ra nge of Coltivirus, ca us es ha nta vi rus pul mona ry s yndrome. 117. The answer is b. (Levinson, Ch 46. Murray, Ch 58. Ryan, Ch 16.) The vi gnette des cri bes vi ra l hemorrha gi c fever tra ns mi tted by conta ct wi th bl ood. Of the three hemorrha gi c fevers gi ven a s choi ces , onl y Ebol a hemorrha gi c fever (b), ca us ed by the Filovirus Ebol a , i s tra ns mi tted by conta ct wi th bl ood a nd body fl ui ds . The fi l ovi rus es a re a l s o a cqui red by col l ecti ng bus h mea t (dea d ca rca s s es of pri ma tes ), a nd epi demi ol ogi c s tudi es s ugges t tha t ba ts ma y a l s o s erve a s vector. Dengue hemorrha gi c fever (a ) a nd yel l ow fever (e) a re ca us ed by a rthropod-borne fl a vi vi rus es , a s i s Wes t Ni l e encepha l i ti s (d). Ha nta vi rus pul mona ry s yndrome i s a cqui red through i nha l a ti on of a eros ol i zed excreta from i nfected rodents . 118. The answer is d. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Al l of the choi ces a re a s s oci a ted wi th EBV. The pa ti ent mos t l i kel y ha s l ymphoprol i fera ti ve di s order (pos ttra ns pl a nt) (d), a pol ycl ona l res pons e to rea cti va ti on or a cqui s i ti on of EBV i n pers ons on i mmunos uppres s i ve thera py to prevent tra ns pl a nt rejecti on. The di s order res ponded to reducti on of the i mmunos uppres s i ve a gent, a res pons e not expected i f the pa ti ent ha d Burki tt l ymphoma (a ) or Hodgki n l ymphoma (b), more a ggres s i ve monocl ona l B-cel l l ymphoma s tha t often requi re a nti l ymphoma trea tment. Infecti ous mononucl eos i s (c) occurs i n i mmunocompetent i ndi vi dua l s . NPC (e) does not fi t the vi gnette. 119. The answer is e. (Katzung, Ch 49. Levinson, Ch 39, 45. Murray, Ch 62. Ryan, Ch 18.) The repl i ca ti on of a retrovi ra l genome i s dependent on the revers e tra ns cri pta s e enzyme, whi ch performs a va ri ety of functi ons —RNA-dependent DNA pol ymera s e, RNa s e, a nd DNA-dependent DNA pol ymera s e. Aba ca vi r (a ), nevi ra pi ne (c), a nd zi dovudi ne (e) a re revers e tra ns cri pta s e i nhi bi tors . However, onl y zi dovudi ne (e) i s us ed a l one for prophyl a xi s to prevent peri na ta l tra ns mi s s i on of HIV duri ng the fi rs t 6 weeks of l i fe. Aba ca vi r s houl d not be us ed wi thout tes ti ng the i nfa nt for HLA-B*5701, a muta ti on tha t renders the i ndi vi dua l hypers ens i ti ve to thi s drug. Ra l tegra vi r (d), the i ntegra s e i nhi bi tor, a nd l opi na vi r (b), a PI, a re not us ed a l one a t a ny ti me—prophyl a cti ca l l y or thera peuti ca l l y. Two regi mens a re currentl y recommended for chi l dren younger tha n 3 yea rs of a ge: nevi ra pi ne pl us two NRTIs (a ba ca vi r, di da nos i ne or zi dovudi ne pl us l a mi vudi ne, or emtri ci ta bi ne) or l opi na vi r/ri tona vi r pl us two NRTIs (s a me choi ces a s for nevi ra pi ne). 120. The answer is a. (Levinson, Ch 42, 43. Murray, Ch 60. Ryan, Ch 16.) The wi des prea d di s tri buti on of WNV (a ) a cros s the Uni ted Sta tes a nd the hi gh i nci dence of i nfecti ons , mos t of whi ch a re a s ymptoma ti c or onl y mi l dl y s ymptoma ti c, ha s l ed centers tha t col l ect bl ood for tra ns fus i on to tes t a l l donors for the vi rus . Thi s i s done by nucl ei c a ci d a mpl i fi ca ti on tes ts (NAAT) on pool s of donors . If a pos i ti ve pool i s found, ea ch donor i s tes ted i ndi vi dua l l y. For 2012, the Centers for Di s ea s e Preventi on a nd Control recorded 5890 ca s es of WNV i l l nes s , of whi ch 2734 were neuroi nva s i ve. Among thos e wi th neuroi nva s i ve di s ea s e, 243 di ed (~9%). Al mos t 600 a s ymptoma ti c bl ood donors were reported. The i nci dence of St. Loui s encepha l i ti s i s too l ow to wa rra nt tes ti ng the bl ood s uppl y a t thi s ti me. Dengue vi rus (c) ra rel y ca us es encepha l i ti s a nd i s currentl y tra ns mi tted endogenous l y onl y i n Fl ori da . Coltivirus (e) ma y be tra ns mi tted to reci pi ents of bl ood from donors i nfected wi th the vi rus , but thi s vi rus i s res tri cted to the Rocky Mounta i n s ta tes a nd i s not routi nel y tes ted for i n other s ta tes . Tra vel hi s tory woul d excl ude dengue vi rus a nd Coltivirus. HSV (d) i s not tra ns mi tted by a rthropods . See the ta bl e a ccompa nyi ng a ns wer to ques ti on 72 for a ddi ti ona l i nforma ti on. 121. The answer is b. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Whi l e the ma jori ty of CMV (b) i nfecti ons a cqui red i n young a dul thood a re a s ymptoma ti c, s ome ma y devel op heterophi l e-nega ti ve mononucl eos i s s yndrome, des cri bed i n the vi gnette. Genera l l y, the l ympha denopa thy a nd pha ryngi ti s a re l es s s evere tha n tha t s een wi th i nfecti ous mononucl eos i s ca us ed by EBV (c). Adul t pri ma ry CMV i nfecti on ma y a l s o ma ni fes t a s hepa ti ti s , but tes ts for HAV, HBV, a nd HCV woul d be nega ti ve. Adeno-vi rus (a ), pa rvovi rus B19 (d), a nd HCV (e) do not ca us e mononucl eos i s s yndrome. 122. The answer is c. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) IFN-α a nd IFN-β a re protei ns tha t a l ter cel l meta bol i s m to i nhi bi t vi ra l repl i ca ti on. They a cti va te 2'-5'-ol i goa denyl a te s yntha s e, whi ch i n turn a cti va tes RNa s e L to degra de pol y(A) mRNA tra ns cri pts . Together wi th ds RNA i ntermedi a tes produced duri ng repl i ca ti on of RNA vi rus es , IFN a cti va tes protei n ki na s e R, whi ch then phos phoryl a tes euka ryoti c i ni ti a ti on fa ctor-2, renderi ng i t nonfuncti ona l . The a cti va ti on of thes e cel l ul a r protei ns i s known a s the a nti vi ra l s ta te (c). Ri ba vi ri n di rectl y i nhi bi ts the vi ra l RNA pol ymera s e (b) a nd i nterferes wi th gua nos i ne-dependent proces s es wi thi n the cel l (e). Nei ther IFN nor ri ba vi ri n bl ocks vi ra l envel ope fus i on wi th hos t cel l membra ne (a ) or i nhi bi ts vi ra l protea s es (d). 123. The answer is b. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) Si nce thi s wa s di a gnos ed a nd confi rmed a s a Hepa ti ti s A i nfecti on, there i s l i ttl e l i kel i hood of l ong-term s equel a e. However, pers ons over 40 a nd thos e younger tha n 12 months a re more l i kel y to ha ve s evere ma ni fes ta ti ons . One dos e of s ta nda rd γ-gl obul i n (b), whi ch conta i ns a nti bodi es from a s eri es of norma l popul a ti on i ndi vi dua l s , wi l l provi de pa s s i ve protecti on to the fa mi l y members for s evera l weeks due to the pres ence of a nti bodi es a ga i ns t HAV. Va cci na ti on wi th the ki l l ed HAV va cci ne (c), whi ch i s recommended by CDC (http://www.cdc.gov/hepatitis/HAV/HAVfaq.htm#general), i s for thos e i n the 12 months to 40 yea rs a ge bra cket. IFN-α (a ) trea tment i s a pproved onl y for HBV a nd HCV i nfecti ons . HAV tra ns mi ts rea di l y, s o the qua ra nti ne a nd obs erve a pproa ch (d) a nd the no-trea tment opti on (e) wi l l not gua ra ntee tha t tra ns mi s s i on wi l l not occur wi thi n the fa mi l y. 124. The answer is b. (Levinson, Ch 37, 39, 43, 45. Murray, Ch 51, 62. Ryan, Ch 10, 1, 18.) The l es i ons des cri bed a nd s hown a re cha ra cteri s ti c of Ka pos i s a rcoma ca us ed by huma n herpes vi rus 8 (b). Thi s i s the mos t common opportuni s ti c s ki n di s ea s e s een i n ma l es wi th AIDS. Ba ci l l a ry a ngi oma tos i s , ca us ed by Bartonella henselae (a ) or B. quintana, i s the s econd mos t common; i t i s cha ra cteri zed by va s cul a r bl ood-fi l l ed nodul es . Huma n T-cel l
l eukemi a vi rus (d) ma y ca us e nodul a r, i ndura ted, or exfol i a ti ve s ki n l es i ons a s s oci a ted wi th a cute T-cel l l eukemi a . HTLV i nfecti ons a re s een mos t frequentl y i n pers ons ori gi na ti ng from or ha vi ng l i ved i n certa i n pa rts of Ja pa n, the Ca ri bbea n, Centra l or Wes t Afri ca , or South Ameri ca , or who i s a Na ti ve Ameri ca n Indi a n. HPV (c) ca us es pa pi l l oma tous , or wa rtl i ke, outgrowths of the s ki n a nd mucous membra nes . Staphylococcus aureus (e) ca us es a bs ces s es i n the s ki n cha ra cteri zed by s wel l i ng, rednes s , wa rmth, a nd pa i n; s uch l es i ons do not us ua l l y a ppea r i n the ora l ca vi ty. 125. The answer is c. (Levinson, Ch 32. Murray, Ch 45, 46. Ryan, Ch 7.) A l a tent i nfecti on i s us ua l l y ma ni fes ted by pers i s tence of vi ra l genomes , expres s i on of none or a few vi ra l genes , a nd s urvi va l of the i nfected cel l s . Rea cti va ti on wi th s heddi ng of i nfecti ous vi ri ons ma y occur s pora di ca l l y or not a t a l l , us ua l l y dependent on i mmune competence. HSV (b) becomes l a tent i n neurons . Adenovi rus (a ) ca n form l a tent i nfecti on of l ymphoi d ti s s ue (tons i l s , a denoi ds , Peyer pa tches ). Eps tei n–Ba rr vi rus (c) becomes l a tent i n B cel l s i n the pres ence of i mmunocompetent T cel l s . Al l three vi rus es ca n be rea cti va ted by l os s of i mmunocompetence, i nfecti on wi th a nother a gent, a nd other tri ggers , dependi ng on the vi rus . Mea s l es vi rus (d) ca n devel op defecti ve muta nts , whi ch ca us e pers i s tent i nfecti on of the bra i n res ul ti ng i n SSPE a pproxi ma tel y 10 yea rs a fter pri ma ry mea s l es . Ra bi es vi rus (e) ha s a l ong i ncuba ti on ti me wi th the vi rus repl i ca ti ng s l owl y i n mus cl e cel l s a nd then peri phera l nerves a t the s i te of entry for 60 to 365 da ys a fter the bi te. Thes e l a tter two i nfecti ons a re pers i s tentl y repl i ca -ti ve ra ther tha n l a tent. 126. The answer is b. (Levinson, Ch 34. Murray, Ch 47. Ryan, Ch 6.) The s ymptoms des cri bed for her i l l nes s es on both November 6 a nd December 5 a re cons i s tent wi th i nfl uenza . However, the November 6 i l l nes s (a ) wa s not ca us ed by nH1N1 i nfl uenza vi rus ; the l ow ti ters (10 on November 6 a nd 10 on November 30) mos t l i kel y repres ent cros s -rea cti ng a nti bodi es from the a gent tha t ca us ed her fi rs t i l l nes s . The grea ter tha n fourfol d ri s e i n ti ter from 10 on November 30 (ba s el i ne) to 160 on December 20 refl ects a defi ni ti ve di a gnos ti c ri s e i n a nti body a ga i ns t nH1N1 i nfl uenza vi rus . Thus , her December 5 i l l nes s (b) wa s i nfl uenza . There i s enough s erol ogi c evi dence to ma ke the di a gnos i s (choi ce e i s i ncorrect). 127. The answer is d. (Levinson, Ch 31. Murray, Ch 44, 49. Ryan, Ch 7.) The des cri pti on of the vi ra l genome a s ds DNA a nd the vi ri on a s nonenvel oped fi ts Mastadenovirus (huma n a denovi rus es ), Papillomavirus (HPV), a nd Polyomavirus (d), whi ch i s the onl y one of the three gi ven a s a choi ce. The new vi rus ha s been gi ven the na me Merkel cel l pol yoma vi rus , or Polyomavirus type MCPyV. It i s the fi rs t Polyomavirus a s s oci a ted wi th a huma n ca ncer; genera l s ci enti fi c opi ni on s ugges ts tha t MCPyV ca us es mos t Merkel cel l ca ncers . Orthohepadnavirus (HBV) (c) i s envel oped a nd pa rti a l l y ds DNA; i t i s a s s oci a ted wi th hepa tocel l ul a r ca rci noma . Erythrovirus (pa rvovi rus B19) (b) i s nonenvel oped, but i s s s DNA. Alphavirus (toga vi rus ) (a ) i s a (+) s s RNA envel oped vi rus , a nd Rotavirus (e) i s a ds RNA nonenvel oped vi rus . Erythrovirus, Alphavirus, a nd Rotavirus ha ve not been a s s oci a ted wi th ca ncer i n huma ns or a ni ma l s . 128. The answer is a. (Levinson, Ch 42, 43. Murray, Ch 60. Ryan, Ch 16.) The i l l nes s des cri bed i n the vi gnette i s dengue (brea kbone fever) (a ) i s the mos t common a rthropod-borne i nfecti on a mong huma ns . There a re four s erotypes of dengue vi rus , whi ch bel ong to the Flaviviridae, ea ch ca us i ng the s a me type of s ymptoms . Yel l ow fever (e), ca us ed by the yel l ow fever vi rus , i s a nother fl a vi vi rus ; i t i s cha ra cteri zed by fever wi th hemorrha ge a nd hepa ti ti s . Hepa ti ti s C (c) i s ca us ed by a nother fl a vi vi rus , the HCV, but thi s i nfecti on ma ni fes ts a s hepa ti ti s , ra ther tha n fever a nd bone pa i n; HCV i s not s prea d by mos qui toes . Hemorrha gi c fever wi th rena l s yndrome (b) i s ca us ed by the Ol d Worl d s tra i ns of Hantavirus (Bunyaviridae), a nd i s s prea d by rodents ; the di s ea s e i s s een i n Ea s t As i a , Ea s tern Europe, wes tern Rus s i a , a nd Ja pa n. Rubel l a (d), a very mi l d di s ea s e, i s ca us ed by Rubivirus, a member of the Togaviridae; unl i ke the Alphavirus genus , Rubivirus i s not s prea d by a rthropods . 129. The answer is d. (Levinson, Ch 31, 41. Murray, Ch 44, 63. Ryan, Ch 6, 13.) The vi gnette des cri bes a pa ti ent wi th chroni c hepa ti ti s mos t l i kel y a cqui red by bl ood tra ns fus i on, whi ch coul d be ca us ed by HBV or HCV. HCV i nfecti on i s fa r more l i kel y to l ea d to chroni c hepa ti ti s (a pproxi ma tel y 85% i n a dul ts ) tha n HBV (a bout 5% i n a dul ts ); a nd HCV i nfecti on l ea ds to a chroni c i l l nes s cha ra cteri zed by fl uctua ti ng l evel s of l i ver enzymes a nd bi l i rubi n, wi th norma l res ul ts obta i ned a t ti mes . Acqui s i ti on of HDV l ea ds to exa cerba ti on of HBV i f s uperi nfecti on occurs or a s a cute i nfecti on i f coi nfecti on occurs ; i f the HBV i nfecti on conti nues a s a chroni c i nfecti on, HDV ma y become chroni c a s wel l . The a ns wer requi res knowl edge of the fa mi l i es of vi rus es i n whi ch the hepa ti ti s vi rus es res i de a s wel l a s thos e tha t a re bl oodborne (HBV, HDV, a nd HCV) vers us thos e tha t a re feca l ora l l y tra ns mi tted (HAV a nd HEV), whi ch do not l ea d to chroni c i nfecti on. HCV i s a s s (+)RNA vi rus bel ongi ng to the Flaviviridae (d). HBV i s a pa rti a l l y ds DNA vi rus bel ongi ng to the Hepadnaviridae (a ); HDV, whi ch ca n onl y be a cqui red when HBV i s pres ent, i s a s s (–)RNA vi rus known a s Deltavirus (e); HAV i s a s s (+)RNA vi rus bel ongi ng to the Picornaviridae (c); a nd HEV i s a s s (+)RNA vi rus bel ongi ng to the new fa mi l y Hepeviridae (b). 130. The answer is c. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) The ma rkers of HBV i nfecti on, i n order of a ppea ra nce, a re hepa ti ti s B s urfa ce a nti gen (c), hepa ti ti s e a nti gen (b), a nti -hepa ti ti s B core a nti gen IgM (e), a nd a nti -hepa ti ti s B e a nti gen (d), fol l owed by a nti -hepa ti ti s B s urfa ce a nti gen IgG i f the i nfecti on res ol ves . Hepa ti ti s B core a nti gen (a ) i s found onl y i n the nucl ei of i nfected hepa tocytes a nd not free i n the bl oods trea m, a l though i t i s pres ent i n ci rcul a ti ng i nta ct hepa ti ti s B vi ri ons (ori gi na l l y ca l l ed “Da ne pa rti cl es ”). 131. The answer is c. (Levinson, Ch 39, 43, 45. Murray, Ch 62. Ryan, Ch 18.) After a l ong i ncuba ti on peri od (up to 30 yea rs ), HTLV-1 (d) ca n ca us e ei ther a cute T-cel l l eukemi a , a di s ea s e of CD4+ T l ymphocytes , or HTLV-a s s oci a ted myel opa thy/tropi ca l s pa s ti c pa res i s . The vi rus i s di s tri buted worl dwi de, but found i n concentra ti ons i n Southwes t Ja pa n, the Ca ri bbea n ba s i n, s ome Sub-Sa ha ra n Afri ca n countri es , a nd South Ameri ca , es peci a l l y countri es a butti ng the Ca ri bbea n Sea . In the Uni ted Sta tes , HTLV-1 i s found ma i nl y i n i mmi gra nts from endemi c a rea s , chi l dren of i mmi gra nts , s ex workers , a nd IV drug us ers . HTLV-2 (d) ca us es ha i ry cel l l eukemi a , a di s ea s e of CD8 T l ymphocytes . It i s found i n hi gh concentra ti ons a mong i ndi genous peopl es i n Centra l , South, a nd North Ameri ca (Na ti ve Ameri ca ns ) a nd i n Europe a mong IV drug us ers . HIV-1 (a ) i s the ca us a ti ve a gent of a cute retrovi ra l s yndrome a nd AIDS. HIV-2 (b) ca us es a l es s -a ggres s i ve i nfecti on s i mi l a r to tha t ca us ed by HIV-1. HIV-2 i s ra re i n the devel oped worl d; mos t ca s es a re found i n Wes t Afri ca . 132. The answer is d. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Al l of the choi ces l i s ted ca n ca us e cornea l ul cera ti on. However, HSV type 1 (d) i s the mos t l i kel y eti ol ogi c a gent, i n pa rt beca us e of the dendri ti c ul cers , whi ch a re cha ra cteri s ti c of HSV cornea l i nfecti on. Funga l i nfecti on (Fusarium, c) i s frequentl y a s s oci a ted wi th a hi s tory of outdoor tra uma i nvol vi ng pl a nt ma teri a l ; a n outbrea k of funga l kera ti ti s wa s a s s oci a ted wi th conta mi na ted conta ct l ens moi s teni ng s ol uti on, but ha s res ol ved. Acanthamoeba kera ti ti s (a ) occurs mos t frequentl y i n conta ct l ens wea rers a nd i s a s s oci a ted wi th wa ter expos ure. Forei gn bodi es (b) ma y ca us e a bra s i ons , but thes e woul d not a ppea r dendri ti c. Al l ergi es (e) a re not a s l i kel y to ca us e ul cera ti on; nor does the young ma n gi ve a hi s tory of connecti ve ti s s ue di s ea s e s uch a s rheuma toi d a rthri ti s or SLE, whi ch ca n be a s s oci a ted wi th ophtha l mi c pa thol ogy. 133. The answer is d. (Katzung, Ch 49. Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Acycl ovi r a nd i ts deri va ti ves va l a cycl ovi r (d), fa mci cl ovi r, a nd penci cl ovi r a l l a re effecti ve i n trea ti ng a cti ve herpes zos ter (s hi ngl es ). There i s s ome evi dence tha t va l a cycl ovi r a nd fa mci cl ovi r a re better i n s peedi ng cuta neous hea l i ng a nd res ol vi ng pa i n tha n a cycl ovi r. Onl y a cycl ovi r ma y be us ed i n chi l dren. Ama nta di ne (a ) bl ocks the M2 cha nnel of i nfl uenza A vi rus , a l though the va s t ma jori ty of s tra i ns ci rcul a ti ng currentl y a re res i s ta nt; boceprevi r (b) i s a n i nhi bi tor of HCV NS3/4A protea s e; ri ba vi ri n (c) i s us ed i n the trea tment of HCV a nd res pi ra tory s yncyti a l vi rus ; a nd zi dovudi ne (e) i s a nucl eos i de revers e tra ns cri pta s e i nhi bi tor us ed i n the trea tment of HIV. 134. The answer is e. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) The vi gnette des cri bes cytomega l i c i ncl us i on di s ea s e (CID) ca us ed by CMV (e).
Sei zures , dea fnes s , ja undi ce, a nd purpura ca n a l s o occur. CID i s a l s o one of the l ea di ng ca us es of menta l reta rda ti on i n the Uni ted Sta tes . Rubel l a vi rus (a ) ca us es CRS, whi ch ha s s ome s i mi l a ri ti es to CID, but di ffers i n ophtha l mi c a nd ca rdi a c ma ni fes ta ti ons a re pa rt of the s yndrome. Mumps vi rus (d) a nd res pi ra tory s yncyti a l vi rus (b) do not cros s the pl a centa . HIV (c) ca n cros s the pl a centa but does not produce the s ymptoms /fi ndi ngs des cri bed i n the vi gnette. 135. The answer is b. (Levinson, Ch 39, 46. Murray, Ch 56. Ryan, Ch 9, 10.) The vi gnette des cri bes a n a dul t woma n wi th mumps vi rus (Rubulavirus) (b) i nfecti on, or mumps , who devel ops oophori ti s , a compl i ca ti on tha t occurs i n pos tpuberta l fema l es . Cytomega l ovi rus (a ), ra bi es vi rus (c), res pi ra tory s yncyti a l vi rus (d), a nd rubel l a vi rus (e) do not ca us e thi s cl i ni ca l pi cture. 136. The answer is a. (Levinson, Ch 30, 39. Murray, Ch 44, 57. Ryan, Ch 6, 9.) Anti geni c dri ft (a ) i n whi ch poi nt muta ti ons gra dua l l y cha nge the a nti geni c s tructure of the hema ggl uti ni n (H) a nd neura mi ni da s e (N) protei ns of Influenzavirus A, ma ki ng a n a nti body devel oped a ga i ns t the ori gi na l s tra i n l es s neutra l i zi ng for the dri fted s tra i n. Anti geni c s hi ft (b) i s a nother na me for rea s s ortment recombi na ti on tha t occurs i n s egmented RNA vi rus es . Wi th Influenzavirus A, two di fferent HN types i nfect the s a me cel l , us ua l l y i n a pi g; duri ng pa cka gi ng, the H (a nd/or N) s egments a re pa cka ged i n di fferent combi na ti ons tha n the ori gi na l vi rus es ; tha t i s H1N1 becomes H2N1. Intra mol ecul a r recombi na ti on (d) occurs by homol ogous recombi na ti on i n DNA vi rus es or s tra nd s wi tchi ng i n nons egmented RNA vi rus es . Compl ementa ti on (c) res ul ts when a protei n from a wi l d type vi rus a l l ows a repl i ca ti on-defecti ve vi rus to be repl i ca ted a nd pa cka ged i nto i nfecti ous vi ri ons ; i t does not repa i r the geneti c defect. Phenotypi c mi xi ng occurs when two or more vi rus es of the s a me genus but di fferent s erotypes repl i ca te i n the s a me cel l ; for exa mpl e, pol i ovi rus type 1 a nd type 2 repl i ca ti ng together coul d produce vi ri ons wi th ca ps i ds conta i ni ng both type 1 a nd type 2 protei ns . 137. The answer is d. (Levinson, Ch 46. Murray, Ch 58. Ryan, Ch 16.) Very few pers ons ha ve s urvi ved s ymptoma ti c ra bi es when untrea ted; of the fi rs t s i x recorded ca s es , three ha d recei ved ra bi es va cci ne before ons et of cl i ni ca l s ymptoms . In 2009, a regi men of a ggres s i ve thera py i nvol vi ng ri ba vi ri n, a ma nta di ne, a nd a keta mi ne–mi da zol a m-i nduced coma wa s s ucces s ful i n s a vi ng the fi rs t pa ti ent on whom i t wa s us ed. The ori gi na l protocol a nd va ri a ti ons ha ve been us ed s i nce wi th l i ttl e s ucces s ; therefore, (c) i s i ncorrect. Thus , ra bi es s houl d be cons i dered a l mos t i nva ri a bl y fa ta l (d) once cl i ni ca l s ymptoms begi n. Adul t pa ti ents recover from s ome forms of vi ra l encepha l i ti s , s uch a s wes tern equi ne a nd ea s tern equi ne encepha l i ti s wi thout compl i ca ti ons (a ), wherea s chi l dren often s uffer s ei zure di s orders (b) a nd other compl i ca ti ons ; thi s i s revers ed wi th St. Loui s a nd Wes t Ni l e encepha l i ti s . 138. The answer is e. (Levinson, Ch 40. Murray, Ch 54. Ryan, Ch 9, 12.) Rhi novi rus es (e) a re the mos t common ca us e of common col ds . They ca n be recovered from peopl e wi th mi l d upper res pi ra tory i l l nes s . Thei r preference for growth a t 33°C confi nes rhi novi rus es to the na s opha rynx a nd oropha rynx; thus , s eri ous i nfecti on ca us ed by rhi novi rus es i s ra re. Neutra l i zi ng IgG a nd IgA a nti bodi es form but l a s t onl y a bout 18 months . More tha n 100 s erotypes a re known, ea ch requi ri ng s peci fi c neutra l i zi ng a nti body. For thes e rea s ons , devel opment of a va cci ne a ga i ns t rhi novi rus es woul d be di ffi cul t, i f not i mpos s i bl e; nor i s s uch a va cci ne neces s a ry due to the mi l d na ture of the i l l nes s es ca us ed. Excel l ent va cci nes a re a va i l a bl e a ga i ns t mumps vi rus (b) a nd ra bi es vi rus (c). A pa s s i ve va cci ne, the monocl ona l a nti body pa l i vi zuma b, i s a va i l a bl e for prema ture i nfa nts for prophyl a xi s a ga i ns t RSV (d). No va cci ne i s a va i l a bl e for CMV (a ). 139. The answer is e. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) The di a gnos i s of hepa ti ti s begi ns wi th the cl i ni ca l s ymptoms a nd i s confi rmed by the res ul ts of s peci fi c s erol ogi c tes ts , i n thi s ca s e the detecti on of a nti -HAV IgM (e). The ca s e pres enta ti on does not s ugges t hepa ti ti s B (l onger i ncuba ti on, i ns i di ous ons et), s o HBs Ag (b) i s unl i kel y to be hel pful . Vi ra l cul ture (a ) i s not routi nel y done for a ny of the hepa ti ti s vi rus es , a l though s ome wi l l grow i n cel l cul ture. El ectron mi cros copy on s tool (c) mi ght be pos i ti ve, but woul d not be s peci fi c a nd i s not genera l l y a va i l a bl e for cl i ni ca l di a gnos i s . Rota vi rus (d) ca us es ga s troenteri ti s , not hepa ti ti s . 140. The answer is c. (Levinson, Ch 39. Murray, Ch 57. Ryan, Ch 9.) The s ymptoms des cri bed by the phys i ci a ns a re thos e of cl a s s i c uncompl i ca ted i nfl uenza (c), whi ch us ua l l y occurs i n s ucces s i ve wa ves of i nfecti on (outbrea ks ) wi th pea k i nci dences duri ng the wi nter months i n tempera te cl i ma tes . The a brupt ons et of s ys temi c s ymptoms (fever, chi l l s , hea d, a nd mus cl e a ches ) fol l owed by res pi ra tory s ymptoms i s typi ca l of i nfl uenza . Nei ther the common col d (a ) or pha ryngi ti s (d) ta kes i nto a ccount the whol e group of s ymptoms . Some pa ti ents ma y devel op pri ma ry vi ra l pneumoni a or s econda ry ba cteri a l pneumoni a , but the s ymptoms a re not cha ra cteri s ti c of pneumoni a (e). Ha nd-foot-a nd-mouth di s ea s e (b) i s not a s s evere a nd i ncl udes ves i cul a r l es i ons . 141. The answer is b. (Levinson, Ch 39, 46. Murray, Ch 56. Ryan, Ch 9, 10.) Li ve, a ttenua ted mea s l es vi rus (b) va cci ne gi ven a t 15 months to 2 yea rs of a ge effecti vel y prevents mea s l es i n 95% of chi l dren. Reva cci na ti on a t 4 to 6 yea rs or 11 to 15 yea rs i s recommended to ma i nta i n i mmuni ty. Ina cti va ted vi rus (a ) does not provi de s uffi ci ent protecti on. Recombi na nt vi ra l protei n (c) ma y be us ed when neutra l i zi ng IgG i s s uffi ci ent to prevent ta rget i nfecti on, whi ch i s not the ca s e wi th mea s l es vi rus . Pool ed i mmunogl obul i n i s us ed for pa s s i ve i mmuni za ti on pos texpos ure i n the i mmunocompromi s ed; vi rus -s peci fi c i mmunogl obul i n (d) i s not a va i l a bl e. Wi l d-type l i ve vi rus es (e) a re never us ed a s va cci nes . 142. The answer is e. (Katzung, Ch 49. Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Acycl ovi r i s a n a na l og of gua nos i ne or deoxygua nos i ne tha t s trongl y i nhi bi ts HSV but ha s l i ttl e effect on other DNA vi rus es . It a l s o ha s few s i de effects beca us e the drug i s a cti va ted onl y wi thi n HSV-i nfected cel l s by the vi ra l enzyme thymi di ne ki na s e (e). HSV does encode a DNA-dependent DNA pol ymera s e (a ) whi ch recogni zes a cycl ovi r tri phos pha te a nd i ncorpora tes the a cti va ted drug i nto the growi ng nucl eoti de cha i n, endi ng DNA s ynthes i s ; but thi s enzyme does not a cti va te a cycl ovi r. Integra s e (b) a nd protea s e (c) a re drug ta rgets for a nti retrovi ra l thera py; protea s es of HCV a nd i nfl uenza vi rus (neura mi ni da s e) a re a l s o ta rgeted by s peci fi c a nti vi ra l s . Ri ba vi ri n ta rgets the RNA-dependent RNA pol ymera s es (d) of s evera l mi nus s ens e s s RNA vi rus es , es peci a l l y res pi ra tory s yncyti a l vi rus a nd La s s a fever vi rus . 143. The answer is e. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) The bes t a pproa ch to prevent HBV i nfecti on i n a neona te born to a n HBV-pos i ti ve mother i s to gi ve HBIg a nd i mmuni ze wi th rHBV va cci ne a t bi rth (e). A pers on wi th chroni c hepa ti ti s B i nfecti on devel ops a nti bodi es to HBcAg, a nd s ometi mes to HBeAg, nei ther of whi ch i s protecti ve (neutra l i zi ng). Therefore, wa i ti ng unti l ma terna l a nti bodi es di mi ni s h (b) woul d l ea ve the ba by unprotected. HBIg a l one (a ) does not provi de i mmuni ty l a ter a nd a dmi ni s tra ti on of HBV va cci ne a l one a t bi rth (c) or a t 1 yea r (d) wi l l not provi de the neces s a ry i mmedi a te protecti on. 144. The answer is e. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) VZV (e) i s a herpes vi rus tha t ca us es chi ckenpox, a hi ghl y conta gi ous di s ea s e of chi l dhood tha t us ed to occur i n outbrea ks i n l a te wi nter a nd ea rl y s pri ng. It i s cha ra cteri zed by a fever, ma l a i s e, a nd genera l i zed ves i cul a r erupti on wi th rel a ti vel y i ns i gni fi ca nt s ys temi c ma ni fes ta ti on i n i mmuno-competent chi l dren. Advent of a n effecti ve l i ve a ttenua ted va cci ne i n 1995 ha s reduced the number of ca s es of chi ckenpox by 90% a nd morta l i ty ha s decrea s ed 66%. Adul ts a nd i mmunocompromi s ed i ndi vi dua l s ha ve more s evere di s ea s e. Mea s l es vi rus (d) produces a ma cul opa pul a r ra s h. Adenovi rus (a ), CMV (b), a nd HPV (c) do not produce ma cul opa pul a r or ves i cul a r ra s hes . 145. The answer is e. (Levinson, Ch 38. Murray, Ch 50. Ryan, Ch 9, 15.) Adenovi rus (e) ha s been a s s oci a ted wi th a cute res pi ra tory di s ea s e i n a dul ts ,
frequentl y a mong newl y enl i s ted mi l i ta ry troops . Cl os e l i vi ng condi ti ons a nd s trenuous exerci s e ma y a ccount for the s evere i nfecti ons s een i n thi s otherwi s e hea l thy group. VZV (a ) often ca us es pneumoni a i n a dul ts wi th chi ckenpox; the typi ca l crops of ves i cul a r s ki n l es i ons woul d us ua l l y be pres ent a s a n a i d to thi s di a gnos i s . Cytomega l ovi rus (d) ca us es pneumoni a i n pers ons i mmunocompromi s ed by l os s of T-cel l functi on (AIDS, orga n tra ns pl a nt reci pi ents , pers ons undergoi ng chemothera py for ca ncer). Pa pi l l oma vi rus (c) ma y ca us e pa pi l l oma s i n the res pi ra tory tra ct (ora l , l a ryngea l ) but does not ca us e the s ymptoms des cri bed or pneumoni a . Rota vi rus (b) does not i nfect the res pi ra tory tra ct. 146. The answer is a. (Kumar, Ch 5. Levinson, Ch 38, 43. Murray, Ch 49. Ryan, Ch 19.) Epi dermodys pl a s i a verruci formi s (EV) (a ), a n i nheri ted di s order mos t commonl y a utos oma l reces s i ve, ha s been l i nked to defecti ve cel l -medi a ted i mmuni ty due to muta ti ons i n EVER1 a nd EVER2, a l though thei r exa ct mecha ni s m of pa thogenes i s i n EV i s not known. EV l ea ds to wi des prea d HPV i nfecti on tha t ma ni fes ts a s fl a t wa rts di s tri buted over the enti re body. The di s order l ea ds to cuta neous s qua mous cel l ca rci noma i n 30% to 70% of the pa ti ents . NPC (d) i s l i nked to Eps tei n–Ba rr vi rus i nfecti on, pri ma ri l y i n pers ons of Southea s t As i a n a nd North Afri ca n des cent. Fa mi l i a l a denoma tous pol ypos i s (b), Li –Fra umeni s yndrome (c), a nd xeroderma pi gmentos um (e) a re i nheri ted di s orders i n the APC gene, p53 gene, a nd mecha ni s ms of DNA repa i r, res pecti vel y. They a re not a s s oci a ted wi th vi ra l i nfecti ons . 147. The answer is e. (Levinson, Ch 40. Murray, Ch 59. Ryan, Ch 9, 15.) Rota vi rus es ca us e the ma jor porti on of di a rrhea l i l l nes s i n i nfa nts a nd chi l dren worl dwi de but not i n a dul ts . They a re nonenvel oped RNA vi rus es conta i ni ng 11 s egments of doubl e-s tra nded RNA genome (e) wi thi n a doubl es hel l ed ca ps i d. Rota vi rus es , l i ke the i nfl uenza vi rus es tha t ha ve a s egmented genome, ca n undergo geneti c rea s s ortment. Other vi rus es tha t ca us e ga s troenteri ti s a re repres ented by a denovi rus 40/41, doubl e-s tra nded DNA (a ) a nd norovi rus , nons egmented s i ngl e-s tra nded pl us -s ens e RNA (d). Segmented s i ngl e-s tra nded mi nus -s ens e RNA vi rus es (c) a nd s i ngl e-s tra nded DNA vi rus es (b) do not ca us e ga s troenteri ti s . See the ta bl e i n a ns wer to ques ti on 114 for a ddi ti ona l i nforma ti on. 148. The answer is b. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Young a thl etes wi th s pl enomega l y from i nfecti ous mononucl eos i s a re a t ri s k of s pl eni c rupture (b). They s houl d be a dvi s ed to refra i n from conta ct s ports unti l thei r s ymptoms ha ve res ol ved. Hea t exha us ti on (a ) coul d occur i n a ny a thl ete a nd i s not a cons equence of EBV i nfecti on; ma l nutri ti on (c) i s unl i kel y to occur i n a n IM pa ti ent i n the Uni ted Sta tes . Apl a s ti c cri s i s (d) i s not a res ul t of EBV i nfecti on but a compl i ca ti on of pa rvovi rus B19 i nfecti on i n pers ons wi th a nemi a or hemogl obi nopa thy s uch a s s i ckl e di s ea s e. 149. The answer is e. (Levinson, Ch 42, 43. Murray, Ch 60. Ryan, Ch 16.) The vi gnette des cri bes cl a s s i c yel l ow fever (e), whi ch i s endemi c i n the tropi ca l regi ons of Afri ca , South Ameri ca , a nd Centra l Ameri ca . There i s a va cci ne a ga i ns t yel l ow fever, a nd tra vel ers to endemi c regi ons a re a dvi s ed to obta i n i mmuni za ti on 9 months i n a dva nce. In 2012, there wa s a n outbrea k of yel l ow fever i n Da rfur tha t res ul ted i n 849 ca s es wi th 171 dea ths . Dengue hemorrha gi c fever (a ) i s a pos s i bi l i ty, but thi s i s preceded by typi ca l dengue a nd i s not a ccompa ni ed by ja undi ce, nor does i t proceed a s qui ckl y. Ha nta vi rus ca rdi opul mona ry s yndrome (b) i s ca us ed by New Worl d ha nta -vi rus es a nd i s s een i n North a nd South Ameri ca . Hemorrha gi c fever wi th rena l s yndrome (c) i s ca us ed by Ol d Worl d ha nta vi rus es a nd i s s een ma i nl y i n Ea s tern As i a , Ea s tern a nd Northern Europe, a nd Ja pa n. SARS (d), ca us ed by the novel SARS corona vi rus , a ppea red i n Chi na i n 2002, beca me pa ndemi c, a nd then di s a ppea red; a new outbrea k occurred i n 2004, but di d not s prea d. In 2012, a nother novel corona vi rus tha t ca us es a SARS-l i ke i l l nes s a ppea red i n Sa udi Ara bi a ; ca s es ha ve occurred i n Sa udi Ara bi a , Qa ta r, a nd Bri ta i n. 150. The answer is b. (Levinson, Ch 34. Murray, Ch 47. Ryan, Ch 6.) Anti body mea s urements a ga i ns t vi rus es ma y be a us eful di a gnos ti c tool i f two s erum s a mpl es a re col l ected from the pa ti ent. The a cute s erum i s col l ected a s ea rl y i n the i l l nes s a s pos s i bl e, a nd the conva l es cent s erum i s col l ected 7 da ys to 2 weeks l a ter. Both a re i ncl uded i n the s a me tes t run a ga i ns t the vi ra l a nti gen. The s era a re di l uted i n a twofol d ma nner begi nni ng wi th a 1:2 or 1:10 di l uti on, dependi ng on the vi rus . A fourfol d or grea ter ri s e i n ti ter between the a cute a nd conva l es cent s era i ndi ca tes recent pri ma ry i nfecti on (b). Ti ters tha t a re equa l or onl y twofol d di fferent (up or down) i ndi ca te pa s t i nfecti on (d). In a n a na mnes ti c res pons e (c), the ti ters a re us ua l l y the s a me, but a re much hi gher tha n the pea k ti ter obs erved duri ng pri ma ry i nfecti on; for exa mpl e, 2560, 5120, or 10,240. However, s uch a res pons e i s us ua l l y detected onl y duri ng epi demi ol ogi c s tudi es a s the pa ti ent i s unl i kel y to s ymptoma ti c duri ng a s econd i nfecti on wi th the s a me vi rus . See the fi gure for compa ri s on of a nti body res pons e to pri ma ry i nfecti on a nd re-expos ure.
Gra phs compa ri ng the a nti body res pons es to pri ma ry i nfecti on to i nfl uenza A vi rus (top) a nd re-expos ure to the s a me vi rus (bottom). 151. The answer is d. (Levinson, Ch 37, 43. Murray, Ch 51. Ryan, Ch 10, 14.) Eps tei n–Ba rr vi rus (d), more commonl y known for ca us i ng i nfecti ous mononucl eos i s , ha s been a s s oci a ted wi th s evera l l ymphoma s , the fi rs t of whi ch wa s Afri ca Burki tt l ymphoma , des cri bed i n the vi gnette. More recentl y, Burki tt l ymphoma (outs i de of Afri ca ) a nd Hodgki n l ymphoma were a dded to the l i s t. In ma l es wi th congeni ta l T-cel l defects , overwhel mi ng B-cel l l eukemi a /l ymphoma ca n occur. Cytomega l ovi rus (c) a nd HSV (e) a re not a s s oci a ted wi th l ymphoprol i fera ti ve di s orders ; nor
a re Borrelia burgdorferi (a ) or Chlamydia trachomatis (b). Anti bodi es to EBV-s peci fi c a nti gens a re us ed a s a n a i d to di a gnos i s of EBV-rel a ted condi ti ons other tha n i nfecti ous mononucl eos i s . Anti bodi es to VCA a nd EBNA a re more commonl y ordered when the heterophi l e i s nega ti ve a nd EBV i nfecti on i s s us pected.
152. The answer is a. (Levinson, Ch 37, 43. Murray, Ch 51. Ryan, Ch 10, 14.) Eps tei n–Ba rr vi rus (a ) ca us es a va ri ety of s yndromes other tha n i nfecti ous mononucl eos i s , i ncl udi ng a n a s s oci a ti on wi th NPC, a di s ea s e commonl y s een i n a dul ts i n As i a , a l though the devel opment of NPC a fter EBV i nfecti on i s not l i mi ted to pers ons of As i a n des cent. EBV components ha ve been detected i n cel l s from pa ti ents wi th NPC by PCR. No s uch evi dence of the pres ence of mumps vi rus , pa rvovi rus B19, rubeol a vi rus , or rubel l a vi rus wi thi n NPC ha s been obs erved. See the a bove ta bl e. 153. The answer is c. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) CMV, whi ch i s us ua l l y a s ymptoma ti c or ca us es mi l d s ymptoms i n i mmunocompetent pers ons , ca n ca us e a va ri ety of deva s ta ti ng di s ea s es i n pa ti ents wi th AIDS, i ncl udi ng reti ni ti s (c), es opha gi ti s , col i ti s , a nd encepha l i ti s . Apl a s ti c cri s i s (a ) i s a s s oci a ted wi th pa rvovi rus B19 i nfecti on i n pers ons wi th s i ckl e cel l a nemi a a nd other hemogl obi nopa thi es ; ki dney fa i l ure (b) ca n res ul t from CMV i nfecti on of a tra ns pl a nted ki dney; Reye s yndrome (d) occurs ma i nl y i n chi l dren a s s oci a ted wi th VZV a nd other vi ra l i nfecti ons i f a s pi ri n i s us ed to reduce fever; SSPE (e) i s a n uncommon, l etha l , l a te compl i ca ti on of mea s l es vi rus i nfecti on. 154. The answer is c. (Levinson, Ch 38, 43. Murray, Ch 49. Ryan, Ch 19.) The di a gnos i s of a vi ra l i nfecti on i s ma de ea s i er by the crea ti on of a grea ter number of di a gnos ti c vi rol ogy l a bora tori es duri ng the l a s t few deca des . In order for vi ra l di a gnos i s to be s ucces s ful , the mos t a ppropri a te s peci men mus t be col l ected for the di s ea s e i n ques ti on. The bes t s creeni ng tes t for cervi ca l HPV i nfecti on i s a Pa p s mea r on cel l s from the cervi x
for the pres ence of koi l ocytes (c), whi ch a re pa thognomoni c for HPV i nfecti on i n a ny s i te. DNA mol ecul a r probe for HPV genomes (i n s i tu hybri di za ti on) (a ) a nd PCR for HPV DNA (d) a re us ed to determi ne the type of HPV i nfecti on. HPV does not grow i n vi ra l cul ture (e) a nd HPV-s peci fi c a nti bodi es (b) a re not hel pful for determi ni ng cervi ca l i nfecti on. 155. The answer is b. (Levinson, Ch 42, 43. Murray, Ch 60. Ryan, Ch 16.) The enti re fa mi l y experi enced dengue (brea kbone fever). The ma n, who ha d previ ous l y been i nfected wi th one dengue vi rus , a nd the 6-yea r-ol d s uffered dengue hemorrha gi c fever (b). Thi s compl i ca ti on i s s een pri ma ri l y i n chi l dren younger tha n 15 yea rs of a ge a nd i n s ome who ha ve been i nfected wi th one s erotype of dengue vi rus a nd a re s ubs equentl y i nfected wi th a nother. Nothi ng i n the vi gnette s ugges ts a cute res pi ra tory di s tres s s yndrome (a ), encepha l i ti s (b), Gui l l a i n–Ba rré s yndrome (d), or a s econda ry ba cteri a l i nfecti on (e). 156. The answer is b. (Levinson, Ch 40. Murray, Ch 54. Ryan, Ch 9, 12.) Coxs a cki evi rus B (b) i s the ma jor ca us e of vi ra l myoca rdi ti s ; thi s group a l s o ca us es pl eurodyni a , pa ncrea ti ti s , orchi ti s , CNS di s ea s e, a nd res pi ra tory i nfecti ons . Stra i ns of Coxs a cki evi rus A (a ) ca us e CNS di s ea s e, herpa ngi na , ha ndfoot-a nd-mouth di s ea s e, a cute hemorrha gi c conjuncti vi ti s , a nd res pi ra tory tra ct i nfecti ons . Echovi rus 11 (c) i s pri ma ri l y a s s oci a ted wi th CNS di s ea s e, ra s hes , a nd res pi ra tory tra ct i nfecti ons . Enterovi rus 70 (d) ca us es a cute hemorrha gi c conjuncti vi ti s . Pol i ovi rus 3 (e) ca us es a s epti c meni ngi ti s a nd pa ra l yti c pol i omyel i ti s . Enterovi rus es a re s hed duri ng the fi rs t da ys of i nfecti on a nd ma y be i s ol a ted from the res pi ra tory tra ct duri ng a cute i nfecti on; they a re s hed from the i ntes ti na l tra ct for up to 30 da ys a fter s ymptoms a ppea r. The bes t s peci men for di a gnos i s i s ti s s ue/fl ui d from the ta rget, i n thi s ca s e the hea rt, but tha t i s not a l wa ys pos s i bl e. Cha ra cteri za ti on of a n enterovi rus i s ol a ted from the s tool a s the eti ol ogi c a gent ca n be corrobora ted by s erol ogy i n the ca s e of vi ra l myoca rdi ti s beca us e the number of s erotypes i s l i mi ted. 157. The answer is a. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) The vi gnette des cri bes a n a dul t wi th chi ckenpox. Adul ts who contra ct VZV ha ve a n i ncrea s ed ri s k for va ri cel l a pneumoni a (the ma jori ty of VZV pneumoni a occur i n a dul ts ) a nd other compl i ca ti ons , i ncl udi ng VZV encepha l i ti s . H&E s ta i ni ng of cel l s obta i ned by bronchoa l veol a r bi ops y woul d s how cel l s wi th eos i nophi l i c i ntra nucl ea r Cowdry A i ncl us i on bodi es (a ) a nd mul ti nucl ea ted gi a nt cel l s , both typi ca l of HSV a nd VZV i nfecti ons . Gua rni eri bodi es (b) i ndi ca te poxvi rus i nfecti on; koi l ocytes (c) a re s een i n HPV i nfected cel l s ; Negri bodi es (d) a re produced by ra bi es vi rus ; a nd owl ’s eye cel l s (e) wi th ba s ophi l i c i ntra nucl ea r i ncl us i ons a re typi ca l of cytomega l o-vi rus i nfecti on. See the di a gra m i n a ns wer to ques ti on 92. 158. The answer is c. (Katzung, Ch 49. Levinson, Ch 39. Murray, Ch 57. Ryan, Ch 9.) Os el ta mi vi r (c) a nd za na mi vi r a re the current drugs of choi ce to trea t i nfl uenza . Both drugs i nhi bi t the neura mi ni da s e of Influenzavirus A a nd Influenzavirus B. Ama nta di ne (a ) a nd i ts a na l og ri ma nta di ne, drugs tha t bl ock the M2 cha nnel of Influenzavirus A onl y, a re no l onger recommended due to wi des prea d res i s ta nce a mong ci rcul a ti ng i nfl uenza vi rus es . Fos ca rnet (b) i s us ed to trea t cytomega l ovi rus i nfecti on, ri ba vi ri n (d) i s us ed to trea t res pi ra tory s yncyti a l vi rus i nfecti on, a nd zi dovudi ne (e) i s a n a nti retrovi ra l drug us ed to trea t HIV i nfecti on. 159. The answer is a. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) The mos t l i kel y hepa ti ti s vi rus i nvol ved i n a pa rti cul a r i l l nes s or outbrea k ca n be pos tul a ted by the route of tra ns mi s s i on, the i ncuba ti on peri od, a nd the type of ons et.
160. The answer is c. (Levinson, Ch 38. Murray, Ch 50. Ryan, Ch 9, 15.) The l a ck of vomi ti ng, dura ti on of her s ymptoms , a nd ti mi ng of ons et of her brothers ’ s ymptoms des cri bed i n the cl i ni ca l vi gnette, a nd her up-to-da te i mmuni za ti on a ga i ns t rota vi rus s trongl y s ugges t tha t a denovi rus i s the eti o-l ogi c a gent. Therefore, a n EIA for a denovi rus types 40/41 (c) i s the bes t tes t. Rotavirus a nd Norovirus i nfecti ons ca n a l s o be di a gnos ed by EIA; however, cul ture for Norovirus (a ) i s not a va i l a bl e a nd s erol ogy for Rotavirus (e) woul d be expected to be pos i ti ve due to her i mmuni za ti ons . An EM exa mi na ti on of s tool for a s trovi rus (d) woul d not l i kel y be a va i l a bl e i n mos t cl i ni ca l s etti ngs , a l though EM ca n a l s o revea l Rotavirus, Norovirus a nd other ca l i ci vi rus es , a nd a denovi rus . Enterovi rus es , a l though they i nfect cel l s of the i ntes ti na l tra ct, do not us ua l l y ca us e a cute ga s troenteri ti s . A DFA for enterovi rus on i ntes ti na l bi ops y (b) woul d not l i kel y be hel pful i n es ta bl i s hi ng the eti ol ogi c a gent. See the ta bl e i n the a ns wer to ques ti on 114 for a ddi ti ona l i nforma ti on. 161. The answer is b. (Levinson, Ch 40. Murray, Ch 59. Ryan, Ch 9, 15.) EIA (b) i s the bes t tes t for cl i ni ca l di a gnos i s of rota vi rus i nfecti on. Cul ture (a ) i s now pos s i bl e, but i s not routi nel y done. El ectron mi cros copy (c) detects rota vi rus i nfecti on a s wel l a s other vi rus es tha t ca us e ga s troenteri ti s , but EM i s not routi nel y a va i l a bl e for cl i ni ca l di a gnos i s . Hi s tol ogi c exa mi na ti on of bi ops y (d) woul d s how cha ra cteri s ti c cha nges i n the s ma l l i ntes ti ne
ca us ed by rota vi rus but the cha nges a re s i mi l a r to thos e ca us ed by norovi rus es ; s uch a n i nva s i ve tes t i s unneces s a ry. Serol ogy (e) i s us ed for epi demi ol ogi c purpos es onl y. See the ta bl e i n the a ns wer to ques ti on 114 for a ddi ti ona l i nforma ti on. 162. The answer is d. (Levinson, Ch 40. Murray, Ch 55. Ryan, Ch 15.) A number of vi rus es tha t ca us e ga s troenteri ti s ha ve been recogni zed. The ta bl e i n the a ns wer to ques ti on 160 s umma ri zes the cha ra cteri s ti cs of thes e vi rus es . Norovirus (d) ha s been a s s oci a ted wi th outbrea ks i n hea l thca re s etti ngs (hos pi ta l s , nurs i ng homes ), l ei s ure s etti ngs (res orts , crui s e chi ps ), s chool s , a nd res ta ura nts . Often the s ource i s a n i nfected food ha ndl er who fa i l s to us e good ha nd wa s hi ng protocol . Rotavirus (e) a nd a denovi rus 40/41 (a ) ca us e i nfecti ons pri ma ri l y i n i nfa nts , a l though a l l a ges ca n be a ffected; both ca n be di a gnos ed by EIA. Astrovirus (b) ha s been demons tra ted by EM i n s tool s of young chi l dren a nd el derl y nurs i ng home res i dents duri ng outbrea ks of di a rrhea . HAV (c) does not ca us e ga s troenteri ti s . See the ta bl e i n the a ns wer to ques ti on 114 for a ddi ti ona l i nforma ti on. 163. The answer is b. (Levinson, Ch 40. Murray, Ch 55. Ryan, Ch 15.) A number of vi rus es tha t ca us e ga s troenteri ti s ha ve been recogni zed. The ta bl e i n the a ns wer to ques ti on 160 s umma ri zes the cha ra cteri s ti cs of thes e vi rus es . Astrovirus (b) ha s been demons tra ted by EM i n s tool s of young chi l dren a nd el derl y nurs i ng home res i dents duri ng outbrea ks of di a rrhea . EIA tes ts a re a va i l a bl e to detect a denovi rus 40/41 (a ), Norovirus (d), a nd Rotavirus (e), s o thes e ca nnot be the ca us a ti ve a gents . HAV (c) does not ca us e ga s troenteri ti s . See the ta bl e i n the a ns wer to ques ti on 114 for a ddi ti ona l i nforma ti on. 164. The answer is e. (Levinson, Ch 39, 42, 46. Murray, Ch 60. Ryan, Ch 10, 16.) Rubel l a (e), a l s o ca l l ed Germa n mea s l es or 3-da y mea s l es , i s a n a cute febri l e i l l nes s cha ra cteri zed by a ma cul opa pul a r ra s h a nd l ympha denopa thy tha t a ffects chi l dren a nd young a dul ts . It i s the mi l des t of the vi ra l exa nthems . Chi ckenpox (a ) i s cha ra cteri zed by ves i cul a r l es i ons a ppea ri ng i n crops begi nni ng on the trunk a nd s prea di ng to the extremi ti es . Les i ons of ha nd-foot-a nd-mouth di s ea s e (d) a re a l s o ves i cul a r i n na ture wi th the ma jori ty of the l es i ons s een i n the s i tes na med. In erythema i nfecti os um (b), the ra s h on the fa ce i s red a nd di s tri buted on the cheeks , whi l e the ra s h on the body i s l a cy or reti cul a r; the ra s h bl a nches a nd returns . Mea s l es (c), a l s o ca l l ed rubeol a or ha rd mea s l es , i s a much more s evere i l l nes s cha ra cteri zed by prodrome of cough, coryza , a nd conjuncti vi ti s . The prodrome i s fol l owed by the a ppea ra nce of Kopl i k s pots on the bucca l mucos a . The ma cul opa pul a r ra s h then a ppea rs begi nni ng on the neck a nd s prea di ng downwa rd. Mea s l es l a s ts much l onger tha n rubel l a . 165. The answer is c. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) HCV i s trea ta bl e wi th combi na ti ons of drugs , a l though whether trea tment s houl d be offered a nd the type of trea tment gi ven mus t be determi ned on a n i ndi vi dua l ca s e ba s i s . In genera l , thos e cons i dered for trea tment s houl d ha ve el eva ted s erum a l a ni ne a mi notra ns fera s e (ALT) l evel s , pos i ti ve HCV a nti body, a nd pos i ti ve HCV RNA by PCR. Addi ti ona l cri teri a , s uch a s genotypi ng of the vi rus , or pres ence of coi nfecti on wi th HIV or HBV, ma y be needed. The types of a nti vi ra l s a va i l a bl e for HCV i nfecti on i ncl ude IFN-α, pegyl a ted-IFN-α, ri ba vi ri n, a nd PIs . The goa l s of a nti vi ra l thera py a re to a tta i n s us ta i ned era di ca ti on of the vi rus a nd to prevent progres s i on to ci rrhos i s , s evere l i ver di s ea s e requi ri ng l i ver tra ns pl a nta ti on, or hepa tocel l ul a r ca rci noma . Trea tment s pa ns from 24 weeks to 1 yea r dependi ng on the drug(s ) us ed a nd the genotype of the vi rus . The tes t us ed to moni tor thera py for ea rl y vi rol ogi c res pons e, a nd for s us ta i ned vi rol ogi c res pons e, i s the HCV RNA l evel (c). The pa ti ent a l rea dy ha s a nti bodi es to HCV, s o tes ti ng for a nti bodi es , whether IgG (a ) or IgM (b), woul d not determi ne effecti venes s of thera py. Serum ALT l evel s (e) ma y be moni tored, but a re l i a bl e to fl uctua te a nd norma l i za ti on of ALT i s not proof of cure. Li ver bi ops y (d) i s us ed i n s ome ca s es to determi ne whether a nti vi ra l trea tment s houl d be i ni ti a ted, but i s not us ed to fol l ow thera py. 166. The answer is d. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) Anti vi ra l trea tment for HBV i nfecti on wa s grea tl y enha nced by the recogni ti on tha t the vi ra l pol ymera s e ha s revers e tra ns cri pta s e functi ons . Si nce 1998, numerous a nti retrovi ra l revers e tra ns cri pta s e i nhi bi tors ha ve been tri ed a nd two were found to be effecti ve a ga i ns t HBV a s wel l —l a mi vudi ne a nd tenofovi r (d). Addi ti ona l a nti vi ra l s s peci fi c for the HBV DNA pol ymera s e ha ve been devel oped: a defovi r i n 2002, enteca vi r i n 2005, a nd tel bi vudi ne i n 2006. The a nti retrovi ra l zi dovudi ne (e) ha s not been effecti ve a ga i ns t HBV. Acycl ovi r (a ) i s s peci fi c for HSVs 1 a nd 2; fos ca rnet (b) for cytomega l ovi rus ; a nd ri ba vi ri n (c) for s evere res pi ra tory s yncyti a l vi rus i nfecti on, HCV i nfecti on, a nd vi ra l hemorrha gi c fever ca us ed by La s s a fever vi rus . 167. The answer is a. (Levinson, Ch 39, 42, 46. Murray, Ch 61. Ryan, Ch 16.) La Cros s e vi rus (a ), a n a rthropod-borne Bunyavirus tha t ca us es vi ra l encepha l i ti s , i s the mos t l i kel y eti ol ogi c a gent. Thi s vi rus i s found throughout the ea s tern ha l f of the Uni ted Sta tes from Mi nnes ota s outh to Loui s i a na a nd a l l s ta tes to the ea s t. The ma jori ty of ca s es ha ve been documented from rura l a rea s of Mi nnes ota , Wi s cons i n, Il l i noi s , Indi a na , a nd Ohi o; a nd mos t occur i n chi l dren younger tha n 16 yea rs of a ge. In contra s t, St. Loui s encepha l i ti s vi rus (d) i s di s tri buted through the enti re Uni ted Sta tes , wi th the ma jori ty of ca s es occurri ng i n pers ons ol der tha n 70 yea rs of a ge, a nd i n urba n a rea s . Symptoms of vi ra l encepha l i ti s a re not s uffi ci ent to determi ne the eti ol ogi c a gent, but geogra phi c di s tri buti on a nd a ge a re good gui des to the pres umpti ve a gent. Serol ogi c s tudi es , PCR, or vi ra l i s ol a ti on a re needed to confi rm the di a gnos i s . Venezuel a n equi ne encepha l i ti s vi rus (e) i s ra rel y encountered i n the Uni ted Sta tes , a nd i s res tri cted to s outh Fl ori da a nd s outh Texa s . Ra bi es vi rus (c) does not ca us e the s ymptoms des cri bed a nd woul d be a s s oci a ted wi th a ni ma l bi te or expos ure to ba ts . Pol i ovi rus (b), whi ch i s a n enterovi rus , wa s rul ed out by the nega ti ve PCR. See the ta bl e a ccompa nyi ng a ns wer to ques ti on 72 for a ddi ti ona l i nforma ti on. 168. The answer is d. (Levinson, Ch 37, 39, 42, 46. Murray, Ch 51, 60. Ryan, Ch 10, 14, 16.) CRS i ncl udes s evera l s i gns a nd s ymptoms tha t overl a p wi th cytomega l i c i ncl us i on di s ea s e. Thes e a re i ntra uteri ne growth reta rda ti on (a ), hepa tos pl enomega l y (b), mi crocepha l y (c), menta l reta rda ti on a nd devel opmenta l del a ys , s ens ori neura l hea ri ng l os s (e), a nd s ki n l es i ons known a s “bl ueberry muffi n s pots ,” a l though the eti ol ogy of the l es i ons i s di fferent i n the two i nfecti ons . CRS i s di fferent i n tha t congeni ta l hea rt defects s uch a s pa tent ductus a rteri os us (d) a nd pul mona ry a rtery s tenos i s , a nd eye defects s uch a s ca ta ra cts a nd i nfa nti l e gl a ucoma a l s o occur. Bl ueberry muffi n s pots i n CRS a re due to derma l erythropoi es i s . Cytomega l i c i ncl us i on di s ea s e i s cha ra cteri zed by the pres ence of i ntercerebra l ca l ci fi ca ti ons , cerebra l a trophy, ventri cul omega l y, hema tol ogi c a bnorma l i ti es i ncl udi ng thrombocytopeni a , a nd chori oreti ni ti s ; the bl ueberry muffi n s pots a re us ua l l y s ma l l er tha n thos e s een i n CRS a nd repres ent petechi a e a nd purpura due to l ow pl a tel ets . Previ ous l y very common, CRS ha s been vi rtua l l y el i mi na ted i n the Uni ted Sta tes wi th the us e of rubel l a va cci ne. 169. The answer is b. (Levinson, Ch 32. Murray, Ch 45, 46. Ryan, Ch 7.) Echovi rus , a n enterovi rus , i s s prea d vi a the feca l –ora l route a nd ca us es a s epti c meni ngi ti s (b). Corona vi rus es (a ) a re more commonl y s prea d vi a res pi ra tory dropl ets a nd ca us e the common col d. HIV (c), the ca us a ti ve a gent of AIDS, i s s prea d vi a bl ood a nd s exua l conta ct. Infl uenza vi rus (d) i s s prea d by res pi ra tory dropl ets a nd ca us es i nfl uenza a nd s ometi mes pri ma ry vi ra l pneumoni a . Ra bi es vi rus (e) i s s prea d by bi tes of ma mma l s a nd ca us es the CNS di s ea s e ra bi es . 170. The answer is a. (Levinson, Ch 42, 43. Murray, Ch 60. Ryan, Ch 16.) The vi gnette des cri bes WNV (a ) encepha l i ti s pres enta ti on i n a pers on over 60. Al though preva l ent i n Europe, Afri ca , a nd the Mi ddl e Ea s t, i t wa s not s een i n the Uni ted Sta tes unti l the s ummer of 1999. Si nce then, the vi rus ha s s prea d a cros s the Uni ted Sta tes a nd i s now endemi c i n a l l 48 conti nenta l s ta tes . It i s tra ns mi tted by mos qui toes a nd bi rds , es peci a l l y crows , a re the res ervoi r. WNV i nfecti on ra nges from a s ymptoma ti c, to a febri l e i l l nes s wi th hea da che, to neuroi nva s i ve di s ea s e, whi ch ra nges from meni ngi ti s i n chi l dren to encepha l i ti s i n a dul ts ; i t i s es peci a l l y s evere i n pers ons over 60 yea r of a ge a nd i n the i mmunocompromi s ed. Up to 10% of the encepha l i ti s pa ti ents s uffer a cute fl a cci d pa ra l ys i s . The morta l i ty ra te ca n be a s hi gh a s 12%, a l mos t a l l i n the el derl y. Si nce 2007, a number of neuroi nva s i ve ca s es reported to CDC ha ve va ri ed from a l ow of 386 i n 2009 to 2779 i n 2012. St. Loui s encepha l i ti s vi rus i s a l s o more l i kel y to
ca us e encepha l i ti s i n the el derl y (mos t i n pers ons over 70), but thi s i nfecti on i s l es s l i kel y to occur tha n WNV; a nd a cute fl a cci d pa ra l ys i s i s not pa rt of the pres enta ti on. Pol i ovi rus (c), the cl a s s i c ca us e of a cute fl a cci d pa ra l ys i s , or pol i omyel i ti s i s not pres ent i n the Uni ted Sta tes . HSV (d) encepha l i ti s i s not a s s oci a ted wi th a cute fl a cci d pa ra l ys i s a nd i s cha ra cteri zed by foca l l es i ons i n the tempora l or occi pi ta l l obes on one s i de of the bra i n. Coltivirus (e) i s confi ned to the Rocky Mounta i n regi on a nd ra rel y ca us es encepha l i ti s . See the ta bl e a ccompa nyi ng the a ns wer to ques ti on 72 for a ddi ti ona l i nforma ti on. 171. The answer is b. (Levinson, Ch 38, 44. Murray, Ch 49. Ryan, Ch 19.) JC vi rus , a pol yoma vi rus , wa s fi rs t i s ol a ted from the di s ea s ed bra i n of a pa ti ent wi th Hodgki n l ymphoma who wa s dyi ng of progres s i ve mul ti foca l l eukoencepha l opa thy (PML), whi ch i s des cri bed i n the vi gnette. Thi s demyel i na ti ng di s ea s e occurs a l mos t excl us i vel y i n i mmunos uppres s ed pers ons (AIDS, l eukemi a , tumors , a nd orga n tra ns pl a nts ). Recentl y, PML ha s occurred i n pa ti ents recei vi ng na ta l i zuma b a nd ri tuxi ma b i mmune thera py. PML i s the res ul t of a borti ve i nfecti on of a s trocytes a nd producti ve i nfecti on of ol i godendrocytes by JC vi rus (b). HPVs ca us e cuta neous a nd mucos a l i nfecti ons . Pri on va ri a nt CJD (c) ma ni fes ts s i mi l a rl y to PML, but bra i n bi ops y or s ecti on a t a utops y s hows a myl oi d pl a ques a nd s pongi form va cuol es . SSPE ca us ed by rubeol a (mea s l es ) vi rus (d) a nd occurs a bout 10 to 11 yea rs a fter cl i ni ca l mea s l es ; s ymptoms i ncl ude cha nges i n beha vi or a nd i ntel l ect a nd s ei zures . WNV (e) ca us es a cute encepha l i ti s wi th s ymptoms tha t i ncl ude hea da che, fever, a nd decrea s ed cons ci ous nes s . 172. The answer is a. (Levinson, Ch 37. Murray, Ch 51. Ryan, Ch 10, 14.) Whi l e pri ma ry HSV-1 i nfecti ons a re us ua l l y a s ymptoma ti c, s ymptoma ti c di s ea s e occurs mos t frequentl y i n s ma l l chi l dren (1-5 yea rs ol d). Bucca l a nd gi ngi va l mucos a a re mos t often i nvol ved, a nd l es i ons , i f untrea ted, ma y l a s t 2 to 3 weeks . Rea cti va ti on res ul ts i n s pora di c ves i cul a r l es i ons tha t hea l more qui ckl y tha n the pri ma ry l es i ons . Fol l owi ng pri ma ry ora l i nfecti on, whether s ymptoma ti c or a s ymptoma ti c, the vi rus enters the tri gemi na l ga ngl i a a nd rema i ns l a tent there throughout l i fe (a ). The vi rus ma y rea cti va te under condi ti ons of phys i ca l , emoti ona l , or menta l s tres s a nd i f the i ndi vi dua l becomes i mmunocompromi s ed from other i nfecti ons or medi ca l condi ti ons . Ea ch i ndi vi dua l i s uni que rega rdi ng rea cti va ti on of HSV (type 1 or type 2), wi th s ome ha vi ng no s ymptoma ti c rea cti va ti on, s ome one or two, a nd s ome mul ti pl e i ns ta nces throughout thei r l i ves ; therefore, one ca nnot s a y tha t the ves i cul a r l es i ons wi l l not recur (b). Gui l l a i n– Ba rré s yndrome (c) i s more wi th other huma n herpes vi rus es (VZV, CMV, a nd EBV) a nd ba cteri a l i nfecti ons (Campylobacter jejuni a nd Mycoplasma pneumoniae). Hepa to-cel l ul a r ca rci noma (d) i s s een i n s ome pa ti ents wi th chroni c hepa ti ti s due to HCV or HBV; a nd SSPE (e) i s a ra re compl i ca ti on of mea s l es vi rus i nfecti on. 173. The answer is d. (Levinson, Ch 37. Murray, Ch 52. Ryan, Ch 11.) The di s ea s e des cri bed i n the vi gnette i s mol l us cum conta gi os um, ca us ed by Molluscipoxvirus (d), a member of the Poxviridae. Thi s s el f-l i mi ti ng di s ea s e i s more common i n chi l dren tha n a dul ts a nd i s s prea d by di rect conta ct (i ncl udi ng s exua l a cti vi ty) a nd fomi tes s uch a s towel s . Bi ops y of the l es i ons di fferenti a tes them from condyl oma a ccumi na tum ca us ed by HPV types 6 a nd 11 (c). Mol l us cum bodi es , s i mi l a r to Gua rni eri bodi es obs erved wi th other poxvi rus es , a re pres ent i n mol l us cum conta gi os um a nd koi l ocytes a re s een i n HPV i nfecti ons . Coxs a cki evi rus A (b) ca n ca us e s ki n l es i ons , but thes e a re ves i cul a r; whi l e the l es i ons ca us ed by orf vi rus (e) a re pus tul a r i n na ture. Adenovi rus (a ) does not ca us e s ki n l es i ons . 174. The answer is b. (Levinson, Ch 39, 46. Murray, Ch 56. Ryan, Ch 9, 10.) The recentl y devel oped monocl ona l a nti body pa l i vi zuma b (b) i s recommended for prophyl a xi s of RSV i nfecti on i n prema ture i nfa nts who a re l es s tha n 12 months of a ge a t the ons et of RSV s ea s on. Pool ed i mmunogl obul i n (c) does not conta i n s uffi ci ent a nti -RSV a nti bodi es to be effecti ve. IFN-α (a ) i s us ed to trea t a cute hepa ti ti s C, chroni c hepa ti ti s B, condyl oma a ccumi na tum, a nd s ome ca ncers . Ri ba vi ri n (d) i s a dmi ni s tered a s a n a eros ol to trea t RSV i nfecti on but i s not us ed for prophyl a xi s . Ri tuxi ma b i s a monocl ona l a nti body tha t rea cts wi th CD20 on B cel l s a nd i s us ed to reduce thei r numbers . 175. The answer is a. (Levinson, Ch 39, 44, 46. Murray, Ch 56. Ryan, Ch 9, 10.) Hi gh-dos e vi ta mi n A (a ) gi ven to ma l nouri s hed chi l dren a nd a nyone wi th vi ta mi n A defi ci ency reduces the ri s k of morta l i ty. The Worl d Hea l th Orga ni za ti on recommends tha t a l l chi l dren wi th mea s l es recei ve vi ta mi n A s uppl ementa ti on (not neces s a ri l y hi gh-dos e). The rema i ni ng vi ta mi ns l i s ted do not ha ve a ny effects on the outcome of mea s l es . 176. The answer is d. (Levinson, Ch 32, 33. Murray, Ch 10, 45, 46. Ryan, Ch, 33.) Na tura l ki l l er cel l s functi on i n i nna te i mmuni ty to ki l l vi rus -i nfected cel l s (c); they ma y be s uffi ci ent to era di ca te a l l i nfected cel l s , but us ua l l y s ome i nfecti ous pa rti cl es es ca pe from the s i te of pri ma ry repl i ca ti on to the reti cul oendothel i a l s ys tem to undergo s econda ry repl i ca ti on. Neutra l i zi ng IgG s peci fi c for the vi rus (d) tha t i s ci rcul a ti ng pri or to i nfecti on (from i mmuni za ti on or pa s t i nfecti on) or tha t devel ops before the ons et of di s s emi na ti on by vi remi a prevents thes e vi rus es from rea chi ng thei r ta rget orga n, i n thi s ca s e the meni nges a nd/or bra i n. Anti body a ga i ns t thes e vi rus es devel ops ra pi dl y; thus , ma ny pers ons ha ve onl y nons peci fi c s ymptoms or rema i n a s ymptoma ti c. Onl y i n thos e i n whom the vi rus repl i ca ti on outs tri ps hos t defens e does meni ngi ti s , encepha l i ti s , or meni ngoencepha l i ti s occur. Cytotoxi c T cel l s (a ) a re neces s a ry to des troy a l l vi rus -i nfected cel l s a nd a re res pons i bl e for pa rt of the da ma ge a t ta rget s i tes , but they ca nnot prevent the vi rus from rea chi ng the ta rget. Compl ement (b) a nd neutrophi l s (e) pl a y l i ttl e to no rol e i n the hos t res pons es to thes e vi rus es . 177. The answer is c. (Levinson, Ch 39, 46. Murray, Ch 61. Ryan, Ch 16.) Bi pha s i c i l l nes s cul mi na ti ng i n encepha l i ti s i s cha ra cteri s ti c of i nfecti on wi th the Arenavirus l ymphocyti c chori omeni ngi ti s vi rus (c), whi ch i s tra ns mi tted i n rodent excreta ; i n thi s ca s e, the common gra y hous e mous e. La s s a fever vi rus i s a l s o a n Arenavirus tra ns mi tted by rodents , but i s found i n Afri ca a nd ca us es hemorrha gi c fever. Si n Nombre ha nta vi rus (d) i s a l s o tra ns mi tted by rodents , but ca us es ha nta vi rus pul mona ry s yndrome. La Cros s e vi rus (a ) a nd wes tern equi ne encepha l i ti s vi rus (e) ca us e encepha l i ti s but a re tra ns mi tted by mos qui toes . 178. The answer is c. (Levinson, Ch 41. Murray, Ch 63. Ryan, Ch 13.) HCV i s a fl a vi vi rus tha t i s tra ns mi tted by pa rentera l l y or s exua l l y i n the ma jori ty of ca s es ; unl i ke the other members of the Flaviviridae known to i nfect huma ns , i t i s not tra ns mi tted by a rthropods . Mos t new HCV i nfecti ons a re s ubcl i ni ca l , a nd 70% to 90% devel op i nto chroni c hepa ti ti s . Mos t HCV chroni c ca s es rema i n wi thout s ymptoms but 10% to 20% ma y devel op to chroni c a cti ve hepa ti ti s a nd ci rrhos i s or hepa tocel l ul a r ca rci noma . Mi xed cryogl obul i nemi a a nd gl omerul onephri ti s compl i ca ti ons a re not uncommon wi th HCV (c). HAV (a ) i s a member of the Enterovirus genus ; tra ns mi tted feca l -ora l l y, i t produces onl y a cute di s ea s e. HBV (b), a member of the Hepadnaviridae, i s tra ns mi tted s i mi l a rl y to HCV; i t ca n produce a cute or chroni c i nfecti ons . HDV (d) i s a mi nus -s ens e RNA vi rus tha t ca n onl y ca us e i nfecti on i n HBV-i nfected i ndi vi dua l s . HEV i s a member of the new fa mi l y Hepeviridae; tra ns mi s s i on a nd di s ea s e ca us ed by HEV i s s i mi l a r to tha t of HAV, a l though the morta l i ty i s hi gher, es peci a l l y i n pregna nt women. 179. The answer is c. (Levinson, Ch 39. Murray, Ch 57. Ryan, Ch 9.) Duri ng the i nfl uenza s ea s on, di a gnos i s i s us ua l l y ba s ed on cl i ni ca l pres enta ti on a nd detecti on of i nfl uenza a nti gens i n res pi ra tory s ecreti ons (c), whi ch i s the mos t ra pi d tes t a va i l a bl e. However, i nfl uenza -l i ke i l l nes s pres enti ng out of s ea s on, i nfecti ons s trongl y s us pected to be i nfl uenza but for whi ch the ra pi d tes t i s nega ti ve, a nd s pora di c ca s es s houl d be tes ted for i nfl uenza vi rus es a nd other res pi ra tory vi rus es by other types of tes ti ng, i ncl udi ng cul ture (b), i mmunofl uores cence a s s a ys for mul ti pl e vi rus es , or RT-PCR a nd PCR. Tes ti ng of pa i red s era (e) i s more frequentl y us ed epi demi ol ogi ca l l y to determi ne the extent of the outbrea k or epi demi c, the number of a s ymptoma ti c ca s es (i f a ny), the effecti venes s of detecti on methods , a nd va cci ne effi ca cy. El ectron mi cros copy (d) i s ra rel y done. The col d a ggl uti ni n tes t (a ) i s us ed to di a gnos e Mycoplasma pneumoniae i nfecti on.
Bacteriology Questions 180. A 65-yea r-ol d ma n pres ents to a n emergency room i n the Uni ted Sta tes . He compl a i ns of a 6-month hi s tory of ni ght s wea ts , fever, a nd cough wi th the producti on of s putum. He a l s o s ta tes tha t he ha s l os t a bout 30 pounds i n the l a s t yea r. He deni es i l l ega l drug us e, but a dmi ts to ha vi ng s ex wi th men. He demons tra ted pos i ti ve i mmunodefi ci ency vi rus s erol ogy a nd a l ow CD4+ l ymphocyte count. Gra m s ta i n of hi s s putum demons tra ted thi n rods tha t di d not s ta i n. When thes e orga ni s ms were s ta i ned wi th the a ci d fa s t s ta i n, they took up the s ta i n. He i s mos t l i kel y to be i nfected wi th whi ch of the fol l owi ng orga ni s ms ? a . Mycobacterium avium-compl ex b. Mycobacterium scrofulaceum c. Mycobacterium tuberculosis d. Mycoplasma hominis e. Mycoplasma pneumoniae 181. A 40-yea r-ol d woma n who ha s l i ved i n s outhwes t Loui s i a na a l l her l i fe pres ents to the emergency room. She ha s s tra nge-l ooki ng, ra i s ed a rea s on her fa ce, a rms , a nd l egs . She a l s o compl a i ns tha t s he i s l os i ng feel i ng i n her fi ngers a nd toes . She s a ys tha t when s he cuts or burns hers el f, s he does not feel i t a nd tha t ma kes the i njury even grea ter beca us e s he does not know to pul l a wa y from the i njuri ng s ource. A Gra m s ta i n of s cra pi ngs from the ra i s ed a rea s on her s ki n s hows thi n ba cteri a l rods tha t do not ta ke up the s ta i n. However, a n a ci d fa s t s ta i n of the s a me ma teri a l s hows numerous ba ci l l i . Wha t di s ea s e i s the woma n mos t l i kel y to ha ve?
(Courtesy of Dr. Charles C. Shepard, Public Health Image Library, Centers for Disease Control and Prevention.) a . Borderl i ne tubercul oi d l epros y b. La dy Wi ndermere s yndrome c. Leproma tous l epros y d. Scroful a e. Tubercul oi d l epros y 182. An 85-yea r-ol d homel es s ma n i s brought to the emergency room. He s a ys tha t he ha s been l i vi ng on the s treet for the pa s t 10 yea rs . There i s a s trong s mel l of a l cohol on hi s cl othi ng a nd you s us pect he i s a n a l cohol i c. He s a ys he ha s cons ta nt hea da ches , a nd a fever tha t comes a nd goes a bout every 5 da ys . He a l s o compl a i ns of grea t pa i ns i n hi s l egs . The nurs es s a y tha t when they cut off hi s cl othes , they found l i ce. You s us pect tha t he ha s trench fever ca us ed by whi ch orga ni s m? a . Bacillus anthracis b. Brucella abortis c. Bartonella bacilliformis
d. Bartonella henselae e. Bartonella quintana 183. A 45-yea r-ol d ma n goes to hi s fa mi l y doctor compl a i ni ng of a cons ta nt, non-producti ve cough. The ma n a l s o ha s s evere ches t pa i ns whi ch he s a ys ha ve bothered hi m for the pa s t week. The ma n a l s o s a ys tha t thi s i s unus ua l for hi m beca us e i t i s s ummer a nd he us ua l l y gets hi s “col ds ” i n the wi nter a nd not i n Jul y. When the phys i ci a n exa mi nes the ma n’s ches t, he hea rs a n a bnorma l or pa thol ogi ca l s ound upon a us cul ta ti on. The ma n ha d pneumoni a wi th cons ol i da ti on i n both l obes . No orga ni s m wa s i s ol a ted from hi s s putum on bl ood a ga r, but the phys i ci a n ga ve hi m a s hot of peni ci l l i n “jus t i n ca s e”. As i t turned out, the peni ci l l i n s hot di d nothi ng to rel i eve the ma n’s di s tres s . After 96 hours , a Gra m-nega ti ve ba cteri um from the ma n’s s putum di d grow on buffered cha rcoa l yea s t extra ct. Wha t di s ea s e di d thi s ma n ha ve? a . Legi onna i res ’ di s ea s e b. Loba r pneumoni a ca us ed by Klebsiella pneumoniae c. Loba r pneumoni a ca us ed by Streptococcus pneumoniae d. Ps i tta cos i s e. Tubercul os i s 184. At a s ta te di nner, the menu i ncl uded s tea k or fri ed chi cken, ba ked pota to or homema de pota to s a l a d, green bea ns , a nd a “green” s a l a d. The s a l a d dres s i ng wa s ei ther Ita l i a n or Rus s i a n. Des s ert i ncl uded ei ther chocol a te ca ke or a ppl e pi e. The bevera ge wa s wa ter, i ced tea , or coffee. After 3 hours , onl y the di ners who ha d ea ten the pota to s a l a d, beca me vi ol entl y i l l wi th vomi ti ng, s toma ch cra mps , a nd/or di a rrhea . It beca me i mmedi a tel y obvi ous tha t the s ource of the food poi s oni ng wa s the pota to s a l a d. When the pota to s a l a d wa s s ent to a cl i ni ca l mi crobi ol ogy l a b, whi ch of the fol l owi ng ba cteri a wa s i s ol a ted i n l a rge numbers ? a . Bacillus cereus b. Clostridium botulinum c. Escherichia coli d. Staphylococcus aureus e. Staphylococcus epidermidis 185. A young boy, 9 yea rs of a ge, i s outs i de pl a yi ng i n the s ummer i n Texa s a nd s teps on a boa rd wi th a rus ty na i l i n i t. The na i l goes ri ght through hi s gym s hoe a nd enters hi s ri ght foot. He does not tel l hi s pa rents a bout i t beca us e he i s s ure hi s mother wi l l yel l a t hi m beca us e s he i s a l wa ys tel l i ng hi m not to do wha t he jus t di d. He i s a l s o a fra i d s he wi l l curta i l hi s pl a yi ng outs i de pri vi l eges . Bes i des , i t di d not bl eed much a nd the bl eedi ng s topped before he went i n for s upper. Bes i des , the boy’s fa mi l y di d not bel i eve i n goi ng to the doctor for every l i ttl e thi ng. In fa ct, the boy ca nnot remember the l a s t ti me he s a w a doctor. About a week l a ter, the boy devel oped a s ore throa t a nd then 4 da ys l a ter hi s pa rents di d ta ke hi m to the hos pi ta l (rel ucta ntl y) wi th di ffi cul ty i n s wa l l owi ng, ta l ki ng, a nd brea thi ng. Al s o, the boy bega n to experi ence mus cl e s pa s ms . The hos pi ta l doctor recogni zed the s i gns of teta nus a nd i mmedi a tel y a dmi ni s tered teta nus i mmune gl obul i n. The doctor a s ked the pa rents when the l a s t ti me the boy ha d recei ved a teta nus s hot a nd they repl i ed tha t they di d not know. After bei ng i n the hos pi ta l for a week, the boy unfortuna tel y di ed of res pi ra tory fa i l ure. Thi s unfortuna te i nci dent occurred beca us e whi ch of the fol l owi ng fa cts repres ents the bes t a ns wer? a . The ca us a ti ve orga ni s m, Clostridium tetani, i s a s tri ct a na erobe b. The ca us a ti ve orga ni s m, Clostridium tetani, is a s tri ct a erobe c. The ca us a ti ve orga ni s m, Clostridium tetani, produces a potent hea t-l a bi l e neurotoxi n d. The ca us a ti ve orga ni s m, Clostridium tetani, i s a s pore producer, a s tri ct a na erobe, a nd produces a potent hea t-l a bi l e neurotoxi n e. The ca us a ti ve orga ni s m, Clostridium tetani, i s a s pore former, a s tri ct a erobe, a nd produces a potent hea t-l a bi l e neurotoxi n 186. A 6-yea r-ol d gi rl i n Rus s i a devel oped a s ore throa t a nd wa s ta ken to the doctor by her pa rents . The doctor di a gnos ed a “s trep throa t” a nd ga ve her a s hot of peni ci l l i n. The peni ci l l i n s hot di d not hel p, a nd the chi l d’s hea l th wors ened a nd s he wa s brought ba ck to the doctor. Now the chi l d compl a i ned of more tha n a s ore throa t. Now s he refus ed to ea t a nd wa s very l etha rgi c. She a l s o ha d a fever of 40°C. When the doctor reexa mi ned the chi l d, he obs erved a norma l ches t s ound, a producti ve pha ryngi ti s , a nd i nfl a med cervi ca l l ymph nodes . A throa t cul ture di d not revea l a ny Group A s treptococci , a nd the chi l d wa s becomi ng i ncrea s i ngl y l etha rgi c. The doctor then noti ced a s tructure i n the ba ck of the chi l d’s throa t tha t l ooked l i ke a l ea ther membra ne. The pa rents tol d the doctor when he a s ked tha t the gi rl ha d recei ved no va cci na ti ons . The doctor then knew wha t di s ea s e he wa s obs ervi ng. The orga ni s m mos t l i kel y to be the ca us a ti ve a gent of thi s i nfecti on wa s whi ch of the fol l owi ng? a . Bacillus anthracis b. Clostridium botulinum c. Clostridium perfringens d. Clostridium tetani e. Corynebacterium diphtheriae 187. A pa ti ent wi th a burni ng epi ga s tri c pa i n i s a dmi tted to the hos pi ta l , a nd a ga s tri c bi ops y i s performed. The ti s s ue i s cul tured on chocol a te a ga r i ncuba ted i n a mi croa erophi l i c envi ronment a t 98.6°F (37°C) for 5 to 7 da ys . On fi fth da y of i ncuba ti on, col oni es a ppea r on the pl a te a nd curved, gra m-nega ti ve, oxi da s e-pos i ti ve rods a re obs erved. Whi ch of the fol l owi ng i s the mos t l i kel y i denti ty of thi s orga ni s m? a . Campylobacter fetus b. Campylobacter jejuni c. Haemophilus influenzae d. Helicobacter pylori e. Vibrio parahaemolyticus 188. A 2-yea r-ol d boy who mi s s ed s evera l s chedul ed i mmuni za ti ons pres ents to the emergency room wi th a hi gh fever, i rri ta bi l i ty, a nd a s ti ff neck. Fl ui d from a s pi na l ta p revea l s 20,000 whi te bl ood cel l s per mi l l i l i ter wi th 85% pol ymorphonucl ea r cel l s . Gra m s ta i n eva l ua ti on of the fl ui d revea l s s ma l l pl eomorphi c gra m-nega ti ve rods tha t grow on chocol a te a ga r. If a n i nhi bi tor i s des i gned to bl ock i ts ma jor vi rul ence, whi ch of the fol l owi ng woul d be the mos t l i kel y ma jor vi rul ence fa ctor? a . Ca ps ul e forma ti on b. Endotoxi n a s s embl y c. Exotoxi n l i bera tor d. Fl a gel l a s ynthes i s
e. IgA protea s e s ynthes i s 189. A l oca l communi ty i s i n di s tres s due to a na tura l di s a s ter. After cons umi ng conta mi na ted wa ter, ma ny i ndi vi dua l s experi ence na us ea , vomi ti ng, a nd di a rrhea tha t produce s tool s res embl i ng ri ce wa ter. An experi menta l compound i s di s covered tha t prevents the a cti va ti on of a denyl a te cycl a s e a nd the res ul ti ng i ncrea s e i n cycl i c a denos i ne monophos pha te (AMP). The toxi c effects of whi ch of the fol l owi ng ba cteri a woul d mos t l i kel y be prevented wi th the us e of thi s experi menta l compound? a . Brucella abortus b. Corynebacterium diphtheriae c. Listeria monocytogenes d. Pseudomonas aeruginosa e. Vibrio cholerae 190. A s i ngl e, 30-yea r-ol d woma n pres ents to her phys i ci a n wi th va gi ni ti s . She compl a i ns of a s l i ghtl y i ncrea s ed, ma l odorous di s cha rge tha t i s gra y-whi te i n col or, thi n, a nd homogenous . Cl ue cel l s a re di s covered when the di s cha rge i s exa mi ned mi cros copi ca l l y. Whi ch of the fol l owi ng orga ni s ms i s the mos t l i kel y ca us e of her i nfecti on? a . Candida albicans b. Trichomonas vaginalis c. Escherichia coli d. Gardnerella vaginalis e. Staphylococcus aureus 191. A 12-yea r-ol d gi rl begi ns to l i mp whi l e pl a yi ng s occer. She ha s pa i n i n her ri ght l eg a nd upper ri ght thi gh. Her tempera ture i s 102°F. X-ra y of the femur revea l s tha t the peri os teum i s eroded. As s umi ng tha t thi s ca s e i s ma na ged a s a n i nfecti ous di s ea s e, whi ch of the fol l owi ng i s the mos t l i kel y eti ol ogi c a gent? a . Listeria monocytogenes b. Salmonella enteritidis c. Staphylococcus saprophyticus d. Staphylococcus aureus e. Streptococcus pneumoniae 192. A s cra pi ng from a pa i nful , i nfl a med wound i s found to conta i n numerous gra m-nega ti ve ba cteri a . Upon ques ti oni ng, the feveri s h pa ti ent s ta tes tha t he wa s bi tten by a ca t whi l e tryi ng to res cue i t from a s torm dra i n ea rl i er i n the da y. Gi ven thes e obs erva ti ons , whi ch of the fol l owi ng orga ni s ms i s the mos t l i kel y ca us e of i nfecti on? a . Aeromonas s peci es b. Campylobacter jejuni c. Pasteurella multocida d. Pseudomonas aeruginosa e. Yersinia enterocolitica 193. A 40-yea r-ol d ma l e, who wa s i n good hea l th ea rl i er, begi ns experi enci ng a chroni c cough. Over the fol l owi ng 6 weeks , the cough gra dua l l y wors ens a nd becomes producti ve. He i s a l s o coughi ng up bl ood, a nd notes wei ght l os s , fever, a nd ni ght s wea ts . A s putum s a mpl e i s pos i ti ve for a ci d-fa s t ba ci l l i . Whi ch of the fol l owi ng pa thogeni c mecha ni s ms ca n be pri ma ri l y a ttri buted to the eti ol ogi c a gent i nvol ved i n thi s di s ea s e? a . Cel l -medi a ted hypers ens i ti vi ty b. Cl oggi ng of a l veol i by l a rge numbers of a ci d-fa s t mycoba cteri a c. Humora l i mmuni ty d. Speci fi c cel l a dhes i on s i tes e. Toxi n producti on by the mycoba cteri a 194. A pers on l i vi ng on s treets i s i nfected wi th a n i nva s i ve s a l monel l a orga ni s m tha t i s res i s ta nt to mos t of the a nti bi oti cs tha t coul d be cons i dered for trea tment. It di d s how s ens i ti vi ty to qui nol ones tha t a re ba cteri oci da l . Whi ch of the fol l owi ng i s the bes t expl a na ti on of thei r mode of a cti on on growi ng ba cteri a ? a . Ina cti va ti on of peni ci l l i n-bi ndi ng protei n II b. Inhi bi ti on of β-l a cta ma s e c. Inhi bi ti on of DNA gyra s e d. Inhi bi ti on of revers e tra ns cri pta s e e. Preventi on of the cros s -l i nki ng of gl yci ne 195. A hi gh s chool s tudent wi th a na tura l i mmunodefi ci ency i s trea ted a ggres s i vel y wi th a va ri ety of potent a nti bi oti cs to overcome s evera l ba cteri a l i nfecti ons . The mos t recent probl em i s ca us ed by S. aureus, whi ch i s reported to be va ncomyci n-i ndetermi na te (VISA). Whi ch of the fol l owi ng s ta tements concerni ng VISA i s correct? a . Pa ti ents wi th VISA i s ol a tes need not be i s ol a ted b. Mi ni mum i nhi bi tory concentra ti on (MIC) for va ncomyci n i s a t l ea s t 1.0 mcg/mL c. VISAs ha ve emerged beca us e of the extended us e of va ncomyci n for methi ci l l i n-res i s ta nt Staphylococcus aureus (MRSA) d. VISA i s ol a tes a re i nfrequent, s o s urvei l l a nce a t the pres ent ti me i s not wa rra nted e. VISA i s ol a tes a re us ua l l y methi ci l l i n s us cepti bl e 196. A 3-yea r-ol d gi rl , who ha s mi s s ed s evera l s chedul ed i mmuni za ti ons , pres ents to the emergency room wi th a fever a nd troubl ed brea thi ng. A s putum s a mpl e i s brought to the l a bora tory for a na l ys i s . Gra m s ta i n revea l s the fol l owi ng: ra re epi thel i a l cel l s , 8 to 10 pol ymorphonucl ea r l eukocytes per hi gh-power fi el d, a nd pl eomorphi c gra m-nega ti ve rods . As a l a bora tory cons ul ta nt, whi ch of the fol l owi ng i nterpreta ti ons i s correct?
a . The a ppea ra nce of the s putum i s s ugges ti ve of H. influenzae b. The pa ti ent ha s pneumococca l pneumoni a c. The pa ti ent ha s Vi ncent di s ea s e d. The s putum s peci men i s too conta mi na ted by s a l i va to be us eful e. There i s no evi dence of a n i nfl a mma tory res pons e 197. A 25-yea r-ol d medi ca l s tudent pres ents wi th a ruptured a ppendi x. A peri tonea l i nfecti on devel ops , des pi te prompt remova l of the orga n a nd extens i ve fl us hi ng of the peri tonea l ca vi ty. An i s ol a te from a pus cul ture revea l s a gra m-nega ti ve rod i denti fi ed a s Bacteroides fragilis. Ana erobi c i nfecti on wi th B. fragilis i s bes t cha ra cteri zed by whi ch of the fol l owi ng? a . A bl a ck exuda te i n the wound b. A foul -s mel l i ng di s cha rge c. A heme-pi gmented col ony forma ti on d. An exqui s i te s us cepti bi l i ty to peni ci l l i n e. Severe neurol ogi c s ymptoms 198. Severa l da ys a fter a n unprotected s exua l encounter, a hea l thy 21-yea r-ol d ma l e devel ops pa i n a nd pus on uri na ti on. A Gra m s ta i n revea l s gra m-nega ti ve di pl ococci . Whi ch of the fol l owi ng s tructures i s res pons i bl e for a dherence of the offendi ng mi crobe to the urethra l mucos a ? a . Ca ps ul e b. Fi mbri a e c. Fl a gel l a d. F pi l i e. Pepti dogl yca n f. Li popol ys a ccha ri de (LPS) 199. A 1-week-ol d newborn devel ops meni ngi ti s . Short, gra m-pos i ti ve rods a re i s ol a ted. Hi s tory revea l s tha t the mother ha d ea ten unpa s teuri zed chees e from Mexi co duri ng pregna ncy, a nd s he reca l l ed ha vi ng a fl u-l i ke i l l nes s . Whi ch of the fol l owi ng i s the mos t l i kel y eti ol ogi c mi croorga ni s m? a . Corynebacterium diphtheriae b. Escherichia coli c. Group B s treptococci d. Listeria monocytogenes e. Streptococcus pneumoniae Questions 200 to 203 200. A 30-yea r-ol d ma l e pa ti ent i s s een by the emergency s ervi ce a nd reports a 2-week hi s tory of a peni l e ul cer. He notes tha t thi s ul cer di d not hurt. Whi ch of the fol l owi ng concl us i ons /a cti ons i s mos t va l i d? a . Dra w bl ood for a herpes a nti body tes t b. Even i f trea ted, the l es i on wi l l rema i n for months c. Fa i l ure to trea t the pa ti ent wi l l ha ve no untowa rd effect, a s thi s i s a s el f-l i mi ti ng i nfecti on d. Perform a da rk-fi el d exa mi na ti on of the l es i on e. Pres cri be a cycl ovi r for pri ma ry geni ta l herpes 201. The l a bora tory reports tha t the Venerea l Di s ea s e Res ea rch La bora tory (VDRL) tes t performed on the a bove pa ti ent i s rea cti ve a t a di l uti on of 1:4 (4 di l s ). The pa ti ent a l s o reports to you tha t he ha s recentl y been di a gnos ed wi th hepa ti ti s A. Whi ch one of the fol l owi ng i s mos t a ppropri a te next s tep i n ma na gement? a . Order a confi rma tory tes t s uch a s the fl uores cent treponema l a nti body (FTA) tes t b. Order a ra pi d pl a s ma rea gi n (RPR) tes t c. Perform a s pi na l ta p to rul e out centra l nervous s ys tem (CNS) s yphi l i s d. Repea t the VDRL tes t e. Report thi s pa ti ent to the hea l th depa rtment, a s he ha s s yphi l i s 202. In the s a me pa ti ent from the previ ous vi gnette, whi ch of the fol l owi ng tes t combi na ti ons for s yphi l i s i s mos t a ppropri a te? a . FTA-Abs (IgG)/FTA-Abs (IgM) b. RPR/cul ture of the l es i on c. RPR/FTA-Abs d. Treponema pallidum hema ggl uti na ti on (TPHA)/mi crohema ggl uti na ti on—Treponema pallidum (MHTP) tes ts e. VDRL/RPR 203. As s ume tha t the s a me pa ti ent from the previ ous vi gnette a bs ol utel y deni es a ny conta ct, s exua l or otherwi s e, wi th a pers on who ha d s yphi l i s . Al s o a s s ume tha t both the RPR a nd the FTA-Abs a re pos i ti ve on thi s pa ti ent. Whi ch of the fol l owi ng tes ts coul d be us ed to s how tha t thi s pa ti ent proba bl y does not ha ve s yphi l i s ? a . Frei tes t b. MHTP tes t c. Qua nti ta ti ve RPR d. Treponema pallidum i mmobi l i za ti on (TPI) tes t e. VDRL 204. A pa ti ent i s hos pi ta l i zed a fter a n a utomobi l e a cci dent. The wounds become i nfected, a nd the pa ti ent i s trea ted wi th tobra myci n, ca rbeni ci l l i n, a nd cl i nda myci n. Fi ve da ys a fter a nti bi oti c thera py wa s i ni ti a ted, the pa ti ent devel ops s evere di a rrhea a nd ps eudomembra nous
enterocol i ti s . Anti bi oti c-a s s oci a ted di a rrhea a nd the more s eri ous ps eudomembra nous enterocol i ti s ca n be ca us ed by whi ch of the fol l owi ng orga ni s ms ? a . Bacteroides fragilis b. Clostridium difficile c. Clostridium perfringens d. Clostridium sordellii e. Staphylococcus aureus 205. A 2-yea r-ol d chi l d ha s a fever, s ti ff neck, a nd i s i rri ta bl e. Gra m s ta i n s mea r of s pi na l fl ui d revea l s gra m-nega ti ve, s ma l l pl eomorphi c coccoba ci l l a ry orga ni s ms . Wha t i s the mos t a ppropri a te procedure to fol l ow i n order to rea ch a n eti ol ogi ca l di a gnos i s ? a . Cul ture the s pi na l fl ui d i n chocol a te a ga r, a nd i denti fy the orga ni s m by growth fa ctors b. Cul ture the s pi na l fl ui d i n ma nni tol -s a l t a ga r c. Perform a ca ta l a s e tes t of the i s ol a ted orga ni s m d. Perform a coa gul a s e tes t wi th the i s ol a te e. Perform a l a tex a ggl uti na ti on (LA) tes t to detect the s peci fi c a nti body i n the s pi na l fl ui d 206. A pa ti ent compl a i ns to hi s denti s t a bout a dra i ni ng l es i on i n hi s mouth. A Gra m s ta i n of the pus s hows a few gra m-pos i ti ve cocci , l eukocytes , a nd ma ny-bra nched gra m-pos i ti ve rods . Bra nched yel l ow s ul fur gra nul es a re obs erved by a mi cros cope. Whi ch of the fol l owi ng i s the mos t l i kel y ca us e of the di s ea s e? a . Actinomyces israelii b. Actinomyces viscosus c. Corynebacterium diphtheriae d. Propionibacterium acnes e. Staphylococcus aureus 207. A 39-yea r-ol d pri mi gra vi d Ca uca s i a n fema l e l a wyer devel ops prema ture rupture of membra nes a t 35 weeks of ges ta ti on. She devel ops fever up to 103°F, a nd the a mni oti c fl ui d revea l s a group B Streptococcus. Whi ch of the fol l owi ng i s the bes t opti on to reduce Group B s treptococca l i nfecti on i n her fetus ? a . Identi fi ca ti on of pos s i bl e hi gh-ri s k bi rths b. Intra venous peni ci l l i n a dmi ni s tered a t l ea s t 4 hours before del i very c. Screeni ng of pregna nt fema l e a t the fi rs t offi ce vi s i t, us ua l l y duri ng the fi rs t tri mes ter d. Screeni ng of pregna nt fema l e i n the l a s t tri mes ter e. Us e of a pol ys a ccha ri de va cci ne 208. A 1-week-ol d neona te pres ents to the pedi a tri c emergency room wi th fever, i rri ta bi l i ty, poor feedi ng, a nd a bul gi ng a nteri or fonta nel l e. Lumba r puncture i s performed, a nd the cerebros pi na l fl ui d (CSF) grows group B Streptococcus. Whi ch of the fol l owi ng i s the mos t l i kel y pa thogeni c mecha ni s m? a . Compl ement C5a , a potent chemoa ttra cta nt, a cti va tes pol ymorphonucl ea r neutrophi l s (PMNs ) b. In the a bs ence of a s peci fi c a nti body, ops oni za ti on, pha gocyte recogni ti on, a nd ki l l i ng do not proceed norma l l y c. The a l terna ti ve compl ement pa thwa y i s a cti va ted d. The s treptococci a re res i s ta nt to peni ci l l i n 209. A ma n who ha s a peni l e cha ncre a ppea rs i n a hos pi ta l ’s emergency s ervi ce. The VDRL tes t i s nega ti ve. Whi ch of the fol l owi ng i s the mos t a ppropri a te cours e of a cti on? a . Perform da rk-fi el d mi cros copy for treponemes b. Perform a Gra m s ta i n on the cha ncre fl ui d c. Repea t the VDRL tes t i n 10 da ys d. Send the pa ti ent home untrea ted e. Swa b the cha ncre a nd cul ture on Tha yer-Ma rti n (TM) a ga r 210. A cl i ni ca l l y depres s ed fa rmer compl a i ns of extreme wea knes s , a da i l y ri s e a nd fa l l i n fever, a nd ni ght s wea ts . Sma l l gra m-nega ti ve rods a re i s ol a ted from bl ood cul tures a fter a 2-week i ncuba ti on peri od. Whi ch of the fol l owi ng orga ni s ms i s the mos t l i kel y eti ol ogi c a gent? a . Brucella melitensis b. Campylobacter jejuni c. Francisella tularensis d. Salmonella enteritidis e. Serratia marcescens 211. An outbrea k occurs i n a communi ty where the wa ter s uppl y i s conta mi na ted. Mul ti pl e pa ti ents experi ence na us ea a nd vomi ti ng a s wel l a s profus e di a rrhea wi th a bdomi na l cra mps ; s tool s a re des cri bed a s “ri ce wa ter.” Curved, gra m-nega ti ve rods a re i s ol a ted on a s ul fa te-ci tra te-bi l es ucros e a ga r. In the trea tment of pa ti ents who ha ve chol era , the us e of a drug tha t i nhi bi ts a denyl cycl a s e woul d be expected to ha ve whi ch of the fol l owi ng cha ra cteri s ti cs ? a . Bl ock the a cti on of chol era toxi n b. Era di ca te the orga ni s m c. Increa s e fl ui d s ecreti on d. Ki l l the pa ti ent i mmedi a tel y e. Reduce i ntes ti na l moti l i ty 212. A box of ha m s a ndwi ches wi th ma yonna i s e, prepa red by a pers on wi th a boi l on hi s neck, i s l eft out of the refri gera tor for the on-ca l l i nterns . Three doctors become vi ol entl y i l l a pproxi ma tel y 2 hours a fter ea ti ng the s a ndwi ches . Whi ch of the fol l owi ng i s the mos t l i kel y ca us e?
a . Clostridium perfringens toxi n b. Coa gul a s e from S. aureus i n the ha m c. Peni ci l l i na s e gi ven to i na cti va te peni ci l l i n i n the pork d. Staphylococcus aureus enterotoxi n e. Staphylococcus aureus l eukoci di n 213. A 34-yea r-ol d di a beti c truck dri ver noti ces ma cera ti on of the web s pa ce of hi s toes on the ri ght foot. Two da ys l a ter he ha s a tempera ture of up to 100°F, exqui s i te tendernes s , erythema , a nd s wel l i ng of the ri ght l eg. Cul ture exuda te from the foot yi el ds S. aureus. Whi ch of the fol l owi ng often compl i ca tes trea tment of S. aureus i nfecti on wi th peni ci l l i n? a . Al l ergi c rea cti on ca us ed by s ta phyl ococca l protei n b. Ina bi l i ty of peni ci l l i n to penetra te the membra ne of S. aureus c. La ck of peni ci l l i n-bi ndi ng s i tes on S. aureus d. Producti on of peni ci l l i n a cetyl a s e by S. aureus e. Producti on of peni ci l l i na s e by S. aureus 214. Two of 3 fa mi l y members ha ve di nner a t a l oca l res ta ura nt a nd, wi thi n 48 hours , s ta rt experi enci ng doubl e vi s i on, di ffi cul ty i n s wa l l owi ng a nd s pea ki ng, a nd brea thi ng probl ems . Thes e s ymptoms a re cons i s tent wi th whi ch of the fol l owi ng? a . Acti va ti on of cycl i c AMP b. Endotoxi n s hock c. Inges ti on of a neurotoxi n d. Inva s i on of the gut epi thel i um by a n orga ni s m e. Secreti on of a n enterotoxi n 215. A cl i ni ca l res ea rch group a ttempti ng to devel op a n i mproved Neisseria meningitidis va cci ne i s gra nted a pprova l to ga ther vol unteers for a cl i ni ca l tri a l . Pa rt of the vol unteer eva l ua ti on i s to s a mpl e ba cteri ol ogi ca l l y for norma l ora l fl ora Neisseria. They fi nd tha t a l mos t a l l of the pa rti ci pa nts ha ve s evera l commens a l s peci es a s pa rt of thei r upper res pi ra tory tra ct (URT) fl ora . Whi ch of the fol l owi ng s ta tements a ccura tel y des cri bes the s i gni fi ca nce of thes e ba cteri a ? a . As a pa rt of the norma l fl ora , Neisseria provi de a na tura l i mmuni ty i n l oca l hos t defens e b. As a pa rt of the res pi ra tory fl ora , they a re the mos t common ca us e of a cute bronchi ti s a nd pneumoni a c. Commens a l ba cteri a s ti mul a te a cel l -medi a ted i mmuni ty (CMI) d. Commens a l Neisseria i n the upper res pi ra tory tra ct i mpede pha gocytos i s by mea ns of l i potei choi c a ci d e. Norma l fl ora , s uch a s nonpa thogeni c Neisseria, provi des effecti ve nons peci fi c B-cel l -medi a ted humora l i mmuni ty 216. A fa mi l y routi nel y cons umes unpa s teuri zed mi l k, cl a i mi ng “better ta s te.” Severa l members experi ence a s udden ons et of cra mpy a bdomi na l pa i n, fever, a nd profus e bl oody di a rrhea . Campylobacter jejuni i s i s ol a ted a nd i denti fi ed from a l l pa ti ents . Whi ch of the fol l owi ng i s the trea tment of choi ce for thi s type of enterocol i ti s ? a . Ampi ci l l i n b. Campylobacter a nti toxi n c. Ci profl oxa ci n d. Erythromyci n e. Pepto-Bi s mol 217. An uni mmuni zed, 2-yea r-ol d boy pres ents wi th drool i ng from the mouth, el eva ted tempera ture, a nd enl a rged tons i l s . Duri ng a ttempts a t i ntuba ti on, no gra y-whi te membra ne i s obs erved but the epi gl otti s a ppea rs “beefy” red a nd edema tous . Whi ch of the fol l owi ng i s the mos t l i kel y orga ni s m? a . Haemophilus haemolyticus b. Haemophilus influenzae c. Klebsiella pneumoniae d. Mycoplasma pneumoniae e. Neisseria meningitidis Questions 218 to 220 218. A 70-yea r-ol d fema l e pa ti ent i s rea dmi tted to a l oca l hos pi ta l wi th fever a nd chi l l s fol l owi ng ca rdi a c s urgery a t a ma jor tea chi ng i ns ti tuti on. A gra m-pos i ti ve coccus grows wi thi n 24 hours from bl ood ta ken from the pa ti ent. Ini ti a l tes ts i ndi ca te tha t thi s i s ol a te i s res i s ta nt to peni ci l l i n. Whi ch of the fol l owi ng i s the mos t l i kel y i denti fi ca ti on? a . Enterococcus species b. Group A Streptococcus c. Group B Streptococcus d. Neisseria s peci es e. Streptococcus pneumoniae 219. Further tes ti ng of the pa ti ent i n the previ ous ques ti on revea l s tha t the i s ol a te pos s es s es the group D a nti gen, a nd i s not β-l a cta ma s epos i ti ve, but i s res i s ta nt to va ncomyci n. Whi ch of the fol l owi ng i s the mos t l i kel y i denti fi ca ti on of thi s i s ol a te? a . Enterococcus casseliflavus b. Enterococcus durans c. Enterococcus faecalis d. Enterococcus faecium e. Streptococcus pneumoniae
220. Whi ch of the fol l owi ng i s the trea tment of choi ce for the i s ol a te i n Ques ti on 219? a . Ci profl oxa ci n b. Genta mi ci n c. Genta mi ci n a nd a mpi ci l l i n d. Ri fa mpi n e. No a va i l a bl e trea tment 221. A young ma n cra s hes hi s bi cycl e, i njuri ng one l eg. Ba cteri a from the wound a nd a s ubs equent bl ood cul ture a re i s ol a ted a nd i denti fi ed, a nd a n a cute hema togenous os teomyel i ti s i s di a gnos ed. Whi ch orga ni s m l i s ted bel ow mos t often ca us es thi s type of i nfecti on? a . Escherichia coli b. Proteus mirabilis c. Staphylococcus aureus d. Staphylococcus epidermidis e. Streptococcus faecalis 222. A 3-yea r-ol d gi rl , wi th no hi s tory of va cci na ti on, i s brought to the hos pi ta l wi th a s ore throa t, fever, ma l a i s e, a nd di ffi cul ty i n brea thi ng. Phys i ca l exa mi na ti on revea l s a gra y membra ne coveri ng the pha rynx. Growth of the eti ol ogi c a gent on cys tei ne-tel l uri te a ga r forms gra y-to-bl a ck col oni es wi th a brown ha l o. The ma jor vi rul ence fa ctor of thi s orga ni s m i s onl y produced by thos e s tra i ns tha t wi l l mos t l i kel y ha ve whi ch of the fol l owi ng cha ra cteri s ti cs ? a . Enca ps ul a ted b. Endotoxi n c. Gl ucos e fermenters d. Lys ogeni c for β-propha ge e. Sucros e fermenters Questions 223 to 225 A 28-yea r-ol d mens trua ti ng woma n a ppea rs i n the emergency room wi th the fol l owi ng s i gns a nd s ymptoms : fever, 104°F (40°C); WBC, 16,000/μL; bl ood pres s ure, 90/65 mm Hg; a s ca rl a ti ni form ra s h on her trunk, pa l ms , a nd s ol es ; extreme fa ti gue; vomi ti ng; a nd di a rrhea . 223. Whi ch of the fol l owi ng i s the mos t l i kel y di a gnos i s ? a . Chi cken pox b. Gui l l a i n–Ba rré s yndrome c. Sca l ded s ki n s yndrome d. Sta phyl ococca l food poi s oni ng e. Toxi c s hock s yndrome (TSS) 224. Cul ture of the mens trua l fl ui d i n thi s ca s e ci ted woul d mos t l i kel y revea l a predomi na nce of whi ch of the fol l owi ng? a . Clostridium difficile b. Clostridium perfringens c. Gardnerella vaginalis d. Staphylococcus aureus e. No orga ni s ms i s ol a ted 225. Whi ch of the fol l owi ng i s the mos t l i kel y s ource a nd cha ra cteri s ti c fi ndi ng not yet revea l ed i n the ca s e jus t pres ented? a . A mea l of chi cken i n a fa s t-food res ta ura nt b. A reta i ned ta mpon c. Hea vy mens trua l fl ow d. Recent expos ure to rubel l a e. Tra vel to Vermont Questions 226 and 227 A s evere URT outbrea k occurs i n the res i dence of s tudents of a pri va te s chool , res ul ti ng i n s evera l ca s es of oti ti s medi a a nd a cute s i nus i ti s . Some s tudents do not ha ve a ny cl i ni ca l evi dence of i nfecti on. The s ta te publ i c hea l th l a bora tory recei ves a nd eva l ua tes a new LA rea gent for H. influenzae pol ys a ccha ri de ca ps ul a r a nti gen i n uri ne (i nta ct a nti gen el i mi na ti on). The res ul ts , s hown bel ow, a re compa red wi th the i s ol a ti on of H. influenzae from pha ryngea l s wa bs . LA POS, CULT POS: 25 LA POS, CULT NEG: 5 LA NEG, CULT POS: 5 LA NEG, CULT NEG: 95 226. Whi ch of the fol l owi ng bes t i ndi ca tes the s ens i ti vi ty of LA? a . 0% b. 30% c. 85% d. 95% e. 100% 227. Whi ch of the fol l owi ng bes t i ndi ca tes the s peci fi ci ty of LA? a . 0%
b. 30% c. 80% d. 95% e. 100% 228. A s everel y burned fi refi ghter devel ops a ra pi dl y di s s emi na ti ng ba cteri a l i nfecti on whi l e hos pi ta l i zed. “Green pus ” i s noted i n the burned ti s s ue, a nd cul tures of both the ti s s ue a nd bl ood yi el d s ma l l , oxi da s e-pos i ti ve, gra m-nega ti ve rods . Whi ch of the fol l owi ng s ta tements bes t des cri bes thi s orga ni s m? a . Endotoxi n i s the onl y vi rul ence fa ctor known to be produced by thes e ba cteri a b. Huma ns a re the onl y known res ervoi r hos ts for thes e ba cteri a c. The ba cteri a a re di ffi cul t to cul ture beca us e they ha ve numerous growth requi rements d. Thes e a re a mong the mos t a nti bi oti c res i s ta nt of a l l cl i ni ca l l y rel eva nt ba cteri a e. Thes e hi ghl y moti l e ba cteri a ca n “s wa rm” over the s urfa ce of cul ture medi a 229. Severa l hours a fter di ni ng on s weet a nd s our chi cken a nd pork fri ed ri ce a t the home of a n As i a n fri end, a 34-yea r-ol d ca r s a l es ma n exhi bi ts a bdomi na l di s comfort, na us ea , a nd vomi ti ng. In the mi ddl e of the ni ght he a wa kens wi th wa tery di a rrhea . Whi ch of the fol l owi ng pa i rs of orga ni s ms i s routi nel y res pons i bl e for food poi s oni ng? a . Clostridium botulinum a nd Bacillus anthracis b. Clostridium difficile a nd C. botulinum c. Clostridium perfringens a nd B. cereus d. Clostridium tetani a nd B. anthracis e. Clostridium tetani a nd B. cereus 230. MRSA i s i s ol a ted from s even pa ti ents i n a 14-bed i ntens i ve ca re uni t. Al l pa ti ents a re i s ol a ted a nd the uni t cl os ed to a ny more a dmi s s i ons . Whi ch of the fol l owi ng bes t expl a i ns thes e ri gorous methods to control MRSA? a . MRSA ca us es TSS b. MRSA i s i nherentl y more vi rul ent tha n other s ta phyl ococci c. MRSA i s res i s ta nt to peni ci l l i n d. MRSA s prea ds more ra pi dl y from pa ti ent to pa ti ent tha n a nti bi oti c-s us cepti bl e s ta phyl ococci do e. The a l terna ti ve for trea tment of MRSA i s va ncomyci n, a n expens i ve a nd potenti a l l y toxi c a nti bi oti c 231. A 2-yea r-ol d i nfa nt i s brought to the emergency room wi th hema turi a , fever, a nd thrombocytopeni a . Whi ch one of the fol l owi ng ba cteri a woul d mos t l i kel y be i s ol a ted from a s tool s peci men? a . Aeromonas s peci es b. Enterobacter aerogenes c. Escherichia coli 0157/H7 d. Salmonella enteritidis e. Shigella flexneri 232. A 65-yea r-ol d hea l thy, reti red fema l e executi ve goes to Mexi co on her yea rl y va ca ti on. Unl i ke her previ ous tri ps , s he deci des to us e the l oca l wa ter to ma ke her fa vori te punch. Thi rty-s i x hours l a ter, s he devel ops profus e wa tery di a rrhea , s evere cra mpi ng, a nd a bdomi na l pa i n. She i s di a gnos ed wi th Escherichia coli-rel a ted di a rrhea . Whi ch of the fol l owi ng E. coli types i s cha ra cteri zed by the pres ence of hea t-l a bi l e (LT) a nd hea ts ta bl e (ST) toxi n protei ns ? a . Enteroi nva s i ve (EIEC) b. Enterotoxi geni c (ETEC) c. Enterohemorrha gi c (EHEC) d. Enteropa thogeni c (EPEC) 233. A 48-yea r-ol d fa rmer i n New Mexi co i s bi tten by a fl ea a nd, 5 da ys l a ter, devel ops a s udden ons et of fever, chi l l s , wea knes s , a nd hea da che. A few hours l a ter he devel ops s wol l en, necroti c l ymph nodes (buboes ) i n the ri ght a xi l l a a nd groi n, whi ch a re i ntens el y pa i nful . Thi s pa ti ent i s s ubs equentl y di a gnos ed wi th buboni c pl a gue a nd does not devel op a ny pneumoni c fea tures of the di s ea s e. Huma n pl a gue ca n be buboni c or pneumoni c. Whi ch of the fol l owi ng i s the pri ma ry epi demi ol ogi c di fference between the two cl i ni ca l forms of pl a gue? a . Age of the pa ti ent b. Geogra phi c l oca ti on of the a ni ma l vector c. Hea l th of the a ni ma l vector d. Route of i nfecti on e. Sea s on of the yea r 234. A 9-yea r-ol d chi l d i s brought to the emergency room wi th the chi ef compl a i nt of enl a rged, pa i nful a xi l l a ry l ymph nodes . The res i dent phys i ci a n a l s o notes a s ma l l , i nfl a med, di me-s i zed l es i on s urroundi ng wha t a ppea rs to be a s ma l l s cra tch on the forea rm. The l ymph node i s a s pi ra ted a nd s ome pus i s s ent to the l a bora tory for exa mi na ti on. A Wa rthi n-Sta rry s i l ver i mpregna ti on s ta i n revea l s ma ny hi ghl y pl eomorphi c, rod-s ha ped ba cteri a . Whi ch of the fol l owi ng i s the mos t l i kel y ca us e of thi s i nfecti on? a . Bartonella henselae b. Brucella canis c. Mycobacterium scrofulaceum d. Yersinia enterocolitica e. Yersinia pestis 235. A s i xth-gra de boy returns from a s ummer ca mp wi th s evera l mi nor cuts a nd a bra s i ons . Wi thi n a week, extens i ve cel l ul i ti s devel ops , a nd i t i s a ppa rent tha t s ubcuta neous ti s s ue i s i nvol ved, requi ri ng s urgi ca l remova l of nonvi a bl e ti s s ue. Anti bi oti cs a re us ed a ggres s i vel y. Cel l ul i ti s i s
us ua l l y ca us ed by whi ch of the fol l owi ng? a . Bacillus cereus b. Clostridium tetani c. Group A s treptococci d. Micrococcus s peci es e. Staphylococcus aureus 236. A 40-yea r-ol d fema l e reports chroni c ga s tri ti s . She tes ts pos i ti ve for H. pylori. After a cours e of the a ppropri a te a nti bi oti c thera py, her s ymptoms s ubs i de. Whi ch of the fol l owi ng i s the mos t effecti ve noni nva s i ve tes t for the di a gnos i s of Helicobacter-a s s oci a ted ga s tri c ul cers ? a . Cul ture of s toma ch contents for H. pylori b. Detecti on of H. pylori a nti gen i n s tool c. Growth of H. pylori from a s toma ch bi ops y d. Growth of H. pylori i n the s tool e. IgM a nti bodi es to H. pylori 237. The fol l owi ng exa mi na ti on a nd tes t res ul ts a re obs erved i n a woma n tes ted i n November who reports bei ng i n the woods i n Penns yl va ni a duri ng the l a s t s ummer. Whi l e there, s he wa s bi tten by a ti ck, a nd now ha s a fl a ttened red a rea nea r the bi te wi th centra l cl ea ri ng. She a l s o ha s fl u-l i ke i l l nes s wi th fever, mya l gi a , a nd hea da che. Whi ch of the fol l owi ng i s the mos t a ppropri a te cours e of a cti on? a . As k the pa ti ent i f s he ha s a s evere hea da che b. Do a s pi na l ta p for CSF c. Obs erve the l es i on d. Order a Lyme di s ea s e a nti body ti ter e. Sta rt trea tment wi th tetra cycl i ne 238. Severa l whi te ma l e pa ti ents , over 50 yea rs of a ge a nd s ufferi ng from ca vi ta ry pul mona ry di s ea s e, bei ng fol l owed a nd trea ted a t a uni vers i ty AIDS cl i ni c a re found to be i nfected by Mycobacterium avium, a ma jor opportuni s t pa thogen. M. avium from thes e pa ti ents i s bes t cha ra cteri zed by whi ch one of the fol l owi ng s ta tements ? a . Few i s ol a tes from AIDS pa ti ents a re a ci d-fa s t. b. Mos t i s ol a tes from AIDS pa ti ents a re s ens i ti ve to i s oni a zi d a nd s treptomyci n c. M. avium ca n be i s ol a ted from the bl ood of ma ny AIDS pa ti ents d. M. avium i s ol a tes from AIDS pa ti ents a re of mul ti pl e s erova rs e. The ma jori ty of M. avium i s ol a tes from AIDS pa ti ents a re nonpi gmented 239. A 12-yea r-ol d gi rl experi ences a group A s treptococcus pha ryngi ti s a nd, wi thi n 3 weeks , ha s ches t pa i n a nd devel ops new murmurs of mi tra l regurgi ta ti on. Whi ch of the fol l owi ng s ta tements bes t typi fi es the di s ea s e s he i s s ufferi ng from? a . It i s a compl i ca ti on of group A s treptococca l s ki n di s ea s e but us ua l l y not of pha ryngi ti s b. It i s cha ra cteri zed by i nfl a mma tory l es i ons tha t ma y i nvol ve the hea rt, joi nts , s ubcuta neous ti s s ues , a nd CNS c. It i s very common i n devel opi ng countri es but extremel y ra re a nd decrea s i ng i n i nci dence i n the Uni ted Sta tes d. Prophyl a xi s wi th benza thi ne peni ci l l i n i s of l i ttl e va l ue e. The pa thogenes i s i s rel a ted to the s i mi l a ri ty between a s ta phyl ococca l a nti gen a nd a huma n ca rdi a c a nti gen 240. After extra cti on of a wi s dom tooth, a n 18-yea r-ol d ma l e s tudent i s di a gnos ed wi th s uba cute ba cteri a l endoca rdi ti s (SBE). He ha s a congeni ta l hea rt di s ea s e tha t ha s been under control . Whi ch of the fol l owi ng i s the mos t l i kel y orga ni s m ca us i ng the i nfecti on? a . Staphylococcus aureus b. Staphylococcus epidermidis c. Streptococcus pneumoniae d. Streptococcus viridans e. Enterococcus faecalis 241. A 70-yea r-ol d ma l e i s ta ken to the emergency room wi th a hi s tory of “col d-l i ke” s ymptoms for a t l ea s t 3 da ys . At the ti me of the vi s i t, hi s tempera ture i s 102°F a nd he experi enced s ha ki ng, chi l l s , ches t pa i n, a nd a producti ve cough wi th bl oody s putum. Bl ood a ga r cul ture revea l s gra mpos i ti ve α-hemol yti c col oni es . If a quel l ung tes t wa s done on the col oni es , whi ch of the fol l owi ng ba cteri a woul d mos t l i kel y be pos i ti ve? a . Corynebacterium diphtheriae b. Enterobacter s peci es c. Haemophilus parainfluenzae d. Neisseria gonorrhoeae e. Streptococcus pneumoniae 242. A 6-month-ol d i nfa nt i s a dmi tted to the hos pi ta l wi th a cute meni ngi ti s . The Gra m s ta i n revea l s gra m-pos i ti ve, s hort rods , a nd the mother i ndi ca tes tha t the chi l d ha s recei ved “a l l ” of the meni ngi ti s va cci na ti ons . Whi ch of the fol l owi ng i s the mos t l i kel y ca us e of the di s ea s e? a . Haemophilus influenzae b. Listeria monocytogenes c. Neisseria meningitidis, group A d. Neisseria meningitidis, group C e. Streptococcus pneumoniae 243. A 40-yea r-ol d ma n pres ents to the emergency medi ci ne depa rtment 1 week fol l owi ng a foot i njury. He i s experi enci ng i ntens e pa i n i n the a rea of i njury a nd the mus cl es of the ja w. Whi ch of the fol l owi ng i s the mos t common porta l of entry for the eti ol ogi c orga ni s m? a . Ga s troi ntes ti na l (GI) tra ct
b. Geni ta l tra ct c. Na s a l tra ct d. Res pi ra tory tra ct e. Ski n 244. A 22-yea r-ol d homel es s pers on wi th a known drug a bus e probl em a nd mul ti pl e opportuni s ti c i nfecti ons ha s a pos i ti ve PPD (puri fi ed protei n) tes t. Whi ch of the fol l owi ng i s the mos t common wa y thi s i nfecti on i s a cqui red? a . GI tra ct b. Geni ta l tra ct c. Na s a l tra ct d. Res pi ra tory tra ct e. Ski n 245. A 31-yea r-ol d s chool tea cher returns from forei gn tra vel a nd experi ences a s udden (1-2 da ys ) ons et of a bdomi na l pa i n, fever, a nd wa tery di a rrhea , ca us ed by a hea t-l a bi l e exotoxi n tha t a ffects both the gut a nd the CNS. Thi s i nfecti on i s ca us ed by a n eti ol ogi c a gent commonl y a cqui red through whi ch of the fol l owi ng routes ? a . GI tra ct b. Geni ta l tra ct c. Na s a l tra ct d. Res pi ra tory tra ct e. Ski n 246. A col l ege s tudent i s s urpri s ed one morni ng by pa i nful uri na ti on a nd a crea m-col ored exuda te. Any pers on who a cqui res the gra m-nega ti ve mi crobe tha t ca us es thi s i nfecti on i s mos t l i kel y to ha ve a cqui red i t vi a whi ch of the fol l owi ng? a . GI tra ct b. Geni touri na ry tra ct c. Na s a l tra ct d. Res pi ra tory tra ct e. Ski n 247. A 25-yea r-ol d col l ege s tudent wi th no hi s tory of a l l ergi c rhi ni ti s ha s a 12-da y hi s tory of fa ci a l pa i n, cl ea r rhi norrhea , fever, hea da che, a nd ba ck pa i n. Her s ymptoms do not res pond to over-the-counter medi ca ti on. Cul ture of the fl ui d from the s i nus revea l s Moraxella (Branhamella) catarrhalis. Whi ch of the fol l owi ng bes t cha ra cteri zes M. catarrhalis? a . A gra m-nega ti ve, pl eomorphi c rod tha t ca n ca us e endoca rdi ti s b. A gra m-nega ti ve rod, fus i form-s ha ped, tha t i s a s s oci a ted wi th peri odonta l di s ea s e but ma y ca us e s eps i s c. The ca us a ti ve a gent of ra t-bi te fever d. The gra m-nega ti ve di pl ococcus , whi ch i s the ca us a ti ve a gent of s i nus i ti s , bronchi ti s , a nd pneumoni a e. The ca us a ti ve a gent of trench fever 248. A 16-yea r-ol d Hi s pa ni c fema l e wi th poor ora l hygi ene a nd s evere gi ngi vi ti s pres ents wi th a tempera ture of 103.5°F a nd hypotens i on. Bl ood cul ture i s pos i ti ve for Capnocytophaga. Whi ch of the fol l owi ng bes t cha ra cteri zes Capnocytophaga? a . A gra m-nega ti ve, pl eomorphi c rod tha t ca n ca us e endoca rdi ti s b. A gra m-nega ti ve rod, fus i form-s ha ped, tha t i s a s s oci a ted wi th peri odonta l di s ea s e but ma y ca us e s eps i s c. The ca us a ti ve a gent of ra t-bi te fever d. The ca us a ti ve a gent of s i nus i ti s , bronchi ti s , a nd pneumoni a e. The ca us a ti ve a gent of trench fever 249. Severa l empl oyees i n a veteri na ry fa ci l i ty experi ence a mi l d i nfl uenza -l i ke i nfecti on a fter worki ng on s i x s heep wi th a n undi a gnos ed i l l nes s . The eti ol ogi c a gent ca us i ng the huma n di s ea s e i s mos t often tra ns mi tted to huma ns by whi ch of the fol l owi ng methods ? a . Feca l conta mi na ti on from fl ea depos i ts on the s ki n b. Inha l a ti on of i nfected pa rti cl es or a eros ol s from the s us pected a ni ma l uri ne a nd feces c. Li ce feces s cra tched i nto the broken s ki n duri ng the l ous e’s bl ood feedi ng d. Ti ck s a l i va duri ng feedi ng on huma n bl ood e. Urethra l di s cha rge from i nfected huma ns 250. An endoca rdi ti s pa ti ent under a phys i ci a n’s ca re devel ops a uri na ry tra ct i nfecti on (UTI). A group D enterococcus (Enterococcus faecium) i s i s ol a ted but the UTI does not res pond to a mpi ci l l i n a nd genta mi ci n trea tments . Whi ch of the fol l owi ng opti ons woul d be cons i dered the mos t cl i ni ca l l y a ppropri a te a cti on? a . Cons i der va ncomyci n a s a n a l terna ti ve drug b. Determi ne i f fl uores cent mi cros copy i s a va i l a bl e for the di a gnos i s of a cti nomycos i s c. Do no further cl i ni ca l workup d. Sugges t to the l a bora tory tha t l ow col ony counts ma y refl ect i nfecti on e. Sugges t a repea t a nti bi oti c s us cepti bi l i ty tes t 251. A pa ti ent wi th s ymptoms of a UTI ha s a cul ture ta ken, whi ch grows 5 × 103 E. coli. The l a bora tory reports i t a s “i ns i gni fi ca nt.” Whi ch of the fol l owi ng i s the mos t a ppropri a te next s tep i n ma na gement? a . Cons i der va ncomyci n a s a n a l terna ti ve drug b. Determi ne i f fl uores cent mi cros copy i s a va i l a bl e for the di a gnos i s of a cti nomycos i s c. Do no further cl i ni ca l workup
d. Sugges t to the l a bora tory tha t l ow col ony counts ma y refl ect i nfecti on; fol l ow up wi th cul ture e. Sugges t a repea t a nti bi oti c s us cepti bi l i ty tes t 252. A pa ti ent a ppea rs i n the emergency room wi th a s ubma ndi bul a r ma s s . A s mea r i s ma de of the dra i na ge a nd a bewi l deri ng va ri ety of ba cteri a a re s een, i ncl udi ng bra nched, gra m-pos i ti ve rods . Whi ch of the fol l owi ng i s the mos t cl i ni ca l l y a ppropri a te a cti on? a . Cons i der va ncomyci n a s a n a l terna ti ve drug b. Determi ne i f fl uores cent mi cros copy i s a va i l a bl e for the di a gnos i s of a cti nomycos i s c. Do no further cl i ni ca l workup d. Sugges t to the l a bora tory tha t l ow col ony counts ma y refl ect i nfecti on e. Sugges t a repea t a nti bi oti c s us cepti bi l i ty tes t 253. A 55-yea r-ol d ma l e devel ops ma l a i s e, fever up to 103.5°F, nonproducti ve cough, hea da che, a nd s hortnes s of brea th a few da ys a fter he repa i red the cool i ng s ys tem of a n ol d hotel . A ches t x-ra y revea l s fl ui d i n hi s l ungs . From a s putum s a mpl e, a gra m-nega ti ve rod grew s l owl y on a buffered cys tei ne conta i ni ng cha rcoa l -yea s t a ga r. Whi ch of the fol l owi ng a nti bi oti c thera pi es i s mos t a ppropri a te for trea ti ng thi s pa ti ent? a . Ampi ci l l i n b. Ceftri a xone c. Erythromyci n d. Peni ci l l i n e. Va ncomyci n 254. A 60-yea r-ol d ma l e res i dent from a nurs i ng home pres ents to the emergency room wi th a fever of 105.8°F (41°C), s ha ki ng chi l l s , s evere pa i n to the ri ght s i de of hi s ches t tha t wors ens wi th brea thi ng, a nd a producti ve cough wi th bl ood-ti nged s putum. Duri ng the previ ous 3 da ys , he noted col d-l i ke s ymptoms . Gra m s ta i n eva l ua ti on of the s putum revea l s gra m-pos i ti ve di pl ococci tha t grow i nto α-hemol yti c col oni es on bl ood a ga r. Whi ch of the fol l owi ng a nti bi oti c thera pi es i s the mos t a ppropri a te trea tment for thi s pa ti ent? a . Ampi ci l l i n b. Ceftri a xone c. Erythromyci n d. Peni ci l l i n e. Va ncomyci n 255. A 12-yea r-ol d boy, a fter a ca mpi ng tri p nea r a wooded a rea i n Northern Ca l i forni a , i s ta ken to the emergency room a fter compl a i ni ng of a hea da che. He ha s a n erythema mi gra ns ra s h a round wha t a ppea rs to be a ti ck bi te. Whi ch of the fol l owi ng i s the a nti bi oti c of choi ce for trea ti ng thi s pa ti ent? a . Ampi ci l l i n b. Ceftri a xone c. Erythromyci n d. Peni ci l l i n e. Va ncomyci n 256. A 6-yea r-ol d gi rl pres ents to her pedi a tri ci a n wi th fever, hea da che, a nd a s ore throa t. She ha s s wol l en, tender cervi ca l l ymph nodes , a nd her oropha rynx i s red wi th a gra y-whi te exuda te coveri ng both her tons i l s . A ra pi d s trep tes t of her throa t s wa b i s pos i ti ve, a nd the cul ture s ubs equentl y grows β-hemol yti c Streptococcus. Whi ch of the fol l owi ng a nti bi oti c thera pi es i s mos t a ppropri a te for trea ti ng thi s pa ti ent? a . Ampi ci l l i n b. Ceftri a xone c. Erythromyci n d. Peni ci l l i n e. Va ncomyci n 257. A young woma n bei ng trea ted wi th a broa d-s pectrum a nti mi crobi a l devel ops endos copi ca l l y obs erved mi croa bs ces s es a nd di a rrhea . Whi ch of the fol l owi ng i s the thera py of choi ce for thi s form of enterocol i ti s ? a . Ampi ci l l i n b. Ceftri a xone c. Erythromyci n d. Peni ci l l i n e. Va ncomyci n 258. Al though chol era , a Vibrio i nfecti on, ha s ra rel y been s een i n the Uni ted Sta tes , there ha ve been recent outbrea ks of cl a s s i c chol era a s s oci a ted wi th s hel l fi s h ha rves ted from the Gul f of Mexi co. Vi bri os a re s ha ped l i ke curved rods , a nd i nfecti ons more common tha n chol era ma y be ca us ed by a va ri ety of curved-rod ba cteri a . Whi ch of the fol l owi ng bes t des cri bes C. jejuni? a . Ca us e of ga s troenteri ti s ; res ervoi r i n bi rds a nd ma mma l s , opti ma l growth a t 107.6°F (42°C) b. Huma n pa thogen, ha l ophi l i c, l a ctos e-nega ti ve, s ucros e-nega ti ve; ca us es GI di s ea s es pri ma ri l y from i nges ti on of under-cooked s ea food c. Huma n pa thogen, ha l ophi l i c, l a ctos e-pos i ti ve; produces hea t-l a bi l e, extra cel l ul a r toxi n wound i nfecti ons d. Orga ni s ms a re s us cepti bl e to a ci d; not a n i nva s i ve orga ni s m e. Urea s e-pos i ti ve; ca us e of feta l di s tres s i n ca ttl e 259. Vibrio cholerae i s worl dwi de i n di s tri buti on a nd conti nues to expa nd a s wa ter s ources become pol l uted. Whi ch of the fol l owi ng bes t des cri bes thi s orga ni s m? a . Ca us e of ga s troenteri ti s ; res ervoi r i n bi rds a nd ma mma l s , opti ma l growth a t 107.6°F (42°C) b. Huma n pa thogen, ha l ophi l i c, l a ctos e-nega ti ve, s ucros e-nega ti ve; ca us es GI di s ea s es pri ma ri l y from i nges ti on of under-cooked s ea food c. Huma n pa thogen, ha l ophi l i c, l a ctos e-pos i ti ve; produces hea t-l a bi l e, extra cel l ul a r toxi n, wound i nfecti ons
d. Orga ni s ms s us cepti bl e to a ci d; not a n i nva s i ve orga ni s m e. Urea s e-pos i ti ve; ca us e of feta l di s tres s i n ca ttl e 260. A 20-yea r-ol d fema l e i n pos t-Ka tri na New Orl ea ns ea ts poorl y cooked s ea food (oys ters , cl a ms , a nd mol l us ks ) for her bi rthda y di nner. Twentyfour hours l a ter, s he devel ops expl os i ve wa tery di a rrhea a nd a bdomi na l cra mps . She i s pos i ti ve for V. parahaemolyticus. Whi ch of the fol l owi ng bes t des cri bes thi s orga ni s m? a . Ca us e of ga s troenteri ti s ; res ervoi r i n bi rds a nd ma mma l s , opti ma l growth a t 107.6°F (42°C) b. Huma n pa thogen, ha l ophi l i c, l a ctos e-nega ti ve, s ucros e-nega ti ve; ca us es GI di s ea s es pri ma ri l y from i nges ti on of under-cooked s ea food c. Huma n pa thogen, ha l ophi l i c, l a ctos e-pos i ti ve; produces hea t-l a bi l e, extra cel l ul a r toxi n, wound i nfecti ons d. Orga ni s ms s us cepti bl e to a ci d; not a n i nva s i ve orga ni s m e. Urea s e-pos i ti ve; ca us e of feta l di s tres s i n ca ttl e 261. A 25-yea r-ol d ma l e, wi th a hi s tory of hepa ti ti s C, ha s to wa de through bra cki s h wa ter i n pos t-Ka tri na New Orl ea ns . He devel ops wors eni ng a bdomi na l pa i n a nd ja undi ce. Rega rdi ng Vibrio vulnificus, whi ch of the fol l owi ng bes t des cri bes thi s orga ni s m? a . Ca us e of ga s troenteri ti s ; res ervoi r i n bi rds a nd ma mma l s , opti ma l growth a t 107.6°F (42°C) b. Huma n pa thogen, ha l ophi l i c, l a ctos e-nega ti ve, s ucros e-nega ti ve; ca us es GI di s ea s es pri ma ri l y from i nges ti on of under-cooked s ea food c. Huma n pa thogen, ha l ophi l i c, l a ctos e-pos i ti ve; produces hea t-l a bi l e, extra cel l ul a r toxi n, wound i nfecti ons d. Orga ni s ms s us cepti bl e to a ci ds ; not a n i nva s i ve orga ni s m e. Urea s e-pos i ti ve; ca us e of feta l di s tres s i n ca ttl e 262. Yersinia enterocolitica, formerl y a Pasteurella, ha s more tha n 50 s ero-types tha t ca n be i s ol a ted from rodents , s heep, ca ttl e, s wi ne, dogs , a nd ca ts a nd wa ter conta mi na ted by them, a nd i s bes t des cri bed by whi ch of the fol l owi ng? a . Commonl y i nha bi ts the ca ni ne res pi ra tory tra ct a nd i s a n occa s i ona l pa thogen for huma ns ; s trongl y urea s e-pos i ti ve b. Gra m-nega ti ve bi pol a r s ta i ned ba ci l l i tha t ca us e di a rrhea by mea ns of a hea t-s ta bl e enterotoxi n, wi th a bdomi na l pa i n tha t ma y be mi s ta ken for a ppendi ci ti s c. Pi ts a ga r, grows both i n ca rbon di oxi de a nd under a na erobi c condi ti ons , a nd i s pa rt of the norma l ora l ca vi ty fl ora d. Typi ca l l y i nfects ca ttl e, requi res 5% to 10% ca rbon di oxi de for growth, a nd i s i nhi bi ted by the dye thi oni ne e. Typi ca l l y i s found i n i nfected a ni ma l bi tes i n huma ns a nd ca n ca us e hemorrha gi c s epti cemi a i n a ni ma l s 263. Four weeks a fter a s s i s ti ng i n s evera l ca l f del i veri es , a fa rmer devel ops fever, wea knes s , mus cl e a ches , a nd s wea ts . The fever ri s es i n the a fternoon a nd fa l l s duri ng the ni ght. Brucella abortus i s i s ol a ted. Whi ch one of the three Brucella s peci es i s a pos s i bl e bi oterrori s m a gent a nd i s bes t des cri bed by one of the fol l owi ng? a . Commonl y i nha bi ts the ca ni ne res pi ra tory tra ct a nd i s a n occa s i ona l pa thogen for huma ns ; s trongl y urea s e-pos i ti ve b. Gra m-nega ti ve bi pol a r s ta i ned ba ci l l i tha t ca us e di a rrhea by mea ns of a hea t-s ta bl e enterotoxi n, wi th a bdomi na l pa i n tha t ma y be mi s ta ken for a ppendi ci ti s c. Pi ts a ga r grows both i n ca rbon di oxi de a nd under a na erobi c condi ti ons , a nd i s pa rt of the norma l ora l ca vi ty fl ora d. Typi ca l l y i nfects ca ttl e, requi res 5% to 10% ca rbon di oxi de for growth, a nd i s i nhi bi ted by the dye thi oni ne e. Typi ca l l y i s found i n i nfected a ni ma l bi tes i n huma ns a nd ca n ca us e hemorrha gi c s epti cemi a i n a ni ma l s 264. Bordetella bronchiseptica coul d be confus ed wi th the a gent of whoopi ng cough s i nce i t occa s i ona l l y ca us es chroni c res pi ra tory tra ct i nfecti ons i n huma ns , but ha s l es s i ntens i ve s ymptoms (rhi ni ti s a nd cough). It i s bes t des cri bed by whi ch of the fol l owi ng? a . Commonl y i nha bi ts the ca ni ne res pi ra tory tra ct a nd i s a n occa s i ona l pa thogen for huma ns ; s trongl y urea s e-pos i ti ve b. Gra m-nega ti ve bi pol a r s ta i ned ba ci l l i tha t ca us e di a rrhea by mea ns of a hea t-s ta bl e enterotoxi n, wi th a bdomi na l pa i n tha t ma y be mi s ta ken for a ppendi ci ti s c. Pi ts a ga r grows both i n ca rbon di oxi de a nd under a na erobi c condi ti ons , a nd i s pa rt of the norma l ora l ca vi ty fl ora d. Typi ca l l y i nfects ca ttl e, requi res 5% to 10% ca rbon di oxi de for growth, a nd i s i nhi bi ted by the dye thi oni ne e. Typi ca l l y i s found i n i nfected a ni ma l bi tes i n huma ns a nd ca n ca us e hemorrha gi c s epti cemi a i n a ni ma l s 265. Pasteurella s peci es ca n produce a ra nge of huma n di s ea s es a nd formerl y i ncl uded a l l yersiniae a nd francisellae orga ni s ms . Pasteurella multocida occurs worl dwi de i n the URT a nd GI tra cts of domes ti c a nd wi l d a ni ma l s . It i s bes t des cri bed by whi ch of the fol l owi ng? a . Commonl y i nha bi ts the ca ni ne res pi ra tory tra ct a nd i s a n occa s i ona l pa thogen for huma ns ; s trongl y urea s e-pos i ti ve b. Gra m-nega ti ve bi pol a r s ta i ned ba ci l l i tha t ca us e di a rrhea by mea ns of a hea t-s ta bl e enterotoxi n, wi th a bdomi na l pa i n tha t ma y be mi s ta ken for a ppendi ci ti s c. Pi ts a ga r grows both i n ca rbon di oxi de a nd under a na erobi c condi ti ons , a nd i s pa rt of the norma l ora l ca vi ty fl ora d. Typi ca l l y i nfects ca ttl e, requi res 5% to 10% ca rbon di oxi de for growth, a nd i s i nhi bi ted by the dye thi oni ne e. Typi ca l l y i s found i n i nfected a ni ma l bi tes i n huma ns a nd ca n ca us e hemorrha gi c s epti cemi a i n a ni ma l s 266. A 26-yea r-ol d ma l e pres ents to hi s fa mi l y phys i ci a n wi th compl a i nts of pa i nful burni ng duri ng uri na ti on a nd a mi l ky di s cha rge. The purul ent di s cha rge revea l s ma ny neutrophi l s wi th i ntra cel l ul a r gra m-nega ti ve di pl ococci . Whi ch of the fol l owi ng medi ums woul d mos t l i kel y be us ed for i s ol a ti ng Neisseria gonorrhoeae, the s us pected orga ni s m? a . Löffl er medi um b. Löwens tei n–Jens en medi um c. Sheep bl ood a ga r d. TM a ga r e. Thi os ul fa te ci tra te bi l e s a l ts s ucros e medi um 267. Twenty-four hours a fter returni ng from a s hort tri p to As i a , a 35-yea r-ol d fema l e ha s a s udden ons et of vomi ti ng a nd ma s s i ve wa tery di a rrhea tha t i s col orl es s , odorl es s , a nd conta i ns fl ecks of mucus . Whi ch of the fol l owi ng medi ums woul d mos t l i kel y be us ed for i s ol a ti ng V. cholerae, the s us pected orga ni s m? a . Löffl er medi um
b. Löwens tei n–Jens en medi um c. Sheep bl ood a ga r d. TM a ga r e. Thi os ul fa te ci tra te bi l e s a l ts s ucros e medi um 268. A 32-yea r-ol d fema l e pros ti tute i s s een a t the publ i c hea l th cl i ni c wi th fever, ni ght s wea ts , a nd reports coughi ng up bl ood. Her medi ca l hi s tory revea l s tha t s he i s HIV pos i ti ve a nd ha s l os t 20 l bs over the pa s t month. Aci d-fa s t ba ci l l i a re obs erved i n the s putum. After di ges ti on of the s putum, i s ol a ti on of the s us pected orga ni s m i s bes t a ccompl i s hed by us i ng whi ch one of the fol l owi ng medi a ? a . Löffl er medi um b. Löwens tei n–Jens en medi um c. Sheep bl ood a ga r d. TM a ga r e. Thi os ul fa te ci tra te bi l e s a l ts s ucros e medi um 269. Bacillus a nd Clostridium s peci es a re s pore-formi ng ba ci l l i a nd ca n s urvi ve i n the envi ronment for yea rs . Severa l s peci es ca us e i mporta nt di s ea s e i n huma ns , a l though mos t wi l l res pond qui ckl y to a ppropri a te a nti bi oti c thera py. However, whi ch orga ni s m l i s ted bel ow woul d not benefi t from s uch prompt a nti bi oti c trea tment? a . Bacillus anthracis b. Clostridium botulinum c. Clostridium difficile d. Clostridium perfringens e. Clostridium tetani 270. A 12-yea r-ol d boy ha s s udden ons et of fever, hea da che, a nd s ti ff neck. Two da ys ea rl i er, he s wa m i n a l a ke tha t i s bel i eved to ha ve been conta mi na ted wi th dog excreta . Leptos pi ros i s i s s us pected. Whi ch of the fol l owi ng l a bora tory tes ts i s mos t a ppropri a te to determi ne whether he ha s been i nfected wi th l eptos pi ra ? a . Aggl uti na ti on tes t for l eptos pi ra l a nti gen b. Counteri mmunoel ectrophores i s of uri ne s a mpl e c. Gra m s ta i n of uri ne s peci men d. Spi na l fl ui d for da rk-fi el d mi cros copy a nd cul ture i n Fl etcher s erum medi um e. Uri ne cul ture on EMB a nd TM a ga r 271. A 60-yea r-ol d fema l e compl a i ns of tendernes s a nd pa i n a round a peri tonea l ca theter. Bl ood cul tures revea l gra m-pos i ti ve, ca ta l a s e-pos i ti ve cocci . Whi ch of the fol l owi ng i s the mos t l i kel y orga ni s m tha t i s a l s o cons i dered a predomi na nt orga ni s m on s ki n? a . α-Hemol yti c s treptococci b. Bacteroides fragilis c. Escherichia coli d. Lactobacillus s peci es e. Staphylococcus epidermidis 272. A hea l thy 45-yea r-ol d fema l e ha d root ca na l trea tment a bout 3 weeks a go. She now pres ents wi th a new hea rt murmur, fever, pa i nful s ki n nodul es , a bdomi na l pa i n, a nd a n a bnorma l l i ver functi on tes t. Whi ch of the fol l owi ng orga ni s ms woul d mos tl y l i kel y ca us e endoca rdi ti s a nd i s i mpl i ca ted i n denta l ca ri es or root ca na l i nfecti ons ? a . α-Hemol yti c s treptococci b. Bacteroides fragilis c. Escherichia coli d. Lactobacillus s peci es e. Staphylococcus epidermidis 273. A 17-yea r-ol d ma n i s hos pi ta l i zed wi th tra uma to the a bdomen fol l owi ng a ga ng-rel a ted fi ght. He devel ops a n i ntra a bdomi na l a bs ces s , whi ch i s dra i ned a nd s ent to the l a bora tory. A mi xture of gra m-nega ti ve a na erobes i s detected. Whi ch of the fol l owi ng mi croorga ni s ms i s the mos t l i kel y a nd i s a l s o the mos t preva l ent ba cteri um i n the gut? a . α-Hemol yti c s treptococci b. Bacteroides fragilis c. Escherichia coli d. Lactobacillus s peci es e. Staphylococcus epidermidis 274. A 25-yea r-ol d fema l e i s trea ted wi th a cours e of broa d-s pectrum a nti bi oti cs for s evere pel vi c i nfl a mma tory di s ea s e. She now reports a thi ck mi l ky whi te pruri ti c va gi na l di s cha rge. Whi ch of the fol l owi ng i s the mos t preva l ent mi croorga ni s m i n the va gi na a nd ma y a l s o be protecti ve? a . α-Hemol yti c s treptococci b. Bacteroides fragilis c. Escherichia coli d. Lactobacillus s peci es e. Staphylococcus epidermidis 275. Vi ri da ns s treptococci (S. mutans, S. mitis) us ua l l y ha ve α-hemol ys i s a nd a re optochi n-res i s ta nt. They a re becomi ng i ncrea s i ngl y i mporta nt a s ca us es of endoca rdi ti s a nd a bs ces s es (mi xed i nfecti ons ). Whi ch of the fol l owi ng bes t des cri bes S. mutans? a . An a na erobi c, fi l a mentous ba cteri um tha t often ca us es cervi cofa ci a l os teomyel i ti s b. A β-hemol yti c orga ni s m tha t ca us es a di ffus e, ra pi dl y s prea di ng cel l ul i ti s
c. A fa cul ta ti ve a na erobe tha t i s hi ghl y ca ri ogeni c a nd s ti cks to teeth by s ynthes i s of a dextra n d. A fa cul ta ti ve a na erobe tha t often i nha bi ts the bucca l mucos a ea rl y i n a neona te’s l i fe a nd ca n ca us e ba cteri a l rheuma ti c fever (RF) e. A fa cul ta ti vel y a na erobi c, rod-s ha ped ba cteri um tha t s ti cks to teeth a nd i s ca ri ogeni c, commonl y i nvol ved i n probl ems i nvol vi ng denta l procedures , tra uma , s urgery, or a s pi ra ti on 276. Streptococcus salivarius, a common i s ol a te, whi ch i s cons i dered a s norma l , nonpa thogeni c fl ora i n the cl i ni ca l l a bora tory, i s bes t des cri bed by whi ch of the fol l owi ng? a . An a na erobi c, fi l a mentous ba cteri um tha t often ca us es cervi cofa ci a l os teomyel i ti s b. A β-hemol yti c orga ni s m tha t ca us es a di ffus e, ra pi dl y s prea di ng cel l ul i ti s c. A fa cul ta ti ve a na erobe tha t i s hi ghl y ca ri ogeni c a nd s ti cks to teeth by s ynthes i s of a dextra n d. A fa cul ta ti ve a na erobe tha t often i nha bi ts the bucca l mucos a ea rl y i n a neona te’s l i fe a nd ca n ca us e ba cteri a l RF e. A fa cul ta ti vel y a na erobi c, rod-s ha ped ba cteri um tha t s ti cks to teeth a nd i s ca ri ogeni c, commonl y i nvol ved i n probl ems i nvol vi ng denta l procedures , tra uma , s urgery, or a s pi ra ti on 277. Actinomyces s peci es a re a l a rge, di vers e group of gra m-pos i ti ve ba ci l l i . Actinomyces israelii i s a n orga ni s m tha t ca us es pyogeni c l es i ons wi th i nterconnecti ng s i nus tra cts tha t conta i n gra nul es of mi crocol oni es embedded i n the ti s s ues . It i s bes t des cri bed by whi ch of the fol l owi ng? a . An a na erobi c, fi l a mentous ba cteri um tha t often ca us es cervi cofa ci a l os teomyel i ti s b. A β-hemol yti c orga ni s m tha t ca us es a di ffus e, ra pi dl y s prea di ng cel l ul i ti s c. A fa cul ta ti ve a na erobe tha t i s hi ghl y ca ri ogeni c a nd s ti cks to teeth by s ynthes i s of a dextra n d. A fa cul ta ti ve a na erobe tha t often i nha bi ts the bucca l mucos a ea rl y i n a neona te’s l i fe a nd ca n ca us e ba cteri a l RF e. A fa cul ta ti vel y a na erobi c, rod-s ha ped ba cteri um tha t s ti cks to teeth a nd i s ca ri ogeni c, commonl y i nvol ved i n probl ems i nvol vi ng denta l procedures , tra uma , s urgery, or a s pi ra ti on 278. Actinomyces viscosus, a ubi qui tous a cti nomycete, grows under mi cro-a erophi l i c or s tri ct a na erobi c condi ti ons a nd produces a yel l ow-ora nge gra nul e i n the typi ca l ti s s ue exuda tes . It i s bes t des cri bed by whi ch of the fol l owi ng? a . An a na erobi c, fi l a mentous ba cteri um tha t often ca us es cervi cofa ci a l os teomyel i ti s b. A β-hemol yti c orga ni s m tha t ca us es a di ffus e, ra pi dl y s prea di ng cel l ul i ti s c. A fa cul ta ti ve a na erobe tha t i s hi ghl y ca ri ogeni c a nd s ti cks to teeth by s ynthes i s of a dextra n d. A fa cul ta ti ve a na erobe tha t often i nha bi ts the bucca l mucos a ea rl y i n a neona te’s l i fe a nd ca n ca us e ba cteri a l RF e. A fa cul ta ti vel y a na erobi c, rod-s ha ped ba cteri um tha t s ti cks to teeth a nd i s ca ri ogeni c, commonl y i nvol ved i n probl ems i nvol vi ng denta l procedures , tra uma to or s urgery of the ora l ca vi ty, or a s pi ra ti on 279. A 3-yea r-ol d gi rl from a fa mi l y tha t does not bel i eve i n i mmuni za ti on pres ents to the emergency room wi th a s ore throa t, fever, ma l a i s e, a nd di ffi cul ty brea thi ng. A gra y membra ne coveri ng the pha rynx i s obs erved on phys i ca l exa mi na ti on. Whi ch of the fol l owi ng bes t des cri bes C. diphtheriae, the eti ol ogi c a gent? a . It produces a t l ea s t one protei n toxi n cons i s ti ng of two s ubuni ts , A a nd B, tha t ca us e s evere s pa s modi c cough, us ua l l y i n chi l dren b. It produces a toxi n tha t bl ocks protei n s ynthes i s i n a n i nfected cel l a nd ca rri es a l yti c ba cteri opha ge tha t produces the geneti c i nforma ti on for toxi n producti on c. It s ecretes a n erythrogeni c toxi n tha t ca us es the cha ra cteri s ti c s i gns of s ca rl et fever d. It s ecretes a n exotoxi n tha t ha s been ca l l ed “verotoxi n” a nd “Shi ga -l i ke toxi n”; i nfecti on i s medi a ted by s peci fi c a tta chment to mucos a l membra nes e. It requi res cys tei ne for growth 280. A 4-yea r-ol d boy i s ta ken to s ee hi s pedi a tri ci a n beca us e of a pers i s tent cough tha t gra dua l l y wors ened over a 12-da y peri od. On the da y of the exa mi na ti on, the cough i s s o s evere tha t i t i s frequentl y fol l owed by vomi ti ng. A bl ood cel l count s hows ma rked l eukocytos i s wi th a predomi na nce of l ymphocytes . Whi ch of the fol l owi ng bes t cha ra cteri zes thi s mi croorga ni s m? a . It produces a toxi n tha t i ncrea s es cAMP l evel s , res ul ti ng i n i ncrea s ed mucus producti on b. It produces a toxi n tha t bl ocks protei n s ynthes i s i n a n i nfected cel l a nd ca rri es a l yti c ba cteri opha ge tha t produces the geneti c i nforma ti on for toxi n producti on c. It s ecretes a n erythrogeni c toxi n tha t ca us es the cha ra cteri s ti c s i gns of s ca rl et fever d. It s ecretes a n exotoxi n tha t ha s been ca l l ed “verotoxi n” a nd “Shi ga -l i ke toxi n”; i nfecti on i s medi a ted by s peci fi c a tta chment to mucos a l membra nes e. It requi res cys tei ne for growth 281. A 48-yea r-ol d deer hunter pres ents to the emergency room wi th l ympha denopa thy a nd a s ki n l es i on, whi ch s ta rted a s a pa i nful pa pul e a t the s i te of a ti ck bi te. The pa pul e then ul cera tes wi th a necroti c center a nd ra i s ed border. As pi ra te of the ul cer i s pos i ti ve for F. tularensis. Whi ch one of the fol l owi ng bes t cha ra cteri zes thi s ba cteri um? a . It produces a t l ea s t one protei n toxi n cons i s ti ng of two s ubuni ts , A a nd B, tha t ca us e s evere s pa s modi c cough, us ua l l y i n chi l dren b. It produces a toxi n tha t bl ocks protei n s ynthes i s i n a n i nfected cel l a nd ca rri es a l yti c ba cteri opha ge tha t produces the geneti c i nforma ti on for toxi n producti on c. It s ecretes a n erythrogeni c toxi n tha t ca us es the cha ra cteri s ti c s i gns of s ca rl et fever d. It s ecretes a n exotoxi n tha t ha s been ca l l ed “verotoxi n” a nd “Shi ga -l i ke toxi n”; i nfecti on i s medi a ted by s peci fi c a tta chment to mucos a l membra nes e. It requi res cys tei ne for growth 282. Ten boy s couts a re hos pi ta l i zed wi th bl oody di a rrhea a nd s evere hema tol ogi ca l a bnorma l i ti es . An i nves ti ga ti on es ta bl i s hes tha t a l l of the boys devel oped s ymptoms fol l owi ng cons umpti on of ha mburgers from the s a me fa s t-food res ta ura nt cha i n. Whi ch of the fol l owi ng bes t des cri bes E. coli 0157/H7, the eti ol ogi c ba cteri um res pons i bl e for the outbrea k? a . It produces a t l ea s t one protei n toxi n cons i s ti ng of two s ubuni ts , A a nd B, tha t ca us e s evere s pa s modi c cough, us ua l l y i n chi l dren b. It produces a toxi n tha t bl ocks protei n s ynthes i s i n a n i nfected cel l a nd ca rri es a l yti c ba cteri opha ge tha t produces the geneti c i nforma ti on for
toxi n producti on c. It s ecretes a n erythrogeni c toxi n tha t ca us es the cha ra cteri s ti c s i gns of s ca rl et fever d. It s ecretes a n exotoxi n tha t ha s been ca l l ed “verotoxi n” a nd “Shi ga -l i ke toxi n”; i nfecti on i s medi a ted by s peci fi c a tta chment to mucos a l membra nes e. It requi res cys tei ne for growth 283. A 4-yea r-ol d gi rl a wa kens a t mi dni ght compl a i ni ng of a s ore throa t a nd hea da che, a nd s he ha s a fever of 101°F. Phys i ca l exa mi na ti on revea l s a n erythema tous throa t. A ra pi d s trep tes t i s pos i ti ve. A throa t s wa b i s s ent to the l a bora tory for further tes ti ng. Whi ch of the fol l owi ng bes t cha ra cteri zes S. pyogenes a s the pres umed eti ol ogi c a gent? a . It produces a t l ea s t one protei n toxi n cons i s ti ng of two s ubuni ts , A a nd B, tha t ca us e s evere s pa s modi c cough, us ua l l y i n chi l dren b. It produces a toxi n tha t bl ocks protei n s ynthes i s i n a n i nfected cel l a nd ca rri es a l yti c ba cteri opha ge tha t produces the geneti c i nforma ti on for toxi n producti on c. It s ecretes a n erythrogeni c toxi n tha t ca us es the cha ra cteri s ti c s i gns of s ca rl et fever d. It s ecretes a n exotoxi n tha t ha s been ca l l ed “verotoxi n” a nd “Shi ga -l i ke toxi n”; i nfecti on i s medi a ted by s peci fi c a tta chment to mucos a l membra nes e. It ha s ca ps ul es of pol ygl uta mi c a ci d, whi ch i s toxi c when i njected i nto ra bbi ts 284. A 19-yea r-ol d mi l i ta ry recrui t who l i ves i n the ba rra cks devel ops a ma cul a r pa pul a r s ki n ra s h, s evere hea da che, photophobi a , fever, s ti ff neck, a nd bl urred vi s i on. He i s pres umed to ha ve N. meningitidis. Whi ch of the fol l owi ng i s a cha ra cteri s ti c phys i ol ogi ca l tra i t of thi s orga ni s m? a . It ca us es s ponta neous a borti on a nd ha s tropi s m for pl a centa l ti s s ue due to the pres ence of erythri tol i n a l l a ntoi c a nd a mni oti c fl ui d b. It ha s a ca ps ul e of pol ygl uta mi c a ci d, whi ch i s toxi c when i njected i nto ra bbi ts c. It pos s es s es N-a cetyl neura mi ni c a ci d ca ps ul e a nd a dheres to s peci fi c ti s s ues by pi l i found on the ba cteri a l cel l s urfa ce d. It s ecretes two toxi ns , A a nd B, i n the l a rge bowel duri ng a nti bi oti c thera py e. It s ynthes i zes protei n toxi n a s a res ul t of col oni za ti on of va gi na l ta mpons 285. A 45-yea r-ol d ca ttl e-fa rm worker goes to the publ i c hea l th cl i ni c a fter experi enci ng 6 weeks of undul a ti ng fever, chi l l s , s wea ti ng, hea da che, fa ti gue, mus cl e pa i n, a nd wei ght l os s . Hi s tory revea l s tha t he enjoys dri nki ng fres h unpa s teuri zed mi l k wi th hi s other coworkers duri ng the mi dmorni ng brea ks . A bl ood s a mpl e i s s ent to the s ta te l a bora tory for s erol ogi c tes ti ng beca us e the phys i ci a n a s s i s ta nt s us pects Brucella i nfecti on. Whi ch of the fol l owi ng bes t cha ra cteri zes thi s orga ni s m? a . It ca us es s ponta neous a borti on a nd ha s tropi s m for pl a centa l ti s s ue due to the pres ence of erythri tol i n a l l a ntoi c a nd a mni oti c fl ui d b. It ha s a ca ps ul e of pol ygl uta mi c a ci d, whi ch i s toxi c when i njected i nto ra bbi ts c. It ha s 82 pol ys a ccha ri de ca ps ul a r types ; ca ps ul e i s a nti pha gocyti c; type 3 ca ps ul e (β-D-gl ucuroni c a ci d pol ymer) mos t commonl y s een i n i nfected a dul ts d. It s ecretes two toxi ns , A a nd B, i n the l a rge bowel duri ng a nti bi oti c thera py e. It s ynthes i zes protei n toxi n a s a res ul t of col oni za ti on of va gi na l ta mpons 286. An 18-yea r-ol d ma l e pa ti ent pres ents to the emergency room wi th a 3-da y hi s tory of fever, dry cough, di ffi cul ty i n brea thi ng, a nd mus cl e a ches a nd pa i ns . Hi s ches t x-ra y s hows a di ffus e l eft upper l obe i nfi l tra te. Mycoplasma pneumoniae pneumoni a (wa l ki ng pneumoni a ) ma y be ra pi dl y i denti fi ed by whi ch of the fol l owi ng procedures ? a . Col d a ggl uti ni n tes t b. Cul ture of res pi ra tory s ecreti ons i n HeLa cel l s a fter centri fuga ti on of the i nocul a ted tubes c. Cul ture of res pi ra tory s ecreti ons on monkey ki dney cel l s d. Detecti on of s peci fi c a nti gen i n uri ne e. El ectron mi cros copy of s putum 287. A 50-yea r-ol d ma l e pres ents wi th s evere bi l a tera l pul mona ry i nfi l tra te, el eva ted tempera ture l eucocytos i s , el eva ted enzymes , a nd el eva ted crea ti ne ki na s e. He recentl y vi s i ted hi s fa vori te res ta ura nt tha t ha d a l a rge wa ter founta i n, whi ch wa s mi s ty on the da y of hi s vi s i t. Whi ch of the fol l owi ng procedures woul d mos t ra pi dl y di a gnos e the s us pected orga ni s m tha t i s the eti ol ogi c a gent of Legi onna i res di s ea s e i n thi s pa ti ent? a . Col d a ggl uti ni n tes t b. Cul ture of res pi ra tory s ecreti ons on a cha rcoa l -ba s ed nutri ent a ga r c. Detecti on of a nti gen i n res pi ra tory s ecreti ons d. Detecti on of s peci fi c a nti gen i n uri ne e. El ectron mi cros copy of s putum 288. A group of el ementa ry s chool -a ge chi l dren meet for a bi rthda y pa rty, a nd i n the next few da ys , a bout ha l f of them experi ence a mi l d upper res pi ra tory i l l nes s , wi th s ore throa t a nd runny nos e. One fa mi l y gets l a bora tory work done a nd fi nds tha t Chlamydia pneumoniae (TWAR) i s i nvol ved. Whi ch of the fol l owi ng procedures woul d be bes t i f the l a bora tory wa nted to i s ol a te thi s ba cteri um? a . Col d a ggl uti ni n tes t b. Cul ture of res pi ra tory s ecreti ons i n HeLa cel l s a fter centri fuga ti on of the i nocul a ted tubes c. Cul ture of res pi ra tory s ecreti ons on monkey ki dney cel l s d. Detecti on of s peci fi c a nti gen i n uri ne e. El ectron mi cros copy of s putum 289. A 70-yea r-ol d ma n wi th a hi s tory of di a betes pres ents wi th s evere pa i n i n hi s ri ght ea r. The pa ti ent wa s di a gnos ed wi th externa l oti ti s . Further tes ts s ugges ted tha t the pa ti ent s uffered bone a nd nerve da ma ge. Cl i ni ca l l a bora tory a na l ys i s s howed tha t the i s ol a ted mi croorga ni s m produced a di s ti nct bl ue pi gment a s wel l a s a n ADP-ri bos yl a ti ng toxi n. Wha t i s the mos t l i kel y ca us a ti ve a gent? a . Staphylococcus epidermidis b. Staphylococcus aureus c. Pseudomonas aeruginosa d. Enterococcus faecalis
e. Candida albicans 290. A 40-yea r-ol d woma n ha s a hi s tory of s evera l months of ga s tri c pa i n tha t wa s tempora ri l y rel i eved wi th a nta ci d. Stoma ch bi ops i es revea l ed the pres ence of comma -s ha ped orga ni s ms . The pa ti ent res ponded very wel l to a combi ned trea tment of proton pump i nhi bi tors a nd a moxi ci l l i n. Whi ch of the fol l owi ng fa ctors produced by the eti ol ogi c a gent i s a s s oci a ted wi th the devel opment of ga s tri c ca ncer i n pers ons wi th chroni c i nfecti ons ? a . Ca gA protei n b. Fl a gel l a c. Muci na s e d. Urea s e e. Va cuol a ti ng toxi n 291. A 60-yea r-ol d ma n s uffered from fever, wa tery di a rrhea , a bdomi na l pa i n, a nd na us ea . Three weeks l a ter, he wa s a dmi tted to the hos pi ta l una bl e to s pea k but coherent a nd ori ented. Neurol ogi ca l exa mi na ti on revea l ed bi l a tera l mus cl e wea knes s i n hi s l egs . Wi thi n hours , the mus cl e wea knes s extended to hi s a rms a nd ches t. He wa s di a gnos ed wi th Gui l l a i n–Ba rré s yndrome. Wi th whi ch orga ni s m wa s he mos t l i kel y i nfected? a . Campylobacter jejuni b. Clostridium tetani c. Cytolmegalovirus d. Salmonella enterica e. Shigella sonnei 292. An outbrea k of ga s troenteri ti s occurred i n a youth group ca mp. Wa ter a t the ca mp, whi ch wa s not chl ori na ted or fi l tered, wa s obta i ned from a s pri ng on the premi s es . The fa rml a nd nea r the ca mp wa s gra zed by ca ttl e a nd s heep. Run-off from the pa s ture entered the ca mp s pri ng. The i s ol a ted mi croorga ni s m requi red a n a tmos phere conta i ni ng reduced oxygen a nd i ncrea s ed ca rbon di oxi de for i ts growth. In mos t ca s es , the ga s troenteri ti s wa s s el f-l i mi ti ng. Thos e requi ri ng a nti bi oti c trea tment res ponded to erythromyci n. Whi ch i s the mos t l i kel y ca us a ti ve a gent? a . Campylobacter jejuni b. Enteroi nva s i ve Escherichia coli (EIEC) c. Enteropathogenic Escherichia coli (EPEC) d. Vibrio cholerae e. Vibrio parahaemolyticus 293. A ma n who ha d been wa di ng whi l e fi s hi ng i n the Gul f of Mexi co devel oped pa i nful s wel l i ngs tha t evol ved i nto ves i cl es a nd bul l a e (i ma ge). Thes e l es i ons beca me necroti c a nd the ma n devel oped s epti cemi a , s evere s eps i s , a nd mul ti orga n dys functi on s yndrome. Whi ch of the fol l owi ng i s the mos t l i kel y ca us e of thi s ma n’s i nfecti on?
(Reproduced, with permission, from Goldsmith LA, Katz SI, Gilchrest BA, et al. Fi tzpa tri ck’s Derma tol ogy i n Genera l Medi ci ne. 8th ed. New York: McGraw-Hill Education; 2012. Fig. 183-4.) a . Pseudomonas aeruginosa b. Staphylococcus aureus c. Streptococcus pyogenes d. Vibrio parahaemolyticus e. Vibrio vulnificus 294. A 60-yea r-ol d ma l e i n the i ntens i ve ca re uni t recoveri ng from ba ck s urgery requi red i ntuba ti on for res pi ra tory s upport. Forty-ei ght hours a fter i ntuba ti on, he devel oped venti l a tor-a s s oci a ted pneumoni a . The mi croorga ni s m i s ol a ted from tra chea l s ecreti ons a s pi ra ted from the pa ti ent i s a gra m-nega ti ve, oxi da s e pos i ti ve, obl i ga te a erobe tha t produces a mul ti tude of vi rul ence fa ctors i ncl udi ng protea s es , toxi ns , a nd rha mnol i pi d. The pa ti ent wa s trea ted wi th broa d-s pectrum a nti bi oti cs for s evera l weeks , but the trea tment wa s uns ucces s ful a nd he di ed. Whi ch i s the mos t l i kel y ca us a ti ve a gent of thi s pa ti ent’s i nfecti on?
a . Escherichia coli b. Haemophilus influenzae c. Klebsiella pneumoniae d. Moraxella catarrhalis e. Pseudomonas aeruginosa 295. Four weeks a fter hurri ca ne Ri ta , a 50-yea r-ol d ma n a nd hi s wi fe from s outhea s tern Loui s i a na devel oped di a rrhea . The ma n ha d mi l d di a rrhea . However, hi s wi fe ha d s evere wa tery di a rrhea , fever, mus cl e cra mps , a nd vomi ti ng, whi ch qui ckl y progres s ed i n to a l os s of rena l functi on a nd res pi ra tory a nd ca rdi a c fa i l ure. She res ponded very wel l to a nti bi oti c a nd a ggres s i ve rehydra ti on thera py. Stool s a mpl es from both pa ti ents conta i ned gra m-nega ti ve comma -s ha ped ba cteri a . Whi ch i s the mos t l i kel y ca us a ti ve a gent? a . Campylobacter jejuni b. Salmonella enterica c. Shigella flexneri d. Vibrio cholerae e. Vibrio vulnificus
Answers 180. The answer is a. (Murray [2009], pp 277-285. Murray [2013], Ch 25; Ryan, Ch 27.) Mycoplasma hominis a nd Mycoplasma pneumoniae a re obvi ous l y i ncorrect beca us e they do not pos s es s a cel l wa l l a nd woul d s ta i n pi nk fol l owi ng the Gra m s ta i n. They a l s o a re not a ci d fa s t. Tha t l ea ves the three Mycobacterium s peci es a s the pos s i bl e correct a ns wer. Mycobacterium scrofulaceum i s i ncorrect beca us e i t i s ra rel y pa thogeni c a nd i s uncommon i n the Uni ted Sta tes . Mycobacterium tuberculosis i nfecti ons i n AIDS pa ti ents a re more common tha n M. avium-compl ex di s ea s es i n pl a ces l i ke As i a a nd Afri ca where tubercul os i s i s more l i kel y to occur. Recentl y, AIDS pa ti ents i n the Uni ted Sta tes a re more l i kel y to be i nfected wi th M. avium-compl ex tha n M. tuberculosis due to the ra ri ty of the di s ea s e tubercul os i s i n thi s country. 181. The answer is c. (Murray [2009], pp 282-285. Murray [2013], Ch 25; Ryan, Ch 27.) La dy Wi ndermere s yndrome i s ca us ed by M. avium-compl ex, us ua l l y i n el derl y fema l e nons mokers , res ul ti ng i n a very s eri ous l ung i nfecti on wi th thi s orga ni s m. Scroful a i s a term us ua l l y res erved for tubercul os i s of the neck, but the di s ea s e i s rea l l y a cervi ca l l ympha denopa thy ca us ed by Mycobacterium tuberculosis. The woma n obvi ous l y ha s l epros y due to the pres ence of a ci d-fa s t s ta i ni ng ba ci l l i i n the s ki n s cra pi ngs a nd the l os s of feel i ng i n her fi ngers a nd toes . Thi s i s ca us ed by the ba cteri um i nfecti ng a nd des troyi ng nervous ti s s ue i n thes e a rea s . Tubercul oi d l epros y (a l s o ca l l ed pa uci ba ci l l a ry Ha ns en di s ea s e) i s the mi l d form of the di s ea s e wi th few orga ni s ms obs erved i n s ki n s cra pi ngs . Leproma tous l epros y i s the ful mi na nt form of the di s ea s e wi th numerous ba ci l l i s een i n s ki n s cra pi ngs . Lepros y i s a l s o known a s Ha ns en di s ea s e, a fter the di s coverer of the ca us a ti ve orga ni s m of the di s ea s e, Mycobacterium leprae. 182. The answer is e. (Murray [2009], pp 371-373. Murray [2013], Ch 35; Ryan, Ch 40.) Bacillus anthracis ca us es a nthra x a nd the ma n obvi ous l y does not ha ve a nthra x whi ch i s us ua l l y ma ni fes ted a s a cuta neous di s ea s e. Brucella abortus tends to produce a mi l d di s ea s e wi th ra re pus formi ng compl i ca ti ons . Therefore, the ques ti on becomes whi ch of the s ta ted Bartonella s peci es ca us es Trench fever a nd i s s prea d by l i ce? Bartonella bacilliformis i s s prea d by s a nd fl i es a nd ca us es Ca rri on di s ea s e, whi ch i s a n a cute febri l e i l l nes s cons i s ti ng of a n a nemi a tha t i s ca l l ed Oroya fever. Thi s i s then fol l owed by the cuta neous form of the di s ea s e ca l l ed verruga perua na . The a nemi a i s ca us ed by the orga ni s m enteri ng the red bl ood cel l s a nd a l teri ng them to the degree tha t they a re cl ea red by the reti cul oendothel i a l s ys tem. Bartonella henselae ca us es a medi ca l probl em ca l l ed ca t s cra tch di s ea s e (CSD). It i s a chroni c regi ona l l ympha denopa thy fol l owi ng the s cra tch of a ca t. It i s not s prea d by a n i ns ect vector. Bartonella quintana ca us es Trench fever, a l s o known a s 5-da y fever beca us e the fever reoccurs a t 5-da y i nterva l s . Thi s di s ea s e i s cha ra cteri zed by s evere hea da ches , pa i n i n the l ong bones , a nd 5-da y fever i nterva l s . It i s s prea d by the huma n body l ous e—Pediculus humanus. Tha t i s why thi s di s ea s e i s often s een i n the homel es s who ha ve a di ffi cul t ti me ba thi ng regul a rl y. 183. The answer is a. (Murray, pp 365-369; Murray [2013], Ch 34; Ryan, Ch 34.) Legi onna i res ’ di s ea s e i s a di s ea s e ca us ed by i nfecti on wi th Legionella pneumophila. It i s a di s ea s e ca us ed by the orga ni s m growi ng i n the a i r condi ti oni ng s ys tems i n bui l di ngs . Therefore, i t i s a di s ea s e tha t i s mos t often s een i n the s ummer. Legi onna i res ’ di s ea s e i s a di s ea s e pri ma ri l y a ffecti ng the l ungs . The orga ni s m wi l l not grow on bl ood a ga r but wi l l grow on buffered cha rcoa l yea s t extra ct a s a Gra m-nega ti ve rod. Beca us e i t produces a peni ci l l i na s e, the a nti bi oti c peni ci l l i n i s i neffecti ve a ga i ns t i t. The mi l d form of Legi onna i res ’ di s ea s e i s ca l l ed Ponti a c fever beca us e i t wa s fi rs t obs erved i n Ponti a c, Mi chi ga n. Ps i tta cos i s , whi ch i s ca us ed by Chlamydophila psittaci, i s a l ung i nfecti on, but the orga ni s m wi l l not grow on buffered cha rcoa l yea s t extra ct a ga r. Klebsiella pneumoniae wi l l ca us e a l oba r l ung i nfecti on a nd i s a Gra m-nega ti ve rod, but i t wi l l grow on bl ood a ga r medi a . Streptococcus pneumoniae wi l l a l s o ca us e a l oba r pneumoni a , but i t i s a Gra m-pos i ti ve coccus , a nd i t wi l l grow on bl ood a ga r medi a . Fi na l l y, tubercul os i s , whi ch i s ca us ed by Mycobacterium tuberculosis, i s not a Gra m-nega ti ve ba cteri um, a nd wi l l not even s ta i n wi th the Gra m-s ta i n due to the hi gh concentra ti on of l i pi d i n i ts cel l wa l l . 184. The answer is d. (Murray [2009], pp 209-217; Murray [2013], Ch 18; Ryan, Ch 24.) Sta phyl ococca l food poi s oni ng i s ca us ed by Staphylococcus aureus a nd not Staphylococcus epidermidis. It i s a res ul t of the i nges ti on of food conta mi na ted wi th S. aureus tha t the ba cteri um ha s grown on a nd produced a hea t-s ta bl e enterotoxi n. Thi s i s a toxemi a a nd not a n i nfecti on a nd tha t i s why no a nti bi oti c i nterventi on i s neces s a ry, a s wel l a s why i t occurs s o qui ckl y (2-3 hours ) fol l owi ng i nges ti on of the conta mi na ted food. It a l s o i s s el f-l i mi ti ng a nd us ua l l y res ol ves i ts el f i n 24 hours . Bacillus cereus a l s o produces a ra pi d food poi s oni ng (3-4 hours a fter the i nges ti on of conta mi na ted food), but the us ua l food i s ri ce beca us e the orga ni s m i s a s pore former a nd the s pores s urvi ve the hea ti ng of the ri ce. Clostridium botulinum a l s o produces a food poi s oni ng but i t ma y ta ke 36 hours to ma ni fes t i ts el f a nd the end res ul t i s a fl a cci d pa ra l ys i s a nd not vomi ti ng a nd di a rrhea . Escherichia coli i s a l s o a wel l -known ca us e of food poi s oni ng but i t ta kes a t l ea s t 24 hours to ma ni fes t i ts el f beca us e the orga ni s m mus t grow i n the gut a nd produce enough enterotoxi n to ca us e the obs erved vomi ti ng a nd di a rrhea . 185. The answer is d. (Murray [2009], pp 381-383; Murray [2013], Ch 36; Ryan, Ch 29.) The boy met hi s unfortuna te end for a va ri ety of di fferent rea s ons . The pri ma ry rea s on the boy di ed wa s beca us e he ha d not recentl y recei ved a teta nus boos ter. If he ha d tol d hi s pa rents a bout the na i l puncture, they coul d ha ve ta ken hi m to the doctor to get a teta nus s hot. Tha t s hot woul d ha ve s a ved hi s l i fe. Now we wi l l go to the mi crobi ol ogy of the ques ti on. The boy ca me down wi th teta nus beca us e Clostridium tetani i s a s pore former, a nd beca us e the s pores ca n be found i n the s oi l , they ca n a l s o be found on rus ty na i l s . The rus t on the na i l does not pl a y a rol e i n thi s ques ti on a t a l l . The s econd i mporta nt thi ng a bout Clostridium tetani i s tha t i t i s a s tri ct a na erobe. So the na i l dri ves the s pores i nto the boy’s foot a nd ca us es ti s s ue da ma ge (necros i s ), a nd where there i s necros i s , there i s no bl ood s uppl y, a nd where there i s no bl ood s uppl y, there i s no oxygen, a nd where there i s no oxygen there a re a na erobi c condi ti ons . Therefore, the Clostridium tetani s pores ca n germi na te (cra ck open) a nd a l l ow the vegeta ti ve form of the orga ni s m to come out, a nd i t i s the vegeta ti ve form tha t produces the potent hea t-l a bi l e neurotoxi n. The Clostridium tetani neurotoxi n bl ocks rel ea s e of the neurotra ns mi tters for i nhi bi tory s yna ps es , thus ca us i ng the i nvol unta ry mus cl e s pa s ms a nd res pi ra tory fa i l ure. 186. The answer is e. (Murray [2009], pp 261-267. Murray [2013], Ch 23. Ryan, Ch 26.) The di s ea s e tha t thi s chi l d ha s i s di phtheri a , whi ch i s ca us ed by Corynebacterium diphtheriae. Bacillus anthracis ca us es the di s ea s e a nthra x a nd there i s no l ea thery membra ne s tructure produced i n the pha rynx i n a nthra x. None of the Clostridium s peci es l i s ted a bove (botulinum, perfringens, or tetani) produce a l ea thery membra ne i n the pha rynx, a nd bes i des they a re a l l s tri ct a na erobes a nd woul d not grow i n the ora l ca vi ty. C. diphtheriae does produce a l ea thery membra ne i n the ora l ca vi ty due to i ts producti on of the di phtheri a toxi n whos e mecha ni s m of a cti on i s i nhi bi ti on of protei n s ynthes i s by i na cti va ti on of el onga ti on fa ctor 2, whi ch i s a ma mma l i a n protei n tha t tra ns fers the a mi no a ci d from the t-RNA to the growi ng pol ypepti de cha i n. 187. The answer is d. (Brooks, pp 275-276. Levinson, pp 146, 496. Murray, pp 328-332. Ryan, pp 381-383. Toy, p 90.) Helicobacter pylori wa s fi rs t recogni zed a s a pos s i bl e ca us e of ga s tri ti s a nd pepti c ul cer by Ma rs ha l l a nd Wa rren i n 1984. Thi s orga ni s m i s rea di l y i s ol a ted from ga s tri c bi ops i es but not from s toma ch contents . It i s s i mi l a r to Campylobacter s peci es a nd grows on chocol a te a ga r a t 98.6°F (37°C) i n the s a me mi croa erophi l i c envi ronment s ui ta bl e for C. jejuni (Ca mpy-Pa k or a na erobi c ja r [Ga s Pa k] wi thout the ca ta l ys t). Helicobacter pylori, however, grows more s l owl y tha n C. jejuni, requi ri ng 5 to 7 da ys ’ i ncuba ti on. C. jejuni grows opti ma l l y a t 107.6°F (42°C), not 98.6°F (37°C), a s does H. pylori.
188. The answer is a. (Brooks, pp 280-282. Levinson, pp 152-153. Murray, pp 343-348. Ryan, pp 399-400.) The ma jor determi na nt of vi rul ence i n H. influenzae i s the pres ence of a ca ps ul e. There i s no demons tra bl e exotoxi n, a nd the rol e of endotoxi n i s uncl ea r. Whi l e one woul d expect tha t IgA protea s e woul d i nhi bi t l oca l i mmuni ty, the rol e of thi s enzyme i n pa thogenes i s i s a s yet uncl ea r. Fl a gel l a producti on i s not cons i dered a vi rul ence fa ctor. See the ta bl e a ccompa nyi ng the a ns wer to ques ti on 190 for a compa ri s on of gra m-nega ti ve rods a s s oci a ted wi th the res pi ra tory tra ct. 189. The answer is e. (Brooks, pp 270-272. Levinson, pp 45, 143-145. Murray, pp 317-322. Ryan, pp 348, 375. Toy, p 102.) The toxi n of V. cholerae a nd LT enterotoxi n from E. coli a re s i mi l a r. The B s ubuni ts of the toxi ns bi nd to ga ngl i os i de GM1 receptors on the hos t cel l . The A s ubuni ts ca ta l yze tra ns fer of the ADP-ri bos e moi ety of ADP to a regul a tory protei n known a s G s . Thi s a cti va ted G s s ti mul a tes a denyl cycl a s e. Cycl i c AMP i s i ncrea s ed, a s i s fl ui d a nd el ectrol yte rel ea s e from the crypt cel l s i nto the l umen of the bowel . Wa tery, profus e di a rrhea ens ues . Brucella abortus di s ea s e s ta rts i n huma ns wi th a n a cute ba cteremi c pha s e fol l owed by a chroni c s ta ge tha t ma y l a s t for yea rs . They a re a da pted to a n i ntra cel l ul a r ha bi ta t wi th compl ex nutri ti ona l requi rements . Brucella abortus does not produce a ny product s i mi l a r to the toxi n of V. cholerae; C. diphtheriae’s toxi n ca us es a n a brupt a rres t of protei n s ynthes i s tha t res ul ts i n the necroti zi ng a nd neurotoxi c effects . Li s teri a enters the body through i nges ti on a nd i nfects cel l s of the CNS. No vi rul ence fa ctor s i mi l a r to tha t of V. cholerae i s produced by Li s teri a orga ni s ms . Pseudomonas aeruginosa i s pa thogeni c onl y when i ntroduced i nto a rea s where there a re no norma l defens es . It produces exotoxi n A, whi ch ca us es ti s s ue necros i s a nd bl ocks protei n s ynthes i s s i mi l a r to C. diphtheriae. 190. The answer is d. (Brooks, pp 317, 751. Levinson, pp 25, 189, 503. Ryan, p 904.) Mi cros copi c exa mi na ti on ca n rea di l y demons tra te cl ue cel l s (epi thel i a l cel l s wi th Gardnerella ba cteri a a tta ched) or ps eudohypha e (Candida). A wet mount wi l l be needed to demons tra te moti l e Trichomonas cel l s . Candida, Trichomonas, a nd ba cteri a l va gi ni ti s a re s een mos t often. Staphylococcus aureus i s i nvol ved much l es s frequentl y. Whi l e E. coli ma y be a common ca us e of geni touri na ry i nfecti on, cl ue cel l s a re us ua l l y a bs ent. See the bel ow ta bl e for a compa ri s on of thes e ba cteri a .
191. The answer is d. (Brooks, pp 224-230. Levinson, pp 106-110, 484. Murray, pp 209-220. Ryan, p 268.) Staphylococcus aureus i s a wel l -known pa thogen tha t i s very opportuni s ti c a nd commonl y ca us es a bs ces s l es i ons . It routi nel y ma y res i s t pha gocytos i s by WBCs due to protei n A. Os teomyel i ti s a nd a rthri ti s , ei ther hema togenous or tra uma ti c, a re commonl y ca us ed by S. aureus, es peci a l l y i n chi l dren. Salmonella a re gra m-nega ti ve. Staphylococcus saprophyticus i s a common s ki n fl ora a nd i s us ua l l y not pa thogeni c. Streptococcus pneumoniae i s s el dom or never i nvol ved i n os teomyel i ti s i nfecti ons , a s i s true for L. monocytogenes. 192. The answer is c. (Brooks, p 293. Levinson, pp 160, 495. Murray, pp 344-350. Ryan, p 490.) Pasteurella (gra m-nega ti ve coccoba ci l l i ) a re pri ma ri l y a ni ma l pa thogens , but they ca n ca us e a wi de ra nge of huma n di s ea s es . They ha ve a bi pol a r a ppea ra nce on s ta i ned s mea rs . Pasteurella multocida occurs worl dwi de i n domes ti c a nd wi l d a ni ma l s . It i s the mos t common orga ni s m i n huma n wounds i nfl i cted by bi tes of ca ts a nd dogs . It i s a common ca us e of hemorrha gi c s epti cemi a i n a va ri ety of a ni ma l s . Wounds commonl y pres ent wi th a n a cute ons et (wi thi n hours ) of rednes s , s wel l i ng, a nd pa i n. The other orga ni s ms a re routi nel y found i n the envi ronment a nd ma y be opportuni s ti c pa thogens . Pasteurella multocida i s a gra m-nega ti ve rod tha t us ua l l y res ponds to peni ci l l i n trea tment. Aeromonas, Campylobacter, Pseudomonas, a nd Yersinia a re a l s o gra m-nega ti ve rods . 193. The answer is a. (Brooks, pp 320-326. Levinson, pp 161-165. Murray, pp 278-281. Ryan, pp 445-446.) Mos t ca s es of tubercul os i s a re ca us ed when pa ti ents i nha l e dropl et nucl ei conta i ni ng i nfecti ous orga ni s ms . Whi l e the ba ci l l i a re depos i ted on the a l veol a r s pa ces , they do not cl og up the a l veol i but a re engul fed by ma cropha ges . Ti s s ue i njury i s not a res ul t of toxi n s ecreti on but of cel l -medi a ted hypers ens i ti vi ty; tha t i s , “i mmunol ogi c i njury.” Humora l (a nti bodi es ) i mmuni ty woul d not be res pons i bl e for ti s s ue da ma ge s i nce CMI i s rea cti ng a ga i ns t the orga ni s m. Adhes i on s i tes a re not i mpl i ca ted a s vi rul ence fa ctors a nd toxi ns a ppa rentl y a re not ma de by the orga ni s ms .
(Reproduced, with permission, from Brooks GF, et al. Ja wetz’s Medi ca l Mi crobi ol ogy. 24th ed. New York: McGraw-Hill; 2007:322.) 194. The answer is c. (Brooks, p 190. Levinson, pp 70, 78-79. Murray, pp 207, 816-817. Ryan, p 33.) A new cl a s s of a nti bi oti cs , the qui nol ones , ha s one member, na l i di xi c a ci d, tha t ha s been a va i l a bl e for yea rs . The new repres enta ti ves a re much more a cti ve bi ol ogi ca l l y a nd a re effecti ve a ga i ns t vi rtua l l y a l l gra m-nega ti ve ba cteri a a nd mos t gra m-pos i ti ve ba cteri a . They i ncl ude norfl oxa ci n, ofl oxa ci n, ci profl oxa ci n, enoxa ci n, a nd the fl uori na ted qui nol ones s uch a s l omefl oxa ci n. Thes e a nti bi oti cs ki l l ba cteri a by i nhi bi ti on of s ynthes i s of nucl ei c a ci d, more s peci fi ca l l y, DNA gyra s e. Res i s ta nce to qui nol ones ha s been obs erved a nd a ppea rs to be a cl a s s -s peci fi c phenomenon. An excepti on i s when a n orga ni s m i s res i s ta nt to na l i di xi c a ci d, el eva ted mi ni ma l i nhi bi tory concentra ti ons (MICs ) wi l l genera l l y a ppl y to other qui nol ones , a l though thes e MICs wi l l s ti l l be wi thi n the ra nge of s us cepti bi l i ty. Peni ci l l i n-bi ndi ng protei ns (PBPs ) a nd β-l a cta ma s e i nvol ve peni ci l l i ns , not qui nol ones , a s does the gl yci ne cros s -l i nki ng. Inhi bi ti on of revers e tra ns cri pta s e (RNA-dependent DNA pol ymera s e) woul d not be i nvol ved i n thi s cl i ni ca l s i tua ti on s i nce RT i nhi bi ti on woul d i ndi ca te HIV or HBV i nvol vement. 195. The answer is c. (Brooks, pp 225, 229. Levinson, pp 106-110. Murray, pp 211-220. Ryan, pp 269-270.) VISA wa s fi rs t recogni zed i n Ja pa n. Emergence i n the Uni ted Sta tes s oon fol l owed. It i s l i kel y tha t the huma n VISA i s ol a tes ha ve res ul ted from i ncrea s ed us e of va ncomyci n for pa ti ents wi th MRSA or perha ps a n i ncrea s ed pool of VISA i n the envi ronment s el ected out by the us e of gl ycopepti des s uch a s a vopa rci n, a growth promoter us ed i n food-produci ng a ni ma l s . In pa ti ents wi th VISA, the Centers for Di s ea s e Control a nd Preventi on (CDC) s trongl y recommend compl i a nce wi th i s ol a ti on procedures a nd other i nfecti on control pra cti ces gea red to control of VISA. Sta phyl ococci a re s us cepti bl e to va ncomyci n i f the MIC i s equa l to or l es s tha n 2 μg/mL a nd of i ntermedi a te s us cepti bi l i ty i f the MIC i s 4 to 8 μg/mL. Va ncomyci n res i s ta nce i n S. aureus i s of ma jor concern worl dwi de a nd s urvei l l a nce s houl d be ma i nta i ned. VISA s tra i ns a re us ua l l y na fci l l i n-res i s ta nt. 196. The answer is a. (Brooks, pp 198, 280. Levinson, pp 62-64. Murray, p 808. Ryan, pp 854-855. Toy, p 90.) Ma ny s putum s peci mens a re cul tured unneces s a ri l y. Sputum i s often conta mi na ted wi th s a l i va or i s a l mos t tota l l y ma de up of s a l i va . Thes e s peci mens ra rel y revea l the ca us e of the pa ti ent’s res pi ra tory probl em a nd ma y provi de l a bora tory i nforma ti on tha t i s ha rmful . The s putum i n the ques ti on a ppea rs to be a good s peci men beca us e there a re few epi thel i a l cel l s . The pl eomorphi c, gra m-nega ti ve rods a re s ugges ti ve of Haemophilus, but cul ture of the s ecreti ons i s neces s a ry. Norma l fl ora from a hea l thy ora l ca vi ty cons i s ts of gra m-pos i ti ve cocci a nd rods , wi th few or no PMNs . Pneumococci a re gra m-pos i ti ve di pl ococci . Vi ncent di s ea s e i s a n ora l i nfecti on, whi ch i nvol ves ora l ti s s ue onl y. The pres ence of PMNs i ndi ca tes a n i nfl a mma tory res pons e. 197. The answer is b. (Brooks, pp 306-309. Levinson, pp 150-151, 497. Murray, pp 400-403. Ryan, pp 324-325.) Bacteroides fragilis i s a cons ti tuent of norma l i ntes ti na l fl ora a nd rea di l y ca us es wound i nfecti ons often mi xed wi th a erobi c i s ol a tes . Thes e a na erobi c, gra m-nega ti ve rods a re uni forml y res i s ta nt to a mi nogl ycos i des a nd us ua l l y to peni ci l l i n a s wel l . Rel i a bl e l a bora tory i denti fi ca ti on ma y requi re mul ti pl e a na l yti ca l techni ques . Genera l l y, wound exuda tes s mel l ba d owi ng to producti on of orga ni c a ci ds by s uch a na erobes a s B. fragilis. Bl a ck exuda tes or a bl a ck pi gment (heme) i n the i s ol a ted col ony i s us ua l l y a cha ra cteri s ti c of Bacteroides (Porphyromonas) melaninogenicus, not B. fragilis. Potent neurotoxi ns a re s ynthes i zed by the gra m-pos i ti ve a na erobes s uch a s C. tetani a nd C. botulinum. 198. The answer is b. (Brooks, pp 296-301. Levinson, pp 119-123. Murray, pp 292-298. Ryan, p 336.) Typi ca l Neisseria a re gra m-nega ti ve di pl ococci . Neisseria gonorrhoeae conta i n pi l i , ha i rl i ke a ppenda ges tha t ma y be s evera l mi crometers l ong. They enha nce a tta chment of the orga ni s m to mucous membra nes , hel pi ng to ma ke the orga ni s m more res i s ta nt to pha gocytos i s by WBCs . Gonococci i s ol a ted from cl i ni ca l s peci mens produce s ma l l col oni es conta i ni ng pi l i a ted ba cteri a . Ca ps ul es a ppea r to be l es s i mporta nt i n gonococca l i nfecti on tha n N. meningitidis i nfecti ons . Fl a gel l a , pepti dogl yca n, LPS, a nd F pi l i do not s i gni fi ca ntl y rel a te to pa thogenes i s , other tha n tha t LPS (endotoxi n) rel ea s e ma y become s i gni fi ca nt l a ter i n i nfecti on.
Col l a ge a nd dra wi ng of N. gonorrhoeae s howi ng pi l i a nd the three l a yers of the cel l envel ope. (Reproduced, with permission, from Brooks GF, et al. Ja wetz’s Medi ca l Mi crobi ol ogy. 22nd ed. New York: McGraw-Hill; 2001:256.) 199. The answer is d. (Brooks, pp 218-219. Levinson, pp 131-132. Murray, pp 255-258. Ryan, pp 302-304. Toy, p 102.) Listeria mul ti pl i es both extra -cel l ul a rl y a nd i ntra cel l ul a rl y, but under mos t ci rcums ta nces , a competent i mmune s ys tem el i mi na tes Listeria. As expected, l i s teri os i s i s s een i n the very young a nd the very ol d, a nd i n peopl e wi th compromi s ed i mmune s ys tems . Reports of Listeria food outbrea ks ha ve i mpl i ca ted s uch foods a s col es l a w a nd mi l k products , es peci a l l y i f not pa s teuri zed. Ea rl y-ons et-s yndrome l i s teri os i s i s the res ul t of i nfecti on i n utero a nd cha ra cteri zed by s eps i s a nd l es i ons i n mul ti pl e orga ns . None of the other opti ons (Corynebacterium, Escherichia, s treptococci type B, or S. pneumoniae) woul d be l i kel y to ca us e a n i n utero i nfecti on. 200 to 203. The answers are 200-d, 201-a, 202-c, and 203-d. (Brooks, pp 332-335. Levinson, pp 8, 173, 501. Murray, pp 405-411. Ryan, pp 424-430. Toy, p 164.) Thi s pa ti ent a ppea rs to ha ve pri ma ry s yphi l i s , a s evi denced by a peni l e cha ncre tha t wa s not tender. One of the di fferences between s yphi l i s a nd herpes s i mpl ex vi rus (HSV) i s tha t a n HSV l es i on i s excruci a ti ngl y pa i nful . The herpes l es i on i s ves i cul a r i n a ppea ra nce wherea s the cl a s s i c s yphi l i s cha ncre ha s a n eroded a ppea ra nce. Treponema l orga ni s ms ma y be s een mi cros copi ca l l y i n the l es i on i f the l es i on i s s cra ped. The s yphi l i s l es i on wi l l res ol ve wi th a nti bi oti c thera py. Acycl ovi r pres cri pti on a t thi s ti me woul d be prema ture. If not trea ted, the cha ncre wi l l di s a ppea r a nd the pa ti ent wi l l be a s ymptoma ti c unti l he/s he exhi bi ts the s i gns a nd s ymptoms of s econda ry s yphi l i s , whi ch i ncl ude a di s s emi na ted ra s h a nd s ys temi c i nvol vement s uch a s meni ngi ti s , hepa ti ti s , or nephri ti s . There a re two ki nds of tes ts for the detecti on of s yphi l i s a nti bodi es : nons peci fi c tes ts s uch a s the RPR a nd VDRL, a nd s peci fi c tes ts s uch a s the FTA, T. pallidum hema ggl uti na ti on tes t (TPHA), a nd the mi crohema ggl uti na ti on—T. pallidum (MHTP). The di fference i s tha t the nons peci fi c tes ts us e a cros s -rea cti ve a nti gen known a s ca rdi ol i pi n, whi l e the s peci fi c tes ts us e a T. pallidum a nti gen. Al though the nons peci fi c tes ts a re s ens i ti ve, they l a ck s peci fi ci ty a nd often cros s -rea ct i n pa ti ents who ha ve di a betes , hepa ti ti s , or i nfecti ous mononucl eos i s , or who a re pregna nt. Some pa ti ents , es peci a l l y thos e wi th a utoi mmune di s ea s es , wi l l ha ve both nons peci fi c (RPR) a nd s peci fi c tes ts (FTA) pos i ti ve even i f they do not ha ve s yphi l i s . Res ol uti on of s uch a s i tua ti on ca n be done by mol ecul a r methods for T. pallidum, s uch a s PCR, or by the i mmobi l i za ti on tes t us i ng l i ve s pi rochetes a nd the pa ti ent’s s erum. In the TPI tes t, the s pi rochetes wi l l di e i n the pres ence of s peci fi c a nti body.
Treponema l a nd nontreponema l tes ts i n s yphi l i s . The ti me cours e of trea ted a nd untrea ted s yphi l i s i n rel a ti on to s erol ogi c tes ts i s s hown. The nontreponema l tes ts (VDRL, RPR) ri s e duri ng pri ma ry s yphi l i s a nd rea ch thei r pea k i n s econda ry s yphi l i s . They s l owl y decl i ne wi th a dva nci ng a ge. Wi th trea tment they revert to norma l over a few weeks . The treponema l tes ts (FTA-Abs , MHTP) fol l ow the s a me cours e but rema i n el eva ted even fol l owi ng s ucces s ful trea tment. (Reprinted, with permission, from Ryan KJ, et al. Sherri s Medi ca l Mi crobi ol ogy. 4th ed. New York: McGraw-Hill; 2001:429.) 204. The answer is b. (Brooks, p 211. Levinson, pp 129, 492-493. Murray, pp 378-387. Ryan, pp 322-324.) Pa ti ents trea ted wi th a nti bi oti cs devel op di a rrhea tha t, i n mos t ca s es , i s s el f-l i mi ti ng. However, i n s ome i ns ta nces , pa rti cul a rl y i n thos e pa ti ents trea ted wi th a mpi ci l l i n or cl i nda myci n, a s evere, l i fe-threa teni ng ps eudomembra nous enterocol i ti s devel ops . Thi s di s ea s e ha s cha ra cteri s ti c hi s topa thol ogy, a nd membra nous pl a ques ca n be s een i n the col on by endos copy. Ps eudomembra nous enterocol i ti s a nd a nti bi oti c-a s s oci a ted di a rrhea a re ca us ed by a n a na erobi c gra m-pos i ti ve rod, C. difficile. It ha s been recentl y s hown tha t C. difficile produces a protei n toxi n wi th a mol ecul a r wei ght of a bout 250,000. The “toxi n” i s , i n fa ct, two toxi ns , toxi n A a nd toxi n B. Both toxi ns a re a l wa ys pres ent i n feca l s a mpl es , but there i s a pproxi ma tel y 1000 ti mes more toxi n B tha n toxi n A. Toxi n A ha s enterotoxi c a cti vi ty—tha t i s , i t el i ci ts a pos i ti ve fl ui d res pons e i n l i ga ted ra bbi t i l ea l l oops —wherea s toxi n B a ppea rs to be pri ma ri l y a cytotoxi n. The ba cteroi des a nd cl os tri di um orga ni s ms a re a na erobi c a nd ca n be found i n the i ntes ti na l tra ct. Al s o, thes e woul d be ki l l ed by the a nti bi oti cs gi ven to the pa ti ent. Staphylococcus aureus i s res i s ta nt to ma ny a nti mi crobi a l s a nd ca n ca us e ga s troenteri ti s i f i t becomes predomi na nt, but i t us ua l l y does not ca us e a s s eri ous di s ea s e a s ps eudomembra nous enterocol i ti s . Commerci a l l a bora tory tes ts a re a va i l a bl e to i denti fy C. difficile toxi n a nd enterotoxi n. 205. The answer is a. (Brooks, pp 280-282. Levinson, pp 152-155. Murray, pp 343-349. Ryan, pp 397-401.) Meni ngi ti s ca us ed by H. influenzae ca nnot be di s ti ngui s hed on cl i ni ca l grounds from tha t ca us ed by pneumococci or meni ngococci . The s ymptoms des cri bed a re typi ca l for a l l three orga ni s ms . H. influenzae i s a s ma l l , gra m-nega ti ve rod wi th a pol ys a ccha ri de ca ps ul e. It i s a bl e to grow on l a bora tory medi a i f two fa ctors a re a dded. Heme (fa ctor X) a nd NAD (fa ctor V) provi de for energy producti on. Us e of the conjuga te va cci ne (type b pol ys a ccha ri de) reduces the di s ea s e i nci dence more tha n 90%. Pneumococci a re gra m-pos i ti ve di pl ococci , a nd meni ngococci a re gra m-nega ti ve di pl ococci , whi ch grow on bl ood a ga r a nd chocol a te a ga r wi th no X a nd V fa ctors needed, res pecti vel y. Sa l t-ma nni tol a ga r i s us ed to di s ti ngui s h S. aureus from other ora l fl ora . Streptococci do not produce ca ta l a s e whi l e ma ny other orga ni s ms do. Coa gul a s e producti on i s a nother tes t to i denti fy S. aureus. Commerci a l ki ts a re a va i l a bl e for i mmunol ogi c detecti on of H. influenzae a nti gens i n s pi na l fl ui ds , but currentl y none a re a va i l a bl e to mea s ure s peci fi c a nti body i n CSF. 206. The answer is a. (Brooks, p 220. Levinson, pp 169-170, 500-501. Murray, pp 391-393. Ryan, pp 458-459.) The pa ti ent pres ented wi th typi ca l s ymptoms of a cti nomycos i s . Actinomyces israelii i s norma l fl ora i n the mouth. However, i t ca us es a chroni c dra i ni ng i nfecti on, often a round the ma xi l l a or the ma ndi bl e, wi th os teomyel i ti c cha nges . Trea tment i s hi gh-dos e peni ci l l i n for 4 to 6 weeks . The di a gnos i s of a cti nomycos i s i s often compl i ca ted by the fa i l ure of A. israelii to grow from the cl i ni ca l s peci men. It i s a n obl i ga te a na erobe. FA rea gents a re a va i l a bl e for di rect s ta i ni ng of A. israelii. A ra pi d di a gnos i s ca n be ma de from the pus . FA conjuga tes a re a l s o a va i l a bl e for A. viscosus a nd A. odontolyticus, a na erobi c a cti nomycetes tha t a re ra rel y i nvol ved i n a cti nomycoti c a bs ces s es . Corynebacterium diphtheriae i s a gra m-pos i ti ve rod, a s i s P. acnes, a nd S. aureus woul d be a l a rge gra mpos i ti ve cocci . 207. The answer is b. (Brooks, pp 238-240. Levinson, pp 112-113, 485. Murray, pp 233-236. Ryan, pp 286-287.) GBS ca n be reduced by i ntra pa rtum a dmi ni s tra ti on of peni ci l l i n. Whi l e GBS i s rel a ti vel y more res i s ta nt to peni ci l l i n tha n group A s treptococci , the grea t ma jori ty of GBS i s ol a tes a re s ti l l peni ci l l i n-s us cepti bl e. An a mi nogl ycos i de s uch a s genta mi ci n ma y be a dded to GBS trea tment regi mens due to the rel a ti ve reduced s us cepti bi l i ty of s ome s tra i ns . Experi menta l l y, GBS pol ys a ccha ri de va cci nes ha ve a l s o been us ed. Screeni ng pregna nt fema l es ea rl y i n pregna ncy proba bl y offers l i ttl e a dva nta ge beca us e of the pos s i bl e a cqui s i ti on of GBS l a te i n the pregna ncy. Identi fi ca ti on of pos s i bl e hi gh-ri s k bi rths woul d be pa rt of the phys i ci a n’s ca re of the pregna nt pa ti ent a nd i s too genera l for thi s ques ti on. Screeni ng for GBS a t the fi rs t offi ce vi s i t i s prema ture s i nce thi s i s a fi rs t-ti me pregna ncy wi th no hi s tory of GBS compl i ca ti ons . Screeni ng of GBS i n the l a s t tri mes ter woul d proba bl y not be done unl es s s ome i ndi ca ti on of probl ems wa s i denti fi ed. GBS i s pa rt of the norma l va gi na l fl ora a nd woul d be i denti fi ed a s s uch on cul turi ng. No
pol ys a ccha ri de va cci ne for GBS i s currentl y a va i l a bl e. 208. The answer is b. (Brooks, pp 238-240. Levinson, pp 112-113, 485. Murray, pp 233-236. Ryan, pp 286-287.) There ha s been s pecul a ti on concerni ng the pa thogenes i s of GBS. Thi s i ncl udes fa i l ure to a cti va te compl ement pa thwa ys a nd i mmobi l i za ti on of pol ymorphonucl ea r l eukocytes due to the i na cti va ti on of compl ement C5a , a potent chemoa ttra cta nt. 209. The answer is a. (Brooks, pp 332-335. Levinson, pp 173-175. Murray, pp 405-411. Ryan, pp 424-429.) In men, the a ppea ra nce of a ha rd cha ncre on the peni s cha ra cteri s ti ca l l y i ndi ca tes s yphi l i s . Even though the cha ncre does not a ppea r unti l the i nfecti on i s 2 or more weeks ol d, the VDRL tes t for s yphi l i s s ti l l ca n be nega ti ve des pi te the pres ence of a cha ncre (the VDRL tes t ma y not become pos i ti ve for 2 or 3 weeks a fter i ni ti a l i nfecti on). However, a l es i on s us pected of bei ng a pri ma ry s yphi l i ti c ul cer s houl d be exa mi ned by da rk-fi el d mi cros copy, whi ch ca n revea l moti l e treponemes . Sendi ng the pa ti ent home untrea ted woul d never occur, es peci a l l y i n l i ght of the l es i on bei ng pres ent. Si nce s yphi l i s wa s s us pected, the s pi rochete woul d not grow on T-M medi um, a nd no pus di s cha rge (s us pect gonorrhea ) wa s reported to jus ti fy cul ture for N. gonorrhoeae. 210. The answer is a. (Brooks, pp 285-286. Levinson, pp 157, 491-492. Murray, pp 358, 361-363. Ryan, pp 483-484.) Brucella a re s ma l l , a erobi c, gra m-nega ti ve coccoba ci l l i . Of the four wel l -cha ra cteri zed s peci es of Brucella, onl y one—B. melitensis—cha ra cteri s ti ca l l y i nfects both goa ts a nd huma ns . Brucel l os i s ma y be a s s oci a ted wi th GI a nd neurol ogi c s ymptoms , l ympha denopa thy, s pl enomega l y, hepa ti ti s , a nd os teomyel i ti s . Sus cepti bi l i ty to dyes (thi oni n a nd ba s i c fuchs i n) ca n hel p i n di fferenti a ti on of the s peci es . None of the rema i ni ng opti ons (C. jejuni, S. enteritidis, a nd S. marcescens) a re known to routi nel y be pa s s ed from a ni ma l s to huma ns . Francisella tularensis i s known to be s o (s ee the ta bl e), but us ua l l y i n connecti on wi th hunti ng a nd cl ea ni ng ga me a ni ma l s . See the ta bl e bel ow for a l i s ti ng of gra m-nega ti ve rods a s s oci a ted wi th a ni ma l s ources .
211. The answer is a. (Brooks, pp 270-272. Levinson, pp 143-145. Murray, pp 317-320. Ryan, pp 376-377.) Chol era i s a toxi cos i s . The mode of a cti on of chol era toxi n i s to s ti mul a te the a cti vi ty of a denyl cycl a s e, a n enzyme tha t converts ATP to cycl i c AMP. Cycl i c AMP s ti mul a tes the s ecreti on of chl ori de i on, a nd a ffected pa ti ents l os e copi ous a mounts of fl ui d. A drug tha t i nhi bi ts a denyl cycl a s e thus mi ght bl ock the effect of chol era toxi n. Wa ter a nd el ectrol yte repl a cement a re pri ma ry ma na gement mecha ni s ms , whi l e ora l tetra cycl i ne ma y hel p reduce s tool output. Ma ny a nti mi crobi a l a gents a re effecti ve a ga i ns t V. cholerae, nota bl y ora l tetra cycl i ne. A s ens i ti vi ty tes t woul d be needed for choos i ng the bes t drug to ki l l the ba cteri a . Fl ui d s ecreti on woul d be l es s ened i f a denyl cycl a s e wa s i nhi bi ted. Our pa ti ent woul d not di e wi th the des cri bed medi ca l trea tment, but be hel ped to overcome the i nfecti on. Reducti on of ba cteri a l moti l i ty ha s no a s s oci a ti on wi th ba cteri a l vi rul ence. 212. The answer is d. (Brooks, pp 226-228. Levinson, pp 106-110. Murray, pp 210-223. Ryan, pp 263-264.) Certa i n s tra i ns of s ta phyl ococci el a bora te a n enterotoxi n tha t i s frequentl y res pons i bl e for food poi s oni ng. Typi ca l l y, the toxi n i s produced when s ta phyl ococci grow on foods ri ch i n ca rbohydra tes a nd i s pres ent i n the food when i t i s cons umed. The res ul ti ng ga s troenteri ti s i s dependent onl y on the i nges ti on of toxi n a nd not
on ba cteri a l mul ti pl i ca ti on i n the GI tra ct. Cha ra cteri s ti c s ymptoms a re na us ea , vomi ti ng, a bdomi na l cra mps , a nd expl os i ve di a rrhea . The i l l nes s ra rel y l a s ts more tha n 24 hours . Campylobacter perfringens toxi n contri butes to a form of food poi s oni ng, but the orga ni s m i s i nges ted a nd grows i n the pa ti ent, then rel ea s i ng the toxi n. Campylobacter perfringens a l s o ha ve toxi ns tha t ca n da ma ge va ri ous ti s s ues (ga s ga ngrene). Staphylococcus aureus produces coa gul a s e tha t cl ots pl a s ma a nd does not contri bute to S. aureus food poi s oni ng. Peni ci l l i na s e (β-l a cta ma s e) does not contri bute to food poi s oni ng s ymptoms . Leukoci di n i na cti va tes WBCs i n the l a bora tory, but cl i ni ca l s i gni fi ca nce i s uncerta i n. 213. The answer is e. (Brooks, pp 224-229. Levinson, pp 106-110. Murray, p 222, Ryan, pp 269-270.) Sta phyl ococci a re gra m-pos i ti ve, non-s pore-formi ng cocci . Cl i ni ca l l y, thei r a nti bi oti c res i s ta nce pos es ma jor probl ems . Ma ny s tra i ns produce β-l a cta ma s e (peni ci l l i na s e), a n enzyme tha t des troys peni ci l l i n by openi ng the l a cta m ri ng. Drug res i s ta nce, medi a ted by pl a s mi ds , ma y be tra ns ferred by tra ns ducti on. No known a l l ergi c rea cti ons occur by rel ea s e of s ta phyl ococca l protei ns . Even i f the peni ci l l i n penetra tes the S. aureus membra ne, externa l peni ci l l i na s e woul d proba bl y ha ve broken the β-l a cta m ri ng, i na cti va ti ng the drug. S. aureus mos t l i kel y conta i ns peni ci l l i n-bi ndi ng protei ns (PBPs ) but nothi ng ha ppens i f the peni ci l l i n i s i na cti va ted. Acetyl i s CH 3 CO. The a cetyl a s e woul d brea k thi s bond, but i t i s uncerta i n whether thi s i na cti va tes peni ci l l i n l i ke βl a cta ma s e does . 214. The answer is c. (Brooks, p 207. Levinson, pp 127-128, 492. Murray, pp 383-386. Ryan, pp 320-322.) Campylobacter botulinum growi ng i n food produces a potent neurotoxi n tha t ca us es di pl opi a , dys pha gi a , res pi ra tory pa ra l ys i s , a nd s peech di ffi cul ti es when i nges ted by huma ns . The toxi n i s thought to a ct by bl ocki ng the a cti on of a cetyl chol i ne a t neuromus cul a r juncti ons . Botul i s m i s a s s oci a ted wi th hi gh morta l i ty; fortuna tel y, C. botulinum i nfecti on i n huma ns i s ra re. Acti va ti on of cycl i c AMP i s i mporta nt i n chol era di s ea s e, not botul i s m. Cl os tri di a a re gra m-pos i ti ve a nd ha ve no endotoxi n. Inges ti on of the botul i s m toxi n i ni ti a tes the di s ea s e. The a ctua l orga ni s m ma y or ma y not be a l i ve when i nges ted. An enterotoxi n, by defi ni ti on, woul d a ffect the i ntes ti na l tra ct. 215. The answer is a. (Brooks, pp 296-303. Levinson, pp 119-123. Murray, pp 73-78, 291-299. Ryan, p 327.) Severa l Neisseria s peci es ma ke up pa rt of the norma l (nonpa thogeni c) fl ora of the huma n upper res pi ra tory tra ct. Whi l e commens a l orga ni s ms s el dom ca us e di s ea s e, they ma y occa s i ona l l y be opportuni s ti c. Thes e orga ni s ms a re a l s o “forei gn” to the i mmune s ys tem a nd ca us e i mmune res pons es to occur, es peci a l l y humora l (a nti body). The pa thogens (N. gonorrhea a nd N. meningitidis) produce fa ctors tha t ens ure s ucces s ful col oni za ti on of ti s s ue i n s pi te of l oca l i mmune defens e mecha ni s ms . Neisseria orga ni s ms a re gra m-nega ti ve a nd ha ve endotoxi n but not l i potei choi c a ci d res i dues . Thes e a re pa rt of gra m-pos i ti ve cel l wa l l s . Si nce even nonpa thogeni c nei s s eri a a re forei gn to the i mmune s ys tem, a ny a nti body res pons e woul d be s peci fi c to the ba cteri a l s tra i n. 216. The answer is d. (Brooks, pp 273-275. Levinson, pp 145-146. Murray, pp 325-328. Ryan, pp 379-380.) Unti l recentl y, both erythromyci n a nd ci profl oxa ci n were the drugs of choi ce for C. jejuni enterocol i ti s . Recentl y, res i s ta nce to the qui nol ones (ci profl oxa ci n) ha s been obs erved. Ampi ci l l i n i s i neffecti ve a ga i ns t thi s gra m-nega ti ve, curved rod. Whi l e Pepto-Bi s mol ma y be a dequa te for a rel a ted ul cer-ca us i ng ba cteri um, Helicobacter, i t i s not us ed for C. jejuni. Whi l e the pa thogenes i s of C. jejuni s ugges ts a n enterotoxi n, a n a nti toxi n i s not a va i l a bl e. 217. The answer is b. (Brooks, pp 280-282. Levinson, pp 152-153. Murray, pp 344-348. Ryan, pp 397-401. Toy, p 96.) Haemophilus influenzae i s a gra m-nega ti ve ba ci l l us . In young chi l dren, i t ca n ca us e pneumoni ti s , s i nus i ti s , oti ti s , a nd meni ngi ti s . Occa s i ona l l y, i t produces a ful mi na ti ve l a ryngotra chei ti s wi th s uch s evere s wel l i ng of the epi gl otti s tha t tra cheos tomy becomes neces s a ry. Cl i ni ca l i nfecti ons wi th thi s orga ni s m a fter the a ge of 3 yea rs a re l es s frequent, es peci a l l y s i nce a pprova l of the type b va cci ne. Haemophilus haemolyticus i s a hemol yti c va ri a nt of H. influenzae whi ch tha t onl y occa s i ona l l y ca us es di s ea s e. Klebsiella pneumoniae i s pres ent i n a bout 5% of i ndi vi dua l s a nd ca us es a bout 1% of pneumoni a s . Treponema pneumoniae i s a promi nent ca us e of pneumoni a i n pers ons 5 to 20 yea rs ol d. Neisseria meningitidis ca n be pa rt of the ora l fl ora but i s s i gni fi ca nt i n di s ea s e when i t enters the bl oods trea m a nd CNS. 218. The answer is a. (Brooks, pp 240-243. Levinson, pp 27, 140, 537. Murray, pp 243-246. Ryan, pp 294-295. Toy, p 70.) Enterococci ca us e a wi de va ri ety of i nfecti ons ra ngi ng from l es s s eri ous —for exa mpl e, UTIs —to very s eri ous , s uch a s s epti cemi a . A gra m-pos i ti ve coccus res i s ta nt to peni ci l l i n mus t be a s s umed to be enterococcus unti l other, more defi ni ti ve bi ochemi ca l tes ti ng pl a ces the i s ol a te i n one of the more es oteri c groups of gra mpos i ti ve cocci . Group A s treptococci ca n ca us e a wi de va ri ety of di s ea s es , i ncl udi ng RF. Certa i n a nti gens of the Group A s treptococci cros s rea ct wi th huma n hea rt a nti gens , ca us i ng da ma ge to hea rt mus cl es a nd va l ves . GBS a re pa rt of the norma l va gi na l fl ora , a re β-hemol yti c, a nd tes t pos i ti ve to the cAMP tes t. Gra m-nega ti ve Neisseria s peci es a re s el dom i nvol ved i n hea rt di s ea s e, even a s opportuni s ts . Streptococcus pneumoniae ca n ca us e upper res pi ra tory di s ea s e, ba cteremi a , a nd meni ngi ti s . 219. The answer is d. (Brooks, p 243. Levinson, pp 111, 489-490. Murray, pp 243-246. Ryan, pp 294-295.) Enterococcus faecalis ca us es 85% to 90% of enterococca l i nfecti ons , whi l e E. faecium ca us es 5% to 10%. The enterococci a re a mong the mos t frequent ca us es of nos ocomi a l i nfecti ons , es peci a l l y i n i ntens i ve ca re uni ts . Streptococcus bovis i s a nonenterococca l Group D s treptococcus . Streptococcus pyogenes i s a Group A s treptococcus , res pons i bl e for 95% of s treptococci i nfecti ons . Streptococcus pneumoniae a re s ens i ti ve to ma ny a nti mi crobi a l s . Once i s ol a ted, there a re a va ri ety of tes ts to s peci a te enterococci . However, peni ci l l i n-res i s ta nt, non-β-l a cta ma s e-produci ng, va ncomyci n-res i s ta nt, gra m-pos i ti ve cocci a re mos t l i kel y E. faecium or E. faecalis. 220. The answer is e. (Brooks, pp 240-243. Levinson, pp 77, 112. Murray, pp 243-246. Ryan, pp 294-295.) There a re a va ri ety of mecha ni s ms for va ncomyci n res i s ta nce i n E. faecium, a nd they ha ve been termed Va n A, B, or C. Thes e i s ol a tes ha ve become one of the mos t fea red nos ocomi a l pa thogens i n the hos pi ta l envi ronment. Unfortuna tel y, no a pproved a nti bi oti cs ca n s ucces s ful l y trea t va ncomyci n-res i s ta nt enterococci (VRE)—onl y s ome experi menta l a nti bi oti cs s uch a s Synerci d. Enterococci a re hi ghl y res i s ta nt to cepha l os pori ns , β-l a cta ma s e-res i s ta nt peni ci l l i ns , a nd monol a cta ms . They ha ve l ow-l evel res i s ta nce to a mi nogl ycos i des a nd i ntermedi a te res i s ta nce to fl uoroqui nol ones . They a re i nhi bi ted by β-l a cta ms (a mpi ci l l i n) but not ki l l ed by them. 221. The answer is c. (Brooks, pp 224-229. Levinson, pp 107-109, 484. Murray, pp 211-220. Ryan, p 824.) Staphylococcus aureus i s i mpl i ca ted i n the ma jori ty of ca s es of a cute os teomyel i ti s , whi ch a ffects chi l dren mos t often. A s uperfi ci a l s ta phyl ococca l l es i on frequentl y precedes the devel opment of bone i nfecti on. In the prea nti bi oti c era , Streptococcus pneumoniae wa s a common ca us e of a cute os teomyel i ti s . M. tuberculosis a nd gra m-nega ti ve orga ni s ms a re i mpl i ca ted l es s frequentl y i n thi s i nfecti on. 222. The answer is d. (Brooks, pp 213-216. Levinson, pp 130-131, 481. Murray, pp 261-265. Ryan, p 170. Toy, p 64.) Al l toxi geni c s tra i ns of C. diphtheriae a re l ys ogeni c for β-pha ge ca rryi ng the Tox gene, whi ch codes for the toxi n mol ecul e. The expres s i on of thi s gene i s control l ed by the meta bol i s m of the hos t ba cteri a . The grea tes t a mount of toxi n i s produced by ba cteri a grown on medi a conta i ni ng very l ow a mounts of i ron. Fra gment B of the toxi n i s requi red for cel l entry, whi l e Fra gment A s tops protei n producti on by i nhi bi ti ng el onga ti on fa ctor 2 (EF-2). Corynebacterium di phtheri a e does not pos s es s a ca ps ul e, whi ch i s norma l l y us ed to i mpede pha gocytos i s by WBCs . Gl ucos e a nd/or s ucros e fermenta ti on i s not a vi rul ence fa ctor. Endotoxi n comes from gra m-nega ti ve ba cteri a whi l e coryneba cteri a a re gra m pos i ti ve.
(Reproduced, with permission, from Brooks GF, et al. Ja wetz’s Medi ca l Mi crobi ol ogy. 24th ed. New York: McGraw-Hill; 2007: 225.) 223 to 225. The answers are 223-e, 224-e, and 225-b. (Brooks, pp 226-228. Levinson, pp 40-44, 107-108. Murray, pp 211-220. Ryan, pp 264-266. Toy, p 156.) TSS i s a febri l e i l l nes s s een predomi na ntl y, but not excl us i vel y, i n mens trua ti ng women. Cl i ni ca l cri teri a for TSS i ncl ude fever grea ter tha n 102°F (38.9°C), ra s h, hypotens i on, a nd a bnorma l i ti es of the mucous membra nes a nd the GI, hepa ti c, mus cul a r, ca rdi ova s cul a r s ys tems , or CNS. Us ua l l y three or more s ys tems a re i nvol ved. Trea tment i s s upporti ve, i ncl udi ng the a ggres s i ve us e of a nti s ta phyl ococca l a nti bi oti cs . Certa i n types of ta mpons ma y pl a y a rol e i n TSS by tra ppi ng O2 a nd depl eti ng ma gnes i um. Mos t peopl e ha ve protecti ve a nti bodi es to the toxi c s hock s yndrome toxi n (TSST-1). Chi cken pox (VZV) or va ri cel l a pres ents wi th a typi ca l ves i cul a r ra s h. Gui l l a i n–Ba rré s yndrome i s a demyel i na ti ng condi ti on of the peri phera l nerves . Sca l ded s ki n s yndrome i s ca us ed by S. aureus exfol i a ti ve toxi n tha t produces epi derma l s ki n l a yer s l oughi ng. Food poi s oni ng i s ca us ed by S. aureus enterotoxi ns , whi ch a re produced i n conta mi na ted food a nd s ymptoms a ppea r a fter i nges ti on. TSS i s ca us ed by a toxi n-produci ng s tra i n of S. aureus (TSST-1). In thi s ca s e, no a ctua l orga ni s ms woul d l i kel y be i s ol a ted s i nce TSS i s ca us ed by a n excreted toxi n, not the a ctua l orga ni s m. Bl ood cul ture woul d a l s o mos t l i kel y be nega ti ve. Whi l e there ha ve been reports tha t S. epidermidis produces TSS, they ha ve l a rgel y been di s counted. Va gi na l col oni za ti on wi th S. aureus i s a neces s a ry a djunct to the di s ea s e. Staphylococcus aureus i s i s ol a ted from the va gi na l s ecreti ons , conjuncti va , nos e, throa t, cervi x, a nd feces i n 45% to 98% of ca s es . The orga ni s m ha s i nfrequentl y been i s ol a ted from the bl ood. Clostridium difficile a nd C. perfringens produce ps eudomembra nous col i ti s a nd ga s ga ngrene, res pecti vel y. Gardnerella vaginalis ca n be found i n the norma l va gi na l fl ora a nd i n va gi nos i s , where i nfl a mma tory cel l s a re not pres ent. “Cl ue cel l s ” a re va gi na l epi thel i a l cel l s covered wi th ma ny gra m-va ri a bl e ba cteri a , i ncl udi ng G. vaginalis. Epi demi ol ogi c i nves ti ga ti ons s ugges t s trongl y tha t TSS i s rel a ted to us e of ta mpons , i n pa rti cul a r, us e of the hi ghl y a bs orbent ones tha t ca n be l eft i n for extended peri ods of ti me. An i ncrea s ed growth of i ntra va gi na l S. aureus a nd enha nced producti on of TSST-1 ha ve been a s s oci a ted wi th the prol onged i ntra va gi na l us e of thes e hypera bs orbent ta mpons a nd wi th the ca pa ci ty of the ma teri a l s us ed i n them to bi nd ma gnes i um. The mos t s evere ca s es of TSS ha ve been s een i n a s s oci a ti on wi th gra m-nega ti ve i nfecti on. TSST-1 ma y enha nce endotoxi n a cti vi ty. Recentl y, group A s treptococci ha ve been reported to ca us e TSS. Purcha s ed fa s t-food i nges ti on, hea vy mens trua l fl ow, rubel l a expos ure, a nd tra vel to Vermont woul d ha ve no rel eva nce to thi s cl i ni ca l s i tua ti on. 226 and 227. The answers are 226-c and 227-d. (http://en.wikipedia.org/wiki/Bayesian_statistics.) Ba yes i a n s ta ti s ti cs a re often us ed to determi ne s ens i ti vi ty, s peci fi ci ty, a nd predi cti ve va l ues of new di a gnos ti c tes ts . A s qua re i s s et up a nd the experi menta l numbers i ns erted: a = true pos i ti ve, b = fa l s e pos i ti ve, c = fa l s e nega ti ve, a nd d = true nega ti ve. The formul a s for s ens i ti vi ty, s peci fi ci ty, a nd predi cti ve va l ues a re a l s o gi ven (s ee the bel ow ta bl e.) It i s neces s a ry to note tha t the i nci dence of the di s ea s e i n the popul a ti on a ffects predi cti ve va l ues but not s ens i ti vi ty or s peci fi ci ty. At a gi ven l evel of s ens i ti vi ty a nd s peci fi ci ty, a s the i nci dence of the di s ea s e i n the popul a ti on i ncrea s es , the predi cti ve va l ue of a pos i ti ve (PVP) i ncrea s es ,
a nd the predi cti ve va l ue of a nega ti ve (PVN) decrea s es . For thi s rea s on, predi cti ve va l ues a re di ffi cul t to i nterpret unl es s true di s ea s e i nci dence i s known.
228. The answer is d. (Brooks, pp 263-265. Levinson, pp 149-150. Murray, pp 333-337. Ryan, pp 387-388.) Ps eudomona ds occur wi del y i n s oi l , wa ter, pl a nts , a nd a ni ma l s . They a re gra m-nega ti ve, moti l e, a erobi c rods tha t produce wa ter-s ol ubl e pi gments (bl ue a nd green). They a re very opportuni s ti c when a bnorma l hos t defens es a re encountered. Whi l e moti l e, they do not “s wa rm” over the s urfa ce of a n a ga r pl a te, a s Proteus does . Bei ng gra mnega ti ve, a s ma ny enteri c a nd envi ronmenta l orga ni s ms a re, thei r cel l wa l l s conta i n endotoxi n (LPS). Ma ny of the ps eudomona ds a re res i s ta nt to a wi de ra nge of a nti mi crobi a l s , enha nci ng thei r opportuni s ti c cha ra cteri s ti cs . 229. The answer is c. (Brooks, pp 203-211. Levinson, pp 127-129. Murray, pp 377-389, 247-251. Ryan, pp 308, 314-317.) Clostridium a nd Bacillus orga ni s ms exi s t wi del y i n na ture. Whi l e ma ny Clostridium a re pa thogeni c due to exotoxi n producti on (C. tetani, C. botulism), a nd a nthra x ha s mul ti pl e vi rul ence fa ctors (ca ps ul e, LF, EF, a nd PA), C. perfringens a nd B. cereus a re found routi nel y i n ga s troenteri ti s outbrea ks . Si nce both a re s pore formers , the us ua l epi demi ol ogi ca l i nves ti ga ti on fi nds tha t hea ti ng foods ki l l s vegeta ti ve ba cteri a but not s pores . If food i s i na ppropri a tel y s tored (>40-140°F), s pores ma y germi na te i nto vegeta ti ve ba cteri a a nd be i nges ted, ca us i ng the di s ea s e. Mos t epi s odes a re s el f-l i mi ted. Both produce enterotoxi ns tha t a ccount for s i mi l a r di s ea s e pres enta ti ons . 230. The answer is e. (Brooks, pp 224-229. Levinson, pp 48, 107-109. Murray, pp 211-220. Ryan, pp 269-270.) The i nci dence of oxa ci l l i n a nd MRSA ha s been ra pi dl y i ncrea s i ng. MRSA a nd methi ci l l i n-s ens i ti ve S. aureus (MSSA) coexi s t i n heterol ogous popul a ti ons . Trea tment of a pa ti ent ha rbori ng thi s heterol ogous popul a ti on ma y provi de a s el ecti ve envi ronment for the MRSA. Pri or to cha ngi ng thera py, the s us cepti bi l i ty of the i s ol a te s houl d be determi ned. Va ncomyci n ha s often been us ed effecti vel y for MRSA, but i t i s expens i ve a nd nephrotoxi c. There i s no evi dence tha t MRSA i s a ny more vi rul ent or i nva s i ve tha n s us cepti bl e s tra i ns . See the ta bl e bel ow for a l i s ti ng of medi ca l l y i mporta nt s ta phyl ococci .
231. The answer is c. (Brooks, pp 253-255. Levinson, pp 136-140, 492. Murray, pp 303-307. Ryan, pp 355-357. Toy, p 76.) Food poi s oni ng wi th E. coli 0157/H7 ca us es hemorrha gi c col i ti s ; i t i s often s een i n peopl e who ha ve ea ten beef ha mburgers . The s a me orga ni s m a l s o ca us es a hemorrha gi c uremi c s yndrome. The toxi n, ca l l ed Shiga-like toxin, ca n be demons tra ted i n Vero cel l s , but the cytotoxi ci ty mus t be neutra l i zed wi th s peci fi c a nti s erum. Wi th the excepti on of s orbi tol fermenta ti on, there i s nothi ng bi ochemi ca l l y di s ti ncti ve a bout thes e orga ni s ms . 232. The answer is b. (Brooks, pp 253-255. Levinson, pp 136-140, 492. Murray, pp 303-307. Ryan, pp 355-357.) ETEC i s a n i mporta nt ca us e of tra vel er’s di a rrhea , produci ng a hea t-l a bi l e exotoxi n (LT) a nd a hea t-s ta bl e enterotoxi n (ST). To ca us e di a rrhea , E. coli mus t produce not onl y LT a nd ST toxi ns but a l s o a dhere to the l i ni ng of the s ma l l i ntes ti ne. Fi mbri a l a nti gens a re i nvol ved i n a dherence. O657/H7 s ta i n i s ca l l ed EHEC, whi l e EPEC i s a l s o a n i mporta nt ca us e of di a rrhea i n i nfa nts . EIEC produces a s hi gel l os i s -type di s ea s e. 233. The answer is d. (Brooks, pp 291-292. Levinson, pp 159-160. Murray, pp 311-313. Ryan, pp 484-488.) Buboni c pl a gue a nd pneumoni c pl a gue di ffer cl i ni ca l l y. Buboni c pl a gue, cha ra cteri zed by s wol l en l ymph nodes a nd fever, i s us ua l l y tra ns mi tted through a fl ea bi te. Pneumoni c pl a gue, whi ch i s cha ra cteri zed by s eps i s a nd pneumoni a , i s tra ns mi tted by the dropl et route, us ua l l y a fter conta ct wi th a n i nfected huma n or a ni ma l . Age of the pa ti ent, geogra phi c l oca ti on a nd/or hea l th of the a ni ma l vector, a nd s ea s on of the yea r woul d a l l be i ns i gni fi ca nt i n cons i deri ng epi demi ol ogi ca l di fferences between the cl i ni ca l pres enta ti ons of the two pl a gues . 234. The answer is a. (Brooks, pp 315, 316. Levinson, pp 32, 186-187. Murray, p 372. Ryan, p 479.) Whi l e the es s enti a l i nforma ti on (i e, the evi dence tha t the chi l d i n ques ti on wa s s cra tched by a ca t) i s mi s s i ng, the cl i ni ca l pres enta ti on poi nts to a number of di s ea s es , i ncl udi ng ca t s cra tch di s ea s e (CSD). Unti l recentl y, the eti ol ogi c a gent of CSD wa s unknown. Evi dence i ndi ca ted tha t i t wa s a pl eomorphi c, rod-s ha ped ba cteri um tha t ha d been na med Afipia. It wa s bes t demons tra ted i n the a ffected l ymph node by a s i l ver i mpregna ti on s ta i n. However, i t now a ppea rs tha t Afipia ca us es rel a ti vel y few ca s es of CSD a nd tha t the s ma l l , pl eomorphi c, gra m-nega ti ve rods pres ent ma i nl y i n the wa l l s of ca pi l l a ri es pri ma ri l y res pons i bl e a re Rochalimaea henselae, whi ch ha s recentl y been rena med B. henselae. Brucella, Mycobacterium, a nd Yersinia s peci es ha ve not been s hown to ha ve a ny a s s oci a ti on wi th CSD. 235. The answer is c. (Brooks, pp 233-239. Levinson, pp 110-115. Murray, pp 225-233. Ryan, p 273.) There ha s been a ma rked i ncrea s e i n fa ta l s treptococca l i nfecti ons , i ncl udi ng thos e tha t a re des cri bed a s “necroti zi ng fa s ci i ti s .” The s tra i ns of group A s treptococci i s ol a ted ha ve a pyrogeni c exotoxi n wi th properti es not unl i ke thos e of the toxi c s hock toxi n of S. aureus. Morta l i ty i s hi gh (30%) i n s pi te of a ggres s i ve a nti bi oti c thera py. 236. The answer is b. (Brooks, pp 275-276. Levinson, pp 146-147, 496. Murray, pp 328-332. Ryan, pp 383-384.) Helicobacter pylori a nti gen tes ts from a s tool s a mpl e us i ng a n ELISA forma t a nd a monocl ona l a nti body to H. pylori a re a s s ens i ti ve a s cul ture of the control porti on of the s toma ch. Urea brea th
tes ts a re a l s o wi del y us ed. Helicobacter pylori ha s a n a cti ve enzyme (urea s e) tha t brea ks down ra di oa cti ve urea . The pa ti ent rel ea s es ra di oa cti ve CO2 i f H. pylori a re pres ent. Helicobacter pylori a nti body tes ts , IgG a nd IgA, i ndi ca te the pres ence of H. pylori a nd us ua l l y decl i ne a fter effecti ve trea tment. Cul ture of s toma ch contents i s i ns ens i ti ve a nd not a ppropri a te a s a di a gnos ti c procedure for H. pylori. Di rect tes ts , s uch a s a nti gen or cul ture of ga s tri c mucos a , a re preferred beca us e they a re the mos t s ens i ti ve i ndi ca ti on of a cure. 237. The answer is e. (Brooks, pp 337-338, Levinson, pp 24, 176-177. Murray, pp 411-415. Ryan, pp 434-437. Toy, p 40.) At pres ent, Lyme di s ea s e ma y be di a gnos ed cl i ni ca l l y a nd s erol ogi ca l l y. Pa ti ents who a re from endemi c a rea s s uch a s ea s tern Penns yl va ni a a nd report joi nt pa i n a nd s wel l i ng months s ubs equent to expos ure to ti cks mus t be eva l ua ted for Lyme di s ea s e a nd trea ted i f the tes t i s pos i ti ve. Pa ti ents ma y a l s o report a va ri ety of neurol ogi c probl ems s uch a s ti ngl i ng of the extremi ti es , Bel l pa l s y, a nd hea da che. IgM a nti body a ppea rs s oon a fter the ti ck bi te (10 da ys -3 weeks ) a nd pers i s ts for 2 months ; IgG a ppea rs l a ter i n the di s ea s e but rema i ns el eva ted for 1 to 2 yea rs , es peci a l l y i n untrea ted pa ti ents . A s i gni fi ca nt IgG ti ter i s a t l ea s t 1:320. Mos t i nves ti ga tors feel tha t IgM ti ters of 1:100 a re s i gni fi ca nt; s ome i nves ti ga tors s a y tha t a ny IgM ti ter i s s i gni fi ca nt. Ma na gement of thi s pa ti ent woul d bes t be done by i mmedi a tel y s ta rti ng trea tment wi th tetra cycl i ne, effecti ve a ga i ns t B. burgdorferi. 238. The answer is c. (Brooks, pp 320-327. Levinson, pp 161-168. Murray, pp 282-285, 289. Ryan, p 613.) There a re s ome i nteres ti ng cha ra cteri s ti cs of M. avium from AIDS pa ti ents . Accordi ng to da ta from the Na ti ona l Jewi s h Hos pi ta l a nd Res ea rch Center i n Denver a nd the CDC, 75% of the i s ol a tes were s erova r 4, a nd 76% produced a deep-yel l ow pi gment. Yel l ow pi gment i s not a cha ra cteri s ti c of mos t i s ol a tes of M. avium. The s i gni fi ca nce of thes e fi ndi ngs i s unknown. Mos t M. avium i s ol a tes a re res i s ta nt to i s oni a zi d a nd s treptomyci n but s us cepti bl e to cl ofa zi mi ne a nd a ns a myci n. In vi tro s us cepti bi l i ty tes ti ng, however, ma y not be rel i a bl e for M. avium. A bl ood cul ture i s often the mos t rel i a bl e wa y to di a gnos e the di s ea s e. Fi na l l y, a l l i s ol a tes of M. avium a re a ci d-fa s t, by defi ni ti on. 239. The answer is b. (Brooks, pp 142, 170, 238. Levinson, pp 115, 470. Murray, pp 231, 233. Ryan, p 279.) Rheuma ti c fever (RF) i s a di s ea s e tha t ca us es pol ya rthri ti s , ca rdi ti s , chorea , a nd erythema ma rgi na tum. The mecha ni s m of da ma ge a ppea rs to be a utoi mmune; tha t i s , a nti bodi es a re s ynthes i zed to a cl os el y rel a ted s treptococca l a nti gen s uch a s M-protei n, but thes e s a me a nti bodi es cros s rea ct wi th certa i n ca rdi a c a nti gens s uch a s myos i n. Unti l recentl y, RF wa s very ra re i n the Uni ted Sta tes . In 1986, there were a t l ea s t 135 ca s es of RF i n Uta h. Subs equentl y, s ca ttered ca s es of RF ha ve occurred i n other s ta tes . Epi demi ol ogi s ts do not ha ve a rea s on for thi s i ncrea s e i n RF. Some evi dence s ugges ts tha t there ma y be a geneti c predi s pos i ti on to the di s ea s e. Intra mus cul a r i njecti on of benza thi ne peni ci l l i n i s effecti ve trea tment for a nd prophyl a xi s a ga i ns t group A s treptococca l i nfecti on. Whi l e i t a ppea rs tha t certa i n s tra i ns of s treptococci conta i n cel l membra ne a nti gens tha t a re i denti ca l to huma n hea rt ti s s ue a nti gens , the s tra i ns ca n i nfect s ki n a nd ca us e pha ryngi ti s . The fi rs t a tta ck of RF (rheuma ti c fever) us ua l l y produces onl y s l i ght ca rdi a c da ma ge. It i s i mporta nt to protect s uch pa ti ents from recurrent S. pyogenes i nfecti ons by prophyl a cti c peni ci l l i n us e to prevent i ncrea s ed da ma ge from mul ti pl e future ba cteri a l a tta cks . Ans wer opti on (e) refers to a s ta phyl ococca l a nti gen a s s i mi l a r, but the correct compa ri s on woul d be wi th s treptococca l a nti gen a nd ca rdi a c a nti gen. 240. The answer is d. (Brooks, pp 198, 240. Levinson, pp 27, 112. Murray, pp 73-78. Ryan, pp 293-294.) In the hea l thy ora l ca vi ty, gra m-pos i ti ve, α-hemol yti c s treptococci ma ke up the predomi na nt fl ora . Any denta l ma ni pul a ti on ca us es bl eedi ng, a l l owi ng the ora l fl ora to get i nto the bl ood (ba cteremi a ). Pha gocyti c a cti vi ty by WBCs us ua l l y cl ea rs thi s i n a few mi nutes . However, thes e s a me orga ni s ms a re qui te effi ci ent a t a tta chi ng to a nd col oni zi ng hea rt va l ve defects . Streptococcus viridans i s a typi ca l member of thi s α-hemol yti c group a nd i s commonl y found i n SBE. Staphylococcus aureus a nd S. epidermidis a re pres ent i n the ora l fl ora i n very s ma l l numbers , a s i s S. pneumoniae. If E. faecalis gets i nto the bl oods trea m from the GI tra ct, i t coul d potenti a l l y a l s o ca us e hea rt va l ve probl ems . The α-hemol yti c vi ri da ns s treptococci a re reported a s bei ng i s ol a ted from SBE mos t often. 241. The answer is e. (Brooks, pp 241-242. Levinson, pp 11, 66, 153. Murray, p 241. Ryan, p 291.) The quel l ung tes t determi nes the pres ence of ba cteri a l ca ps ul es . Speci fi c a nti body i s mi xed wi th the ba cteri a l s us pens i on or wi th cl i ni ca l ma teri a l . The pol ys a ccha ri de ca ps ul e–a nti body compl ex i s vi s i bl e mi cros copi ca l l y. The tes t i s a l s o termed capsular swelling. The ca ps ul es of S. pneumoniae a s wel l a s N. meningitidis, H. influenzae, a nd K. pneumoniae pl a y a rol e i n the pa thogeni ci ty of the orga ni s ms . Thes e s urfa ce s tructures i nhi bi t pha gocytos i s , perha ps by preventi ng a tta chment of the l eukocyte ps eudopod. Corynebacterium diphtheriae, Enterobacter, a nd H. parainfluenzae a re nonenca ps ul a ted. 242. The answer is b. (Brooks, pp 218, 280. Levinson, pp 112, 114, 136, 139. Murray, pp 255-258. Ryan, pp 302-305. Toy, p 102.) No va cci ne i s a va i l a bl e for Listeria. Except duri ng a meni ngococca l epi demi c, H. influenzae i s the mos t common ca us e of ba cteri a l meni ngi ti s i n chi l dren. The orga ni s m i s occa s i ona l l y found to be a s s oci a ted wi th res pi ra tory tra ct i nfecti ons or oti ti s medi a . Haemophilus influenzae, N. meningitidis, S. pneumoniae, a nd Listeria a ccount for 80% to 90% of a l l ca s es of ba cteri a l meni ngi ti s . A puri fi ed pol ys a ccha ri de va cci ne conjuga ted to protei n for H. influenzae type B i s a va i l a bl e. A tetra va l ent va cci ne i s a va i l a bl e for N. meningitidis a nd a 23-s erotype va cci ne for S. pneumoniae. 243. The answer is e. (Brooks, p 149. Levinson, pp 30-37. Murray, pp 73-76.) Orga ni s ms ma y be tra ns mi tted i n a number of wa ys , s uch a s by a i r, food, ha nds , s exua l conta ct, a nd i nfected needl es . However, for ea ch di s ea s e or di s ea s e ca tegory, there i s us ua l l y a porta l of entry not a l wa ys uni que to the orga ni s m. The s ki n i s a tough i ntegument a nd, i n fa ct, i s res i s ta nt to mos t i nfecti ous orga ni s ms except thos e tha t ma y brea kdown huma n s ki n. Brea ches of the s ki n a s by wounds , burns , a nd the l i ke predi s pos e pa ti ents to a va ri ety of i nfecti ons s uch a s teta nus ca us ed by wound conta mi na ti on wi th s pores of C. tetani, or di rect i nfecti on by Staphylococcus, Streptococcus, or gra m-nega ti ve rods (s uch a s Serratia or Pseudomonas). 244 to 246. The answers are 244-d, 245-a, and 246-b. (Brooks, pp 148-151. Levinson, pp 30-37. Murray, pp 73-76.) The res pi ra tory tra ct i s a common porta l of entry to s uch a i rborne orga ni s ms a s M. tuberculosis. Thi s i s why res pi ra tory preca uti ons mus t be ta ken when pa ti ents a re ha rbori ng vi a bl e M. tuberculosis. The GI tra ct i s us ua l l y i nfected from i nges ti on of conta mi na ted food or wa ter (Shigella, Salmonella, a nd Campylobacter) or by a n a l tera ti on of the norma l mi crobi a l fl ora s uch a s wi th C. difficile di s ea s e. The geni ta l tra ct ma y become i nfected ei ther by s exua l conta ct or by a l tera ti on of the geni ta l envi ronment, a s often occurs wi th yea s t i nfecti ons . Severa l ba cteri a s uch a s N. gonorrhoeae, Chlamydia, a nd T. pallidum a re tra ns mi tted by di rect s exua l conta ct wi th i nfected pa rtners . 247. The answer is d. (Brooks, pp 268, 296, 303-304. Levinson, pp 190, 504. Murray, pp 334, 338-340. Ryan, pp 390-391.) Whi l e a dmi ttedl y ra re i n huma n medi ci ne, the ba cteri a referred to s houl d be a ppreci a ted for thei r rol e i n huma n di s ea s e. Branhamella i s a gra m-nega ti ve di pl ococcus . It ha s recentl y been rena med Moraxella catarrhalis. Whi l e i t i s a member of the norma l fl ora , i t ma y ca us e s evere upper a nd l ower res pi ra tory tra ct i nfecti on, pa rti cul a rl y i n the i mmunos uppres s ed pa ti ent. Mos t i s ol a tes produce β-l a cta ma s e a nd a re res i s ta nt to peni ci l l i n. M. catarrhalis i s not a gra m-nega ti ve rod tha t ca us es endoca rdi ti s , nor a gra m-nega ti ve, fus i formed (poi nted ends ) rod a s s oci a ted wi th peri odonta l di s ea s e or s eps i s . It i s not the ca us e of ra t-bi te fever or the ca us a ti ve a gent of trench fever. 248. The answer is b. (Brooks, pp 220, 267. Levinson, p 187. Murray, pp 372, 374. Ryan, pp 390-391.) Capnocytophaga grows bes t i n a ca rbon di oxi de a tmos phere, a s the na me i mpl i es . It i s i s ol a ted frequentl y from pa ti ents wi th peri odonta l di s ea s e but ma y a l s o ca us e s epti cemi a i n s us cepti bl e pa ti ents . Ra t-bi te fever i s ca us ed by Spirillum, a nd the a gent of CSD i s B. henselae. 249. The answer is b. (Brooks, pp 350-354. Levinson, pp 183, 503. Murray, pp 436-440. Ryan, pp 477-478.) Coxiella burnetii i s a ri cketts i a l orga ni s m tha t ca us es
upper res pi ra tory i nfecti ons i n huma ns . Thes e ca n ra nge from s ub-cl i ni ca l i nfecti on to i nfl uenza -l i ke di s ea s e a nd pneumoni a . Tra ns mi s s i on to huma ns occurs from i nha l a ti on of dus t conta mi na ted wi th ri cketts i a e from pl a centa , dri ed feces , uri ne, or mi l k, or from a eros ol s i n s l a ughterhous es . Campylobacter burnetii ca n a l s o be found i n ti cks , whi ch ca n tra ns mi t the a gent to s heep, goa ts , a nd ca ttl e. No s ki n ra s h occurs i n thes e i nfecti ons . Trea tment i ncl udes tetra cycl i ne a nd chl ora mpheni col . Coxiella burnetii i s not tra ns mi tted by fl ea or ti ck vectors . Si nce Q fever i nvol ves the upper res pi ra tory tra ct, l i ver, or CNS, there i s no tra ns mi s s i on by urethra l di s cha rge. 250 to 252. The answers are 250-a, 251-d, and 252-b. (Brooks, pp 243, 219-221. Levinson, pp 69-84. Murray, pp 199-208. Ryan, pp 294, 457-459, 870-871.) Thes e ques ti ons demons tra te commonl y occurri ng cl i ni ca l i nfecti ous di s ea s es a nd mi crobi ol ogi c probl ems . Enterococci ma y be res i s ta nt to a mpi ci l l i n a nd genta mi ci n. Va ncomyci n woul d be the drug of choi ce. However, l a bora tory res ul ts do not a l wa ys correl a te wel l wi th cl i ni ca l res pons e. The Na ti ona l Commi ttee on Cl i ni ca l La bora tory Sta nda rds recommends tes ti ng enterococci onl y for a mpi ci l l i n a nd va ncomyci n. Some s ymptoma ti c pa ti ents ma y ha ve 10 l eukocytes per mi l l i l i ter of uri ne but rel a ti vel y few ba cteri a . The pa ti ent i s l i kel y i nfected a nd the orga ni s ms , pa rti cul a rl y i f i n pure cul ture, s houl d be further proces s ed. The pa ti ent i n Ques ti on 252 proba bl y ha s a cti nomycos i s . Thes e l a bora tory da ta a re not uncommon. There i s no rea s on to work up a l l the conta mi na ti ng ba cteri a . A fl uores cent mi cros copy tes t for A. israelii i s a va i l a bl e. If pos i ti ve, the FA provi des a ra pi d di a gnos i s . In a ny event, i t ma y be i mpos s i bl e to recover A. israelii from s uch a s peci men. Hi gh-dos e peni ci l l i n ha s been us ed to trea t a cti nomycos i s . One of the opti ons s ugges ts no further cl i ni ca l work-up on the pa ti ents be done. Cl ea rl y, l a bora tory res ul ts ma y hel p the cl i ni ci a n ma ke pa ti ent ma na gement deci s i ons but ea ch of thes e three ca s es s how tha t phys i ci a ns need to ha ve a good unders ta ndi ng tha t l a bora tory tes ts ma y gi ve confl i cti ng i nforma ti on for the pa ti ent bei ng trea ted. The phys i ci a n mus t hel p the l a bora tory to unders ta nd how to us e the da ta produced to gi ve the pa ti ent the bes t pos s i bl e medi ca l ca re. Anti bi oti c s ens i ti vi ty tes ts toda y a re mos tl y a utoma ted a nd rel i a bl e. If a repea t i s needed, a new bl ood s a mpl e s houl d be dra wn for the new tes t. 253 to 257. The answers are 253-c, 254-d, 255-b, 256-d, and 257-e. (Brooks, pp 170-172. Levinson, pp 69-84. Murray, pp 199-208. Ryan, p 195. Toy, p 40.) There a re few ba cteri a for whi ch a nti mi crobi a l s us cepti bi l i ty i s hi ghl y predi cta bl e. However, s ome a gents a re the drug of choi ce beca us e of thei r rel a ti ve effecti venes s . Among the three a nti bi oti cs tha t ha ve been s hown to trea t l egi onel l os i s effecti vel y (erythromyci n, ri fa mpi n, a nd mi nocycl i ne), erythromyci n i s cl ea rl y s uperi or, even though i n vi tro s tudi es s how the orga ni s m to be s us cepti bl e to other a nti bi oti cs . Peni ci l l i n rema i ns the drug of choi ce for S. pneumoniae a nd the group A s treptococci , a l though a few i s ol a tes of peni ci l l i n-res i s ta nt pneumococci ha ve been obs erved. Res i s ta nce a mong the pneumococci i s ei ther chromos oma l l y medi a ted, i n whi ch ca s e the mi ni ma l i nhi bi tory concentra ti ons (MICs ) a re rel a ti vel y l ow, or pl a s mi d-medi a ted, whi ch res ul ts i n hi ghl y res i s ta nt ba cteri a . The s a me i s genera l l y true for H. influenzae. Unti l the mi d-1970s , vi rtua l l y a l l i s ol a tes of H. influenzae were s us cepti bl e to a mpi ci l l i n. There ha s been a ra pi dl y i ncrea s i ng i nci dence of a mpi ci l l i nres i s ta nt i s ol a tes —a l mos t 35% to 40% i n s ome a rea s of the Uni ted Sta tes . Res i s ta nce i s ordi na ri l y medi a ted by β-l a cta ma s e, a l though a mpi ci l l i nres i s ta nt, β-l a cta ma s e-nega ti ve i s ol a tes ha ve been s een. No res i s ta nce to peni ci l l i n ha s been s een i n group A s treptococci . Lyme di s ea s e, ca us ed by B. burgdorferi, ha s been trea ted wi th peni ci l l i n, erythromyci n, a nd tetra cycl i ne. Trea tment fa i l ures ha ve been obs erved. Ceftri a xone ha s become the drug of choi ce, pa rti cul a rl y i n the a dva nced s ta ges of Lyme di s ea s e. The mos t common i nfecti on due to β-hemol yti c S. pyogenes (GAS) i s s trep s ore throa t or pha ryngi ti s . From here, the i nfecti on i s a bl e to s prea d to a l l pa rts of the body. Si gni fi ca nt s ymptoms , a s des cri bed, a re often experi enced, wi th onl y 20% of i nfecti ons bei ng a s ymptoma ti c. The orga ni s ms grow fa i rl y wel l i n the l a bora tory a nd ea s i l y i denti fi ed. Al l S. pyogenes s tra i ns a re s us cepti bl e to peni ci l l i n G, a nd mos t a re s us cepti bl e to erythromyci n. Anti mi crobi a l drugs ha ve no effect on es ta bl i s hed gl omerul onephri ti s a nd RF. In a cute i nfecti ons , efforts mus t be ma de to era di ca te s treptococci from the pa ti ent qui ckl y to el i mi na te the a nti geni c s ti mul us . Campylobacter difficile ca us es toxi n-medi a ted ps eudomembra nous enterocol i ti s a s wel l a s a nti bi oti c-a s s oci a ted di a rrhea . Ps eudomembra nous enterocol i ti s i s norma l l y s een duri ng or a fter a dmi ni s tra ti on of a nti bi oti cs . One of the few a gents effecti ve a ga i ns t C. difficile i s va ncomyci n. Al terna ti vel y, ba ci tra ci n ca n be us ed. 258 to 261. The answers are 258-a, 259-d, 260-b, and 261-c. (Brooks, pp 270-276. Levinson, pp 133-146. Murray, pp 325-328. Ryan, pp 373-378. Toy, p 172.) Some orga ni s ms ori gi na l l y thought to be vi bri os , s uch a s C. jejuni, ha ve been recl a s s i fi ed. Campylobacter jejuni, whi ch grows bes t a t 107.6°F (42°C), ha s i ts res ervoi r i n bi rds a nd ma mma l s a nd ca us es ga s troenteri ti s i n huma ns . Vibrio cholerae ca us es chol era , whi ch i s worl dwi de i n di s tri buti on. Vi bri os a re the mos t common ba cteri a i n s urfa ce wa ters worl dwi de. They a re curved rods wi th a pol a r fl a gel l um. Vibrio cholerae s ubgroups O1 a nd O139 (ol der s erotype des i gna ti ons : Oga wa [AB], Ina ba [AC], Jol pka [ABC]) ca us e chol era i n huma ns . A pers on wi th norma l ga s tri c a ci di ty ma y ha ve to i nges t 1010 or more V. cholerae to become i nfected when the vehi cl e i s wa ter beca us e the orga ni s ms a re s us cepti bl e to a ci d. When i nges ted wi th food, a s few a s 102 to 104 ma y be a bl e to produce di s ea s e. The orga ni s ms do not rea ch the bl oods trea m but rema i n i n the i ntes ti na l tra ct. Vibrio parahaemolyticus i s a ha l ophi l i c ma ri ne vi bri o tha t ca us es ga s troenteri ti s i n huma ns , pri ma ri l y from i nges ti on of cooked s ea food. It i s l a ctos e-nega ti ve a nd s ucros e-nega ti ve. Vibrio vulnificus i s a l s o ha l ophi l i c. It ha s been s ugges ted tha t thes e ha l ophi l i c vi bri os do not bel ong to the genus Vibrio but i n the genus Beneckea. Vibrio vulnificus i s l a ctos e-pos i ti ve a nd produces hea t-l a bi l e, extra cel l ul a r toxi n. Orga ni s ms tha t, unl i ke V. cholerae, do not a ggl uti na te i n 0 to 1 a nti s erum were once ca l l ed nona ggl uti na bl e (NAG), or nonchol era (NC), vi bri os . Such a cl a s s i fi ca ti on ca n be confus i ng beca us e V. vulnificus, whi ch i s a n NCV, neverthel es s ca us es s evere chol era -l i ke di s ea s e. In a ddi ti on, V. vulnificus ca n produce wound i nfecti ons , s epti cemi a , meni ngi ti s , pneumoni a , a nd kera ti ti s . 262 to 265. The answers are 262-b, 263-d, 264-a, and 265-e. (Brooks, pp 280-287. Levinson, pp 152-156. Murray, pp 311-313, 358-363. Ryan, pp 401-402, 481-488.) Al l the orga ni s ms des cri bed i n the ques ti ons a re s hort, ovoi d, gra m-nega ti ve rods . For the mos t pa rt, they a re nutri ti ona l l y fa s ti di ous a nd requi re bl ood or bl ood products for growth. Thes e a nd rel a ted orga ni s ms a re uni que a mong ba cteri a i n tha t, though they ha ve a n a ni ma l res ervoi r, they ca n be tra ns mi tted to huma ns . Huma ns become i nfected by a va ri ety of routes , i ncl udi ng i nges ti on of conta mi na ted a ni ma l products (B. abortus i n ca ttl e), di rect conta ct wi th conta mi na ted a ni ma l ma teri a l or wi th i nfected a ni ma l s thems el ves (Y. enterocolitica a nd B. bronchiseptica i n dogs ), a nd a ni ma l bi tes (P. multocida i n ma ny di fferent a ni ma l s ). The l a bora tory di fferenti a ti on of thes e mi crobes ma y be di ffi cul t a nd mus t rel y on a number of pa ra meters , i ncl udi ng bi ochemi ca l a nd s erol ogi c rea cti ons , devel opment of s peci fi c a nti body res pons e i n a ffected pers ons , a nd epi demi ol ogi c evi dence of i nfecti on. Yersinia enterocolitica a re moti l e a t 77°C (25°C) a nd nonmoti l e a t 98.6°F (37°C). They a re found i n the i ntes ti na l tra ct of a ni ma l s a nd ca us e a va ri ety of cl i ni ca l s yndromes i n huma ns . Tra ns mi s s i on to huma ns proba bl y occurs vi a a ni ma l feca l conta mi na ti on of food, dri nk, or fomi tes . The brucel l a e a re obl i ga te pa ra s i tes of a ni ma l s a nd huma ns a nd a re l oca ted i ntra cel l ul a rl y. Brucella abortus i s typi ca l l y found i n ca ttl e. Brucel l os i s (undul a nt fever) ha s a n a cute ba cteremi c pha s e fol l owed by a chroni c s ta ge tha t ma y l a s t yea rs a nd i nvol ve ma ny ti s s ues . Brucella abortus requi res CO2 for growth a nd i s mos t often i s ol a ted from bl ood a nd bone ma rrow. Speci es di fferenti a ti on i s due to dye (thi oni ne) s ens i ti vi ty. Bordetella bronchiseptica ca us es di s ea s es i n a ni ma l s (kennel cough i n dogs ) a nd occa s i ona l l y res pi ra tory di s ea s e a nd ba cteremi a i n huma ns .
Bordetella requi res enri ched medi um (Bordet-Gengou) a nd i s s trongl y urea s e-pos i ti ve. Pasteurella multocida occurs worl dwi de i n the res pi ra tory a nd GI tra cts of ma ny domes ti c a nd wi l d a ni ma l s . It i s the mos t common orga ni s m i n huma n wounds i nfl i cted by ca t a nd dog bi tes . It i s one of the common ca us es of hemorrha gi c s epti cemi a i n ra bbi ts , ra ts , hors es , s heep, fowl , ca ts , a nd s wi ne. It ca n a ffect ma ny s ys tems i n huma ns , a s wel l a s bi te wounds . 266 to 268. The answers are 266-d, 267-e, and 268-b. (Brooks, pp 63-71. Levinson, pp 62-68. Murray, pp 189-198. Ryan, pp 339, 373, 449. Toy, p 122.) The medi um of choi ce for the i s ol a ti on of pa thogeni c Neisseriae i s TMTM a ga r. TM a ga r i s both a s el ecti ve a nd a n enri ched medi um; i t conta i ns hemogl obi n, the s uppl ement Is ovi ta l ex, a nd the a nti bi oti cs va ncomyci n, col i s ti n, nys ta ti n, a nd tri methopri m. Vibrio cholerae a s wel l a s other vi bri os , i ncl udi ng V. parahaemolyticus a nd V. alginolyticus, a re i s ol a ted bes t on thi os ul fa te ci tra te bi l e s a l ts s ucros e medi um, a l though medi a s uch a s ma nni tol s a l t a ga r a l s o s upport the growth of vi bri os . Ma xi ma l growth occurs a t a pH of 8.5 to 9.5 a nd a t 98.6°F (37°C) i ncuba ti on. Löwens tei n– Jens en s l a nts or pl a tes , whi ch a re compos ed of a nutri ent ba s e a nd egg yol k, a re us ed routi nel y for the i ni ti a l i s ol a ti on of mycoba cteri a . Sma l l i nocul a of M. tuberculosis ca n a l s o be grown i n ol ei c a ci d a l bumi n medi a ; l a rge i nocul a ca n be cul tured on s i mpl e s yntheti c medi a . Loeffl er medi um i s a n enri ched nons el ecti ve medi um us ed for the cul ti va ti on of coryneba cteri a , es peci a l l y C. diphtheriae. Hors e s erum a nd egg coa gul a te duri ng s teri l i za ti on a nd provi de nutri ents . Thi s medi um enha nces the producti on of meta chroma ti c gra nul es (obs erved wi th methyl ene bl ue s ta i n). Col umbi a a ga r wi th 5% s heep bl ood i s a genera l -purpos e medi um for i s ol a ti on of a va ri ety of orga ni s ms , i ncl udi ng fa s ti di ous orga ni s ms . Al ong wi th nutri ti on, bl ood a ga r a l l ows the obs erva ti on of a l pha (i ncompl ete) a nd beta (compl ete l ys i s ) hemol ys i s ca us ed by ba cteri a . 269. The answer is b. (Brooks, pp 206-207. Levinson, pp 127-128. Murray, pp 383-386. Ryan, pp 320-322.) Botul i s m i s a di s ea s e brought a bout by i nges ti ng a preformed toxi n. Ana erobi c ba cteri a ha ve grown i n food, depos i ted the botul i s m toxi n, a nd di ed. The toxi n a ffects the CNS by i nhi bi ti ng the rel ea s e of a cetyl chol i ne a t the neurona l s yna ps e. Thi s res ul ts i n a fl a cci d pa ra l ys i s a nd dea th by res pi ra tory fa i l ure. At no s ta ge of the di s ea s e wi l l a ny a nti bi oti c be a bl e to modi fy or a rres t the di s ea s e. Anti toxi ns (A, B, a nd E) mus t be promptl y a dmi ni s tered, a nd venti l a ti on a s s i s ted mecha ni ca l l y. In a l l other choi ces , a nti bi oti cs wi l l provi de a mecha ni s m to ki l l or i nhi bi t the mi croorga ni s ms , bri ngi ng the i nfecti on under control . 270. The answer is d. (Brooks, pp 339-340. Levinson, pp 67, 174-177, 541. Murray, pp 416-418. Ryan, pp 430-431.) Leptos pi ros i s i s a zoonos i s of worl dwi de di s tri buti on. Huma n i nfecti on res ul ts from i nges ti on of wa ter or food conta mi na ted wi th l eptos pi ra e. Ra ts , mi ce, wi l d rodents , dogs , s wi ne, a nd ca ttl e excrete the orga ni s ms i n uri ne a nd feces duri ng a cti ve i l l nes s a nd duri ng a n a s ymptoma ti c ca rri er s ta te. Dri nki ng, s wi mmi ng, ba thi ng, or food cons umpti on ma y l ea d to huma n i nfecti on. Chi l dren a cqui re the di s ea s e from dogs more often tha n do a dul ts . Trea tment ca n i ncl ude doxycycl i ne, a mpi ci l l i n, or a moxi ci l l i n. Symptoms i n huma ns ra nge from fever a nd ra s h to ja undi ce through a s epti c meni ngi ti s . Leptospirae a re ti ghtl y coi l ed, thi n, fl exi bl e s pi rochetes 5 to 15μm l ong, wi th one end bent i nto a hook. It s ta i ns bes t where s i l ver ca n be i mpregna ted i nto the orga ni s m. The gra m s ta i n woul d not be us eful . The orga ni s ms deri ve energy from oxi da ti on of fa tty a ci ds , s o EMB or TM a ga r woul d be i na dequa te. Aggl uti na ti on tes ti ng a nd CIE i s compl i ca ted by the fa ct tha t a l l Leptospirae s tra i ns exhi bi t cros s -rea cti vi ty i n s erol ogi c tes ts . 271 to 274. The answers are 271-e, 272-a, 273-b, and 274-d. (Brooks, pp 196-201. Levinson, pp 25-30. Murray, pp 73-78. Ryan, p 143.) An unders ta ndi ng of norma l , or i ndi genous , mi crofl ora i s es s enti a l i n order to a ppreci a te the a bnorma l . Us ua l l y, a na tomi c s i tes conti guous to mucous membra nes a re not s teri l e a nd ha ve cha ra cteri s ti c norma l fl ora . The s ki n fl ora di ffers a s a functi on of l oca ti on. Ski n a dja cent to mucous membra nes ma y s ha re s ome of the norma l fl ora of the GI s ys tem. Overa l l , the predomi na nt ba cteri a on the s ki n s urfa ce a re S. epidermidis a nd Propionibacterium, a n a na erobi c di phtheroi d. The mouth i s pa rt of the GI tra ct, but i ts i ndi genous fl ora s hows s ome di s ti nct di fferences . Whi l e a na erobes a re pres ent i n l a rge numbers , pa rti cul a rl y i n the gi ngi va l crevi ce, the erupti on of teeth a t 6 to 9 months of a ge l ea ds to col oni za ti on by orga ni s ms s uch a s S. mutans a nd Streptococcus sanguis, both α-hemol yti c s treptococci . An edentul ous pers on l os es β-hemol yti c s treptococci a s norma l fl ora . The GI tra ct i s s teri l e a t bi rth a nd s oon devel ops cha ra cteri s ti c fl ora a s a functi on of di et. In the a dul t, a na erobes s uch a s B. fragilis a nd Bifidobacterium ma y outnumber col i forms a nd enterococci by a ra ti o of 1000:1. The col on conta i ns 1011 to 1012 ba cteri a per gra m of feces . Soon a fter bi rth, the va gi na becomes col oni zed by l a ctoba ci l l i . As the fema l e ma tures , l a ctoba ci l l i ma y s ti l l be predomi na nt, but a na erobi c cocci , di phtheroi ds , a nd a na erobi c, gra m-nega ti ve rods a l s o a re found a s pa rt of the i ndi genous fl ora . Cha nges i n the chemi ca l or mi crobi ol ogi c ecol ogy of the va gi na ca n ha ve ma rked effects on norma l fl ora a nd ma y promote i nfecti on s uch a s va gi ni ti s or va gi nos i s . Escherichia coli a re a mong the mos t common group of gra m-nega ti ve rods i s ol a ted i n the l a bora tory. It i s fa i rl y ea s i l y i denti fi ed i n the l a bora tory. It ferments ma nni tol a nd i s l a ctos e pos i ti ve. The orga ni s m i s pa rt of norma l body fl ora , but i s a very effi ci ent opportuni s t. Uri na ry tra ct i nfecti ons a re commonl y ca us ed wi th thi s orga ni s m. 275 to 278. The answers are 275-c, 276-d, 277-a, and 278-e. (Brooks, pp 196-201. Levinson, pp 25-30. Murray, pp 73-78. Ryan, pp 274-275, 457-459.) Streptococcus salivarius, S. mutans, A. israelii, a nd A. viscosis a re a l l pa rt of the norma l mi crobi ota of the huma n mouth. Both genera a re common ca us es of ba cteri a l endoca rdi ti s . Streptococcus mutans i s hi ghl y ca ri ogeni c (i e, ca pa bl e of produci ng denta l ca ri es ), i n l a rge pa rt beca us e of i ts uni que a bi l i ty to s ynthes i ze a dextra n bi oa dhes i ve tha t s ti cks to teeth. S. salivarius s ettl es onto the mucos a l epi thel i a l s urfa ces of the huma n mouth s oon a fter bi rth a nd i s often found i n the s a l i va . Streptococcus pyogenes (group A s treptococcus ) i s res pons i bl e for a bout 95% of huma n i nfecti ons ca us ed by s treptococci a nd i s the ca us e of RF. Members of the genus Actinomyces tha t a re cl i ni ca l l y s i gni fi ca nt a nd ca n be di fferenti a ted by s peci fi c FA mi cros copy a s wel l a s a ba ttery of phys i ol ogi c tes ts , s uch a s thos e a s s es s i ng requi rements for oxygen. Actinomyces orga ni s ms a re opportuni s ti c members of the norma l ora l mi crobi ota . Both A. israelii a nd A. viscosis a re pa thogeni c a nd ca n ca us e os teomyel i ti s i n the cervi cofa ci a l regi on. Of the two s peci es , A. israelii, whi ch i s a na erobi c, i s the more common ca us a ti ve a gent of a cti nomycos i s . A viscosis, a fa cul ta ti ve a na erobe, a ppea rs to be ca ri ogeni c. Group A s treptococci (GAS) a re β-hemol yti c a nd produces cel l ul i ti s a s a typi ca l l es i on. Cel l ul i ti s i s recogni zed a s a di ffus e, ra pi dl y s prea di ng l es i on i n the body ti s s ues . 279 to 285. The answers are 279-b, 280-a, 281-e, 282-d, 283-c, 284-c, and 285-a. (Brooks, pp 213-216, 283-287, 253-255. Levinson, pp 130-131, 138, 153-155, 158159. Murray [2009], pp 261-265, 303-307, 351-361. Toy, p 122.) Di phtheri a , a di s ea s e ca us ed by C diphtheriae, us ua l l y begi ns a s pha ryngi ti s a s s oci a ted wi th ps eudomembra ne forma ti on a nd l ympha denopa thy. Growi ng orga ni s ms l ys ogeni c for a propha ge produce a potent exotoxi n tha t i s a bs orbed i n mucous membra nes a nd ca us es remote da ma ge to the l i ver, ki dneys , a nd hea rt; the pol ypepti de toxi n i nhi bi ts protei n s ynthes i s of the hos t cel l . Al though C. diphtheriae ma y i nfect the s ki n, i t ra rel y i nva des the bl oods trea m a nd never a cti vel y i nva des deep ti s s ue. Di phtheri a toxi n (DT) ki l l s s ens i ti ve cel l s by bl ocki ng protei n s ynthes i s . DT i s converted to a n enzyme tha t i na cti va tes EF-2, whi ch i s res pons i bl e for the tra ns l oca ti on of pol ypepti dyl -tRNA from the a cceptor to the donor s i te on the euka ryoti c ri bos ome. The rea cti on i s a s fol l ows : NAD + EF-2 = ADP-ri bos yl – EF-2 + ni coti na mi de + H + Bordetella pertussis a nd B. parapertussis a re s i mi l a r a nd ma y be i s ol a ted together from a cl i ni ca l s peci men. However, B. parapertussis does not produce pertus s i s toxi n. Pertus s i s toxi n, l i ke ma ny ba cteri a l toxi ns , ha s two s ubuni ts : A a nd B. Subuni t A i s a n a cti ve enzyme, a nd B promotes bi ndi ng of the toxi n to hos t cel l s . Pertus s i s toxi n ha s ADP-ri bos yl a ti ng a cti vi ty, wi th a n A/B s tructure a nd mecha ni s m of a cti on s i mi l a r to tha t of
chol era toxi n (cAMP). Francisella tularensis i s a s hort, gra m-nega ti ve orga ni s m tha t i s ma rkedl y pl eomorphi c; i t i s nonmoti l e a nd ca nnot form s pores . It ha s a ri gi d growth requi rement for cys tei ne. Huma n tul a remi a us ua l l y i s a cqui red from di rect conta ct wi th ti s s ues of i nfected ra bbi ts but a l s o ca n be tra ns mi tted by the bi tes of fl i es a nd ti cks . Francisella tularensis ca us es a va ri ety of cl i ni ca l s yndromes , i ncl udi ng ul cerogl a ndul a r, ocul ogl a ndul a r, pneumoni c, a nd typhoi da l forms of tul a remi a . The pa thogenes i s of i nfecti on wi th E. coli i s a compl ex i nterrel a ti on of ma ny events a nd properti es . Escherichia coli ma y s erve a s a model for other members of the Enteroba cteri a cea e. Some s tra i ns of E. coli a re EIEC, s ome ETEC, s ome EHEC, a nd others EPEC. At pres ent, there i s l i ttl e cl i ni ca l s i gni fi ca nce i n routi nel y di s cri mi na ti ng the va ri ous types , wi th the pos s i bl e excepti ons of the ETEC a nd the E. coli 0157/H7 tha t a re hemorrha gi c. Escherichia coli 0157/H7 s ecretes a toxi n ca l l ed verotoxin. The toxi n i s very a cti ve i n a Vero cel l l i ne. More correctl y, the toxi n(s ) s houl d be ca l l ed Shiga-like. Streptococca l i nfecti on us ua l l y i s a ccompa ni ed by a n el eva ted ti ter of a nti body to s ome of the enzymes produced by the orga ni s m. Among the a nti geni c s ubs ta nces el a bora ted by group A β-hemol yti c s treptococci a re erythrogeni c toxi n, s treptodorna s e (s treptococca l DNa s e), hya l uroni da s e, a nd s treptol ys i n O (a hemol ys i n). Streptol ys i n S i s a nona nti geni c hemol ys i n. Speci fi ca l l y, erythrogeni c toxi n ca us es the cha ra cteri s ti c ra s h of s ca rl et fever. Ma ny fa ctors pl a y a rol e i n the pa thogenes i s of N. meningitidis. A ca ps ul e conta i ni ng N-a cetyl neura mi ni c a ci d i s pecul i a r to Neisseria a nd E. coli K1. Fres h i s ol a tes ca rry pi l i on thei r s urfa ces , whi ch functi on i n a dhes i on. Neisseria ha s a va ri ety of membra ne protei ns , a nd thei r rol e i n pa thogenes i s ca n onl y be s pecul a ted upon a t thi s ti me. The LPS of Neisseria, more correctl y ca l l ed l i pool i gos a ccha ri de (LOS), i s the endotoxi c component of the cel l . There a re no known toxi ns , hemol ys i ns , or cel l -wa l l cons ti tuents known to pl a y a rol e i n the pa thogenes i s of di s ea s e by Brucella. Ra ther, the a bi l i ty of the orga ni s ms to s urvi ve wi thi n the hos t pha gocyte a nd to i nhi bi t neutrophi l degra nul a ti on i s a ma jor di s ea s e-ca us i ng fa ctor. Brucel l a ha s a predi l ecti on for ti s s ues a nd orga ns ri ch i n erythri tol s uch a s the uterus a nd pl a centa . Tropi s m to thes es ti s s ues res ul ts i n a borti on i n ca ttl e. 286 to 288. The answers are 286-a, 287-c, and 288-b. (Ryan, pp 851-855. Toy, pp 90, 96.) “Atypi ca l pneumoni a ” i s a n ol d cl a s s i fi ca ti on us ed for res pi ra tory di s ea s e tha t i s not l oba r a nd i s not “typi ca l .” Tha t i s , i t does not i ncl ude pneumoni a ca us ed by pneumococcus , Klebsiella, Haemophilus, or βhemol yti c s treptococci tha t res ul ts i n a typi ca l l obul a r i nfi l tra te. In recent yea rs , the a typi ca l pneumoni a s ha ve become much more frequent tha n pneumococca l pneumoni a . They a re cha ra cteri zed by a s l ower ons et wi th hea da che, joi nt pa i n, fever, a nd s i gns of a n a cute upper res pi ra tory i nfecti on. There a re us ua l l y no s i gns of a cute res pi ra tory di s tres s , but pa ti ents report ma l a i s e a nd fa ti gue. The mos t common ca us e of a typi ca l pneumoni a i s M. pneumoniae. A qui ck tes t for M. pneumoniae i nfecti on i s col d a ggl uti ni ns . The tes t ma y l a ck both s ens i ti vi ty a nd s peci fi ci ty, but i t i s ra pi d a nd rea di l y a va i l a bl e compa red wi th cul ture of M. pneumoniae or s peci fi c a nti body forma ti on. In certa i n a ge groups (men over 55 yea rs ol d), Legi onna i res di s ea s e mus t be rul ed out. Whi l e di rect mi cros copy, cul ture, a nd s erol ogy a re a va i l a bl e, the detecti on of Legionella a nti gen i n res pi ra tory s ecreti ons i s the mos t s ens i ti ve tes t a va i l a bl e. Campylobacter pneumoniae ma y a l s o ca us e res pi ra tory i nfecti on pa rti cul a rl y i n, but not l i mi ted to, chi l dren. Di a gnos i s i s bes t ma de by growi ng thes e energy-defecti ve ba cteri a i n ti s s ue cul ture s uch a s HeLa cel l s . Serol ogy i s us ua l l y not hel pful . Duri ng the wi nter months , Bordetella i nfecti on ma y be qui te preva l ent, pa rti cul a rl y i n thos e pa ti ents whos e i mmuni za ti ons a re not upda ted. Adul t Bordetella i nfecti on ma y not pres ent wi th typi ca l whoopi ng cough s ymptoms a nd mus t be di fferenti a ted from other forms of a cute bronchi ti s by cul ture on s peci fi c medi a or di rect fl uores cent mi cros copy. Di rect mi cros copy of s putum i s a n i mporta nt prel i mi na ry tes t for s putum a nd other exuda te s peci mens . One needs to be a wa re tha t the i nforma ti on obta i ned i s l i mi ted i n i nterpreta ti on. No s peci fi c i denti ty of a mi croorga ni s m ca n be determi ned by gra m s ta i ni ng a nd even mi xtures of ba cteri a ca n be i nferred. On the other ha nd, exa mi na ti on of gra m s ta i ns ma y provi de enough i nforma ti on for the phys i ci a n to ma ke i mmedi a te deci s i ons on trea tment a nd other ma na gement tha t ma y be modi fi ed by future l a bora tory res ul ts . Fl uores cent Ab detecti on of a n orga ni s m i n s putum i s more s peci fi c tha n gra m s ta i ni ng. Here s peci fi c known Abs (s i ngl e or i n a mi xture) a re us ed to i denti fy orga ni s ms pres ent. 289. The answer is c. (Murray: Medical Microbiology [2013], Ch 18, 20, 30, and 66.) Externa l oti ti s or s wi mmer’s ea r i s a n i nfl a mma ti on of the outer ea r a nd the ea r ca na l . In the vi rul ent form of the di s ea s e—ma l i gna nt externa l oti ti s , whi ch occurs i n peopl e wi th di a betes , da ma ge to the cra ni a l nerves a nd bone ma y occur. Externa l oti ti s i s ca us ed by ei ther ba cteri a l or funga l pa thogens . Ba cteri a l pa thogens i ncl ude Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, a nd Enterococcus faecalis. Funga l pa thogens i ncl ude Candida albicans a nd Aspergillus s pp. The ma jori ty of ba cteri a l externa l oti ti s i s ca us ed by P. aeruginosa. P. aeruginosa produces pyocya ni n, whi ch i s a bl ue pi gment tha t ca ta l yzes the producti on of s uperoxi de a nd hydrogen peroxi de. Pyocya ni n a l s o s ti mul a tes the rel ea s e of IL-8 (CXCL8 i n huma ns ). P. aeruginosa a l s o produces exotoxi n A, whi ch ADP-ri bos yl a tes EF-2 i n the euka ryoti c cel l l ea di ng to the ces s a ti on of protei n s ynthes i s a nd cel l dea th. Nei ther pyocya ni n nor exotoxi n A i s produced by the other pa thogens l i s ted (S. aureus, S. epidermidis, E. faecalis, a nd C. albicans). 290. The answer is a. (Murray: Medical Microbiology [2013], Ch 29; Ryan: Sherris Medical Microbiology [2010], Ch 32.) The vi rul ence fa ctors produced by Helicobacter pylori a re urea s e, fl a gel l a , muci na s e, va cuol a ti ng toxi n, a nd the Ca g protei n. Urea s e neutra l i zes ga s tri c a ci d by hydrol yzi ng urea produced by ga s tri c cel l s to produce a mmoni a a nd CO2 . Urea s e a l s o s ti mul a tes the producti on of i nfl a mma tory cytoki nes . Muci na s e degra des ga s tri c mucus a nd reduces mucus vi s cos i ty to fa ci l i ta te ba cteri a l movement. H. pylori ca rry 4-7 pol a r fl a gel l a whi ch provi de the ba cteri um wi th moti l i ty tha t i s es s enti a l to penetra te ga s tri c mucus . H. pylori i s s ens i ti ve to the a ci di c l umen of the s toma ch. Therefore, the hi ghl y moti l e H. pylori qui ckl y penetra te the l umen a nd col oni ze the mucus l a yer tha t covers ga s tri c mucos a where the pH i s s l i ghtl y a l ka l i ne. The va cuol a ti ng cytotoxi n, whi ch produces l a rge cytopl a s mi c va cuol es , ca us es a poptos i s i n epi thel i a l cel l s . The Ca gA protei n, whi ch i s i njected i nto cel l s vi a the type III s ecreti on s ys tem, tri ggers reorga ni za ti on of the a cti n s kel eton wi thi n the i ntoxi ca ted cel l s . It a l s o s ti mul a tes neutrophi l mi gra ti on to the ga s tri c mucos a . Whi l e the s peci fi c mecha ni s m of H. pylori ca rci nogenes i s i s unknown, the Ca gA protei n i s the l ea di ng ca ndi da te for the oncogeni c protei n i nvol ved. 291. The answer is a. (Murray: Medical Microbiology [2003], Ch 23, 29, 36.) Gui l l a i n–Ba rré s yndrome i s a n a utoi mmune di s order a ffecti ng the peri phera l nervous s ys tem. The s yndrome i s a n uncommon compl i ca ti on of i nfecti on wi th Campylobacter jejuni (the l ea di ng i nfecti ous ca us e i n the Uni ted Sta tes ). The a s cendi ng pa ra l ys i s i s cha ra cteri zed by wea keni ng tha t begi ns i n the feet a nd ha nds a nd mi gra tes towa rd the trunk. The s ymptoms occur wi thi n few da ys a nd the recovery i s s l ow. The l i kel y ca us e of the di s ea s e i s a nti geni c cros s -rea cti vi ty between ol i gos a ccha -ri des of C. jejuni a nd gl ycos phi ngol i pi ds on the s urfa ce of neurona l ti s s ues . Anti bodi es to certa i n s tra i ns of C. jejuni (pri ma ri l y s erotype O:19) ma y a l s o da ma ge the myel i n of the peri phera l nervous s ys tem l ea di ng to mus cl e pa ra l ys i s . Cytomega l ovi rus i s the s econd mos t common i nfecti ous a gent a s s oci a ted wi th GBS, but i t does not ca us e the cl i ni ca l s ymptoms des cri bed for thi s pa ti ent. Clostridium tetani produces a hea t l a bi l e neurotoxi n (teta nos pa s mi n) whi ch ca us es ei ther l oca l i zed or genera l i zed mus cl e s pa s ms ; di a rrhea i s not a cl i ni ca l s yndrome ca us ed by C. tetani. Salmonella a nd Shigella a re a s s oci a ted wi th the a utoi mmune condi ti on. Rei ter s yndrome, a form of rea cti ve a rthri ti s , cha ra cteri zed by conjuncti vi ti s pl us a rthri ti s a nd, when ca us ed by Chlamydia trachomatis a nd other geni touri na ry pa thogens , urethri ti s . Campylobacter jejuni ca n a l s o ca us e Rei ter s yndrome.
292. The answer is a. (Murray: Medical Microbiology [2013], Ch 27, 28, 29.) Campylobacter jejuni ma y be pa rt of the norma l fl ora of di fferent domes ti ca ted a ni ma l s i ncl udi ng poul try, s heep, a nd ca ttl e. Surfa ce wa ters a nd s oi l where a ni ma l gra ze ma y be conta mi na ted wi th C. jejuni. Therefore, C. jejuni outbrea ks , whi ch a re zoonoti cs , ma y res ul t from the i nges ti on of conta mi na ted wa ter tha t ha s not been trea ted. The ma i n s ymptoms of C. jejuni i nfecti on a re ga s troenteri ti s , a bdomi na l pa i n, fever, a nd ma l a i s e. The s ymptoms often pea k a t 24 to 48 hours a fter ons et or ma y l a s t for 7 to 10 da ys . The di s ea s e i s genera l l y s el f-l i mi ted. Due to the s us cepti bi l i ty of Campylobacter to di fferent a nti bi oti cs i ncl udi ng ma crol i des , erythromyci n i s the drug of choi ce to trea t s evere enteri ti s ca us ed by C. jejuni. Opti mum growth of Campylobacter occurs under reduced oxygen a nd i ncrea s ed ca rbon di oxi de (5%-10%). Infecti on wi th V. cholerae res ul ts i n a ma s s i ve wa tery di a rrhea tha t progres s es to s evere dehydra ti on a nd hypovol emi c s hock. Infecti on wi th V. parahaemolyticus i s a s s oci a ted wi th expl os i ve wa tery di a rrhea , a bdomi na l pa i n, a nd fever. The ga s troenteri ti s i s s el f-l i mi ted. V. parahaemolyticus i s us ua l l y found i n a n es tua ri ne a nd ma ri ne envi ronment a nd i s a s s oci a ted wi th i nges ti on of conta mi na ted s hel l fi s h. Enteropa thogeni c a nd enteroi nva s i ve E. coli s tra i ns a re ma jor ca us es of di a rrhea i n underdevel oped countri es . Both ca us e wa tery di a rrhea a nd vomi ti ng. E. coli grows ra pi dl y under a erobi c condi ti ons . 293. The answer is e. (Murray: Medical Microbiology [2013], Ch 18, 19, 28, 30.) Vibrio vulnificus i s a gra m-nega ti ve rod tha t produces a number of vi rul ence fa ctors i ncl udi ng ca ps ul e, cytol ys i n, col l a gena s e, a nd protea s e. The ba cteri a ma y enter the body whi l e one i s s wi mmi ng or wa di ng i n conta mi na ted s ea wa ter. It a l s o enters the body through open wounds . Ini ti a l fea tures of V. vulnificus–i nfected wounds a re s wel l i ng, erythema , a nd pa i n. Thi s i s us ua l l y fol l owed by the devel opment of ves i cl es or bul l a e, eventua l ti s s ue necros i s , a nd s epti cemi a . V. vulnificus, whi ch ma y produce l a rge di s fi guri ng ul cers , i s commonl y found i n the Gul f of Mexi co. In s everel y burned pa ti ents , Pseudomonas aeruginosa ca us es wound i nfecti on fol l owed by l oca l i zed ti s s ue necros i s a nd ba cteremi a . Immers i on i n P. aeruginosa–conta mi na ted hot tubs or s wi mmi ng pool s ma y res ul t i n l oca l i zed i nfecti on of ha i r fol l i cl es (fol l i cul i ti s ), but not us ua l l y the devel opment of bul l a e. Sta phyl ococcus a ureus ma y i nfect tra uma ti c or s urgi ca l wounds . Infected a rea s a re cha ra cteri zed by erythema , edema , pa i n, a nd the a ccumul a ti on of purul ent di s cha rge. The i nfecti on i s us ua l l y trea ted by openi ng the wound a nd dra i ni ng the purul ent di s cha rge. Streptococcus pyogenes (Group A Streptococcus) ca us es va ri ous s uppura ti ve i nfecti ons i ncl udi ng pyoderma , a l oca l i zed s ki n i nfecti on cha ra cteri zed by ves i cl es tha t progres s to pus tul es ; erys i pel a s , a l oca l i zed s ki n i nfecti on cha ra cteri zed by i nfl a mma ti on a nd l ympha denopa thy; a nd necroti zi ng fa s ci i ti s , whi ch i nvol ves extens i ve des tructi on of mus cl es a nd fa t. V. parahaemolyticus ca us es ga s troenteri ti s a nd wound i nfecti on. However, V. parahaemolyticus wounds do not ha ve the s peci a l fea tures of V. vulnificus– i nfected wounds . 294. The answer is e. (Murray: Medical Microbiology [2013], Ch 27, 30.) Pseudomonas aeruginosa i s a ma jor ca us e of nos ocomi a l pneumoni a i n hea l th-ca re rel a ted s etti ngs . A ma jor porti on of the P. aeruginosa-a s s oci a ted nos ocomi a l pneumoni a occurs i n i mmunocompromi s ed pa ti ents i n i ntens i ve ca re uni ts who ha ve undergone i ntuba ti on (venti l a tor-a s s oci a ted pneumoni a ). Among the condi ti ons tha t predi s pos e i mmunocompromi s ed pa ti ents to P. aeruginosa i nfecti on i s the uti l i za ti on of conta mi na ted res pi ra tory equi pment duri ng i ntuba ti on. P. aeruginosa i s a gra m-nega ti ve, oxi da s epos i ti ve, obl i ga te a erobe tha t produces numerous extra cel l ul a r vi rul ence fa ctors i ncl udi ng exotoxi ns , protea s es , a nd rha mnol i pi d. Al l of the mi crobes ca n ca us e pneumoni a . However, none of the other mi croorga ni s ms l i s ted produce rha mnol i pi ds . Escherichia coli a nd Klebsiella pneumoniae a re members of the Enteroba cteri a cea e, whi ch a re oxi da s e nega ti ve. Moraxella catarrhalis i s a gra m-nega ti ve di pl ococcus tha t i s a l s o oxi da s e pos i ti ve, but i t does not produce toxi ns a nd i s more fa s ti di ous i n i ts growth tha n P. aeruginosa. Haemophilus influenzae i s a fa s ti di ous , fa cul ta ti ve a na erobe tha t requi res hemi n a nd NAD for growth. 295. The answer is d. (Murray: Medical Microbiology [2013], Ch 27, 28, 29.) Vibrio cholerae ca us es chol era , whi ch i s a cqui red by dri nki ng wa ter tha t ha s been conta mi na ted wi th huma n feces . V. cholerae ca n a l s o be a cqui red by ea ti ng food tha t ha s been wa s hed wi th conta mi na ted wa ter. Chol era outbrea ks us ua l l y occur i n communi ti es wi th poor s a ni ta ry s ys tems . Even i n devel oped countri es , a brea kdown i n the s a ni ta ry s ys tems by na tura l di s a s ters s uch a s fl oods or hurri ca nes ma y produce chol era outbrea k. Infecti on wi th V. cholerae ma y res ul t i n s i mpl e col oni za ti on, mi l d ga s troenteri ti s , or a s evere often fa ta l wa tery di a rrhea . Chol era i s cha ra cteri zed by a brupt ons et of wa tery di a rrhea a nd vomi ti ng. As the di s ea s e progres s es , the s tool becomes col orl es s a nd s peckl ed wi th mucus (ri ce s tool ). Conti nuous fl ui d l os s res ul ts i n s evere dehydra ti on, meta bol i c a ci dos i s , a nd hypovol emi c s hock (l os s of pota s s i um). Thi s l ea ds to a ca rdi a c a rrhythmi a a nd rena l fa i l ure. To a voi d the hypovol emi c s hock, chol era pa ti ents mus t be i mmedi a tel y trea ted wi th el ectrol ytes a nd fl ui d repl a cements . In untrea ted pa ti ents , the morta l i ty ra te ma y rea ch 60% but i s reduced to 1% wi th the i mmedi a te trea tment wi th el ectrol ytes a nd fl ui d repl a cements . Salmonella enterica i nfecti on ca us es ga s troenteri ti s , na us ea , a nd vomi ti ng. Salmonella enterica ma y a l s o ca us e ba cteremi a . Shigella flexneri i nva des the col oni c mucos a . Therefore, s hi gel l os i s i s cha ra cteri zed by a bdomi na l cra mps , fever, a nd di a rrhea wi th bl ood i n s tool . Campylobacter jejuni i nfecti on res ul ts i n di a rrhea , fever, a nd a bdomi na l pa i n. Mos t i nfecti ons a re s el f-l i mi ted. Vibrio vulnificus ca us es wound i nfecti ons cha ra cteri zed by ti s s ue necros i s a nd a ccompa ni ed by s epti cemi a . V. vulnificus i nfecti on ha s a hi gh morta l i ty ra te.
Rickettsiae, Chlamydiae, and Mycoplasma Questions 296. Mycopl a s ma s ha ve been cul ti va ted from huma n mucous membra nes a nd ti s s ues , es peci a l l y from the geni ta l , uri na ry, a nd res pi ra tory tra cts . Chl a mydi a ca n be i s ol a ted from ma ny of thes e s ources a s wel l . Both ca us e res pi ra tory a nd geni ta l tra ct i nfecti ons . Adul ts ma y pres ent wi th a s ymptoma ti c res pi ra tory i nfecti on to s eri ous pneumoni ti s , a nd i denti fi ca ti on of the eti ol ogi c a gent us ua l l y determi nes the bes t a nti mi crobi a l trea tment. Whi ch of the fol l owi ng bes t des cri bes the di fference between mycopl a s ma s a nd chl a mydi a e? a . Abl e to ca us e di s ea s e i n huma ns b. Abl e to ca us e uri na ry tra ct i nfecti on c. Abl e to grow on a rti fi ci a l cel l -free medi a d. Bei ng a bl e to s ta i n wel l wi th Gra m s ta i n e. Sus cepti bl e to peni ci l l i n 297. A 39-yea r-ol d ma n pres ents wi th s udden, i nfl uenza -l i ke s ymptoms . He s ta tes tha t he works i n a s l a ughterhous e, a nd s evera l of hi s coworkers ha ve s i mi l a r s ymptoms . Ea rl y s ta ges of pneumoni a a re detected. Whi ch of the fol l owi ng i s the mos t l i kel y eti ol ogi c orga ni s m? a . Coxiella burnetii b. Rickettsia rickettsiae c. Taenia solium d. Taenia saginata 298. Ma ny s urvi vors of mi l i ta ry or na tura l di s a s ters a re a t ri s k of i nfecti on due to l os s of publ i c hea l th s ervi ces . Ri cketts i a l i nfecti ons —except Q fever a nd the ehrl i chi os i s —typi ca l l y a re ma ni fes ted by fever, ra s hes , a nd va s cul i ti s . Whi ch of the fol l owi ng bes t cha ra cteri zes ri cketts i a e, whi ch i ncl ude the s potted fevers , Q fever, typhus , a nd s crub typhus ? a . Ea s i l y s ta i ned (gra m-nega ti ve) wi th a Gra m s ta i n b. Ma i nta i ned i n na ture, wi th huma ns a s the ma mma l i a n res ervoi r c. Obl i ga te i ntra cel l ul a r pa ra s i tes d. Sta bl e outs i de the hos t cel l e. The ca us e of i nfecti ons i n whi ch a ra s h i s a l wa ys pres ent 299. A ma n wi th chi l l s , fever, a nd hea da che i s thought to ha ve “a typi ca l ” pneumoni a . Hi s tory revea l s tha t he ra i s es chi ckens , a nd tha t a pproxi ma tel y 2 weeks a go he l os t a l a rge number of them to a n undi a gnos ed di s ea s e. Whi ch of the fol l owi ng i s the mos t l i kel y di a gnos i s of thi s ma n’s condi ti on? a . Anthra x b. Leptos pi ros i s c. Orni thos i s d. Rel a ps i ng fever e. Q fever 300. An i l l pa ti ent deni es bei ng bi tten by i ns ects . However, he s pent s ome ti me i n a mi l ki ng ba rn a nd i ndi ca tes tha t i t wa s dus ty. Of the fol l owi ng ri cketts i a l di s ea s es , whi ch one ha s he mos t l i kel y contra cted? a . Bri l l –Zi ns s er di s ea s e b. Q fever c. Ri cketts i a l pox d. Rocky Mounta i n s potted fever (RMSF) e. Scrub typhus 301. A 23-yea r-ol d col l ege s eni or pres ents to the s tudent hea l th cl i ni c wi th s ymptoms of a s us pected s exua l l y tra ns mi tted di s ea s e (STD). Nei s s eri a a nd chl a mydi a a gents a re rul ed out. Whi ch of the fol l owi ng orga ni s ms i s the mos t l i kel y ca us e of hi s nongonococca l urethri ti s (NGU)? a . Mycoplasma fermentans b. Mycoplasma hominis c. Mycoplasma mycoides d. Mycoplasma pneumoniae e. Ureaplasma urealyticum 302. A young ma n, home on l ea ve from the mi l i ta ry, went ca mpi ng i n the woods to detect deer movement for future hunti ng. Ten da ys l a ter, he devel oped fever, ma l a i s e, a nd mya l gi a . Leukopeni a a nd thrombocytopeni a were obs erved, a s wel l a s s evera l ti ck bi tes . Whi ch of the fol l owi ng s ta tements bes t des cri bes huma n monocyti c ehrl i chi os i s (HME)? a . Cl i ni ca l di a gnos i s i s ba s ed on the pres ence of erythema mi gra ns (EM) b. Di a gnos i s i s us ua l l y ma de s erol ogi ca l l y but morul a e ma y be s een i n the cytopl a s m of monocytes c. It i s a fa ta l di s ea s e tra ns mi tted by the bi te of a dog d. Symptoms i ncl ude vomi ti ng a nd pa ra l ys i s e. The HME a gent grows on a rti fi ci a l medi a 303. A coupl e, who di d not know ea ch other very wel l , da ted a nd ha d s exua l conta ct. Severa l weeks l a ter, the ma n noti ced a s ma l l , pa i nl es s ves i cl e on hi s peni s , whi ch ruptured a nd then hea l ed. Soon, hi s i ngui na l l ymph nodes enl a rged a nd di s cha rged pus through mul ti pl e s i nus tra cts . Lymphogra nul oma venereum (LGV) i s a venerea l di s ea s e ca us ed by s erotype L1, L2, or L3 of Chlamydia trachomatis. The di fferenti a l di a gnos i s s houl d i ncl ude whi ch of the fol l owi ng? a . Ba bes i os i s
b. Cha ncroi d c. Mononucl eos i s d. Ps i tta cos i s e. Shi ngl es 304. A fores t worker experi ences a s udden ons et of fever, hea da che, mya l gi a s , a nd pros tra ti on. A ma cul a r ra s h devel ops s evera l da ys l a ter, wi th i t a ppea ri ng fi rs t on the ha nds a nd feet before movi ng onto hi s trunk. Whi ch of the fol l owi ng trea tments i s mos t a ppropri a te? a . Amphoteri ci n B b. Cepha l os pori n c. Erythromyci n d. Sul fona mi des e. Tetra cycl i ne 305. Chl a mydi a e a re true ba cteri a wi th a n unus ua l three-s ta ge cycl e of devel opment. Thes e cha ra cteri s ti cs a re i mporta nt to unders ta nd to be a bl e to di s ti ngui s h them from other ba cteri a a nd vi rus es tha t ca n ca us e s i mi l a r di s ea s e pres enta ti ons a nd choi ce of trea tments . For the growth of Chlamydia, whi ch of the fol l owi ng i s the correct s equence of thes e events ? a . Devel opment of a n i ni ti a l body, s ynthes i s of el ementa ry body progeny, penetra ti on of the hos t cel l b. Penetra ti on of the hos t cel l , devel opment of a n i ni ti a l body, s ynthes i s of el ementa ry body progeny c. Penetra ti on of the hos t cel l , s ynthes i s of el ementa ry body progeny, devel opment of a n i ni ti a l body d. Synthes i s of el ementa ry body progeny, devel opment of a n i ni ti a l body, penetra ti on of the hos t cel l e. Synthes i s of el ementa ry body progeny, penetra ti on of the hos t cel l , devel opment of a n i ni ti a l body 306. Young chi l dren i n a s ma l l Egypti a n vi l l a ge ha ve eye i nfecti ons tha t pres ent wi th l a cri ma ti on, di s cha rge, a nd conjuncti va l hyperemi a . Sca rri ng of the conjuncti va a nd noti cea bl e l os s of vi s i on occur i n s ome. Whi ch of the fol l owi ng s ta tements bes t des cri bes the eti ol ogi c a gent tha t ca us ed thes e i nfecti ons a nd rel a ti ve trea tment? a . The orga ni s ms a re gra m-pos i ti ve a nd trea ta bl e wi th peni ci l l i n b. The orga ni s ms ha ve no cel l wa l l a nd wi l l onl y res pond to tetra cycl i ne c. The orga ni s ms a re gra m-nega ti ve, a nd prophyl a cti c us e of tetra cycl i nes ca n prevent i nfecti ons d. Gra m s ta i ns of conjuncti va l s cra pi ngs a re us eful di a gnos ti c tes ts to jus ti fy trea tment wi th s ul fona mi des e. The orga ni s ms a re i s ol a ted on bl ood a ga r pl a tes a nd res pond to cel l wa l l -i nhi bi ti ng a nti bi oti cs 307. The ehrl i chi a group orga ni s ms a re obl i ga te i ntra cel l ul a r ba cteri a tha t a re ta xonomi ca l l y grouped wi th the ri cketts i a e a nd ha ve ti ck vectors . Huma n gra nul ocyti c ehrl i chi os i s (HGE) i s a di s ea s e tra ns mi tted to huma ns by the bi te of a ti ck, Ixodes scapularis. Three ehrl i chi a s peci es a re pres ent i n di fferent pa rts of the Uni ted Sta tes a nd produce i ncl us i ons i n ci rcul a ti ng WBCs . Whi ch of the fol l owi ng s ta tements a bout HGE i s correct? a . Cl i ni ca l di a gnos i s i s ba s ed on the pres ence of EM b. HGE i s ca us ed by Ehrlichia chaffeensis c. HGE i s a s el f-l i mi ti ng di s ea s e d. HGE i s cha ra cteri zed by a n a cute ons et of fever, s evere hea da che, a nd i nfl uenza -l i ke s ymptoms e. The ca us a ti ve orga ni s m ca n be grown on ordi na ry l a bora tory medi a 308. The “s potted fever” group of ri cketts i a l di s ea s es i s ca us ed by a va ri ety of ri cketts i a l s peci es . Whi l e not cri ti ca l for trea tment of di s ea s e, the s peci a ti on of thes e orga ni s ms i s es s enti a l for epi demi ol ogi c s tudi es . Whi ch of the fol l owi ng ri cketts i a e i s found i n the Uni ted Sta tes a nd i s a member of the s potted fever group? a . Rickettsia akari b. Rickettsia australis c. Rickettsia conorii d. Rickettsia prowazekii e. Rickettsia sibirica 309. A 36-yea r-ol d ma n pres ents to hi s pri ma ry ca re phys i ci a n’s offi ce compl a i ni ng of fever a nd hea da che. On exa mi na ti on, he ha s l eucopeni a , i ncrea s ed l i ver enzymes , a nd i ncl us i on bodi es a re s een i n hi s monocytes . Hi s tory revea l s tha t he i s outdoors ma n a nd tha t he remembers removi ng a ti ck from hi s l eg. Whi ch of the fol l owi ng i s the mos t l i kel y di a gnos i s ? a . Ehrl i chi os i s b. Lyme di s ea s e c. Q fever d. Rocky Mounta i n s potted fever e. Tul a remi a 310. Ri cketts i a l orga ni s ms i nfect huma ns worl dwi de, a l though geogra phi c l oca ti ons ma y be l i mi ted for s ome s peci es a nd pos s i bl y produce s ome cha l l enges i n medi ca l di a gnos i s . Al l a re obl i ga te i ntra cel l ul a r pa ra s i tes , except C. burnetii, a nd tra ns mi tted by a n i ns ect vector. Typhus , s potted fever, a nd s crub typhus s ha re whi ch of the fol l owi ng ma ni fes ta ti ons of di s ea s e? a . Arthri ti s b. Common vector c. Fever a nd ra s h d. Short i ncuba ti on peri od (<48 hours ) e. Si mi l a r geogra phi c di s tri buti on 311. Huma ns a re the na tura l hos ts for C. trachomatis, whi ch i s wi des prea d i n the popul a ti on a nd a wel l -known ca us e of STD. The orga ni s m i s a wel l -documented ca us e of NGU i n men a nd urethri ti s , cervi ci ti s , a nd pel vi c i nfl a mma tory di s ea s e i n women. Thi s orga ni s m i s a l s o i mpl i ca ted i n
whi ch of the fol l owi ng? a . Bl i ndnes s b. Mi ddl e ea r i nfecti on i n young chi l dren c. Peri na ta l reti ni ti s d. Sexua l l y tra ns mi tted ca rdi a c di s ea s e i n a dul ts e. Uri na ry tra ct i nfecti on i n chi l dren 312. A homos exua l ma l e pres ents to hi s phys i ci a n wi th bi l a tera l i ngui na l buboes (l ymph nodes ), one of whi ch s eems rea dy to rupture. He reca l l s ha vi ng two s ma l l , pa i nl es s geni ta l l es i ons tha t hea l ed ra pi dl y. The eti ol ogi c a gent i s i s ol a ted us i ng McCoy cel l s . Whi ch of the fol l owi ng s ta tements bes t cha ra cteri zes LGV? a . It i s mos t common i n tempera te regi ons b. In the Uni ted Sta tes , i t i s more common a mong women c. The ca us a ti ve a gent i s C. trachomatis d. LGV does not become chroni c e. Peni ci l l i n i s effecti ve i n ea rl y trea tment 313. Dozens of pol i ti ca l refugees fl eei ng from a cti ve wa rfa re a nd l i vi ng i n a dens e fores t envi ronment wi th crowded, uns a ni ta ry condi ti ons experi enced nons peci fi c s ymptoms , fol l owed by hi gh fever, s evere hea da che, chi l l s , mya l gi a , a nd a rthra l gi a . Al l ha d body l i ce. Improved l i vi ng condi ti ons i n a refugee ca mp a nd trea tment wi th tetra cycl i ne brought res ol uti on to mos t i ndi vi dua l s . Whi ch of the fol l owi ng s ta tements des cri bes the eti o-l ogi ca l a gent res pons i bl e for thei r i nfecti on? a . The di s ea s e wa s ca us ed by a n orga ni s m wi th no cel l wa l l s b. The di s ea s e wa s ca us ed by a vi ra l a gent c. The di s ea s e wa s deri ved from rodents l i vi ng i n the fores t a rea d. Reoccurrence of mi l der di s ea s e ma y occur i n l a ter yea rs e. The di s ea s e wa s ca us ed by a ti ck vector 314. An 18-yea r-ol d s tudent devel ops s ymptoms cons i s tent wi th pri ma ry a typi ca l pneumoni a (PAP). Thi s i s genera l l y a mi l d di s ea s e, ra ngi ng from s ubcl i ni ca l i nfecti on to s eri ous pneumoni ti s ; the l a tter cha ra cteri zed by ons et of fever, hea da che, s ore throa t, a nd cough but requi res l a bora tory tes ts to determi ne whi ch orga ni s m i s i nvol ved a nd a ba s i s for a nti mi crobi a l choi ces . Whi ch of the fol l owi ng orga ni s ms ca us es thi s di s ea s e i n huma ns ? a . Mycoplasma fermentans b. Mycoplasma hominis c. Mycoplasma pneumoniae d. Mycoplasma orale e. Ureaplasma urealyticum 315. NGU i s the mos t common STD i n men. Wi thi n 2 weeks , the s ymptoms us ua l l y i ncl ude pa i nful uri na ti on a nd a urethra l di s cha rge. Beca us e of the s i mi l a ri ty of NGU s ymptoms wi th Neisseria gonococcus i nfecti on, di a gnos i s depends on cul ture of the di s cha rge. Whi l e the ma jori ty of NGU a re ca us ed by C. trachomatis, whi ch of the fol l owi ng orga ni s ms i s very s i gni fi ca nt i n ca us i ng a ddi ti ona l ca s es i n huma ns ? a . Mycoplasma fermentans b. Mycoplasma hominis c. Mycoplasma pneumoniae d. Mycoplasma orale e. Ureaplasma urealyticum 316. A hea l thy ora l ca vi ty ha s a mi crobi a l popul a ti on cons i s ti ng of gra m-pos i ti ve s treptococci a nd di phtheroi ds . Ana erobi c rods a nd s pi rochetes a re pres ent i n l ow numbers a nd ma y be opportuni s ti c for di s ea s e. Whi ch of the fol l owi ng orga ni s ms a l s o norma l l y i nha bi ts the hea l thy huma n ora l ca vi ty? a . Mycoplasma fermentans b. Mycoplasma hominis c. Mycoplasma pneumoniae d. Mycoplasma orale e. Ureaplasma urealyticum 317. At l ea s t 15 s peci es of Mycoplasma a re of huma n ori gi n, a nd fi ve a re of pri ma ry i mporta nce. Whi ch of the fol l owi ng orga ni s ms norma l l y i nha bi ts the fema l e geni ta l tra ct a nd i s s trongl y a s s oci a ted wi th s a l pi ngi ti s a nd ova ri a n a bs ces s es ? a . Mycoplasma fermentans b. Mycoplasma hominis c. Mycoplasma pneumoniae d. Mycoplasma orale e. Ureaplasma urealyticum 318. Suppura ti ve i ngui na l a deni ti s us ua l l y s ta rts by the a ppea ra nce of s ma l l , pa i nl es s l es i ons on the externa l geni ta l i a tha t hea l s ponta neous l y. Then regi ona l l ymph nodes enl a rge a nd become pa i nful a nd often di s cha rge pus through mul ti pl e s i nus tra cts . Whi ch orga ni s m l i s ted bel ow i s res pons i bl e for thi s STD? a . Bartonella (Rochalimaea) henselae b. Chlamydia trachomatis c. Coxiella burnetii d. Ehrlichia chaffeensis
e. Rickettsia rickettsii 319. Whi ch of the fol l owi ng i s tra ns mi tted by the bi te of a ha rd Ixodes ti ck, where ci rcul a ti ng l eukocytes a re i nfected a nd morul a e (cl us ters of mi croorga ni s ms ) form, whi ch ca n be trea ted wi th tetra cycl i nes a nd ri fa myci ns ? a . Bartonella (Rochalimaea) henselae b. Chlamydia trachomatis c. Coxiella burnetii d. Ehrlichia chaffeensis e. Rickettsia rickettsii 320. Si x l a bora tory techni ci a ns a t the s ta te hea l th l a bora tory were worki ng on a s tudy us i ng ra bbi ts . The experi ments i nvol ved a n outbrea k of a cute febri l e i l l nes s es i n workers from a s l a ughterhous e. The orga ni s m of i nteres t wa s a gra m-nega ti ve ba cteri um wi th tropi s m for mononucl ea r cel l s . A dys functi on of the a ni ma l ca ge a i r s a fety s ys tem a l l owed conta mi na ted a i r to es ca pe i nto the a ni ma l ca re fa ci l i ty a nd res ea rch l a bora tori es . Four of the s i x techni ci a ns now s uffer from a fl u-l i ke i l l nes s a nd pneumoni ti s . Whi ch orga ni s m l i s ted bel ow i s mos t l i kel y the ca us e of thi s outbrea k? a . Bartonella (Rochalimaea) henselae b. Chlamydia trachomatis c. Coxiella burnetii d. Ehrlichia chaffeensis e. Rickettsia rickettsii 321. A 56-yea r-ol d woma n i n Uga nda pres ents to a n emergency cl i ni c. The woma n i s homel es s a nd extremel y di rty. She i s a l s o very dehydra ted a nd the duty nurs e noti ces l i ce i n her ha i r a nd cl othi ng. The pa ti ent reported hi gh fever, s evere hea da ches , a nd mus cl e pa i n. A petechi a l ra s h wa s obs erved a l l over her body. After 72 hours i n the hos pi ta l , the woma n di ed. A Gra m-s ta i n of the orga ni s m s howed a wea kl y s ta i ni ng Gra m-nega ti ve ba cteri um tha t coul d not be grown i n vi tro. Wha t orga ni s m wa s the mos t l i kel y ca us e of her i nfecti on? a . Chlamydia trachomatis b. Coxiella burnetii c. Rickettsia prowazekii d. Rickettsia rickettsii e. Rickettsia typhi 322. A 25-yea r-ol d ma l e pa ti ent pres ents to the emergency room i n Jul y i n Texa s . He compl a i ns of s hortnes s of brea th a nd a l ow-gra de fever. The emergency room phys i ci a n s us pects tra cheobronchi ti s . The pa ti ent a l s o compl a i ns of a dry, nonproducti ve cough. A pa tchy bronchopneumoni a wa s obs erved on x-ra y. Col d a ggl uti ni ns were obs erved i n the pa ti ent’s s erum. The phys i ci a n s us pects a Mycoplasma pneumoniae i nfecti on. Whi ch of the fol l owi ng a nti bi oti cs does the phys i ci a n know tha t he ca nnot or s houl d not a dmi ni s ter i n thi s s i tua ti on? a . Cl i nda myci n b. Erythromyci n c. Ka na myci n d. Peni ci l l i n e. Tetra cycl i ne 323. A 45-yea r-ol d ma n l i vi ng i n Uga nda pres ents to the emergency cl i ni c. He compl a i ns tha t he ha s a “groi n s wel l i ng.” He s a ys tha t thi s “groi n s wel l i ng” ha s broken open a nd a thi ck, whi te fl ui d ha s l ea ked out. Thi s pa ti ent s ta ted tha t he ha d been s exua l l y a cti ve for 30 yea rs a nd tha t he obs erved a “s ore” on hi s peni s a bout a month a go. The pa ti ent a l s o compl a i ned of recent hea da ches , fever, a nd mus cl e pa i n. A ba cteri um wa s i s ol a ted from thi s thi ck whi te fl ui d, but i t woul d not grow i n vi tro. It woul d onl y grow i n ti s s ue cul ture. The orga ni s m wa s a Gra m-nega ti ve rod. Whi ch of the fol l owi ng ba cteri a wa s the ca us e of thi s ma n’s i nfecti on? a . Chlamydophila psittaci b. Chlamydophila pneumoniae c. Chlamydia trachomatis d. Neisseria gonorrheae e. Treponema pallidum 324. A week a fter returni ng from a Jul y ca mpi ng tri p to the Bl ue Ri dge Mounta i ns i n North Ca rol i na , a 10-yea r-ol d boy i s brought to the emergency room wi th a s evere hea da che, fever, a nd mus cl e pa i n. He a l s o ha s a ma cul opa pul a r ra s h on hi s a rms a nd l egs . Al though the ra s h bega n on hi s a rms a nd l egs , i t ha s now s prea d to hi s trunk. He remembers removi ng s evera l ti cks from a round hi s a nkl es on the ca mpi ng tri p. Wha t i s the orga ni s m mos t l i kel y to the ca us e of thi s young ma n’s i nfecti on?
(From Public Health Image Library. Content provider: Center for Disease Control.) a . Coxiella burnetii b. Group A s treptococci (Streptococcus pyogenes) c. Rickettsia prowazekii d. Rickettsia ricketsii e. Salmonella typhi 325. A 19-yea r-ol d col l ege s tudent pres ents to the uni vers i ty i nfi rma ry wi th wha t the doctor thought wa s NGU. The phys i ci a n ha d a very ha rd ti me i s ol a ti ng a ca us a ti ve orga ni s m from the young ma n. The cl i ni ca l l a b fi na l l y got the orga ni s m to grow i n vi tro a nd they reported tha t the offendi ng orga ni s m produced extremel y s ma l l col oni es a nd woul d onl y grow i n the pres ence of urea . The orga ni s m often di ed ra pi dl y a fter the i ni ti a l i s ol a ti on. The orga ni s m ca us i ng thi s s tudent’s NGU wa s whi ch of the fol l owi ng? a . Coxiella burnetii b. Mycoplasma genitalium c. Mycoplasma hominis d. Mycoplasma pneumoniae e. Ureaplasma urealyticum 326. A 15-yea r-ol d boy pres ents to hi s fa mi l y doctor a nd reports tha t he wa s not feel i ng very good. He s a ys tha t he ha s been feel i ng “l ous y” for the pa s t 2 weeks wi th a fever, runny nos e, hea da ches , a nd no energy. He a l s o ha s a nonproducti ve cough. The doctor orders a pul mona ry x-ra y tha t demons tra tes no cons ol i da ti on a nd onl y pa tchy opa ci ty i n the l ower l obes of the l ungs . The boy’s s erum i s pos i ti ve for col d a ggl uti ni ns a nd a nti bodi es a ga i ns t Streptococcus MG. Whi ch of the fol l owi ng ba cteri a i s res pons i bl e for hi s i nfecti on? a . Chlamydia trachomatis b. Chlamydophila pneumoniae c. Chlamydophila psittaci d. Mycoplasma hominis e. Mycoplasma pneumoniae 327. A 40-yea r-ol d ma n devel ops a cough tha t i s nonproducti ve a nd goes to s ee hi s fa mi l y doctor. He s a ys tha t he ha s been feel i ng “l ous y” a nd ha s bronchi ti s , s i nus i ti s , a nd a s ore throa t. The doctor orders a n x-ra y tha t does not s how cons ol i da ti on, but ra ther a pa tchy i nfi l tra te i n hi s upper ri ght l ung. The ma n deni es ta ki ng a ny new pets or a ni ma l s recentl y i nto hi s hous e. A Gra m-s ta i n of the s putum s peci men s hows a few Gra m-nega ti ve rods tha t do not s ta i n very wel l . Sa mpl es s ent to the cl i ni ca l l a bora tory do not grow on norma l l a bora tory medi a (eg, bl ood a ga r), but do grow i n monol a yer cel l s i n ti s s ue cul ture. Wha t ba cteri um i s mos t l i kel y to be the ca us e of thi s ma n’s i nfecti on? a . Chlamydia trachomatis b. Chlamydophila psittaci c. Chlamydophila pneumoniae d. Mycoplasma pneumoniae e. Streptococcus pneumoniae 328. A 35-yea r-ol d woma n l i vi ng i n Mi nnes ota goes to her fa mi l y phys i ci a n. She compl a i ns tha t for the pa s t 8 da ys s he ha s experi enced a fl u-l i ke i l l nes s . The i l l nes s cons i s ted of mus cl e pa i n, l etha rgy, hea da ches , a nd a hi gh fever (a l mos t 41°C). She s ta tes tha t s he ha d removed s evera l ti cks
from a round her a nkl es a bout 14 da ys a go. The phys i ci a n gi ves her a s hot of peni ci l l i n, but when s he returns to s ee hi m a bout a week l a ter, s he reports no i mprovement. The phys i ci a n then dra ws her bl ood a nd s ubmi ts i t to a cl i ni ca l l a bora tory for i denti fi ca ti on. No ba cteri a grew out on bl ood a ga r, but a Gi ems a s ta i n of the bl ood cul ture s howed coccoba ci l l a ry orga ni s ms i ns i de pol ymorphonucl ea r neutrophi l s . Whi ch of the fol l owi ng ba cteri a wa s mos t l i kel y to be the ca us e of her i l l nes s ? a . Anaplasma phagocytophilum b. Coxiella burnetii c. Chlamydophila pneumoniae d. Chlamydophila psittaci e. Rickettsia rickettsii 329. A 27-yea r-ol d ma n pres ents to hi s fa mi l y doctor beca us e he ha s been ha vi ng a mucopurul ent di s cha rge from hi s peni s . He ha d recentl y vi s i ted a pros ti tute a nd he ha d unprotected s ex wi th her. He wa s a fra i d tha t he ha d ca ught the “cl a p”. He di d not ha ve a fever a nd he s a i d he experi enced no pa i n upon uri na ti on. The doctor noted a whi te urethra l di s cha rge from the ma n’s peni s . Thi s di s cha rge wa s then s ent to the cl i ni ca l l a bora tory. Beca us e the phys i ci a n s us pected Neisseria gonorrheae i nfecti on, the l a b s ta i ned the s peci men a nd tri ed to grow i t on bl ood a ga r. The ca us a ti ve orga ni s m di d not grow on bl ood a ga r, but woul d onl y grow i n certa i n cel l s l i nes . Wha t wa s the orga ni s m tha t ca us ed thi s ma n’s i nfecti on? a . Chlamydophila pneumoniae b. Chlamydophila psittaci c. Chlamydia trachomatis d. Neisseria gonorrheae e. Treponema pallidum 330. A phys i ci a n wa s a s ked to come to a n Indi a n res erva ti on i n South Da kota beca us e of a n outbrea k of a s eri ous eye i nfecti on. The i nfecti on wa s bel i eved to ha ve s prea d from pers on to pers on by i nfected towel s a t the gymna s i um. Pa ti ents reported conjuncti vi ti s wi th wi des prea d i nfl a mma ti on. In s ome ca s es , the pa ti ent’s conjuncti va beca me s o da ma ged, tha t the eyel i ds turned i nwa rd, thus s cra tchi ng the eyeba l l every ti me they bl i nked. In s ome pa ti ents , there wa s cornea l s ca rri ng a nd i nva s i on of bl ood ves s el s i nto the cornea . Fortuna tel y, the phys i ci a n recogni zed wha t the di s ea s e wa s , i ts ca us e, a nd how to trea t i t. He a dmi ni s tered a zi thromyci n i n one dos e a nd the i nfecti ons res ol ved. Wha t orga ni s m wa s ca us i ng the des cri bed s ymptoms ? a . Chlamydia trachomatis b. Chlamydophila pneumoniae c. Chlamydophila psittaci d. Rickettsia prowazekii e. Rickettsia rickettsii 331. A 45-yea r-ol d ma n reported to the emergency room i n res pi ra tory di s tres s . Hi s s ymptoms i ncl uded mus cl e pa i n, conges ti on, a dry cough, a nd di ffi cul ty brea thi ng. He a l s o wa s experi enci ng fever a nd chi l l s . A ches t x-ra y s howed cons ol i da ti on of the l eft l ower l obe, a nd a pa tchy i nfi l tra te of hi s ri ght upper l obe. He wa s gi ven a s hot of peni ci l l i n a nd hos pi ta l i zed. He di d not i mprove on thi s a nti bi oti c s o he wa s gi ven doxycycl i ne, whi ch a l l owed for hi s i mprovement. It wa s deci ded to gi ve doxycycl i ne a fter hi s a ttendi ng phys i ci a n l ea rned he wa s a bi rd enthus i a s t a nd ha d recentl y recei ved a n Afri ca n pa rrot tha t ha d a rri ved s i ck a nd ha d di ed. Wha t wa s the na me of the orga ni s m wi th whi ch the ma n wa s i nfected? a . Chlamydophila pneumoniae b. Chlamydophila psittaci c. Chlamydia trachomatis d. Rickettsia prowazekii e. Rickettsia rickettsii 332. A 50-yea r-ol d ma n pres ented to hi s fa mi l y doctor compl a i ni ng of fl u-l i ke s ymptoms . The doctor ga ve hi m a s hot of peni ci l l i n a nd s ent hi m home. The ma n ca me ba ck a week l a ter a nd i n fa ct, fel t wors e. The ma n wa s a ra ncher a nd ra i s ed a l ot of ca ttl e. He tol d the doctor tha t he ha d congeni ta l hea rt di s ea s e a nd a n a tta ck of rheuma ti c fever when he wa s young. The ma n now compl a i ned of fever, ni ght s wea ts , conti nua l coughi ng, wei ght l os s , a nd l etha rgy. The doctor ha d the ma n hos pi ta l i zed beca us e he now s us pected s uba cute ba cteri a l endoca rdi ti s (SBE). A cul ture of hi s bl ood di d not s how a ny ba cteri a l growth, but a s erum a na l ys i s for a nti bodi es a ga i ns t a certa i n ba cteri um wa s pos i ti ve. As a res ul t of fi ndi ng a nti bodi es to thi s orga ni s m, trea tment wi th doxycycl i ne wa s begun a nd the pa ti ent i mproved a nd wa s rel ea s ed from the hos pi ta l . Wha t wa s the na me of the orga ni s m wi th whi ch the ma n wa s i nfected? a . Chlamydophila psittaci b. Chlamydophila pneumoniae c. Chlamydia trachomatis d. Coxiella burnetii e. Vi ri da ns s treptococci 333. In Jul y of 1987 i n Texa s , a ma n went to hi s fa mi l y doctor compl a i ni ng of fl u-l i ke s ymptoms , hi gh fever, l etha rgy, mus cl e pa i n, a nd a hea da che. He compl a i ned tha t he jus t fel t “l ous y”. When the doctor took the pa ti ent’s hi s tory, he l ea rned tha t the ma n wa s a n a vi d hi ker a nd ca mper. In fa ct, the ma n jus t ca me ba ck from a recent ca mpi ng tri p to South Ca rol i na . The ma n remembered removi ng a bl ood-fi l l ed ti ck from hi s l eg on tha t tri p. He ha d ki l l ed the ti ck a nd thought nothi ng more of i t. Now, he fel t i t mi ght be rel eva nt. The doctor a l s o fel t thi s i nforma ti on wa s rel eva nt a nd a s ked for a Gi ems a s ta i n of the ma n’s bl ood by the cl i ni ca l l a b. The res ul ts ca me ba ck s ta ti ng tha t there were morul a e i ns i de the monocytes i n the ma n’s bl ood. The doctor, ba s ed on thes e res ul ts , i mmedi a tel y s ta rted the ma n on doxycycl i ne beca us e he fel t the ma n wa s i nfected wi th whi ch orga ni s m? a . Amblyomma americanum b. Anaplasma phagocytophilum c. Ehrlichia canis d. Ehrlichia ewingii e. Ehrlichia chaffeensis 334. A Uni ted Sta tes bus i nes s ma n pres ented to the emergency room i n New York Ci ty. He compl a i ned of s evere hea da ches , mus cl e pa i n, a nd fever.
He ha d a ma cul opa pul a r ra s h on hi s trunk tha t wa s movi ng to hi s a rms a nd l egs . The emergency room doctors were s tumped a s to wha t mi ght be ca us i ng thi s di s ea s e s ta te. When they took hi s hi s tory, he tol d them tha t he ha d jus t come ba ck from a bus i nes s tri p to Ja pa n where he ha d s pent a few da ys ca mpi ng i n the mounta i ns a nd ha d been bi tten by s ome i ns ects . He s ta ted tha t he never s a w the i ns ects , s o he di d not know wha t ki nd they were. He s a i d he knew wha t fl ea s a nd ti cks l ooked l i ke a nd he wa s s ure tha t he wa s not bi tten by ei ther of thos e. In fa ct, he coul d s how the doctors the es cha rs of the i ns ect bi tes . When a s ked how l ong a go thi s wa s , he repl i ed “a bout 11 da ys ”. Beca us e of thi s i nforma ti on ga thered by ta ki ng the pa ti ent’s hi s tory, the emergency room doctors fel t confi dent they knew wha t ha d ca us ed the pa ti ent’s s ymptoms . They ga ve the pa ti ent doxycycl i ne a nd tol d hi m to s ee hi s fa mi l y doctor for a fol l ow-up a fter 1 week. When thi s ma n went to hi s fa mi l y doctor, he wa s grea tl y i mproved. Wha t orga ni s m di d the New York bus i nes s ma n ha ve tha t ha d ca us ed hi s i nfecti on? a . Dermacentor andersoni b. Orientia tsutsugamushi c. Rickettsia prowazekii d. Rickettsia rickettsii e. Rickettsia typhi
Answers 296. The answer is c. (Brooks, pp 344-345. Levinson, pp 171-172. Murray, pp 421-426. Ryan, pp 409, 463. Toy, p 116.) Unl i ke chl a mydi a e, mycopl a s ma s ca n repl i ca te i n cel l -free medi a . They l a ck a ri gi d cel l wa l l a nd a re bound by a tri pl e-l a yer uni t membra ne. For thi s rea s on, they a re compl etel y res i s ta nt to the a cti on of peni ci l l i ns . 297. The answer is a. (Brooks, pp 353-354. Levinson, pp 182-184. Murray, pp 438-439. Ryan, p 477.) Q fever i s a n a cute, fl u-l i ke i l l nes s ca us ed by C. burnetii. It i s one ri cketts i a l di s ea s e not tra ns mi tted by the bi te of a ti ck. C. burnetii i s found i n hi gh concentra ti ons i n the uri ne, feces , a nd pl a centa l ti s s ue/a mni oti c fl ui d of ca ttl e, goa ts , a nd s heep. Tra ns mi s s i on to huma ns i s by a eros ol i nha l a ti on of thos e s peci mens . Rickettsia i s pres ent i n the Uni ted Sta tes a nd South Ameri ca , but i s tra ns mi tted by ti cks tha t feed on rodents or dogs . The pa ra s i ti c Taenia s peci es a re tra ns mi tted by i nges ti on of under-cooked mea t. 298. The answer is c. (Brooks, pp 350-354. Levinson, pp 182-184. Murray, pp 427-436. Ryan, pp 472-473.) Ri cketts i a e a re obl i ga te i ntra cel l ul a r pa ra s i tes tha t depend on hos t cel l s for thei r phos phoryl a ted energy compounds . The s i gni fi ca nt ri cketts i a l di s ea s es i n North Ameri ca i ncl ude RMSF (R. rick-ettsii), Q fever (C. burnetii), a nd typhus (R. prowazekii, R. typhi). La bora tory di a gnos i s of ri cketts i a l di s ea s e i s ba s ed on s erol ogi c a na l ys i s ra ther tha n i s ol a ti on of the orga ni s m. 299. The answer is c. (Brooks, pp 364-365. Levinson, pp 179-181. Murray, pp 441-450. Ryan, p 469.) Orni thos i s (ps i tta cos i s ) i s ca us ed by C. psittaci. Huma ns us ua l l y contra ct the di s ea s e from i nfected bi rds kept a s pets or from i nfected poul try, i ncl udi ng poul try i n dres s i ng pl a nts . Al though orni thos i s ma y be a s ymptoma ti c i n huma ns , s evere pneumoni a ca n devel op. Fortuna tel y, the di s ea s e i s cured ea s i l y wi th tetra cycl i ne. Bacillus anthracis i s a s pore-formi ng, gra m-pos i ti ve ba ci l l us tha t ha s a protecti ve ca ps ul e ma de of gl uta mi c a ci d (a mi no a ci d) res i dues . Huma ns a re i nfected a cci denta l l y by conta ct wi th i nfected a ni ma l s or thei r products . Ski n l es i ons , s een mos t often, a re known a s wool s orter’s di s ea s e. Leptospira orga ni s ms a re ti ghtl y coi l ed s pi rochetes . Huma n conta ct i s often i n wa ter, where the orga ni s m enters brea ks i n the s ki n. They produce hemorrha ge a nd necros i s i n the l i ver a nd ki dneys a nd often pres ent a s a s epti c meni ngi ti s . Rel a ps i ng fever i s ca us ed by Borrelia recurrentis a nd i s tra ns mi tted by the body l ous e or Ornithodoros ti cks . An unus ua l fea ture of thi s di s ea s e i s the s el ecti on of new a nti geni c forms of the orga ni s m a fter hos t a nti body forma ti on. Q fever i s ca us ed by a ri cketts i a l orga ni s m, C. burnetii. 300. The answer is b. (Brooks, pp 350-354. Levinson, pp 182-184. Murray, pp 427-436. Ryan, p 477.) Mos t ri cketts i a l di s ea s es a re tra ns mi tted to huma ns by wa y of a rthropod vectors . The onl y excepti on i s Q fever, whi ch i s ca us ed by C. burnetii. Thi s orga ni s m i s tra ns mi tted by i nha l a ti on of conta mi na ted dus t a nd a eros ol s or by i nges ti on of conta mi na ted mi l k. Bri l l –Zi ns s er di s ea s e i s a recurrence of epi demi c typhus (l ous e borne). Ri cketts i a l pox i s tra ns mi tted by a mi te from the mous e res ervoi r. RMSF i s ca us ed by R. rickettsii a nd i s tra ns mi tted by ti cks from the rodent or dog res ervoi rs . Scrub typhus i s a n As i a n/Pa ci fi c a rea di s ea s e wi th a mi te tra ns ferri ng the orga ni s m from a rodent res ervoi r. 301. The answer is e. (Brooks, p 347. Levinson, pp 171-172. Murray, pp 421-426. Ryan, p 413.) Ureaplasma urealyticum ha s been a s s oci a ted wi th NGU a s wel l a s i nferti l i ty. Mycoplasma pneumoniae i s the eti ol ogi c a gent of PAP. Mycoplasma hominis, a l though i s ol a ted from up to 30% of pa ti ents wi th NGU, ha s yet to be i mpl i ca ted a s a ca us e of tha t di s ea s e. Mycoplasma fermentans ha s , on ra re occa s i ons , been i s ol a ted from the oropha rynx a nd geni ta l tra ct. Mycoplasma mycoides ca us es bovi ne pl europneumoni a . 302. The answer is b. (Brooks, p 355. Levinson, pp 182-184. Murray, pp 435-437. Ryan, p 478.) HME, ca us ed by the bi te of the ti ck Amblyomma americanum i nfected wi th E. chaffeensis, ca us es a n i l l nes s not unl i ke RMSF, except a ra s h us ua l l y does not occur. Di a gnos i s i s us ua l l y ma de s erol ogi ca l l y, a nd trea tment of choi ce i s tetra cycl i ne. Symptoms i ncl ude hi gh fever, s evere hea da che, a nd mya l gi a s . EM i s the cha ra cteri s ti c s ki n l es i on s een i n Lyme di s ea s e. HME i s tra ns mi tted by a ti ck vector, a s menti oned previ ous l y, a nd not by a dog bi te. Vomi ti ng a nd pa ra l ys i s a re not us ua l s ymptoms s een i n HME ca s es . Cul tures ca n be i s ol a ted us i ng ti s s ue cul ture cel l l i nes , but not a rti fi ci a l medi a (a ga r, broth, etc). 303. The answer is b. (Brooks, p 362. Levinson, pp 179-181. Murray, pp 441-450. Ryan, pp 466-467.) The di fferenti a l di a gnos i s of LGV i ncl udes s yphi l i s , geni ta l herpes , a nd cha ncroi d. Severa l cl i ni ca l tes ts ca n be us ed to rul e out s yphi l i s a nd geni ta l herpes . Thes e i ncl ude a nega ti ve (nega ti ve to rul e out; pos i ti ve to rul e i n) da rk-fi el d exa mi na ti on a s wel l a s pos i ti ve s ero-l ogi c fi ndi ngs for s yphi l i s a nd the demons tra ti on of herpes s i mpl ex vi rus by cytol ogy or cul ture. Haemophilus ducreyi ca n us ua l l y be i s ol a ted from the ul cer i n cha ncroi d. Ba bes i os i s i s a n RBC-i nfecti ng ti ck-borne di s ea s e, us ua l l y deri ved from dogs or Texa s ca ttl e. Mos t ca s es a re a s ymptoma ti c, but cl i nda myci n or a zi thromyci n a re effecti ve trea tments . Mononucl eos i s i s s een mos t often i n i nfecti ous mononucl eos i s ca us ed by EBV. Ps i tta cos i s i s ca us ed by i nha l i ng a eros ol s or di rect conta ct wi th bi rds i nfected wi th C. psittaci a nd i s us ua l l y a mi l d upper res pi ra tory i l l nes s . Shi ngl es woul d be evi denced by ma s s es of pa i nful herpeti c l es i ons ca us ed by rea cti va ti on of VZV (chi cken pox). 304. The answer is e. (Brooks, pp 350-354. Levinson, pp 182-184. Murray, pp 427-436. Ryan, p 475.) Tetra cycl i nes a nd chl ora mpheni col a re effecti ve, provi ded tha t trea tment i s s ta rted ea rl y for ri cketts i a l di s ea s es , i ncl udi ng RMSF, a s i n thi s ca s e. Thos e s houl d be gi ven ora l l y da i l y a nd conti nued for s evera l da ys a fter the ra s h s ubs i des . Intra venous dos a ge ca n be us ed i n s everel y i l l pa ti ents . Sul fona mi des enha nce the di s ea s e a nd a re contra i ndi ca ted. The other a nti bi oti cs a re i neffecti ve. Anti bi oti cs onl y s uppres s the ba cteri a ’s growth, a nd the pa ti ent’s i mmune s ys tem mus t era di ca te them. 305. The answer is b. (Brooks, p 359. Levinson, pp 179-181. Murray, pp 441-450, Ryan, p 465. Toy, p 52.) The devel opmenta l cycl e of Chlamydia begi ns wi th the el ementa ry body a tta chi ng to a nd then penetra ti ng the hos t cel l . The el ementa ry body, now i n a va cuol e bounded by hos t-cel l membra ne, becomes a n i ni ti a l body. Wi thi n a bout 12 hours , the i ni ti a l body ha s di vi ded to form ma ny s ma l l el ementa ry pa rti cl es enca s ed wi thi n a n i ncl us i on body i n the cytopl a s m; thes e progeny a re l i bera ted by hos t-cel l rupture. 306. The answer is c. (Brooks, pp 360-361. Levinson, pp 179-181. Murray, pp 441-450. Ryan, pp 464-466.) Chlamydia trachomatis s erova rs A, B, Ba , a nd C a re res pons i bl e for endemi c tra choma . Whi l e di a gnos i s i s us ua l l y dependent upon obs erva ti on of i ntra cel l ul a r i ncl us i ons wi th a gl ycogen ma tri x i n whi ch el ementa ry bodi es a re embedded, Gra m s ta i n prepa ra ti ons a re not us eful di a gnos ti c tool s . The cel l wa l l mos t cl os el y res embl es a hi gh l i pi d content a nd ma y s ta i n gra m-nega ti ve or va ri a bl e. A s i ngl e monthl y dos e of doxycycl i ne ca n res ul t i n s i gni fi ca nt cl i ni ca l i mprovement a nd be preventa ti ve. Cel l wa l l i nhi bi tors (peni ci l l i ns , cepha l os pori ns ) res ul t i n cel l -wa l l defecti ve forms but a re not effecti ve i n cl i ni ca l di s ea s es trea tment. Inhi bi tors of protei n s ynthes i s (tetra cycl i nes , erythromyci n) a re effecti ve i n mos t cl i ni ca l i nfecti ons . 307. The answer is d. (Brooks, p 355. Levinson, pp 182-184. Murray, pp 435-437. Ryan, p 478.) HGE i s ca us ed by the bi te of I. scapularis i nfected wi th ei ther E. phagocytophila or E. ewingii or Ehrlichia equi. A ra s h ra rel y occurs a nd EM does not occur, but the s ymptoms (fever, chi l l s , hea da che, mya l gi a , na us ea , vomi ti ng, a norexi a , a nd wei ght l os s ) a re s i mi l a r to thos e s een i n RMSF. Serol ogi ca l tes ts s how tha t s ubcl i ni ca l ehrl i chi os i s occurs frequentl y. Ehrlichia chaffeensis ca us es huma n monocyte ehrl i chi os i s a nd ma y ca us e s evere or fa ta l i l l nes s . Seropreva l ence s tudi es s ugges t tha t s ub-cl i ni ca l ehrl i chi os i s occurs frequentl y. The orga ni s ms ca n be i s ol a ted us i ng cel l cul ture procedures .
308. The answer is a. (Brooks, pp 350-354. Levinson, pp 182-184. Murray, pp 427-436. Ryan, p 473.) The pri ma ry ca us e of RMSF i s R. rickettsii, a l though ri cketts i a l pox i s ca us ed by R. akari, the onl y other member of the s potted fever group tha t res i des i n the Uni ted Sta tes . Rickettsia sibirica i s res pons i bl e for ti ck typhus i n Chi na ; R. australis ca us es typhus i n Aus tra l i a , a s the na me s i gni fi es ; a nd R. conorii ca us es Europea n a nd Afri ca n ri cketts i os es . Rickettsia prowazekii i s not a member of the s potted fever group; i t ca us es epi demi c typhus . 309. The answer is a. (Brooks, p 355. Levinson, pp 182-184. Murray, pp 435-437. Ryan, p 478.) Al l the l i s ted di s ea s es except Q fever a re ti ck-borne. Two huma n forms of ehrl i chi os i s ca n occur: HME, ca us ed by E. chaffeensis, a nd HGE, ca us ed by E. ewingii. Ehrl i chi os i s wa s previ ous l y recogni zed onl y a s a veteri na ry pa thogen. HME i nfecti on i s tra ns mi tted by the brown dog ti ck a nd A. americanum. HGE i nfecti on i s tra ns mi tted by I. scapularis, the s a me ti ck tha t tra ns mi ts Lyme di s ea s e. Both i nfecti ons ca us e fever a nd l eukopeni a . A ra s h ra rel y occurs . E. chaffeensis i nfects monocytes , a nd HGE i nfects gra nul ocytes ; both orga ni s ms produce i ncl us i on bodi es ca l l ed morulae. Francisella tularensis i s a s ma l l , gra m-nega ti ve, nonmoti l e coccoba ci l l us . Huma ns mos t commonl y a cqui re the orga ni s m a fter conta ct wi th the ti s s ues or body fl ui d of a n i nfected ma mma l or the bi te of a n i nfected ti ck. The Ri cketts i a C. burnetii ca us es Q fever, a nd huma ns a re us ua l l y i nfected by a eros ol of a s porel i ke form s hed i n mi l k, uri ne, feces , or pl a centa of i nfected s heep, ca ttl e, or goa ts . Lyme di s ea s e i s ca us ed by a s pi rochete, B. burgdorferi, a nd produces the cha ra cteri s ti c l es i on erythema chroni cum mi gra ns (ECM). The eti ol ogi c a gent of RMSF i s R. rickettsii. It us ua l l y produces a ra s h tha t begi ns i n the extremi ti es a nd then i nvol ves the trunk. 310. The answer is c. (Brooks, pp 350-354. Levinson, pp 182-184. Murray, pp 427-436. Ryan, pp 473-475.) Typhus , s potted fever, a nd s crub typhus a re a l l ca us ed by ri cketts i a e (R. prowazekii, R. rickettsii, a nd R. tsutsugamushi, res pecti vel y). Cl i ni ca l l y, the di s ea s es ha ve s evera l s i mi l a ri ti es . Ea ch ha s a n i ncuba ti on peri od of 1 to 2 weeks , fol l owed by a febri l e peri od, whi ch us ua l l y i ncl udes a ra s h. Duri ng the febri l e peri od, ri cketts i a e ca n be found i n the pa ti ent’s bl ood, a nd there i s di s s emi na ted foca l va s cul i ti s of s ma l l bl ood ves s el s . The geogra phi c a rea a s s oci a ted wi th thes e di s ea s es i s us ua l l y di fferent. Scrub typhus i s us ua l l y found i n Ja pa n, Southea s t As i a , a nd the Pa ci fi c, whi l e s potted fever i s us ua l l y found i n the wes tern hemi s phere. Typhus ha s a worl dwi de i nci dence. (Typhus i s ca us ed by l i ce a nd fl ea s , s potted fever i s ca us ed by ti cks a nd mi tes , a nd s crubs a re ca us ed by mi tes .) 311. The answer is a. (Brooks, p 360. Levinson, pp 179-181. Murray, pp 441-450. Ryan, p 464. Toy, p 52.) Tra choma ha s been the grea tes t s i ngl e ca us e of bl i ndnes s i n the worl d. Chlamydia trachomatis i s the mos t common ca us e of STD i n the Uni ted Sta tes a nd i s a l s o res pons i bl e for the ma jori ty of ca s es of i nfa nt conjuncti vi ti s a nd i nfa nt pneumoni a . Mi ddl e ea r i nfecti on i n chi l dren i s mos t often ca us ed by ba cteri a norma l l y found i n the ora l ca vi ty or upper res pi ra tory s ys tem. Gra m-pos i ti ve cocci , Pseudomonas s peci es , a nd a hos t of other norma l fl ora ca n be i nvol ved. Tra choma i nvol ves the kera toconjuncti va a rea of the eye, not the reti na . Sexua l l y tra ns mi tted ca rdi a c i n a dul ts a nd chi l dren’s uri na ry tra ct i nfecti ons a re not reported to be ca us ed by C. trachomatis. 312. The answer is c. (Brooks, p 362. Levinson, p 179. Murray, pp 441-450. Ryan, pp 466-468.) LGV i s a n STD ca us ed by C. trachomatis of i mmuno-types L1, L2, a nd L3. It i s more commonl y found i n tropi ca l cl i ma tes . In the Uni ted Sta tes , the s ex ra ti o i s reported to be 3.4 ma l es to 1 fema l e. Tetra cycl i ne ha s been s ucces s ful i n trea ti ng thi s di s ea s e i n the ea rl y s ta ges ; however, l a te s ta ges us ua l l y requi re s urgery. Unl es s effecti ve a nti mi crobi a l drug trea tment i s gi ven promptl y, chroni c i nfl a mma tory proces s es ca n l ea d to fi bros i s , l ympha ti c obs tructi on, a nd recta l s tri ctures . 313. The answer is d. (Brooks, pp 350-354. Levinson, pp 182-184. Murray, pp 427-436. Ryan, pp 475-476.) The di s ea s e des cri bed i s epi demi c typhus or l ous eborne typhus . It i s ca us ed by R. prowazekii a nd i s s prea d by the huma n body l ous e, Pediculus humanus. Li ce obvi ous l y occur mos t rea di l y i n uns a ni ta ry condi ti ons brought on by wa r or na tura l di s a s ters , where norma l hea l thy l i vi ng condi ti ons a re una va i l a bl e. Ri cketts i a l di s ea s es res pond to tetra cycl i ne trea tment a nd vector control . The orga ni s ms repl i ca te i n endothel i a l cel l s , res ul ti ng i n va s cul i ti s . Recrudes cent di s ea s e (recurrence i n l a ter yea rs ) ha s been demons tra ted i n peopl e expos ed to epi demi c typhus duri ng Worl d Wa r II. Thi s form of di s ea s e i s genera l l y mi l der, a nd conva l es cence i s s horter. Ri cketts i a e a re pl eomorphi c cocco-ba ci l l i wi th cel l wa l l s tha t do not s ta i n wel l i n Gra m s ta i n procedures . No vi rus es were i nvol ved i n thi s probl em beca us e tetra cycl i ne wa s a bl e to ki l l the i nfecti ng orga ni s ms . Huma ns a re the ma i n res ervoi r of the ca us a ti ve a gent. 314 to 317. The answers are 314-c, 315-e, 316-d, and 317-b. (Brooks, pp 344-347. Levinson, pp 171-172. Murray, pp 421-426. Ryan, pp 409-412. Toy, p 116.) Members of the mycopl a s ma group tha t a re pa thogeni c for huma ns i ncl ude M. pneumoniae a nd U. urealyticum. Mycoplasma pneumoniae i s bes t known a s the ca us a ti ve a gent of PAP, whi ch ma y be confus ed cl i ni ca l l y wi th i nfl uenza or l egi onel l os i s . It a l s o i s a s s oci a ted wi th a rthri ti s , peri ca rdi ti s , a s epti c meni ngi ti s , a nd the Gui l l a i n–Ba rré s yndrome. M. pneumoniae ca n be cul ti va ted on s peci a l medi a a nd i denti fi ed by i mmunofl uores cence s ta i ni ng a nd “fri ed egg” col oni es on a ga r. Ureaplasma urealyticum (once ca l l ed tiny, or T. strain) ha s been i mpl i ca ted i n ca s es of NGU. As the na me i mpl i es , thi s orga ni s m i s a bl e to s pl i t urea , a fa ct of di a gnos ti c s i gni fi ca nce. Ureaplasma urealyticum i s pa rt of the norma l fl ora of the geni touri na ry tra ct, pa rti cul a rl y i n women. Both M. orale a nd M. salivarium a re i nha bi ta nts of the norma l huma n ora l ca vi ty. Thes e s peci es a re commens a l s a nd do not pl a y a rol e i n di s ea s e. The onl y other s peci es of Mycoplasma a s s oci a ted wi th huma n di s ea s e i s M. hominis. A norma l i nha bi ta nt of the geni ta l tra ct of women, thi s orga ni s m ha s been demons tra ted to produce a n a cute res pi ra tory i l l nes s tha t i s a s s oci a ted wi th s ore throa t a nd tons i l l a r exuda te, but not wi th fever. M. hominis ca n ca us e di s ea s e outs i de the uri na ry tra ct i n i mmunos uppres s ed pa ti ents or i mmunocompetent pa ti ents a fter tra uma of the geni touri na ry tra ct. Other opportuni s ti c i nfecti ons known to be ca us ed by M. hominis i ncl ude wound i nfecti ons , os teomyel i ti s , bra i n a bs ces s , pneumoni a , a nd peri toni ti s . It ha s been a s s oci a ted wi th neona ta l pneumoni a a nd s eps i s . Mycoplasma fermentans i s a n a ni ma l i s ol a te. 318. The answer is b. (Brooks, pp 360-361. Levinson, pp 179-181. Murray, pp 441-450. Ryan, pp 463-470, 471-479. Toy, p 52.) Chl a mydi a e a re gra m-nega ti ve ba cteri a tha t a re obl i ga te, i ntra cel l ul a r pa ra s i tes . They a re di vi ded i nto three s peci es : C. trachomatis, C. pneumoniae, a nd C. psittaci. Chl a mydi a e ha ve a uni que devel opmenta l cycl e. The i nfecti ous pa rti cl e i s the el ementa ry body. Once i ns i de the cel l , the el ementa ry body undergoes reorga ni za ti on to form a reti cul a te body. After s evera l repl i ca ti ons , the reti cul a te bodi es di fferenti a te i nto el ementa ry bodi es , a re rel ea s ed from the hos t cel l , a nd become a va i l a bl e to i nfect other cel l s . Three of the 15 s erova rs of C. trachomatis (L1, L2, a nd L3) a re known to ca us e LGV, a n STD. C. trachomatis i s a l ea di ng ca us e of STD i n the Uni ted Sta tes . It i s i ns i di ous beca us e s o ma ny ea rl y i nfecti ons a re a s ymptoma ti c, pa rti cul a rl y i n women. The pa i nl es s pa pul e or ves i cl e devel ops on a ny pa rt of the externa l geni ta l i a , a nus , rectum, or el s ewhere. Thi s l es i on ma y ul cera te a nd hea l wi thout noti ce. Lymph nodes enl a rge a nd di s cha rge pus through s i nus es . Unl es s effecti ve a nti bi oti cs (tetra cycl i ne, erythromyci n) a re gi ven promptl y, a chroni c i nfl a mma tory proces s ma y l ea d to fi bros i s a nd l ympha ti c obs tructi on. 319. The answer is d. (Brooks, p 355. Levinson, pp 182-184. Murray, pp 435-437. Ryan, pp 463-470, 471-479.) Ehrlichia i s a n obl i ga te, i ntra cel l ul a r pa ra s i te tha t res embl es Rickettsia. Ehrlichia chaffeensis ha s been l i nked to huma n ehrl i chi os i s , a l though thi s i nfecti on i s pri ma ri l y s een i n a ni ma l s . The ma jori ty of pa ti ents wi th thi s di s ea s e report expos ure to ti cks . It i s thought tha t I. scapularis ca rri es Ehrlichia, a l though the Lone Sta r ti ck, A. americanum, ma y a l s o tra ns mi t the di s ea s e. Thes e gra m-nega ti ve ba cteri a i nfect ci rcul a ti ng l eukocytes where they mul ti pl y wi thi n pha gocyti c va cuol es , formi ng cl us ters wi th i ncl us i on-l i ke a ppea ra nce. Thes e cl us ters of ehrl i chi a e a re ca l l ed morul a e (mul berry-l i ke). Di a gnos i s i s confi rmed by obs ervi ng thes e morul a e i n whi te bl ood cel l s .
320. The answer is c. (Brooks, pp 350-351. Levinson, pp 182-184. Murray, pp 438-439. Ryan, pp 463-470, 471-479.) Coxiella i s tra ns mi tted through the res pi ra tory tra ct ra ther tha n through the s ki n, a nd B. henselae from a ni ma l s cra tches . Coxiella ma y ca us e chroni c endoca rdi ti s tha t i s not very res pons i ve to ei ther a nti mi crobi a l thera py or va l ve repl a cement. About 50% of Q-fever ca s es i n huma ns a re a s ymptoma ti c. Symptoma ti c ca s es us ua l l y pres ent wi th a n a cute febri l e i l l nes s (fl u-l i ke di s ea s e, fever, pneumoni ti s , a nd pos s i bl y hepa ti ti s ). Di a gnos i s depends on a hi s tory wi th conta ct wi th newborn or i nfected a dul t a ni ma l s (s heep, ca ttl e, ca ts , ra bbi ts , a nd dogs ). About 2% to 10% of Q-fever pa ti ents progres s to a chroni c i nfecti on wi th endoca rdi ti s , whi ch occurs i n a bout 60% to 70% of thos e ca s es . No va cci ne exi s ts a nd doxycycl i ne i s effecti ve when s ymptoms a ppea r. 321. The answer is c. (Murray [2009], pp 427-433. Murray [2013], Ch 41; Ryan, Ch 40.) The s ource of the woma n’s i nfecti on i s Rickettsia prowazekii. Her di s ea s e i s l ous e-borne typhus . Lous e-borne typhus i s a di s ea s e wi th a morta l i ty of a pproxi ma tel y 30%. Chlamydia trachomatis i s obvi ous l y i ncorrect beca us e the woma n does not ha ve tra choma , whi ch i s pri ma ri l y a di s ea s e of the eye or geni ta l tra ct. Coxiella burnetii i s i ncorrect beca us e thi s orga ni s m ca us es Q fever, whi ch i s pri ma ri l y a di s ea s e pres enti ng wi th nons peci fi c fl u-l i ke s ymptoms . Rickettsia rickettsii ca us es Rocky Mounta i n s potted fever, whi ch i s the mos t common Rickettsia di s ea s e i n the Uni ted Sta tes , but i s s prea d by ti cks . Rickettsia typhi ca us es endemi c typhus or muri ne typhus a nd i s s prea d by fl ea s . Therefore, i t i s i mporta nt to know the a rthropod vectors tha t s prea d Rickettsia di s ea s es to be a bl e to tel l them a pa rt. 322. The answer is d. (Murray [2009], pp 199-208. Murray [2013], Ch 40; Ryan, Ch 38.) Peni ci l l i n ca us es di s rupti on of the cel l wa l l of ba cteri a . The Mycoplasma a re uni que a mong ba cteri a (a l ong wi th the Ureaplasma) beca us e they do not pos s es s a cel l wa l l . Thei r cel l membra nes conta i n a hi gh concentra ti on of s terol s , whi ch s trengthen them by a l l owi ng the orga ni s m to res i s t the di fference between the i nterna l a nd externa l os moti c pres s ure. The other four a nti bi oti cs (cl i nda myci n, erythromyci n, ka na myci n, a nd tetra cycl i ne) a re a l l protei n s ynthes i s i nhi bi tors a nd woul d be expected to ha ve s ome a cti vi ty a ga i ns t M. pneumoniae. Erythromyci n, the fl uoroqui nol ones , a nd the tetra cycl i nes ha ve been us ed to trea t i nfecti ons by thi s orga ni s m. The fl uoroqui nol ones a nd the tetra cycl i nes a re more commonl y us ed i n a dul ts . 323. The answer is c. (Murray [2009], pp 441-449. Murray [2013], Ch 43; Ryan, Ch 39.) Thi s ma n ha s LGV, whi ch i s a STD ca us ed by the L s erotypes of Chlamydia trachomatis. Whi l e C. trachomatis ca n ca us e di s ea s es s uch a s ocul a r i nfecti ons a nd i nfa nt pneumoni a , i t ca n a l s o ca us e the very s eri ous STD of LGV. Di fferent s erotypes (i n thi s ca s e the L s erotypes ) of C. trachomatis a re res pons i bl e for the di fferent di s ea s es . Chlamydophila psittaci ca us es huma n res pi ra tory i nfecti ons i n ma n. Chlamydophila pneumoniae ca n a l s o ca us e res pi ra tory i nfecti ons i n ma n tha t ra nge from a s ymptoma ti c to s eri ous a typi ca l pneumoni a s . Neisseria gonorrheae i s a Gra m-nega ti ve coccus tha t ca n ca us e STD, a nd Treponema pallidum i s a Gra m-nega ti ve s pi rochete tha t ca n a l s o ca us e STDs . 324. The answer is d. (Murray [2009], pp 427-433. Murray, Ch 41; Ryan, Ch 40.) The di s ea s e tha t thi s young ma n ha s i s Rocky Mounta i n s potted fever (RMSF). RMSF i s the mos t common Rickettsia di s ea s e i n the Uni ted Sta tes a nd i s s prea d by ti cks . Thi s di s ea s e ca us es a ma cul opa pul a r ra s h on the a rms a nd l egs tha t s prea ds to the trunk. The s ki n di s ea s e mos t often a s s oci a ted wi th the group A s treptococci i s erys i pel a s . Coxiella burnetii ca us es Q-fever, whi ch i s pri ma ri l y a di s ea s e pres enti ng wi th nons peci fi c fl u-l i ke s ymptoms . Typhoi d fever, whi ch i s ca us ed by Salmonella typhi, i s a febri l e i l l nes s wi th s evere ga s troi ntes ti na l di s tres s . Rickettsia prowazekii ca us es the di s ea s e typhus , whi ch i s a di s ea s e wi th a 30% fa ta l i ty ra te a nd a ma cul opa pul a r ra s h tha t i s s prea d by l i ce a nd i s ra re i n the Uni ted Sta tes . 325. The answer is e. (Murray [2009], pp 421-425. Murray [2013], Ch 40; Ryan, Ch 38.) Ureaplasma urealyticum ca n ca us e NGU a nd i t produces col oni es even s ma l l er tha n the col oni es of the Mycoplasma. The Ureaplasma s peci es requi re the pres ence of urea i n order to grow a nd i t i s thought tha t they us e urea to genera te energy. They a l s o often di e ra pi dl y a fter thei r i ni ti a l i s ol a ti on. Coxiella burnetii does not ca us e NGU a nd does not requi re urea to grow. The three Mycoplasma s peci es (genitalium, hominis, a nd pneumoniae) do not requi re urea to grow a nd a re therefore i ncorrect. 326. The answer is e. (Murray [2009], pp 421-425. Murray, Ch 40; Ryan, Ch 38.) Mycoplasma pneumoniae produces a n a typi ca l pneumoni a tha t s hows up a s a pa tchy opa ci ty on ches t x-ra y. The mos t common cl i ni ca l pres enta ti on wi th thi s orga ni s m i s tra cheobronchi ti s . The a typi ca l pneumoni a produced by M. pneumoniae i s often referred to a s “wa l ki ng pneumoni a ”. Col d a ggl uti ni ns a re a nti bodi es tha t a ggl uti na te type O red bl ood cel l s a t 4°C. Streptococcus MG i s a cl i ni ca l s tra i n of ba cteri a tha t ra rel y ca us es di s ea s e. Thes e a nti bodi es a re often found i n the s erum of pers ons i nfected wi th M. pneumoniae. Anti bodi es to thes e orga ni s ms a nd col d a ggl uti ni ns a re not found i n the s erum of pa ti ents i nfected wi th Chlamydia trachomatis, Chlamydophila pneumoniae, Chlamydophila psittaci, or Mycoplasma hominis. 327. The answer is c. (Murray [2009], pp 441-449. Murray [2013], Ch 43; Ryan, Ch 39.) Chlamydophila pneumoniae produces pha ryngi ti s , bronchi ti s , s i nus i ti s , a nd pneumoni a i n huma ns . The l ungs wi l l s how a pa tchy i nfi l tra te upon x-ra y. It i s a Gra m-nega ti ve ba cteri um tha t does not s ta i n wel l upon Gra m-s ta i n. It wi l l not grow i n vi tro (eg, on bl ood a ga r), but wi l l grow i n ti s s ue cul ture cel l s beca us e i t i s a s tri ct i ntra cel l ul a r ba cteri a l pa thogen. Streptococcus pneumoniae a nd Mycoplasma pneumoniae wi l l both ca us e pneumoni a , but they wi l l both grow i n vi tro a nd a re not obl i ga te i ntra cel l ul a r ba cteri a l pa thogens . Both C. trachomatis a nd C. psittaci a re obl i ga te i ntra cel l ul a r ba cteri a l pa thogens . C. trachomatis ca us es ocul a r a nd geni ta l i nfecti ons , s o i s therefore i ncorrect. C. psittaci ca n ca us e pneumoni a , but i s a l s o i ncorrect beca us e the ma n ha s not recentl y obta i ned a ny new bi rds i nto hi s hous ehol d. 328. The answer is a. (Murray [2009], pp 435-440. Murray [2013], Ch 42; Ryan, Ch 40.) Huma n a na pl a s mos i s i s ca us ed by Anaplasma phagocytophilum. The cel l s tha t a re pri ma ri l y i nfected by thi s orga ni s m a re gra nul ocytes , whi ch i ncl ude neutrophi l s , ba s ophi l s , a nd eos i nophi l s . Huma n a na pl a s mos i s pres ents a s fl u-l i ke s ymptoms , wi th mus cl e pa i n, l etha rgy, hi gh fever, a nd hea da ches . The di s ea s e i s obs erved fol l owi ng the bi te of a ti ck a bout 7 to 21 da ys a fter the i njury. Anti bi oti cs s uch a s peni ci l l i n, cepha l os pori n, a nd the a mi nogl ycos i des a re not effecti ve a ga i ns t huma n a na pl a s mos i s . Coxiella burnetii ca us es Q-fever, whi ch i s pri ma ri l y a res pi ra tory di s ea s e. Both Chlamydophila psittaci a nd Chlamydophila pneumoniae ca us e res pi ra tory di s ea s es , a nd Rickettsia rickettsii ca us es Rocky Mounta i n s potted fever, whi ch i s cha ra cteri zed by a ra s h, whi ch thi s pa ti ent does not ha ve. 329. The answer is c. (Murray [2009], pp 441-449. Murray [2013], Ch 43; Ryan, Ch 39.) Chlamydia trachomatis i s the mos t common s exua l l y tra ns mi tted orga ni s m i n the Uni ted Sta tes , s o i t i s not s urpri s i ng tha t thi s ma n pi cked up thi s orga ni s m a fter a n unprotected s exua l encounter wi th a pros ti tute. Mos t C. trachomatis geni ta l i nfecti ons i n men a re s ymptoma ti c. However, i n women a s ma ny a s 80% of thei r geni ta l tra ct i nfecti ons wi th thi s orga ni s m a re a s ymptoma ti c. As ymptoma ti c women a re a n i mporta nt res ervoi r for the di s tri buti on of thi s orga ni s m. C. trachomatis wi l l not grow on bl ood a ga r a nd i s a n obl i ga te i ntra cel l ul a r ba cteri a l pa thogen. Both the Chlamydophila (pneumoniae a nd psittaci) ca us e res pi ra tory tra ct i nfecti ons . The i nfecti ng orga ni s m di d not grow on bl ood a ga r, s o i t wa s not N. gonorrheae. The i nfecti ng orga ni s m wa s not T. pallidum beca us e the i ni ti a l cha ncre i s on the geni ta l s , a nd the s econd pha s e of s yphi l i s , whi ch i s a ra s h, di d not occur i n thi s ma n. 330. The answer is a. (Murray [2009], pp 441-449. Murray [2003], Ch 43. Ryan, Ch 39.) The des cri bed di s ea s e i s tra choma , a n ocul a r di s ea s e ca us ed by the A, B, a nd C s erotypes of C. trachomatis. Tra choma i s the mos t i mporta nt ca us e of preventa bl e bl i ndnes s i n the worl d. Thi s i nfecti on i s s prea d from eye to eye by fomi tes l i ke conta mi na ted towel s . The conjuncti va becomes s ca rred a s the i nfecti on conti nues a nd bl i ndnes s ca n be the end res ul t. The i nfecti on ca n be cured by one dos e of a zi thromyci n or by a s even da y cours e of doxycycl i ne. The two Chlamydophila (psittaci a nd pneumoniae)
ca us e res pi ra tory tra ct i nfecti ons , whi l e the two Rickettsia (prowazekii a nd rickettsii) produce ra s hes a nd thes e pa ti ents ha d no ra s hes . 331. The answer is b. (Murray [2009], pp 441-449. Murray [2013], Ch 43; Ryan, Ch 39.) Chlamydophila psittaci i s the ca us e of ps i tta cos i s , whi ch ca n be tra ns mi tted to huma ns from i nfected bi rds . When bi rds a re s hi pped l ong di s ta nces (eg, from Afri ca ), i f they a re i nfected wi th C. psittaci, thei r i mmune s ys tem begi ns to wa ne. If they get s i ck, the di s ea s e i s ca l l ed s hi ppi ng fever. So when the pers on who ordered the pa rrot gets the bi rd, they ma y become i nfected wi th C. psittaci by i nha l a ti on. The orga ni s m then moves by hema togenous s prea d to the s pl een a nd l i ver where the ba cteri a mul ti pl y. The l ungs a re then i nfected from the bl ood s trea m whi ch i nduces a n i nfl a mma tory rea cti on i n the a l veol i . Mucous pl ugs ca n then be produced i n the s ma l l er a i rwa ys ca us i ng di ffi cul ty i n brea thi ng. Chlamydophila pneumoniae i s i ncorrect beca us e thi s orga ni s m i s not s prea d by bi rds , a nd bi rds a l s o do not s prea d Chlamydia trachomatis. The two Rickettsia orga ni s ms (prowazekii a nd rickettsii) do not ca us e res pi ra tory tra ct i nfecti ons a nd a re not s prea d by bi rds . 332. The answer is d. (Murray [2009], pp 435-440. Murray [2013], Ch 42; Ryan, Ch 40.) The ma n ha d Q-fever. Thi s di s ea s e i s ca us ed by i nfecti on wi th Coxiella burnetii. Thi s orga ni s m i s extremel y s ta bl e a nd ca n s urvi ve i n mi l k a nd s oi l for a very l ong ti me. Infecti ons i n ma n occur when the orga ni s ms become a i rborne from a conta mi na ted s ource s uch a s s oi l or mi l k from a fa rm. Ma n ca n a l s o become i nfected by dri nki ng conta mi na ted mi l k. Tha t i s why i t i s a good i dea to dri nk onl y pa s teuri zed mi l k. Mos t of the peopl e expos ed to Coxiella burnetii s uffer a n a s ymptoma ti c i nfecti on a nd mos t s ymptoms tha t peopl e do experi ence a re fl u-l i ke. Q-fever ca n occur a l ong ti me a fter the ori gi na l expos ure to the orga ni s m a nd thi s occurs pri ma ri l y i n peopl e wi th congeni ta l hea rt di s ea s e. In thi s ca s e, SBE i s mos t commonl y s een. The two Chlamydophila orga ni s ms (psittaci a nd pneumoniae) a re i ncorrect. The ma n got hi s i nfecti on worki ng on hi s ca ttl e ra nch. The Chlamydophila a re not extremel y s ta bl e a nd do not s urvi ve i n dus t. Chlamydia trachomatis i s i ncorrect beca us e thi s orga ni s m i s not extremel y s ta bl e a nd does not s urvi ve i n dus t. Whi l e the vi ri da ns s treptococci do ca us e SBE, they di d not ca us e thi s ma n’s i nfecti on beca us e they a re s ens i ti ve to peni ci l l i n a nd they woul d ha ve grown out i n hi s bl ood cul ture ha d they been pres ent. 333. The answer is e. (Murray [2009], pp 435-440. Murray [2013], Ch 42; Ryan, Ch 40.) The ma n ha d HME. Thi s di s ea s e i s s prea d by ti cks a nd i s ca us ed by Ehrlichia chaffeensis. Thi s orga ni s m res ul ts i n the i nfecti on of monocytes i n the pa ti ent’s bl ood. Gi ems a s ta i ni ng of the pa ti ent’s peri phera l bl ood s houl d be performed to exa mi ne the monocytes for morul a e (s tructures i ns i de the monocytes tha t conta i n the i ntra cel l ul a r orga ni s ms ), beca us e thi s i s di a gnos ti c of thi s di s ea s e. Pa ti ents wi th HME s houl d be trea ted wi th doxycycl i ne. Ehrlichia canis i s i ncorrect beca us e thi s orga ni s m ca us es i nfecti ons i n dogs . Ehrlichia ewingii i s i ncorrect beca us e thi s orga ni s m ca us es pri ma ry gra nul ocyti c ehrl i chi os i s . Amblyomma america-num i s the ti ck a rthropod vector for E. chafeensis a nd therefore i ncorrect. 334. The answer is b. (Murray [2009], pp 427-433. Murray [2013], Ch 41. Ryan, Ch 40.) The New York bus i nes s ma n ha d s crub typhus , whi ch i s ca us ed by Orientia tsutsugamushi. Thi s di s ea s e i s s prea d by the bi te of mi tes ca rryi ng the orga ni s m. Mi tes a re s o s ma l l tha t mos t peopl e tha t get bi t by them never s ee them. Scrub typhus devel ops s uddenl y a fter a bout a 2-week i ncuba ti on peri od. It occurs i n ea s tern As i a , Ja pa n, Aus tra l i a , a nd other wes tern Pa ci fi c i s l a nds . The bus i nes s ma n’s tri p to Ja pa n expl a i ns hi s i nfecti on. The di s ea s e i s cha ra cteri zed by mya l gi a , fever, a nd s evere hea da ches . A ra s h devel ops a bout 50% of the ti me. It ca n be trea ted wi th doxycycl i ne. The three Rickettsia orga ni s ms (prowazekii, rickettsii, a nd typhi) a re i ncorrect beca us e the bus i nes s ma n ha d no l i ce (prowazekii), no fl ea bi tes (typhi), a nd no ti ck bi tes (rickettsii). Doxycycl i ne woul d ha ve cured a l l thes e orga ni s ms i f they ha d been pres ent. Dermacentor andersoni i s the na me of the wood ti ck tha t s prea ds Rocky Mounta i n s potted fever, s o tha t i s obvi ous l y i ncorrect.
Mycology Questions 335. About 90 da ys pos t-bone ma rrow tra ns pl a nt, a 55-yea r-ol d whi te woma n bega n to compl a i n of dry cough, s hortnes s of brea th, a nd ches t pa i n. She wa s s ta rted on a nti bi oti cs a nd bl ood cul ture obta i ned a t the ti me wa s nega ti ve a nd there wa s not i mprovement. A computed tomogra phy (CT) s ca n of the l ungs s howed a ha l o of l ow a ttenua ti on a round a nodul a r l es i on. Ana l ys i s of l ung bi ops y wa s s i mi l a r to methena mi ne s i l ver-s ta i ned s ecti on bel ow. The mos t l i kel y di a gnos i s for thi s pa ti ent i s
(Courtesy of Dr. William Kaplan; Public Health Image Library, Centers for Disease Control and Prevention; Atlanta, Georgia.) a . As pergi l l os i s b. Ca ndi di a s i s c. Hi s topl a s mos i s d. Mucormycos i s 336. A 65-yea r-ol d ma n wa s di a gnos ed wi th ps eudomembra nous ca ndi di a s i s a nd gi ven a pres cri pti on for ora l fl ucona zol e. Thi s drug a cts by: a . Bi ndi ng to membra ne ergos terol b. Incorpora ti on i nto RNA l ea di ng to mi s tra ns l a ti on a nd i nhi bi ts DNA s ynthes i s c. Inhi bi ti on of 1,3-β-gl uca n bi os ynthes i s d. Inhi bi ti on of mi tos i s e. Inhi bi ti on of s qua l ene 2,3-epoxi da s e f. Inhi bi ti on P450-dependent s terol demethyl a s e (l a nos terol 14α-demethyl a s e) 337. An AIDS pa ti ent wi th a CD4 count i n the ra nge 100 to 50 cel l s /mm 3 compl a i ns of hea da che a nd neck s ti ffnes s a nd a ppea rs di s ori ented. The pos s i bi l i ty of funga l meni ngi ti s i s cons i dered a nd tes ts for the common funga l eti ol ogy of meni ngi ti s ordered. Tes ts i ncl uded di rect exa mi na ti on of s pi na l fl ui d for the orga ni s m a nd s erol ogy. The purpos e of the s erol ogy tes t i s detecti on of a . Anti body to ca ps ul a r pol ys a ccha ri de b. Anti body to cel l wa l l ma nnoprotei n c. Ca ps ul a r pol ys a ccha ri de d. Cel l wa l l ma nnoprotei n 338. A 6-yea r-ol d Afri ca n Ameri ca n gi rl res i dent of a very l a rge US ci ty pres ents to a cl i ni c wi th s ca l y pa tches a nd a rea s of a l opeci a on the s ca l p wi th ha i r s ha fts broken off cl os e to the s ca l p. The ha i r di d not fl uores ce under Wood’s l i ght. If thi s chi l d ha s ti nea ca pi ti s , the mos t l i kel y eti ol ogy is a . Epidermophyton floccosum b. Microsporum audouinii c. Microsporum canis
d. Trichophyton rubrum e. Trichophyton tonsurans 339. A 25-yea r-ol d ma l e phys i ca l thera pi s t tra i ns regul a rl y wi th the hope of qua l i fyi ng for the Bos ton Ma ra thon. He devel ops i tchi ng i n i nterdi gi ta l s pa ces on hi s l eft foot. Sus pecti ng ti nea pedi s he trea ts the a rea wi th a n over-the-counter product. The a rea i mproves a fter a cours e of trea tment but two months l a ter rea ppea rs a nd a ga i n res ponded to the s a me trea tment. However, there wa s rea ppea ra nce 3 months l a ter. If the s el fdi a gnos i s i s correct, the norma l ha bi ta t of the eti ol ogi c a gent i s mos t l i kel y des cri bed a s a . Anthropophi l i c b. Geophi l i c c. Zoophi l i c 340. A pa ti ent recei vi ng corti cos teroi d trea tment for l upus devel oped hea da che a nd fever a nd when s he bega n to di s pl a y s ome memory l os s s he wa s brought to her phys i ci a n by her s pous e. Cons i dered i n the di fferenti a l di a gnos i s wa s cryptococca l meni ngi ti s . Whi ch of the fol l owi ng, i f found upon exa mi na ti on of cerebros pi na l fl ui d woul d s upport tha t di a gnos i s ? a . Enca ps ul a ted yea s t cel l s b. Hypha e c. Intra cel l ul a r yea s t cel l s d. Yea s t cel l s wi th mul ti pl e buds e. Yea s t cel l s wi th a broa d ba s e between mother a nd da ughter cel l s 341. A 35-yea r-ol d ma l e, a l ega l res i dent i n the USA, pres ented wi th a compl a i nt of a l es i on on the bottom of hi s foot tha t wa s s mooth a nd s hi ny a nd s omewha t di s col ored. He reported tha t i t bothered hi m when wea ri ng s ome s hoes . He reported no chroni c di s ea s es or recent i l l nes s es a nd he wa s a nons moker. Tra vel hi s tory determi ned tha t he frequentl y vi s i ted rel a ti ves i n Indi a . Hi s topa thol ogy of the bi ops y s peci men s howed a t 2.4mm gra nul e s urrounded by neutrophi l s . Ti s s ue s ta i ni ng s ugges ted tha t the gra nul e conta i ned fi l a ments >1 μm i n wi dth. The mos t l i kel y di a gnos i s is a . Acti nomycetoma b. As pergi l l os i s c. Chromomycos i s d. Eumycetoma e. Pha eohyphomycos i s 342. A hea l thy 55-yea r-ol d ma n res i dent of Loui s vi l l e, Kentucky, pres ented to hi s phys i ci a n compl a i ni ng of fever, hea da che, nonproducti ve cough, a nd ches t pa i n of 10 da ys dura ti on. As pa rt of the hi s tory, the pa ti ent reported tha t he wa s s ti l l empl oyed a s a cons tructi on worker a nd for s evera l weeks pri or to becomi ng i l l ha d been enga ged i n tea ri ng down hous es a nd s tructures a s pa rt of a n urba n renewa l project. The mos t l i kel y funga l i nfecti on cons i dered i n the di fferenti a l di a gnos i s i s a . Bl a s tomycos i s b. Cocci di oi domycos i s c. Cryptococcos i s d. Hi s topl a s mos i s e. Pa ra cocci di oi domycos i s f. Sporotri chos i s 343. A 40-yea r-ol d woma n s ees her pri ma ry ca re phys i ci a n compl a i ni ng of a n ul cer on her fi nger. She reported tha t i t s ta rted a s a red bump. Knowi ng tha t her pa ti ent wa s a l ong-ti me a vi d ga rdener, the phys i ci a n a s ked i f tha t fi nger ha d been i njured by a thorn. The pa ti ent res ponded tha t s he di d not remember a bout tha t pa rti cul a r fi nger but s he certa i nl y ha d recei ved thorn punctures i n pa s t weeks . Ba s ed on thi s i nforma ti on, whi ch of the fol l owi ng i s the mos t l i kel y funga l eti ol ogy? a . Fonsecaea pedrosoi b. Malassezia furfur c. Microsporum canis d. Sporothrix schenckii e. Stachybotrys chartarum 344. Severa l young men from the l oca l hi gh s chool footba l l tea m compl a i n of a s udden ons et of a thl ete’s foot (ti nea pedi s ). Whi ch of the fol l owi ng obs erva ti ons i n a s ki n s cra pi ng wi l l s upport the di a gnos i s ? a . Hya l i ne hypha e a nd a rthroconi di a b. Pi gmented hypha e c. Scl eroti c bodi es d. Spherul es e. Yea s t cel l s 345. A 57-yea r-ol d obes e, whi te fema l e wi th type 1 di a betes mel l i tus i s di a gnos ed wi th s trep throa t a nd pres cri bed peni ci l l i n. A week l a ter s he returns compl a i ni ng of a s ore mouth a nd whi te pa tches on the tongue. Your exa mi na ti on confi rms the whi te ps eudomembra nous l es i ons . Ma teri a l from the l es i on i s obta i ned a nd prepa red for mi cros copi c exa mi na ti on. Your s us pi ci on of the mos t l i kel y cl i ni ca l di a gnos i s wi l l be confi rmed by obs erva ti on of bucca l epi thel i a l cel l s , l eukocytes , a nd whi ch of the fol l owi ng a . Gra m-pos i ti ve ba cteri a b. Gra m-nega ti ve ba cteri a c. Hypha e wi th s epta a nd a cute a ngl e bra nchi ng d. Spherul es conta i ni ng endos pores e. Yea s t cel l s , hypha e, a nd ps eudohypha e
346. A s ma l l browni s h i rregul a r ma cul e on the pa l m of a 13-yea r-ol d gi rl i s exa mi ned by a derma tol ogi s t i n her Loui s i a na home town. A s ki n s cra pi ng from the l es i on i s obta i ned for mi cros copi c obs erva ti on a nd cul ture. Mi cros copi c exa mi na ti on of the s peci men s hows browni s h fi l a ments or hypha e a nd yea s t cel l s . The mos t l i kel y di a gnos i s i s a . Ti nea ca pi ti s b. Ti nea corpori s c. Ti nea ma nuum d. Ti nea ni gra e. Ti nea pedi s 347. You ha ve been des i gna ted a s a coordi na tor of cons tructi on of a bone ma rrow tra ns pl a nt uni t (BMTU). There wi l l be extens i ve remova l of wa l l s a nd fl oors i n order to i ns ta l l the l a mi na r fl ow rooms requi red for a BMTU. From the s ta ndpoi nt of frequency a nd l etha l i ty, whi ch of the fol l owi ng fungi s houl d be your bi gges t concern? a . Aspergillus s peci es b. Candida s peci es c. Cryptococcus s peci es d. Penicillium s peci es e. Pneumocystis jiroveci 348. A 50-yea r-ol d ma n, newl y empl oyed by a commerci a l fa rm tha t s uppl i es eggs a nd chi ckens to i ndus try, devel ops a fl u-l i ke s yndrome wi th fever, chi l l s , mya l gi a , hea da che, a nd a nonproducti ve cough. He i s di a gnos ed wi th hi s topl a s mos i s . A pos i ti ve ti s s ue bi ops y woul d s how the pres ence of a . Arthros pores b. Ova l buddi ng yea s t cel l s i ns i de ma cropha ges c. Spherul es conta i ni ng endos pores d. Tubercul a te ma croconi di a e. Yea s t cel l s , hypha e, a nd ps eudohypha e f. Yea s t cel l s wi th broa d-ba s ed bud 349. A 65-yea r-ol d fema l e pa ti ent wi th a l ong hi s tory of di a betes i s brought the emergency room by her da ughter wi th a n i mmedi a te compl a i nt of s udden s wel l i ng on the ri ght s i de of the fa ce a nd bl eedi ng from the ri ght nos tri l . Ques ti oni ng of the pa ti ent a nd da ughter s ugges ts the pos s i bi l i ty of ketoa ci dos i s . The na s a l bl eedi ng i s troubl es ome a nd a s wa b of the na res i s rus hed to the cl i ni ca l l a bora tory for i mmedi a te a ttenti on a l ong wi th bl ood to tes t for a ci dos i s . The pa ti ent wa s a dmi tted. The fa ci a l l es i on beca me pa rti a l l y necroti c a nd there wa s s l i ght protrus i on of the ri ght eye a nd fa ci a l pa ra l ys i s . The pa ti ent di ed on the s econd da y. If thi s pa ti ent di ed of a funga l i nfecti on, hi s topa thol ogi c exa mi na ti on of the l es i ons woul d mos t l i kel y s how… a . Hypha e, s ome wi th a rthroconi di a b. Septa te dema ti a ceous hypha e c. Septa te hypha e wi th a cute a ngl e bra nchi ng d. Nons epta te hypha e e. Na rrow (<1 μm) Gra m-pos i ti ve fi l a ments f. Yea s t cel l s 350. A norma l l y hea l thy young ma n i n Ari zona wa s di a gnos ed wi th cocci di oi domycos i s . The mos t l i kel y route of i nfecti on for the eti ol ogi c a gent i s a . As pi ra ti on b. Cuta neous conta ct c. Inges ti on d. Inha l a ti on e. Impl a nta ti on 351. An i mmunocompromi s ed pa ti ent i s s us pected of ha vi ng a s pergi l l os i s due to A. fumigatus. Whi ch of the fol l owi ng cl i ni ca l condi ti ons i s mos t l i kel y to occur? a . Al l ergi c bronchopul mona ry res pons e b. As pergi l l oma c. Inva s i ve pul mona ry i nfecti on d. Otomycos i s e. Wound i nfecti on 352. A 25-yea r-ol d pregna nt woma n, l i vi ng i n the Sa n Joa qui n Va l l ey (Ca l i forni a ), experi ences a n i nfl uenza -l i ke i l l nes s wi th fever a nd cough. She i s di a gnos ed wi th Coccidioides i nfecti on. The mos t l i kel y recommended trea tment for the i nfecti on of thi s pa ti ent i s a . Amphoteri ci n B or fl ucona zol e b. 5-fl uorocytos i ne c. None, the i nfecti on res ol ves wi thout trea tment d. Supporti ve trea tment onl y for s ymptoms e. Terbi na fi ne 353. Months a fter a ki dney tra ns pl a nt, a 45-yea r-ol d woma n who wa s recei vi ng i mmunos uppres s i ve thera py experi enced a ra pi d ons et of res pi ra tory i ns uffi ci ency a nd a dry cough. Hi gh-res ol uti on computed tomogra phi c s ca nni ng wa s ordered of the l ungs . There were fi ndi ngs of i nters ti ti a l di s ea s e. Bronchoa l veol a r l a va ge wa s performed a nd the ma teri a l exa mi ned by Gi ems a s ta i ni ng. The report s ta ted tha t trophi c forms a nd cys ts were obs erved. The mos t l i kel y i nfecti ng orga ni s m i s a . Aspergillus fumigatus b. Candida albicans
c. Pneumocystis jiroveci d. Rhizopus arrhizus (oryzae) 354. Ba cteri a a nd fungi s ha re s ome common mecha ni s ms of res i s ta nce to drugs us ed i n trea tment of ba cteri a l or funga l i nfecti on. However, ba cteri a ha ve a res i s ta nce mecha ni s m not des cri bed i n fungi . Thi s mecha ni s m i s a . Al tera ti on i n the drug ta rget b. Effl ux of drug c. Ina cti va ti on of drug d. Infl ux of drug e. Overexpres s i on of drug ta rget 355. An i s ol a te of Candida albicans wa s found to be res i s ta nt to ca s pofungi n due to muta ti on i n the drug ta rget whi ch i s a . Cytos i ne permea s e b. Ergos terol c. P450 14-α-demethyl a s e d. Squa l ene 2,3-epoxi da s e e. Subuni t of β-1,3-gl uca n s yntha s e 356. A 25-yea r-ol d ma n ma de a s el f-di a gnos i s of a thl ete’s foot a nd purcha s ed a product a dverti s ed to trea t thi s condi ti on tha t l i s ted the a cti ve i ngredi ent a s tol na fta te. The mode of a cti on of thi s drug i s a . Bi ndi ng to membra ne ergos terol b. Incorpora ti on i nto RNA l ea di ng to mi s tra ns l a ti on a nd i nhi bi ti on DNA s ynthes i s c. Inhi bi ti on of 1,3-β-gl uca n bi os ynthes i s d. Inhi bi ti on of mi tos i s e. Inhi bi ti on of s qua l ene 2,3-epoxi da s e f. Inhi bi ti on P450-dependent s terol demethyl a s e (l a nos terol 14α-demethyl a s e) 357. A 37-yea r-ol d HIV-pos i ti ve ma l e pres ented wi th fever, cough, fa ci a l pa pul es , a nd pus tul es . Mi cros copi c exa mi na ti on of a s ta i ned s mea r of ma teri a l obta i ned from a pus tul e s howed s tructures tha t coul d be des cri bed a s thos e s ta i ned red or da rk i n the peri odi c a ci d Schi ff s ta i ned ti s s ue s peci men bel ow. Thes e pus tul a r l es i ons a re mos t l i kel y a ttri buta bl e to i nfecti on wi th
(Courtesy of Dr. Libero Ajello; Public Health Image Library, Centers for Disease Control and Prevention; Atlanta, Georgia.) a . Blastomyces dermatitidis b. Candida albicans c. Cryptococcus s pp. d. Histoplasma capsulatum e. Penicillium marneffei 358. An 18-yea r-ol d whi te ma l e hi gh-s chool s tudent vi s i ts the fa mi l y phys i ci a n compl a i ni ng of a di ffus e, pa i nful ra s h extendi ng from hi s mi dthi gh to hi s na vel regi on. In recounti ng the hi s tory of the ra s h, he i ndi ca tes tha t one of hi s footba l l tea mma tes ga ve hi m topi ca l hydrocorti s one to trea t a mi nor groi n ra s h. A KOH s cra pi ng of the l es i on revea l s hya l i ne hypha e a nd a porti on of the s cra pi ng i s s ubmi tted for cul ture. A s chema ti c of the mi cros copi c obs erva ti on of the cul ture i s s hown bel ow. The mos t l i kel y eti ol ogy i s
(Reproduced, with permission, from Brooks GF et al. Ja wetz’s Medi ca l Mi crobi ol ogy. 22nd ed. New York: McGraw-Hill; 2001:536.) a . Epidermophyton floccosum b. Microsporum canis c. Trichophyton rubrum d. Trichophyton tonsurans 359. A 37-yea r-ol d ma l e pres ented wi th a l es i on on the l eft l eg. He reported recei vi ng a bra s i ons i n the a rea 3 or 4 months ea rl i er whi l e on tour i n Bra zi l . The l es i on wa s a pi nk, s mooth pa pul a r l es i on, whi ch he reported i tched. The l es i on wa s bi ops i ed a nd the cl i ni ca l pa thol ogy l a bora tory reported the pres ence of s hort, browni s h hypha l fra gments a nd s cl eroti c or Medl a r bodi es . The mos t l i kel y di a gnos i s for thi s pa ti ent i s a . Bl a s tomycos i s b. Chromobl a s tomycos i s c. La ca zi os i s d. Eumycetoma e. Sporotri chos i s 360. An 87-yea r-ol d ma n compl a i ned tha t hi s feet hurt when he put on s hoes beca us e of hi s toena i l s . Upon i ns pecti on s evera l toena i l s on both feet s howed yel l owi ng a nd thi ckeni ng. A s cra pi ng wa s obta i ned from one na i l a s wel l a s s ubungua l debri s a nd prepa red for cul ture a nd di rect exa mi na ti on wi th pota s s i um hydroxi de a nd Ca l cofl uor. Mi cros copi c exa mi na ti on s howed fl uores cent hypha e. The mos t l i kel y di a gnos i s i s a . Ti nea ca pi ti s b. Ti nea corpori s c. Ti nea ma nuum d. Ti nea pedi s e. Ti nea ungui um 361. A 55-yea r-ol d ma n from Mi s s i s s i ppi pres ented wi th a l es i on bel ow hi s l eft eye. Exa mi na ti on s howed a wel l -dema rca ted l es i on wi th a ra i s ed border, s ca l i ng, a nd pus tul es . He reported no pa i n. Ma teri a l from the edge of the l es i on wa s s ubmi tted for hi s topa thol ogy a nd cul ture. The pa thol ogy l a bora tory reported the pres ence of broa d-ba s ed buddi ng yea s t cel l s . The di a gnos i s for thi s pa ti ent i s a . Bl a s tomycos i s b. Chromomycos i s c. Pa ra cocci di oi domycos i s d. Peni ci l l i os i s e. Sporotri chos i s 362. A 47-yea r-ol d ma n from Ci nci nna ti , Ohi o, s us pected to ha ve communi ty-a cqui red pneumoni a wa s trea ted wi th a nti bi oti cs . When he fa i l ed to i mprove, hi s topl a s mos i s wa s cons i dered. Among the tes ts ordered were s erol ogy, di rect exa mi na ti on, a nd cul ture of i nduced s putum. In cul ture, the mi cros copi c morphol ogy mos t us eful i n i denti fi ca ti on of the eti ol ogi c a gent i s a . Arthroconi di a b. Mi croconi di a c. Scl eroti c bodi es d. Spherul es e. Tubercul a te ma croconi di a 363. A 25-yea r-ol d fema l e ha d s urgery for a crus h i njury to the ches t. She ha d a centra l venous ca theter, wa s i ntuba ted, a nd wa s on a mecha ni ca l venti l a tor. Three da ys pos ts urgery s he devel oped a fever a nd wa s trea ted empi ri ca l l y for ba cteri a l i nfecti on but fever pers i s ted. Fungemi a wa s s us pected a nd bl ood cul ture for fungi wa s ordered. Empi ri c a nti funga l thera py wa s i ni ti a ted a nd the centra l venous ca theter l i ne wa s removed. Remova l of the ca theter i s i ndi ca ted beca us e a . Of the s us pected pres ence of Aspergillus fumigatus bi ofi l m b. Of the s us pected pres ence of Candida albicans bi ofi l m c. Of the s us pected pres ence of Cryptococcus neoformans bi ofi l m
d. Of the s us pected pres ence of Aspergillus fumigatus pl a nktoni c orga ni s ms e. Of the s us pected pres ence of Candida albicans pl a nktoni c orga ni s ms f. Of the s us pected pres ence of Cryptococcus neoformans pl a nktoni c orga ni s ms 364. A 75-yea r-ol d Afri ca n Ameri ca n ma l e who ha d recentl y reti red to the Tucs on, Ari zona a rea from Ohi o, pres ented wi th hi s tory of cough, fever, a nd chi l l s for 3 weeks . Beca us e of the recent move a nd ethni ci ty, the pa ti ent wa s tes ted for cocci di oi domycos i s . Thi s i nfecti on i s i ni ti a ted fol l owi ng i nha l a ti on of s tructures bes t des cri bed a s a . Arthroconi di a b. Bl a s toconi di a c. Endos pores d. Spherul es e. Spora ngi os pores 365. A 4-yea r-chi l d devel ops ti nea corpori s (ri ngworm). The l es i ons cl ea r us i ng a prepa ra ti on for trea tment of a thl ete’s foot obta i ned from l oca l drug s tore. The l es i ons rea ppea r on the chi l d a nd a pl a yma te i n a few weeks . Internet res ea rch s ugges ted to the mother tha t the fa mi l y pet mi ght be the s ource of i nfecti on a nd s houl d be ta ken to a veteri na ri a n. If thi s i s the mode of tra ns mi s s i on, the eti ol ogy i s mos t l i kel y a . Epidermophyton floccosum b. Hortaea werneckii c. Malassezia s pp. d. Microsporum canis e. Trichosporon beigelii 366. A pa ti ent from a s ma l l Mi s s i s s i ppi town pres ented wi th a compl a i nt of s evera l weeks of producti ve cough, hemoptys i s , wei ght l os s , a nd ches t pa i n. Ra di ol ogi c fi ndi ngs were cons i s tent wi th a pul mona ry i nfi l tra te. Among the pos s i bl e di a gnos es , bl a s tomycos i s wa s cons i dered a nd cul ture for thi s orga ni s m wa s i ncl uded i n the orders for the cl i ni ca l l a bora tory. The s tructure di s ti ncti ve for i denti fi ca ti on i n mi cros copi c exa mi na ti on of a cul ture of the eti ol ogi c a gent i s a . Arthroconi di a b. Broa d-ba s ed buddi ng yea s t cel l s c. Enca ps ul a ted yea s t cel l s d. Mul ti pl y buddi ng yea s t cel l s e. Tubercul a te ma croconi di a 367. Candida albicans i s i s ol a ted i n bl ood cul ture from a pa ti ent i n a s urgi ca l i ntens i ve ca re uni t. Thi s mos t l i kel y s ource of the i nfecti ng orga ni s m i s a . A hea l th ca re worker b. A vi s i tor c. Ambi ent a i r d. The pa ti ent e. The s urgeon 368. A 30-yea r-ol d fema l e of the US mi l i ta ry wa s on a s s i gnment i n a s ubtropi ca l a rea . She reported to the phys i ci a n wi th a compl a i nt of pa tchy l i ght-col ored l es i ons on her ches t a nd upper a rms . She reported no other s ymptoms . Upon exa mi na ti on the l es i ons were i rregul a r a nd wel l dema rca ted. Incl uded i n the di fferenti a l di a gnos i s wa s pi tyri a s i s vers i col or. A s cra pi ng on a n a ffected a rea wa s obta i ned. If the di a gnos i s of pi tyri a s i s vers i col or i s correct, the bes t des cri pti on of wha t wi l l be obs erved i n a pos i ti ve s peci men i s a . Hya l i ne hypha e b. Hya l i ne hypha e a nd a rthroconi di a c. Dema ti a ceous hypha e d. Yea s t cel l s wi th broa d-ba s ed buds e. Yea s t cel l s a nd s hort hypha e 369. A 56-yea r-ol d ma n reti red from the mi l i ta ry to hi s hometown i n Wi s cons i n. Whi l e i n the mi l i ta ry he ha d been s ta ti oned i n s evera l s ta tes a nd s erved i n s evera l pa rts of the worl d i ncl udi ng South Ameri ca , Afri ca , Southea s t As i a , a nd mos t recentl y i n Ira q a nd Afgha ni s ta n. He compl a i ned to hi s phys i ci a n of a l es i on i ns i de hi s mouth on the l eft s i de. Hi s topa thol ogy of a bi ops y s peci men s ta i ned wi th methena mi ne s i l ver wa s s i mi l a r to tha t s hown bel ow. The mos t l i kel y di a gnos i s i s
(Courtesy of the Public Health Image Library, Centers for Disease Control and Prevention; Atlanta, Georgia.) a . Bl a s tomycos i s b. Ca ndi di a s i s c. Hi s topl a s mos i s d. Lei s hma ni a s i s e. Pa ra cocci di oi domycos i s 370. The overexpres s i on of drug effl ux pumps i n Candida albicans i s a n i mporta nt mecha ni s m i n reduced s us cepti bi l i ty to a . Azol e cl a s s drugs b. Echi noca ndi n cl a s s drugs c. Fl ucytos i ne d. Pol yene cl a s s drugs 371. A 28-yea r-ol d woma n experi enced va gi na l a nd vul va r i tchi ng, a s l i ghtl y wa tery di s cha rge a nd pa i n wi th i ntercours e. Her gynecol ogi s t performed phys i ca l exa mi na ti on of the vul va , va gi na , a nd cervi x. The va gi na l pH wa s es ti ma ted a s 4.4. Mi cros copi c exa mi na ti on wa s performed on s ome Gra m-s ta i ned di s cha rge ma teri a l . The obs erva ti on wa s s i mi l a r to bel ow. The mos t l i kel y di a gnos i s i s
(Courtesy of Dr. Stuart Brow; Public Health Image Library, Centers for Disease Control and Prevention; Atlanta, Georgia.) a . Ba cteri a l va gi nos i s b. Ca ndi di a s i s c. Chl a mydi a l va gi ni ti s d. Tri chomoni a s i s e. Vi ra l va gi ni ti s 372. A 53-yea r-ol d whi te woma n wi th end-s ta ge rena l di s ea s e recei ved a ki dney tra ns pl a nt a nd wa s ma i nta i ned on a n i mmunos uppres s i ve regi men. Three months l a ter s he ha d a fever (38.3°C) a nd wa s found to ha ve a cute rena l fa i l ure. Rena l tra ns pl a nt bi ops y wa s performed. Peri odi c a ci d-Schi ff s ta i ni ng of a bi ops y s ecti on s howed yea s t cel l s a nd hypha e. The mos t l i kel y di a gnos i s for thi s pa ti ent i s i nfecti on wi th a . Aspergillus fumigatus b. Candida albicans c. Candida glabrata d. Cryptococcus neoformans e. Rhizopus arrhizus (oryzae) 373. Amphoteri ci n B i s noted for both i ts a nti funga l effi ca cy a nd s i de effects when a dmi ni s tered to huma ns . The ba s i s for the s i de effects i s mos t l i kel y a . Bi ndi ng of drug to chol es terol b. Bi ndi ng of drug to ergos terol c. Bi ndi ng of drug to phos phol i pi ds d. Inhi bi ti on of chol es terol bi os ynthes i s e. Inhi bi ti on of ergos terol bi os ynthes i s 374. A funga l tel eomorph i s a . As exua l reproducti ve form b. Infecti ve form for huma ns c. Sexua l l y reproducti ve form d. Dorma nt form
Answers 335. The answer is a. (Brooks, pp 646-647. Levinson, pp 351-352. Murray, Ch 73. Ryan, pp 723-733, 743-746.) Aspergillus i s wi des prea d i n na ture a nd produces s ma l l coni di a tha t a re ea s i l y a eros ol i zed. Atopi c i ndi vi dua l s often devel op s evere a l l ergi c rea cti ons to the coni di a l a nti gens . In i mmunocompromi s ed pa ti ents , the coni di a ma y germi na te to produce hypha e tha t i nva de the l ungs a nd other ti s s ues . Progres s of di s ea s e ca n be ra pi d. A di a gnos i s of a s pergi l l os i s i s s upported by a ti s s ue bi ops y s howi ng i nva s i on by the orga ni s m a nd a pos i ti ve cul ture from a norma l l y s teri l e s i te. As pergi l l i ma y be a i rborne i n the envi ronment a nd be l a bora tory cul ture conta mi na nts or pres ent i n ora l l y obta i ned s a mpl es from pa ti ents wi thout a ppa rent cl i ni ca l i l l nes s a nd a t l ow ri s k for i nva s i ve a s pergi l l os i s a nd s uch fi ndi ng s houl d be i nterpreted wi th ca uti on. In ti s s ue Aspergillus s pp. (mos t commonl y A. fumigatus) ha ve s epta te hypha e 3 to 6 μm i n wi dth tha t a re des cri bed a s ha vi ng a cute a ngl e bra nchi ng. In bone ma rrow tra ns pl a nt pa ti ents i nfecti on ma y occur ea rl y a fter tra ns pl a nt or a fter s evera l months a s i n thi s ca s e. The other i nfecti ons ca n occur i n a compromi s ed hos t but woul d di ffer from wha t i s s hown. Pa rti cul a rl y, the s epta te hypha e a nd a cute a ngl e bra nchi ng a re not cons i s tent wi th a gents of mucormycos i s tha t ha ve wi de nons epta te hypha e. Histoplasma capsulatum, whi ch ca us es hi s topl a s mos i s i n huma ns , grows i n yea s t form i n the i nfected pers on. Norma l hea l thy i ndi vi dua l s ma y be i nfected; however, i n the i mmunocompromi s ed hos t the i nfecti on ca n be more s evere. 336. The answer is f. (Brooks, Ch 45. Levinson, Ch 47. Murray, Ch 69. Ryan, pp 707-710.) Ergos terol i s the ma jor s terol component of the funga l cel l membra ne whi l e chol es terol i s found i n ma mma l i a n membra nes (s ee ta bl e on the next pa ge). The di fference i s expl oi ted by ma jor a nti funga l drugs . Azol e (i mi da zol e a nd tri a zol e) cl a s s drugs , for exa mpl e mi cona zol e, fl ucona zol e, i tra cona zol e, a nd vori cona zol e, i nhi bi t a cytochrome P450dependent demethyl a s e (l a nos terol 14-α-demethyl a s e), whi ch i s i n the l a tter pa rt of the bi os yntheti c pa thwa y for ergos terol . Thi s pa thwa y i s a l s o i nhi bi ted a t a n ea rl i er s ta ge pri or to ri ng forma ti on by a l l yl a mi nes (Terbi na fi ne, na fti fi ne) a nd tol na fta te. Thes e drugs i nhi bi t s qua l ene-2,3epoxi da s e. The i nhi bi ti on of ergos terol producti on res ul ts i n a berra nt cel l membra ne. Pol yene cl a s s drugs , for exa mpl e a mphoteri ci n B, a l s o expl oi t ergos terol by bi ndi ng the s terol l ea di ng to cha nnel forma ti on i n the membra ne tha t a l l ows l ea ka ge of i ntra cel l ul a r cons ti tuents , for exa mpl e pota s s i um, a nd cel l dea th. 5-Fl uorocytos i ne (5FC, fl ucytos i ne) i s a pyri mi di ne a na l og tha t a fter convers i on to other compounds (5fl uoroura ci l , 5-fl uorodeoxyuri dyl i c a ci d, a nd 5-fl uorouri di ne) l ea ds to i nhi bi ti on of DNA s ynthes i s a nd RNA mi s codi ng. Echi noca ndi ns , for exa mpl e ca s pofungi n, i nhi bi t the s ynthes i s of 1,3-β-gl uca n wi th i nhi bi ti on of the gl uca n s ynthes i s enzyme compl ex. Gri s eoful vi n i s thought to i nhi bi t funga l growth by i ntera cti on wi th mi crotubul es res ul ti ng i n a berra nt mi tos i s a nd cel l di vi s i on.
337. The answer is c. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 73. Ryan, pp 739-742.) Cryptococcus neoformans i s the mos t common ca us e of meni ngi ti s i n AIDS pa ti ents . The frequency ha s decl i ned i n a rea s wi th robus t a nti retrovi ra l trea tment but ca n s ti l l occur i n pa ti ents recei vi ng trea tment. Pa ti ents i mmunocompromi s ed by other fa ctors , for exa mpl e ma i nta i ned on corti cos teroi ds , a re a l s o a t ri s k. The orga ni s m i s i nha l ed a s a des i cca ted, mi ni ma l l y enca ps ul a ted orga ni s m or perha ps a ba s i di os pore often a fter di s turba nce of s oi l ri ch i n a vi a n feces s uch a s pi geon gua no. The ca ps ul e ca n enl a rge upon rea chi ng the l ung. Ini ti a l pul mona ry i nfecti on ma y be a s ymptoma ti c a nd expos ure ma y occur ea rl y i n l i fe. Symptoma ti c i nfecti on ma y mi mi c a n i nfl uenza -l i ke res pi ra tory i nfecti on a nd res ol ve s ponta neous l y. Pa rti cul a rl y i n i mmunocompromi s ed pa ti ents the orga ni s m ma y mul ti pl y a nd di s s emi na te wi th a predi l ecti on for the CNS ca us i ng meni ngoencepha l i ti s . Thi s i s often the pres enti ng compl a i nt. The orga ni s m grows a s enca ps ul a ted yea s t tha t, i n cul ture a nd cerebros pi na l fl ui d, ma y be hi ghl i ghted by mounti ng i n Indi a i nk. Frequentl y, detecti on of ca ps ul a r pol ys a ccha ri de a nti gen i s us ed a s a di a gnos ti c tool . There a re commerci a l ki ts ba s ed on l a tex a ggl uti na ti on or enzyme i mmunoa s s a y tha t ca n be us ed to detect a nti gen i n s erum or cerebros pi na l fl ui d. 338. The answer is e. (Brooks, Ch 45. Levinson, Ch 48. Murray, Ch 70. Ryan, pp 713-718.) The l a rge ma jori ty of funga l cuta neous s ki n i nfecti ons a re due to derma tophytes . Thes e i nfecti ons ca n occur from hea d to toe a nd the i nfecti ons a re termed ti nea fol l owed by a des cri pti on of the s i te (s ee ta bl e on the precedi ng pa ge). Thes e i nfecti ons ha ve been ca l l ed ri ngworm, a mi s nomer from the mi s concepti on tha t the ca us e wa s a worm. However, tha t noti on i s perpetua ted i n the current termi nol ogy a s ti nea i s from the La ti n for a gna wi ng worm. The ca s e i s a cl a s s i c des cri pti on of ti nea
ca pi ti s tha t occurs pri ma ri l y i n chi l dren before puberty. There a re two forms of chi l dhood ti nea ca pi ti s . One ma ni fes ta ti on whos e eti ol ogy i s M. audouinii i s s ometi mes ca l l ed “gra y pa tch”. Over the pa s t deca des , thi s form ha s a l mos t di s a ppea red i n the USA a nd been repl a ced by the s econd form. The s econd ma ni fes ta ti on of chi l dhood ti nea ca pi ti s i s ca us ed by T. tonsurans a nd i s s ometi mes ca l l ed “bl a ck dot” beca us e of the “dot” vi s i bl e wi thi n the a rea of ha i r l os s where a ha i r s ha ft broke off l ea vi ng a s tump. Infecti ons a re pri ma ri l y s een i n chi l dren 3 to 9 yea rs of a ge, a l though s ome a dul ts ma y be a s ymptoma ti c ca rri ers . If not res ol ved by trea tment, the i nfecti on genera l l y res ol ves wi th puberty. Among i nner-ci ty chi l dren the preva l ence ma y be a s hi gh a s 8%. Both M. audouinii a nd T. tonsurans a re a nthropophi l i c derma tophytes . Mi cros copi c obs erva ti on of i nfected ha i rs s hows a rthroconi di a a round the ha i r s ha ft (ectothri x) wi th M. audouinii i nfecti on a nd i ns i de (endothri x) the ha i r s ha ft wi th T. tonsurans i nfecti on. Wood’s l i ght i s a devi ce tha t produces ul tra vi ol et l i ght ra ys . Ha i rs i nfected wi th M. audouinii fl uores ce wi th a yel l ow-green col or under Wood’s l i ght, whi l e T. tonsurans does not. Other s peci es ma y be more preva l ent i n other pa rts of the worl d a s the ca us e of i nfecti on.
339. The answer is a. (Brooks, Ch 45. Levinson, Ch 48. Murray, Ch 70. Ryan, pp 715-718.) Ti nea pedi s (a thl ete’s foot) i s ca us ed by derma tophytes . There a re s evera l eti ol ogi es of thi s i nfecti on (s ee ta bl e on the precedi ng pa ge). Derma tophytes a re a da pted to one of three na tura l ha bi ta ts : ma n (a nthropophi l i c derma tophytes ), a ni ma l s other tha n ma n (zoophi l i c derma tophytes ) a nd s oi l (geophi l i c derma tophytes ). Infecti ons wi th a nthropophi l i c derma tophytes tend to be mi l der, recurrent or chroni c, a nd l es s l i kel y to compl etel y res ol ve wi th topi ca l trea tment whi l e thos e wi th the other two ha bi ta ts tend to produce more i nfl a mma tory l es i ons tha t a re not recurrent a nd res pond wel l to trea tment. The pa ti ent, i n thi s i ns ta nce ha s recurrent epi s odes , whi ch i s us ua l l y a s s oci a ted wi th a nthropophi l i c s peci es of whi ch the mos t common i s Trichophyton rubrum. 340. The answer is a. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 73. Ryan, pp 740-742.) Cryptococcus neoformans occurs wi del y i n na ture, pa rti cul a rl y i n s oi l conta mi na ted wi th bi rd droppi ngs a nd i s frequentl y a s s oci a ted wi th pi geon gua no. The orga ni s m grows predomi na tel y i n the yea s t form a s a n enca ps ul a ted s tructure but a s a ba s i di omycete ma y form hypha e a nd produce s pores . Funga l s tructures ma y become des s i ca ted i n the envi ronment a nd s ma l l enough to be i nha l ed i nto the l ungs when ma teri a l conta i ni ng the orga ni s ms i s di s turbed. In the l ung, the ca ps ul e ca n enl a rge a nd enca ps ul a ted yea s t cel l s a re found i n ti s s ue. Lung i nfecti on i s often a s ymptoma ti c, pa rti cul a rl y i n a norma l hos t, but ca n res ul t i n pneumoni a . Meni ngi ti s occurs through di s s emi na ti on, pa rti cul a rl y i n i mmunos uppres s ed pa ti ents . Indi a i nk prepa ra ti ons of CSF revea l a buddi ng yea s t wi th a wi de, uns ta i ned ca ps ul e i n i nfected pers ons . A s econd s peci es , C. gattii, a l s o ca us es i nfecti ons . Thi s s peci es ha s a more l i mi ted geogra phi c di s tri buti on a nd i s not a s s oci a ted wi th bi rd gua no but wi th vegeta ti on, for exa mpl e red gum trees . In the Uni ted Sta tes , the orga ni s ms i s found on the wes t coa s t wi th recent i nfecti ons i n the Pa ci fi c Northwes t a nd i nfecti ons wi th thi s s peci es a re reporta bl e i n Oregon a nd Wa s hi ngton. Thi s s peci es tends to i nfect competent hos ts a nd CNS di s s emi na ti on i s mos t often s een a s a cryptococcoma . The di s ti ncti ve fea ture of Cryptococcus s pp. yea s t cel l s i s the ca ps ul e. Other orga ni s ms tha t a re found a s yea s t i n hos t ti s s ue ha ve other di s ti ngui s hi ng fea tures s uch a s the mul ti pl e buddi ng form of Paracoccidioides brasiliensis, the s ma l l i ntra cel l ul a r yea s t cel l s of Histoplasma capsulatum a nd broa d-ba s e buddi ng yea s t cel l s of Blastomyces dermatitidis. Aspergillus s pp. a nd a gents of mucormycos i s a re exa mpl es of fungi tha t prol i fera te a s hypha e i n ti s s ue. 341. The answer is d. (Brooks, Ch 45. Levinson, Ch 48. Murray, Ch 71. Ryan, pp 721-722.) Mycetoma i s a s l owl y progres s i ng di s ea s e of the s ubcuta neous ti s s ues tha t i s ca us ed by a va ri ety of fungi (eumycetoma or eumycoti c mycetoma ) or ba cteri a (a cti nomycetoma or a cti nomycoti c mycetoma ). The term Madura foot ha s been us ed to des cri be the foot l es i on. Whi l e mycetoma of ei ther funga l or ba cteri a l eti ol ogy i s progres s i ve over yea rs , eumycetoma progres s es more s l owl y tha n a cti nomycetoma . A l oca l i zed s wol l en l es i on begi ns to devel op a t the s i te of tra uma ti c i nocul a ti on, us ua l l y on the ha nd or foot. Les i ons conta i n s uppura ti ve a bs ces s es wi th s i nus es tha t dra i n the a bs ces s . Orga ni s ms coa l es ce i nto gra nul es or gra i ns . As i nfecti on a dva nces there i s s wel l i ng a nd di s torti on of the s i te of i nfecti on wi th s i nus tra cts wa xi ng a nd wa ni ng. In thi s ca s e, the i nfecti on ha s not rea ched the s ta ge of dra i ni ng s i nus tra cts . The a gents of a cti nomycetoma a l s o form fi l a ments . A di s ti ncti on between the two ma jor eti ol ogi c groups ca n be ma de by obs ervi ng the wi dth of the fi l a ments . Agents of a cti nomycetoma s ha ve fi l a ments 0.5 to 1 μm i n wi dth whi l e funga l hya phe a re grea ter tha n 1 μm. There a re mul ti pl e ba cteri a or fungi tha t ha ve been i s ol a ted from i nfecti on a nd s peci fi c eti ol ogy requi res cul ture i denti fi ca ti on. Al though s evera l fungi ha ve been i s ol a ted i n the Uni ted Sta tes from pers ons who ha ve mycetoma , Pseudallescheria boydii a ppea rs to be one of the mos t common. P. boydii i s the tel eomorph of Scedosporium apiospermum a nd Graphium eumorpum. In the other
s ubcuta neous funga l i nfecti ons , the orga ni s ms do not a ggrega te or coa l es ce i nto gra nul es a nd ha ve other fea tures tha t ma y be us eful i n es ta bl i s hi ng eti ol ogy of thos e i nfecti ons . 342. The answer is d. (Brooks, Ch 45. Levinson, Ch 49. Murray, Ch 72. Ryan, pp 743-746.) Al though pul mona ry funga l i nfecti ons i n the hea l thy hos t a re genera l l y a s ymptoma ti c to s ubcl i ni ca l , i n s ome i ndi vi dua l s they a re s ymptoma ti c (s ee ta bl e on the next pa ge). The degree a nd dura ti on ma y be rel a ted to expos ure or pos s i bl y s tra i n. The fungi a s s oci a ted wi th thes e i nfecti ons whi l e found to va ryi ng degrees worl dwi de ha ve endemi c a rea s . In the Uni ted Sta tes , Kentucky i s i n the endemi c a rea (hea vi es t a l ong the Mi s s i s s i ppi a nd Ohi o Ri vers ) for hi s topl a s mos i s , a n i nfecti on of Histoplasma capsulatum. Soi l wi th hi gh ni trogen content s uch a s tha t conta i ni ng bi rd or ba t gua no promotes growth of the orga ni s ms . Exca va ti on or a cti vi ty tha t di s turbs s oi l ca n a eros ol i ze orga ni s ms s o outdoor a cti vi ti es s uch a s cons tructi on work i ncrea s e the ri s k of expos ure. In i ts norma l ha bi ta t, the orga ni s m grows i n the mol d form produci ng both tubercul a te ma croconi di a a nd mi croconi di a . The former a re di s ti ncti ve s tructures i n cul ture i denti fi ca ti on a nd the l a ter a re s ma l l enough to be i nha l ed i nto the l ungs . Thi s i s the mos t common of the pul mona ry mycos es a nd more tha n 80% of i ndi vi dua l s i n the hi ghl y endemi c a rea ha ve evi dence of expos ure. Al though men a nd women a re equa l l y expos ed, men a re more l i kel y to get s ymptoma ti c di s ea s e tha n women (a bout 4:1). The pri ma ry pul mona ry i nfecti on ma y di s s emi na te. Exa mi na ti on a nd cul ture of s putum i s often nega ti ve i n pul mona ry i nfecti on. In the hos t, the orga ni s m converts to a yea s t growth form a nd ca n propa ga te i ntra cel l ul a rl y wi thi n ma cropha ge. The endemi c a rea for bl a s tomycos i s overl a ps tha t of hi s topl a s mos i s but i nfecti on i s much l es s common a nd i s not a s s oci a ted wi th demol i ti on a nd cons tructi on expos ure. In the Uni ted Sta tes , the endemi c a rea for cocci di oi domycos i s i s i n the des ert s outhwes t a l ong the border wi th Mexi co wi th hi gh endemi ci ty i n Ca l i forni a a nd Ari zona . The endemi c a rea of pa ra cocci di oi domycos i s i s i n pa rts of South Ameri ca . There i s a nother s peci es or va ri a nt of Histoplasma, Histoplasma duboisii. Thi s s peci es i s found i n s ome a rea s of Afri ca , a nd ha s a l a rger yea s t cel l i n the hos t, a nd i n i nfecti on, s ki n a nd s kel eton a re the orga ns mos t frequentl y a ffected.
343. The answer is d. (Brooks, Ch 45. Levinson, Ch 48. Murray, Ch 71. Ryan, pp 719-720.) Lymphocuta neous s porotri chos i s , ca us ed by S. schenckii, begi ns a t the s i te of i nocul a ti on, us ua l l y on a n extremi ty or the fa ce. The orga ni s m i s mos t often i s ol a ted from s oi l , pl a nts , or pl a nt products , for exa mpl e s tra w. Whi l e the i nfecti on i s gl oba l , i t i s more often reported from tropi ca l a nd s ubtropi ca l regi ons wi th a rea s of frequency, for exa mpl e Mexi co. Infecti on i s us ua l l y a s s oci a ted wi th tra uma ti c i nocul a ti on. Expos ure i s genera l l y occupa ti ona l or hobby. In the USA, the puncture i s often a s s oci a ted wi th ros e bus h thorns . Recentl y the pos s i bi l i ty of zoonoti c tra ns mi s s i on, pa rti cul a rl y from i nfected ca ts , ha s recei ved more a ttenti on. The i ni ti a l l es i on a ppea rs a t the s i te of puncture. The l es i on often ul cera tes a nd ma y devel op a ra i s ed erythema tous border. Addi ti ona l new l es i ons ma y a ppea r a l ong l ympha ti cs tha t dra i n the pri ma ry l es i on a bout 2 weeks a fter the pri ma ry l es i on. Extra cuta neous s porotri chos i s i s s een pri ma ri l y i n bones a nd joi nts . There i s no evi dence to s ugges t tha t a ny porta l of entry bes i des s ki n i s i mporta nt. The pri ma ry l es i on ma y become “fi xed”, ma y not s prea d, a nd ma y res embl e a ma l i gna nt proces s . S. schenckii i s a therma l l y di morphi c fungus growi ng a s a mol d i n i ts na tura l ha bi ta t a nd a s a yea s t i n i nfected ti s s ue. The orga ni s ms a re often s pa rs e i n ti s s ue compl i ca ti ng di rect exa mi na ti on. Other s peci es Blastomyces, Coccidioides, Histoplasma, a nd Paracoccidioides a re a l s o di morphi c but ra rel y ca us e pri ma ry cuta neous i nfecti on. Fonsecaea pedrosoi i s the mos t common ca us e of a nother s ubcuta neous mycos i s , chromomycos i s . Malassezia furfur i s a component of norma l s ki n fl ora tha t ma y ca us e s uperfi ci a l di s ea s e, pi tyri a s i s vers i col or whi l e Microsporum canis i s a zoophi l i c derma tophyte tha t ca n ca us e ti nea corpori s . Stachybotrys chartarum i n recent yea rs ha s been a s s oci a ted wi th growth on cel l ul os e-ri ch ma teri a l s i n wa ter da ma ged bui l di ngs . 344. The answer is a. (Brooks, p 626. Levinson, pp 342-343. Murray, pp 718-724.) The derma tophytes a re a group of fungi tha t i nfect onl y s uperfi ci a l kera ti ni zed ti s s ue (s ki n, ha i r, a nd na i l s ; s ee the ta bl e i n Ques ti on 338). Derma tophytes a re proba bl y res tri cted to nonvi a bl e s ki n beca us e mos t a re una bl e to grow a t 37°C or i n the pres ence of s erum. Such l es i ons a re a mong the mos t preva l ent i n the worl d. They a re not l i fe-threa teni ng, but ca n be pers i s tent a nd troubl es ome. The orga ni s ms form hypha e a nd a rthroconi di a i n s ki n (s ee the i ma ge a t the bottom of a ns wer to Ques ti on 374). In
ha i r, the hypha e a nd a rthoconi di a ma y be ei ther i ns i de (endothri x) or outs i de (ectothri x) the ha i r s ha ft. Infecti ons by derma tophyte a re termed ti nea fol l owed by the body s i te i nfected, for exa mpl e ti nea pedi s for i nfecti on of the foot. More tha n one s peci es ma y ca us e the s a me ma ni fes ta ti on. In cul ture, ma cros copi c (col or, texture, etc) obs erva ti on of col oni es a nd mi cros copi c (coni di a ) morphol ogy a nd nutri ti ona l requi rements ca n be us ed i n i denti fi ca ti on. The coni di a tha t a re formed a re genera l l y i ndi ca ti ve of one of the three genera of derma tophytes . Identi fi ca ti on of Microsporum s pp. i s a i ded by the a ppea ra nce of ma croconi di a , Trichophyton s pp. by mi croconi di a , a nd Epidermophyton floccosum by di s ti ncti ve ma croconi di a ma y s ometi mes des cri bed a s “bea ver ta i l ” (s ee Ques ti on 358). Ti nea pedi s , or a thl ete’s foot, i s the mos t common derma tophytos i s . The orga ni s m ma y be a cqui red from des qua ma ted epi thel i a l cel l s . Cl a s s i ca l l y, thi s occurs i n common ba thi ng a rea s us ed by groups of i ndi vi dua l s s uch a s a thl etes a nd s ha red us e of towel s . Among preventi on efforts i n a thl eti c fa ci l i ti es a re ma i nta i ni ng cl ea nl i nes s of s ha red fa ci l i ti es , da i l y wa s hi ng of towel s , educa ti on of a thl etes , a nd s ta ff on i nfecti on control for s ki n di s ea s es . 345. The answer is e. (Brooks, Ch 45. Levinson, Ch 50. Murray, pp 754-756. Ryan, pp 723-729.) Candida albicans i s the mos t i mporta nt s peci es of Candida a nd i s pa rt of the norma l fl ora of s ki n, mouth, GI tra ct, a nd va gi na . When hos t defens e i s compromi s ed i t ca n ca us e opportuni s ti c cuta neous a nd mucos a l i nfecti ons s uch a s thrus h (ps eudomembra nous ca ndi di a s i s ), va gi ni ti s , s ki n, a nd na i l i nfecti ons a s wel l a s ca ndi demi a a nd deep-s ea ted i nfecti on. As a commens a l , i t i s genera l l y i n the yea s t form whi l e l es i ons i n i nfecti on genera l l y s how the a ddi ti ona l pres ence of hypha e a nd ps eudohypha e. Ma teri a l from a ps eudomembra ne wi l l s how hos t cel l s , ba cteri a a nd ma s s of yea s t cel l s , ps eudohypha e, a nd hypha e. Si nce the orga ni s ms ca n be pres ent a s a commens a l , cul ture i s not a confi rma ti on of i nfecti on. The di a gnos i s i s ma de by cl i ni ca l pres enta ti on of the ps eudomembra ne a nd the mi cros copi c obs erva ti on. Thi s pa ti ent ha s two ri s k fa ctors for the devel opment of ps eudo-membra nous ca ndi di a s i s ; di s turba nce of the norma l ba cteri a l fl ora due to the us e of peni ci l l i n a nd di a betes . Candida i nfecti on ca n be trea ted wi th topi ca l nys ta ti n or cl otri ma zol e troches or ora l fl ucona zol e. Hypha e wi th a cute a ngl e bra nchi ng i s cha ra cteri s ti c of Aspergillus s pp., whi ch ma y be recovered i n s putum a s ma y s pherul es conta i ni ng endos pores found i n Coccidioides s pp. But nei ther a re a s s oci a ted wi th ora l ps eudomembra nous l es i ons . 346. The answer is d. (Brooks, Ch 45. Levinson, Ch 48. Murray, Ch 70. Ryan, Ch 44.) Ti nea ni gra i s a s uperfi ci a l i nfecti on of the s tra tum corneum tha t i s us ua l l y a s ol i ta ry l es i on on the pa l ms or s ol e tha t ma y ra nge i n col or from ta n to bl a ck. The l es i on i s chroni c a nd a s ymptoma ti c. The i nfecti on i s found mos t often i n tropi ca l cl i ma tes a nd coa s ta l regi ons i n chi l dren a nd young a dul ts wi th a grea ter i nci dence i n women. The eti ol ogy i s a dema ti a ceous fungus , Hortaea werneckii (previ ous l y Cladosporium, Exophiala, or Phaeoannellomyces werneckii). Dema ti a ceous (da rk-col ored) fungi produce mel a ni n found i n thei r cel l wa l l s . The mel a ni n i mpa rts a da rk col or to the orga ni s ms i n hos t ti s s ue a s wel l a s cul ture where col oni es ma y a ppea r da rk brown, green-brown, or bl a ck. Mi cros copi c exa mi na ti on of cul tured orga ni s ms s hows the pi gmenta ti on i n the orga ni s m. The da rk col ori za ti on of the l es i on i s from the fungus . The l es i on ma y gros s l y res embl e a ma l i gna nt mel a noma a nd more i nva s i ve procedures for thi s condi ti on ma y be a voi ded by exa mi na ti on of s ki n s cra pi ngs of the l es i on for funga l el ements . The i nfecti on res ponds to topi ca l trea tment wi th kera tol yti c s ol uti ons or a zol e a nti funga l drugs . Al though ti nea ma nuum i s a n i nfecti on of the ha nd by fungi , the eti ol ogy i s a derma tophyte. The other i nfecti ons , ti nea ca pi ti s , ti nea corpori s , a nd ti nea pedi s , a re a l s o i nfecti ons by derma tophytes a t other body s i tes (s ee the ta bl e i n Ques ti on 336). 347. The answer is a. (Brooks, Ch 45. Levinson, Ch 59. Murray, Ch 73. Ryan, Ch 44.) Funga l i nfecti ons a re potenti a l l y s eri ous i n a bone ma rrow tra ns pl a nt uni t (BMTU), Candida a nd Aspergillus a re the mos t common ca us es of i nfecti on i n BMT pa ti ents a nd both ha ve a ri s k of morta l i ty. However, the two di ffer i n tha t Candida i s a huma n commens a l a nd ca nnot be excl uded by cons tructi on pra cti ces a nd envi ronmenta l a i r moni tori ng. On the other ha nd, a s pergi l l i a re ubi qui tous i n the envi ronment. There a re i ns ta nces of mul ti pl e i nfecti ons i n new uni ts tha t ha ve not been moni tored pri or to openi ng or i n uni ts a dja cent to cons tructi on projects . Stri ct preca uti ons s houl d be ta ken to excl ude dus t a nd debri s from the BMTU a rea duri ng cons tructi on, but i n a ny event, the envi ronment s houl d be moni tored for a i rborne mi croorga ni s ms , es peci a l l y Aspergillus, pri or to openi ng the uni t. Zygomycetes ma y a l s o be pres ent i n the a i r but a re a l es s frequent ca us e of opportuni s ti c i nfecti on i n the BMT pa ti ent. Whi l e Penicillium orga ni s ms a re a l s o frequent i n a i r, the s peci es a s s oci a ted wi th opportuni s ti c i nfecti on, P. marneffei, i s endemi c i n Southea s t As i a where i t ca us es di s ea s e i n the AIDS pa ti ent. Pneumocystis jiroveci i s a n a nthropophi l i c orga ni s m wi th a huma n res ervoi r a nd, l i ke, Candida not excl uded by cons tructi on pra cti ces . Al though pa rti cul a rl y recogni zed for opportuni s ti c i nfecti on i n AIDS pa ti ents , other i mmunocompromi s ed pa ti ents ma y a l s o ha ve i nfecti on, i ncl udi ng the occa s i ona l BMT pa ti ent. 348. The answer is b. (Brooks, Ch 45. Levinson, Ch 49. Murray, Ch 72. Ryan, Ch 46.) Histoplasma capsulatum i s a therma l l y di morphi c fungus s oi l s a prophyte tha t i n the envi ronment or room tempera ture grows a s a mol d tha t produces two types of coni di a : tubercul a te ma croconi di a a nd mi cro-coni di a . Inha l a ti on of the mi croconi di a whi ch a re s ma l l enough to rea ch the l ungs , i ni ti a tes i nfecti on. Inha l ed mi croconi di a a re engul fed by ma cropha ges a nd devel op i nto yea s t forms . Mos t i nfecti ons rema i n a s ymptoma ti c; s ma l l gra nul oma tous foci hea l by ca l ci fi ca ti on. However, pneumoni a ca n occur. In ti s s ue, the yea s ts a re typi ca l l y s een wi thi n ma cropha ges s i nce the orga ni s m i s a fa cul ta ti ve i ntra cel l ul a r pa ra s i te. Arthros pores (a rthroconi di a ) res ul t from the fra gmenta ti on of hypha l cel l s . Coccidioides s pp. produce a rthroconi di a i n thei r na tura l ha bi ta t. In the i nfected hos t, thi s therma l l y di morphi c orga ni s m grows a s s pherul es produci ng endos pores . Another di morphi c fungus , Blastomyces dermatitidis, grows a s yea s t cel l s produci ng buds on a broa d ba s e i n the huma n hos t. Yea s t cel l s , hypha e, a nd ps eudohypha e a re a s s oci a ted wi th i nfecti ons of Candida albicans (s ee the ta bl e i n Ques ti on 342). 349. The answer is d. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 73. Ryan, Ch 45.) Thi s des cri pti on i s a typi ca l pi cture of mucormycos i s (a l s o ha s been ca l l ed zygomycos i s ) occurri ng i n a di a beti c pa ti ent. Eti ol ogi c a gents of the genera Rhizopus, Mucor, Lichtheimia (former Absidia), Rhizomucor, a nd others bel ong to the order Mucora l es . Thes e orga ni s m ha ve wi de (10-15 μm), uneven thi cknes s , a nd i rregul a r bra nchi ng hypha e tha t a re a s epta te or ha ve ra re s epta ti on. Hypha e ma y be s pa rs e i n i nfected ti s s ue. The orga ni s ms do not conta i n mel a ni n a nd a re not dema ti a ceous . Hortaea werneckii, eti ol ogi c a gent of ti nea ni gra , ha s dema ti a ceous hypha e i n ti s s ue. In s ki n s ome of the hya l i ne hypha e of derma tophytes ma y ha ve a rthroconi di a . Among opportuni s ti c mol ds , Aspergillus s pp. ha ve s epta te a cute a ngl e bra nchi ng i n ti s s ue. Orga ni s ms tha t grow i n yea s t forms i n the hos t i ncl ude Histoplasma a nd Blastomyces whi l e C. albicans genera l l y ha s both yea s t cel l s , hypha e, a nd ps eudohypha e i n l es i ons . Funga l hypha e a re genera l l y grea ter tha n 1 μm whi l e na rrow fi l a ments a re a s s oci a te wi th ba cteri a s uch a s Nocardia s pp. 350. The answer is d. (Brooks, Ch 45. Levinson, Ch 49. Murray, Ch 72. Ryan, Ch 46.) Cocci di oi domycos i s i s a pri ma ry pul mona ry i nfecti on whi ch i s a s ymptoma ti c or s ubcl i ni ca l i n a bout 60% of i nfected i ndi vi dua l s a nd i s i ni ti a ted from i nha l a ti on of a rthroconi di a (a rthros pores ) (s ee the ta bl e i n Ques ti on 342). Cocci di oi domycos i s i s endemi c to the des s ert s outhwes t, pa rts of Mexi co, a nd Centra l a nd South Ameri ca . There a re two s peci es wi th C. immitis concentra ted i n Ca l i forni a a nd C. posadasii el s ewhere. The i nfecti on i s the s a me rega rdl es s of s peci es . The orga ni s m grows a s a mol d i n s oi l . Some hypha e gi ve ri s e to a rthroconi di a , whi ch a re produced i n a l terna ti ng cel l s . When the di s junctor cel l s s epa ra ti ng the a rthroconi di a l ys e, the ba rrel -s ha ped a rthroconi di a a re rel ea s ed. Thes e coni di a ca n be a eros ol i zed when the s oi l i s di s turbed. Subcuta neous funga l i nfecti ons s uch a s s porotri chos i s a re i ni ti a ted by tra uma ti c i mpl a nta ti on. Some i ndi vi dua l s wi th cocci di oi domycos i s ha ve fa ctors tha t i ncrea s e the ri s k of di s s emi na ti on a nd extra pul mona ry i nfecti on. The mos t common s i te of di s s emi na ti on i s the s ki n. However, thes e s ki n l es i ons a re not i ni ti a ted by cuta neous conta ct or i mpl a nta ti on but di s s emi na ti on from the ori gi na l pri ma ry pul mona ry i nfecti on. 351. The answer is c. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 73. Ryan, Ch 45.) Aspergillus ca n ca us e a va ri ety of hos t i nfecti ons or res pons es . In
i mmunocompromi s ed pers ons , i nva s i ve di s ea s e i s the concern. Bl ood ves s el i nva s i on ca n res ul t i n thrombos i s a nd i nfa rcti on. Infecti on ca n progres s ra pi dl y a nd ma y di s s emi na te. Inva s i ve pul mona ry i nfecti on i s a s s oci a ted wi th morta l i ty ri s k. The orga ni s m ca n i nfect wounds , for exa mpl e burn wounds , cornea fol l owi ng tra uma , or s urgery. In pul mona ry ca vi ti es (from preexi s ti ng condi ti ons , eg, tubercul os i s , hi s topl a s mos i s ), “fungus ba l l ” forma ti on ca n occur, whi ch ca n be s een on x-ra y. Infecti on of the bronchi ca n res ul t i n a l l ergi c bronchopul mona ry a s pergi l l os i s , cha ra cteri zed by a s thma ti c s ymptoms . Otomycos i s i s typi ca l l y due to A. niger a nd i s a s uperfi ci a l col oni za ti on wi th cl i ni ca l fea tures s i mi l a r to other ca us es of externa l oti ti s . 352. The answer is a. (Brooks, Ch 45. Levinson, Ch 49. Murray, Ch 72. Ryan, pp 749-753.) Mos t i ndi vi dua l s i nfected wi th Coccidioides s pp. ha ve a s ymptoma ti c or s ubcl i ni ca l i nfecti ons . Onl y a bout 40% ha ve s ymptoma ti c pri ma ry pul mona ry di s ea s e. In a s ma l l fra cti on of thes e i ndi vi dua l s (a bout 5% of s ymptoma ti c i ndi vi dua l s ), the orga ni s m ma y di s s emi na te a nd ca us e extra pul mona ry di s ea s e. The ri s k of di s s emi na ti on i s grea ter a mong s ome popul a ti on groups tha n others . Thos e a t i ncrea s ed ri s k i ncl ude i nfa nts a nd el derl y, men, da rk-s ki nned i ndi vi dua l s , for exa mpl e Fi l i pi nos , Afri ca n Ameri ca ns , a nd i mmunocompromi s ed i ndi vi dua l s i ncl udi ng AIDS pa ti ents , a nd pregna nt women. Women i n the thi rd tri mes ter or i mmedi a te pos tpa rtum peri od a re a t very hi gh ri s k of di s s emi na ti on a nd dea th. Si nce the i nfecti on i s s el f-l i mi ti ng, i n i ndi vi dua l s wi thout ri s k fa ctors , a nti funga l thera py i s not i ndi ca ted a l though s upporti ve thera py for s ymptoms ma y be offered. Thos e wi th ri s k fa ctors or s evere pri ma ry di s ea s e genera l l y meri t trea tment to reduce ri s k of di s s emi na ti on. Women i n the thi rd tri mes ter requi re trea tment. Amphoteri ci n B a nd fl ucona zol e a re us ua l l y cons i dered. Reports tha t s evera l a zol es pos s es s tera togeni c potenti a l pa rti cul a rl y ea rl y i n pregna ncy s ugges t tha t a zol es s houl d be us ed wi th ca re i n pregna nt women. A recent s et of recommenda ti ons s ugges t a mphoteri ci n B duri ng the fi rs t tri mes ter a nd a zol es l a ter (Bercovi tch et a l . Clin. Infect Dis 2011;53(4):353–368.) 353. The answer is c. (Brooks, Ch. 45. Levinson, Ch. 50, 52. Murray, Ch. 73, Ryan, Ch. 45.) Pneumocystis jiroveci ca us es a n i nters ti ti a l pneumoni a i n i mmunocompromi s ed pa ti ents a nd s everel y ma l nouri s hed i nfa nts . The i nfecti on beca me more promi nent wi th the AIDS epi demi c a s a n AIDSdefi ni ng opportuni s ti c i nfecti on i n the Uni ted Sta tes . Wi th current trea tment s tra tegi es for HIV/AIDS a nd prophyl a xi s , there ha s been a decrea s e i n thos e wi th a cces s to trea tment. However, i t rema i ns a l ea di ng ca us e of i nfecti on i n thos e wi thout a cces s , who do not tol era te trea tment, or who do not know of thei r HIV i nfecti on. Pa ti ents wi thout HIV i nfecti on now a ccount for the ma jori ty of ca s es i n the devel oped worl d. Thes e non-HIV i mmunocompromi s ed pa ti ents i ncl ude thos e wi th hema tol ogi c ma l i gna nci es a nd orga n tra ns pl a nts . Trea tment-rel a ted ri s k fa ctors for thes e pa ti ents i ncl ude s teroi d a nd cytotoxi c thera py. P. jiroveci (formerl y P. carinii) wa s ori gi na l l y cl a s s i fi ed a s a protozoa n but ha s been recl a s s i fi ed i n the funga l ki ngdom for ma ny yea rs . It i s not a typi ca l fungus a s i t l a cks ergos terol i n the pl a s ma membra ne, a nd thus a nti funga l drugs tha t ta rget ergos terol or i ts bi os ynthes i s a re not effecti ve. The orga ni s ms ha ve not been ma i nta i ned i n cul ture a nd di a gnos i s depends on obs ervi ng the orga ni s m i n cl i ni ca l s peci mens . The na mes of the forms tha t s eem to be mos t commonl y us ed s ti l l refl ect the former protozoa n des i gna ti on. Thes e a re va ri ous l y des cri bed a s free trophi c forms or trophozoi tes , whi ch a re ha pl oi d, a nd the di pl oi d cys t tha t when ma ture ma y conta i n up to ei ght s pores or i ntra cys ti c bodi es . Pneumocystis i s found i n huma ns a nd a va ri ety of ma mma l s a nd ea ch funga l s peci es a ppea rs to ha ve hos t s peci fi ci ty s o the P. jiroveci i s i s ol a ted from huma ns a nd P. carinii from ra ts . Al though the s peci es i nfecti ng huma ns i s now des i gna ted P. jiroveci, the na me PCP (P. carinii pneumoni a ) ha s been reta i ned by ma ny for conveni ence. In AIDS pa ti ents , the ons et of s ymptoms ma y be s ubtl e wi th progres s i on whi l e i n other i mmunocompromi s ed pa ti ents the ons et ma y be a cute. 354 and 355. The answers are 354-c and 355-e. (Brooks, Ch 45. Levinson, Ch 47. Murray, Ch 69. Ryan, Ch 43.) See the a ns wer for Ques ti on 336 a nd the bel ow ta bl e). Severa l mecha ni s ms of res i s ta nce to a nti funga l drugs ha ve been i denti fi ed. Thes e i ncl ude a l tera ti ons i n the drug ta rget by muta ti on or overexpres s i on, drug effl ux pumps , cha nges i n ergos terol or s terol content, a nd cha nges i n upta ke a nd meta bol i s m. Al tera ti on of the drug ei ther through modi fi ca ti on or degra da ti on to i na cti ve moi eti es ha s not been reported. Res i s ta nce to tol na fta te a nd a l l yl a mi nes tha t i nhi bi t s qua l ene epoxi da s e i s not common but l i kel y mecha ni s ms i ncl ude effl ux pumps , muta ti on or overexpres s i on of the enzyme a nd nons peci fi c s tres s a da pta ti on. Res i s ta nce to fl ucytos i ne ma y occur vi a a l tera ti on of the permea s e tha t reduces entry i nto the funga l cel l or a t enzyma ti c s teps , cytos i ne dea mi na s e or ura ci l phos phori bos yl tra ns fera s e, i nvol ved i n meta bol i s m of the drug to the a cti ve compounds . Res i s ta nce to a zol e cl a s s drugs ma y devel op through expres s i on of drug effl ux pumps a nd a l tera ti on or over-expres s i on of the drug ta rget. In s ome res i s ta nt i s ol a tes , more tha n one mecha ni s m ma y be opera ti ve. Res i s ta nce to pol yenes ma y refl ect a decrea s e i n ergos terol content of the membra ne or producti on of other non-pol yene bi ndi ng s terol s . 356. The answer is e. (Brooks, Ch 45. Levinson, Ch 47. Murray, Ch 69. Ryan, Ch 43.) See the a ns wer to Ques ti on 336 a nd the ta bl e i n tha t ques ti on. Ergos terol i n the funga l cel l membra ne i s expl oi ted by s evera l drug cl a s s es . The s qua l ene epoxi da s e i s i nhi bi ted by both tol na fta te a nd a l l yl a mi nes . A l a ter s tep i n the pa thwa y, a cytochrome P450 enzyme 14-α-demethyl a s e i s i nhi bi ted by a zol e (i mi da zol e, tri a zol e) cl a s s drugs . Di s rupti on of ergos terol bi os ynthes i s res ul ts i n a berra nt cel l membra nes . Amphoteri ci n B ta rgets ergos terol by bi ndi ng to the s terol . 357. The answer is e. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 72.) Penicillium marneffei i s a di morphi c fungus tha t ca us es opportuni s ti c di s s emi na ted peni ci l l i os i s tha t devel ops fol l owi ng i nha l a ti on of coni di a (s ee the ta bl e i n Ques ti on 342). Infecti on i s pri ma ri l y s een i n HIV-i nfected i ndi vi dua l s , a l though i t i s a l s o reported i n other i mmunocompromi s ed hos ts . The orga ni s m i s endemi c i n Southea s t As i a (eg, Tha i l a nd, s outhern Chi na , Vi et Na m, a porti on of Indi a ) a nd i s a s s oci a ted wi th ba mboo ra ts . A few i mported ca s es ha ve been reported el s ewhere i n pa ti ents wi th a tra vel hi s tory to the endemi c regi on. A ma jori ty of pa ti ents ha ve di s s emi na ti on to the s ki n wi th ra s hes , pa pul es , a nd pus tul es tha t a re often l oca ted on the fa ce. In the envi ronment a nd cul ture a t envi ronmenta l tempera ture the orga ni s m grows a s a mol d wi th typi ca l Penicillium morphol ogy a nd produces a red di ffus i bl e pi gment. In the hos t, the orga ni s m grows a s a fi s s i on yea s t unl i ke other i nfecti ous fungi wi th a yea s t form tha t grow by buddi ng. Mi cros copi c detecti on of the fi s s i on yea s t i n cl i ni ca l s peci mens s uch a s s mea rs from s ki n l es i ons i s di a gnos ti c. 358. The answer is a. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 70. Ryan, Ch 45.) The pres ence of hya l i ne hypha e s upports a di a gnos i s of a derma tophyte i nfecti on (s ee the ta bl e i n Ques ti on 336). Derma tophyte i nfecti ons ma y be exa cerba ted by the us e of topi ca l s teroi ds . Wi th s uch expos ure the i nfecti on ma y not gi ve the typi ca l pi cture a nd ma y be ca l l ed ti nea i ncogni to. Thi s i nfecti on s ta rted i n the groi n regi on where s uch i nfecti ons a re known a s ti nea cruri s or jock i tch. Derma tophytes a re i denti fi ed i n cul ture by the ma cros copi c morphol ogy of the col ony a nd the mi cros copi c morphol ogy of a s exua l producti on of coni di a . Both ma croconi di a a nd mi croconi di a ma y be produced but one i s more a bunda nt a nd us ed i n i denti fi ca ti on whi l e the other i s ra re. Trichophyton s peci es produce numerous mi croconi di a whos e a ppea ra nce a nd l oca ti on a re us eful i n thei r i denti fi ca ti on. Microsporum s peci es (except M. audouinii) produce ma croconi di a tha t a re borne s i ngl y a nd tha t ha ve di s ti ncti ve s ha pes a nd rough wa l l s . Epidermophyton floccosum produces onl y ma croconi di a . Thes e a re us ua l l y produced i n cl us ters a nd ha ve a di s ti ncti ve cl a va te s ha pe s ometi mes des cri bed a s “bea ver-ta i l ”. The s chema ti c s hows cl a va te ma croconi di a wi th thi s s ha pe, whi ch i s cons i s tent wi th E. floccosum. 359. The answer is b. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 71. Ryan, Ch 44.) Chromobl a s tomycos i s a l s o ca l l ed chromomycos i s i s a s ubcuta neous funga l i nfecti on i n whi ch the eti ol ogi c a gent ga i ns entry to the hos t through tra uma ti c i mpl a nta ti on or i nocul a ti on. The recogni zed a gents of thi s i nfecti on i ncl ude Phialophora verrucosa, Fonsecaea pedrosoi, Rhinocladiella aquaspersa, F. compacta, a nd Cladophialophora carrionii. The a gents of thi s i nfecti on, a s i ndi ca ted by the term “chromo,” a re a l l dema ti a ceous fungi tha t ha ve pi gmented cel l wa l l s due to the pres ence of mel a ni n. The orga ni s m i s a l s o pi gmented i n ti s s ue hence the pres ence of pi gmented funga l s tructures . The cha ra cteri s ti c fea ture i s the pres ence of muri form
cel l s known a s s cl eroti c cel l s or Medl a r bodi es , whi ch a re thi ck-wa l l ed s epta ted cel l s . The i nfecti on occurs ma i nl y i n the tropi cs a nd i n ma l es a nd more often on l egs tha n on the upper body. The i nfecti on devel ops s l owl y a nd ma y ha ve a hi s tory of ma ny yea rs devel opment. In thi s ca s e, the i nfecti on i s i n a n ea rl y s ta ge. When i nfecti on devel ops over a l onger peri od, the l es i on ma y become verrucous a nd wa rty a nd devel op ca ul i fl owerl i ke l es i ons , whi ch proba bl y s prea d by a utoi nocul a ti on or l oca l l ympha ti c s prea d. Bl a s tomycos i s i s i ni ti a ted a s pri ma ry pul mona ry i nfecti on tha t ma y di s s emi na te, wi th s ki n l es i ons bei ng the mos t common extra pul mona ry ma ni fes ta ti on. Blastomyces dermatitidis i s a therma l l y di morphi c fungus tha t i n ti s s ue i s found i n the yea s t form wi th cel l s tha t ha ve a broa d ba s e between mother a nd da ughter cel l . La ca zi os i s (l obomycos i s ) i s a s ubcuta neous mycos i s ca us ed by Lacazia loboi (formerl y Loboa loboi) tha t i s found pri ma ri l y i n South a nd Centra l Ameri ca n tropi cs . The i nfecti on i s cha ra cteri zed by s l owl y devel opi ng nodul es tha t va ry i n s i ze, s ha pe, a nd a ppea ra nce, tha t ma y s prea d by a utoi nocul a ti on, a nd tha t progres s over deca des . In ti s s ue the orga ni s ms a re found a s l a rge, thi ck-wa l l ed yea s t cel l s tha t ma y a ppea r a s a cha i n of cel l s wi th na rrow bri dges . The orga ni s m ha s not been cul tured. The i nfecti on i s a l s o found i n dol phi ns a nd a n a qua ti c ha bi ta t i s pos tul a ted. Eumycetoma i s a nother s l owdevel opi ng s ubcuta neous funga l i nfecti on, frequentl y found on the l egs or feet. The i nfecti on i s more common i n tropi ca l a rea s a nd i s pres ent a t hi gher frequency i n s ome a rea s s uch a s Indi a , Afri ca , a nd La ti n Ameri ca . A number of funga l a gents ha ve been i denti fi ed, ma ny of them dema ti a ceous . There i s l oca l i zed s wel l i ng a nd a bs ces s forma ti on a nd dra i ni ng s i nus es . In ti s s ue the orga ni s ms a re found a s gra nul es tha t conta i n s epta te hypha e tha t ma y be di s torted a t the peri phery. Gra nul es ma y a l s o be found i n s i nus tra ct exuda te. A s i mi l a r di s ea s e ma y ha ve a ba cteri a l eti ol ogy known a s a cti nomycetoma wi th gra nul es tha t a l s o conta i n fi l a ments tha t a re na rrower tha n funga l hypha e. Mycetoma i s a term tha t covers both funga l a nd ba cteri a l eti ol ogy. Sporotri chos i s i s yet a nother s ubcuta neous mycos i s tha t, l i ke the others , i s i ni ti a ted by tra uma ti c i mpl a nta ti on. The i ni ti a l l es i on a ppea rs a t the s i te of tra uma , a nd wi th di s ea s e devel opment a ddi ti ona l l es i ons ma y a ppea r a l ong the l ympha ti c dra i ni ng the regi on (s ee the a ns wer to 343). In ti s s ue, the orga ni s m i s a buddi ng yea s t tha t i s s ometi mes des cri bed a s ci ga r-s ha ped a nd there ma y be few pres ent i n a s peci men. 360. The answer is e. (Brooks, Ch 45. Levinson, Ch 48. Murray, Ch 70. Ryan, Ch 44.) Onychomycos i s i s the mos t common na i l di s ea s e i n a dul ts a nd the ma jori ty a re a ttri buted to derma tophytes a nd ca l l ed ti nea ungui um (s ee the ta bl e i n Ques ti on 338). Trea tment for ti nea ungui um i s prol onged. Wi thout determi ni ng a funga l eti ol ogy, there ma y be expens i ve, i neffecti ve trea tment, a nd unneces s a ry drug expos ure. The other i nfecti ons a re a l s o derma tophyte i nfecti ons a t other body s i tes . 361. The answer is a. (Brooks, Ch 45. Levinson, Ch 49. Murray, Ch 72. Ryan, Ch 46.) Bl a s tomycos i s i s a pri ma ry pul mona ry i nfecti on tha t i s frequentl y a s ymptoma ti c or s ubcl i ni ca l a s a re the other i nfecti ons , cocci di oi domycos i s , hi s topl a s mos i s , a nd pa ra cocci di oi domycos i s , wi th s ys temi c di morphi c pa thogens (s ee the ta bl e i n Ques ti on 342). Infecti on ma y di s s emi na te hema togenous l y wi th a bout two-thi rds of extra pul mona ry bl a s tomycos i s ca s es i nvol vi ng s ki n a nd bones . Pul mona ry s ymptoms ma y not be pres ent i n di s s emi na ted di s ea s e. Infecti on i s endemi c i n North Ameri ca borderi ng the Mi s s i s s i ppi a nd Ohi o Ri ver ba s i ns , the Mi dwes t a nd Ca na di a n provi nces a round Grea t La kes a nd St. La wrence Ri ver, a nd i n the Southea s t. Blastomyces dermatitidis i s a di morphi c fungus growi ng a s mol d i n i ts norma l ha bi ta t. The ha bi ta t ha s not been wel l cha ra cteri zed but ma y wel l i nvol ve pa tches of moi s t s oi l wi th a bunda nce of orga ni c ma teri a l . The coni di a of the envi ronmenta l form a re nondes cri pt. They ma y be i nha l ed when the ha bi ta t i s di s turbed a nd i ni ti a te i nfecti on. The i nha l ed orga ni s m converts to a yea s t pha s e, cha ra cteri zed by a broa d ba s e between mother a nd bud. The obs erva ti on of thes e di s ti ncti ve s tructures i n a cl i ni ca l s peci men i s a ba s i s for di a gnos i s tha t s houl d be confi rmed by cul ture. 362. The answer is e. (Brooks, Ch 45. Levinson, Ch 49. Murray, Ch 72. Ryan, Ch 46.) In hi s topl a s mos i s , i nha l ed H. capsulatum coni di a devel op i nto yea s t cel l s , whi ch a re engul fed by a l veol a r ma cropha ges (s ee the ta bl e i n Ques ti on 342). The yea s t cel l s ca n repl i ca te i ntra cel l ul a rl y. Thes e ma y gi ve ri s e to i nfl a mma tory rea cti ons tha t become gra nul oma tous . In cul ture a t 25°C, H. capsulatum devel ops hypha e wi th mi croconi di a a nd l a rge, s pheri ca l ma croconi di a wi th peri phera l projecti ons of cel l wa l l ma teri a l s . The ma croconi di a a re a l s o ca l l ed tubercul a te ma croconi di a . The ma croconi di a a re us eful i n cul ture i denti fi ca ti on, whi l e the mi croconi di a a re s ma l l enough to be i nha l ed to i ni ti a te i nfecti on. Arthroconi di a (a rthros pores ) res ul t from the fra gmenta ti on of hypha l cel l s of Coccidioides s pp. Spherul es res ul t when a rthroconi di a a re i nha l ed a nd enl a rge i nto l a rger bodi es tha t conta i n endos pores . Spherul es ca n be produced i n the l a bora tory us i ng a compl ex medi um. Scl eroti c bodi es a re found i n chromobl a s tomycos i s i nfecti ons . The a gents of chromobl a s tomycos i s res i de i n s oi l a nd vegeta ti on a nd ma y ca us e i nfecti ons when i ntroduced i nto s ubcuta neous ti s s ue. In ti s s ue, the fungi a ppea r a s s pheri ca l brown cel l s termed muni form or s cl eroti c bodi es tha t di vi de by tra ns vers e s epa ra ti on. Sepa ra ti on i n di fferent pl a nes ma y gi ve ri s e to a cl us ter of 4 to 8 cel l s . 363. The answer is b. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 73. Ryan, Ch 45.) Candida albicans i s a component of norma l mi crobi a l fl ora of the s ki n a nd mucos a l s urfa ces . Candida ma y rea ch the bl ood s trea m by tra ns l oca ti on from the gut or more often vi a ca theters . Ca ndi demi a ha s a hi gh a ttri buta bl e morta l i ty, a nd once i n the bl ood the fungus ca n ca us e i nfecti on i n a ny orga n. Va s cul a r ca theters a re a n es ta bl i s hed ri s k fa ctor for i nfecti on. Endogenous orga ni s ms or occa s i ona l l y exogenous orga ni s ms (eg, from s ki n of hea l th ca re worker) rea ch the l umen of the ca theter a nd a bi ofi l m devel ops . Whi l e pl a nktoni c orga ni s ms a re orga ni s ms l i vi ng a l one, a bi ofi l m i s a communi ty of orga ni s ms a tta ched to a s urfa ce a nd s urrounded by a n extra cel l ul a r ma tri x of i ts own producti on. Bi ofi l ms ma y ha ve a compl ex s peci es compos i ti on, for exa mpl e tooth pl a que, or be compos ed of a s i ngl e s peci es . As bi ofi l ms ma ture, pl a nktoni c orga ni s ms a re rel ea s ed, a nd i n the ca s e of ca theter bi ofi l ms , the rel ea s ed orga ni s ms conti nuous l y i nocul a te the bl ood. Orga ni s ms i n bi ofi l ms a cqui re new phenotypi c properti es . One of the properti es i s reduced s us cepti bi l i ty to a nti funga l drugs (or a nti ba cteri a l drugs i n the ca s e of ba cteri a ). Drug concentra ti ons tha t a re effecti ve a ga i ns t pl a nktoni c orga ni s ms a re i neffecti ve a ga i ns t bi ofi l ms . Cons equentl y, a pa ti ent ma y recei ve a thera peuti c drug dos e tha t a cts s ucces s ful l y a ga i ns t pl a nktoni c orga ni s ms i n ci rcul a ti on or ti s s ue but i s not effecti ve a ga i ns t the bi ofi l m orga ni s ms . Bi ofi l ms ca n conti nue to rel ea s e pl a nktoni c orga ni s ms to i nfect s urroundi ng ti s s ue or bl ood. As noted, the s ource of bl ood s trea m i nfecti on ma y be i nocul a ti on from a bi ofi l m i n the ca theter. Therefore, the ca theter i s removed to el i mi na te a potenti a l s ource of i nfecti on. Whi l e Aspergillus a nd Cryptococcus, a s wel l a s s ome other fungi ca n form bi ofi l ms on devi ces , the reports a re s ti l l few a nd fungemi a i s uncommon. Candida i s the mos t common ca us e of funga l bi ofi l m-rel a ted i nfecti on a nd ra nks hi gh on the l i s t of ca us es of nos ocomi a l bl oods trea m i nfecti on. 364. The answer is a. (Brooks, Ch 45. Levinson, Ch 49. Murray, Ch 72. Ryan, Ch 46.) Cocci di oi domycos i s (a l s o known a s Va l l ey fever) i s ca us ed by C. immitis or C. posadasii (s ee the ta bl e i n Ques ti on 342). The i nfecti on i s endemi c i n the s emi a ri d regi ons of the s outhwes tern Uni ted Sta tes , a s wel l a s Centra l a nd South Ameri ca . Mos t C. immitis i s ol a tes a re from Ca l i forni a whi l e C. posadasii ha s been found el s ewhere. The s peci es ha ve few phenotypi c di fferences a nd cl i ni ca l ma ni fes ta ti ons a ppea r the s a me. Hypha e form cha i ns of a rthroconi di a (a rthros pores ), whi ch often devel op i n a l terna te cel l s of a hypha . Indi vi dua l a rthroconi di a a re rel ea s ed from cha i ns , become a i rborne, a nd a re res i s ta nt to ha rs h envi ronmenta l condi ti ons . Fol l owi ng i nha l a ti on, a rthroconi di a become s pheri ca l , enl a rge formi ng s pherul es tha t conta i n endos pores . Such s pherul es ha ve a thi ck, refra cti ve cel l wa l l a nd a re di a gnos ti c of Coccidioides s pp. Bl a s tos pores repres ent coni di a l forma ti on through a buddi ng proces s , a s s een i n yea s t. Spora ngi os pores a re a s exua l s tructures cha ra cteri s ti c of zygomycetes produced wi thi n a n encl os ed s pora ngi um, often s upported by one s pora ngi ophore (Rhizopus, Mucor). 365. The answer is d. (Brooks, Ch 45. Levinson, Ch 48. Murray, Ch 70. Ryan, Ch 44.) Derma tophytos es a re cuta neous mycos es ca us ed by three genera of fungi : Microsporum, Trichophyton, a nd Epidermophyton (s ee the ta bl e i n Ques ti on 338). Derma tophytes ma y ha ve a s thei r norma l ha bi ta t the s oi l ,
a ni ma l s (other tha n ma n), or ma n a nd a re des cri bed, res pecti vel y, a s geophi l i c, zoophi l i c, or a nthropophi l i c orga ni s ms . Derma tophytes a re found worl dwi de. Mos t i s ol a tes from i nfecti on toda y a re a nthropophi l i c wi th Trichophyton rubrum the mos t common i s ol a te. There a re di fferences i n geogra phi c di s tri buti on of s peci es . Infecti on occurs i n kera ti ni zed ti s s ue. Infecti on ca n be tra ns mi tted by tra ns fer of a rthroconi di a or hypha e or kera ti nous ma teri a l conta i ni ng the fungi . Some s peci es rema i n vi a bl e i n des qua ma ted s ki n s ca l es or ha i r for l ong peri ods a nd conta ct ma y be di rect or i ndi rect vi a fomi tes . There i s a genera l correl a ti on between norma l ha bi ta t a nd i nfecti on wi th i nfecti ons due to a nthropophi l i c s peci es , tendi ng to be chroni c, l es s res pons i ve to trea tment a nd recurrent whi l e geophi l i c a nd zoophi l i c s peci es a re a s s oci a ted wi th more a cute hos t res pons e a nd res pond to trea tment. However, i nfecti on ca n reoccur, i f the expos ure conti nues . Microsporum canis i s the mos t frequent zoophi l i c s peci es i s ol a ted i n the USA. Des pi te the na me, there a re more i nfected ca ts tha n dogs . In thi s ca s e, the ca t i s l i kel y i nfected, whi ch ma y or ma y not be obvi ous to the hous ehol d. As l ong a s a n i ndi vi dua l conti nues i n conta ct wi th the a ni ma l , there ma y be rei nfecti on. To i nterrupt thi s cycl e the pet wi l l a l s o need trea tment. Ma ny of the s a me drugs us ed to trea t huma ns a re us ed i n the trea tment of pets . Infecti on of the s mooth s ki n i s ti nea corpori s . The i nfecti on s prea ds outwa rd, crea ti ng the round a ppea ra nce i ndi ca ted by ri ngworm. The l es i on ma y ha ve a cl ea red center a nd ra i s ed erythema tous or ves i cul a r border. Les i ons ma y overl a p gi vi ng a more i rregul a r border a nd i nfecti ons wi th a nthropophi l i c i s ol a tes genera l l y ha ve a l es s i nfl a mma tory res pons e. 366. The answer is b. (Brooks, Ch 45. Levinson, Ch 49. Murray, Ch 72. Ryan, Ch 46.) Blastomyces dermatitidis, the eti ol ogi c a gent of bl a s tomycos i s , i s a therma l l y di morphi c fungus (s ee the ta bl e i n Ques ti on 342). In the envi ronment, i t grows a s a mol d produci ng coni di a . The coni di a a re i nha l ed a nd convert to the yea s t pha s e i n the l ung. The yea s t pha s e i s cha ra cteri zed by a broa d ba s e between the pa rent yea s t cel l a nd the da ughter bud. At 25°C i n the l a bora tory, the fungus grows a s mol d produci ng coni di a . The coni di a a re not di s ti ncti ve a nd l ook s i mi l a r to coni di a of other s peci es . On the other ha nd, when grown on the a ppropri a te medi um a t 37°C i n the l a bora tory, the cha ra cteri s ti c yea s t form wi th broa d-ba s ed buddi ng i s obs erved. Li ke B. dermatitidis, Paracoccidioides brasiliensis produces coni di a i n the mol d form tha t a re not di s ti ncti ve i n s peci es i denti fi ca ti on, whi l e the mul ti pl y-buddi ng yea s t form found i n ti s s ue a nd a l s o grown i n the l a bora tory i s a di s ti ncti ve s tructure i n cul ture i denti fi ca ti on. Hypha e of the therma l l y di morphi c Coccidioides s pp. ca n produce a rthroconi di a i n na ture a nd a t room tempera ture i n the l a bora tory. Histoplasma capsulatum, a l s o one of the therma l l y di morphi c fungi tha t i s a n a gent of s ys temi c di s ea s e, produces both mi croconi di a a nd ma croconi di a i n na ture a nd a t room tempera ture i n the l a bora tory. The ma croconi da a re tubercul a te a nd di s ti ncti ve. In ti s s ue the orga ni s m i s a s ma l l buddi ng yea s t cel l often found wi thi n ma cropha ge. Cryptococcus s pp. grow a s enca ps ul a ted buddi ng yea s t i n routi ne l a bora tory cul ture a nd a l s o i n ti s s ue. 367. The answer is d. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 73. Ryan, Ch 5.) Candida albicans i s a component of norma l huma n fl ora of mucos a l (ora l , ga s troi ntes ti na l , a nd va gi na l ) a nd cuta neous s urfa ces . Mos t i nfecti ons a re of endogenous ori gi n a t or from thes e s urfa ces . There a re occa s i ona l reports of i nfecti ons tra ced to fl ora of hea l th ca re workers . Beca us e orga ni s ms ca n be i s ol a ted from norma l l oca ti ons i n the a bs ence of di s ea s e, i s ol a ti on from thes e s urfa ces (or i n conta ct wi th a s urfa ce, eg, s putum) mus t be correl a ted wi th cl i ni ca l s ymptoms . On the other ha nd, i s ol a ti on from a s teri l e s i te s uch a s bl ood i s s i gni fi ca nt. C. albicans i s thought to rea ch the bl ood s trea m ei ther by tra ns l oca ti on from the gut or from a ca theter i n whi ch a bi ofi l m ha s devel oped a fter i nocul a ti on from s ki n orga ni s ms (s ee the a ns wer to Ques ti on 363). 368. The answer is e. (Brooks, Ch 45. Levinson, Ch 48. Murray, Ch 70. Ryan, Ch 44.) Pi tyri a s i s vers i col or i s ca us ed by s peci es of Malassezia (thi s genus na me i s a ccepted over Pityrosporum tha t wa s s ometi mes us ed) tha t a re norma l s ki n fl ora . In 1996, s even ta xa were recogni zed, of whi ch M. furfur i s onl y one. Al l s even s peci es ha ve been i s ol a ted from i nfecti on wi th geogra phi ca l va ri a ti on. Di a gnos i s i s ma de by vi s ua l i za ti on of the funga l el ements i n epi derma l s ki n s ca l es trea ted wi th KOH wi th or wi thout s ta i ni ng. Round yea s t cel l s a nd hypha e, us ua l l y s hort, a re pres ent. The mi xture of funga l el ements ha s s ometi mes been des cri bed a s “s pa ghetti a nd mea tba l l s ”. Cul ture i s us ua l l y not neces s a ry for thes e norma l fl ora s peci es a s they ca n be i s ol a ted i n the a bs ence of di s ea s e. Arthroconi di a a re di s ti ncti ve s tructures us ed i n cul ture i denti fi ca ti on of Coccidioides s pp. In derma tophyte i nfecti ons , i nfected s ki n a nd ha i r wi l l s how the pres ence of hya l i ne (cl ea r) hypha e a nd a rthroconi di a wi th the l a ter pa rti cul a r a bunda nt i n i nfected ha i r s ha ft s peci mens . Dema ti a ceous hypha e a re found i n s ki n s ca l es removed from the s uperfi ci a l s ki n i nfecti on ti nea ni gra . Yea s t cel l s wi th broa d-ba s ed buddi ng i s obs erved i n ti s s ue i nfected wi th Blastomyces dermatitidis. 369. The answer is e. (Brooks, Ch 45. Levinson, Ch 49. Murray, Ch 72. Ryan, Ch 46.) The s i l ver-s ta i ned s tructure i s a pa rent yea s t cel l wi th mul ti pl e buds (s ee the ta bl e i n Ques ti on 342). Thi s i s a di s ti ncti ve s tructure found i n ti s s ue i nfected wi th Paracoccidioides brasiliensis, a di morphi c fungus . Thi s i s a l s o the form obs erved i n cul ture a t 37°C. The mol d pha s e i s found i n the envi ronment a nd i n cul ture a t room tempera ture. The orga ni s m i s found i n a rea s of Centra l a nd South Ameri ca . The s ki n tes t for expos ure i s a bout equa l for men a nd women i n the endemi c a rea s . However, a mong a dul ts s ymptoma ti c di s ea s e i s more tha n 10:1 i n men. After i ni ti a l pul mona ry i nfecti on, there ma y be a l a tent peri od tha t ma y be ma ny yea rs before a ddi ti ona l pul mona ry s ymptoms a nd potenti a l di s s emi na ti on. Whi l e di s s emi na ti on ma y occur i n a ny orga n there i s predi l ecti on for mucos a l ti s s ue a nd l es i ons a re often s een i n the mouth. The orga ni s m i s a s s umed to grow i n s oi l a nd expos ure i s by i nha l a ti on of coni di a or hypha l fra gments . Whi l e expos ure coul d be by fomi te tra ns mi s s i on, the pa ti ent wa s mos t l i kel y expos ed duri ng the peri od he wa s s ta ti oned i n South Ameri ca . Pri ma ri l y i n men thi s di morphi c fungus ca n convert to the yea s t forms . Convers i on ca n be i nhi bi ted by phys i ol ogi ca l l evel s of ergos terol i n women. Thi s fa i l ure to convert i s the l i kel y expl a na ti on for the s exua l bi a s i n s ymptoma ti c di s ea s e. 370. The answer is a. (Brooks, pp 642-644. Levinson, pp 349-352. Murray, pp 751-759. Ryan, Ch 43.) Candida albicans ha s s evera l mecha ni s ms of res i s ta nce or reduced s us cepti bi l i ty to a zol e cl a s s drugs (s ee the ta bl e i n Ques ti on 336). Thes e mecha ni s ms i ncl ude cha nges i n or overexpres s i on of the P450 14-α-demethyl a s e a nd drug effl ux pumps . Some res i s ta nt s tra i ns ma y ha ve a l l three mecha ni s ms . Res i s ta nce to fl ucytos i ne ma y refl ect a l tered upta ke or cha nge i n enzymes tha t a re i nvol ved i n meta bol i zi ng the drug to a cti ve s tructures . Res i s ta nce to echi noca ndi ns ha s been reported a ri s i ng from muta ti on i n a s ubuni t i n the β-1,3-gl uca n s yntha s e compl ex. Res i s ta nce to a mphoteri ci n B, whi ch bi nds to ergos teri ol ca n a ri s e from reducti on i n the a mount of membra ne ergos terol or cha nge i n membra ne s terol compos i ti on. 371. The answer is b. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 73. Ryan, Ch 45.) Va gi ni ti s i s one of the mos t frequent rea s ons for pa ti ent vi s i ts to a gynecol ogi s t. The mos t common ca us e of i nfecti ous va gi ni ti s i s ba cteri a (40%-50% ca s es ) wi th yea s t, vul vova gi na l ca ndi di a s i s , a ccounti ng for a bout 40%. Candida albicans i s the mos t common ca us e of yea s t va gi ni ti s . It i s es ti ma ted tha t a bout 75% of women i n the Uni ted Sta tes wi l l ha ve one epi s ode of yea s t va gi na l i nfecti on duri ng chi l dbea ri ng yea rs , whi ch mea ns mi l l i ons of ca s es a nnua l l y. Al ong wi th phys i ca l exa mi na ti on, prepa ra ti on a nd exa mi na ti on of a wet mount of va gi na l di s cha rge i s uti l i zed. For C. albicans i nfecti on, both yea s t cel l s a nd hypha e a nd potenti a l l y ps eudohypha e (cha i ns of el onga ted yea s t cel l s tha t di d not s epa ra te a fter cel l di vi s i on) s houl d be obs erved. C. albi-cans i s found a s a component of norma l fl ora of the va gi na l mucos a i n ma ny women; thus the pres ence of the orga ni s m i n cul ture of va gi na l ma teri a l i s not s uffi ci ent for a di a gnos i s of i nfecti on. Trichomonas vaginalis a ccounts for 10% to 15% of i nfecti ous va gi ni ti s ca s e. Tri chomoni a s i s i s the mos t preva l ent nonvi ra l s exua l l y tra ns mi tted di s ea s e (STD) i n the Uni ted Sta tes i n a 2013 report (Sa tterwhi te et a l . Sex Transm Dis 40:187). Thi s pa ra s i te i s us ua l l y a ma rker of hi gh-ri s k s exua l beha vi or a nd ma y be pres ent wi th other s exua l l y tra ns mi tted orga ni s ms . Va gi na l s mea rs a re exa mi ned for trophozoi tes . 372. The answer is b. (Brooks, Ch 45. Levinson, Ch 50. Murray, Ch 73. Ryan, Chs 45-46.) Immunos uppres s i ve a gents ha ve reduced the i nci dence of rejecti on of tra ns pl a nted s ol i d orga ns but ha ve i ncrea s ed ri s k of opportuni s ti c i nfecti on. Funga l i nfecti ons , whi l e not the ma jori ty of i nfecti ons i n thes e pa ti ents , ca rry a hi gh ri s k of morta l i ty. Candida a nd Aspergillus a re res pons i bl e for mos t of thes e opportuni s ti c i nfecti ons tha t ca n occur wi thi n a
month or a fter s evera l months . A. fumigatus (mos t common s peci es ) i nfecti ons a re pri ma ry pul mona ry i nfecti ons tha t ma y be a ra pi dl y necroti zi ng pneumoni a wi th a potenti a l to di s s emi na te. The orga ni s m i s a mol d i n the envi ronment a nd i n the hos t. The hypha e a re s epta te wi th a cute a ngl e, di chotomous , bra nchi ng. Candida i nfecti ons genera l l y s ta rt a s ca ndi demi a , whi ch ma y rea ch the bl ood s trea m by ca theters or tra ns l oca ti on from the gut. C. albicans i s the mos t frequent Candida i s ol a te. Thi s component of norma l fl ora i s genera l l y i n the yea s t form a s a commens a l a nd when i nfecti on occurs the a ddi ti ona l pres ence of hypha e a nd ps eudo-hypha e i s obs erved. C. glabrata, whi ch i s s een wi th i ncrea s i ng frequency, does not form hypha e. Cryptococcus neoformans i s a n enca ps ul a ted yea s t. Other fungi ha ve been reported wi th l es s frequency. 373. The answer is a. (Brooks, Ch 45. Levinson, Ch 47. Murray, Ch 69. Ryan, Ch 43.) Pol yenes , s uch a s a mphoteri ci n B, bi nd to ergos terol i n funga l membra nes a nd genera te i on cha nnel s tha t a ffect os mol a ri ty, membra ne i ntegri ty, a nd a l l ow l ea ka ge of i ntra cel l ul a r contents (s ee the ta bl e i n Ques ti on 336). The pol yene i s not compl etel y s el ecti ve a nd bi ndi ng to chol es terol i n the ma mma l i a n membra ne a ccounts for mos t of the toxi ci ty. 374. The answer is c. (Brooks, Ch 45. Levinson, Ch 47. Murray, Ch 65. Ryan, Ch 41.) As exua l reproducti on i nvol ves onl y mi tos i s a nd s exua l reproducti on i ncl udes mei os i s . Mei os i s i s preceded by ma ti ng of two compa ti bl e ma ti ng types wi th protopl a s t a nd nucl ea r fus i on. The form of a fungus wi th s exua l reproducti on i s the tel eomorph form, whi l e the form tha t reproduces a s exu-a l l y i s the a na morph. Some fungi ca n reproduce both s exua l a nd a s exua l s pores a nd i n other fungi the tel eomorph form ha s ei ther di s a ppea red or not been di s covered. Norma l l y, the tel eomorph na me ha s precedence. In numerous ca s es wi th a gents of huma n di s ea s e, the a na morph wa s i s ol a ted from i nfecti on a nd na med before the tel eomorph wa s i denti fi ed i n the l a bora tory a nd a l s o na med. It ca n be confus i ng, pa rti cul a rl y to nonmycol ogi s ts , when a n orga ni s m ha s two na mes . Even for a fungus tha t ca n reproduce s exua l l y, i t i s pra cti ce i n the cl i ni ca l s etti ng to refer to orga ni s ms by thei r a s exua l na mes a s i s ol a ted from cl i ni ca l ma teri a l . Even wi th thi s pra cti ce, mol ecul a r ta xonomy a nd further s tudy ha ve l ed to s ome na me cha nges . For exa mpl e, Hortaea werneckii, eti ol ogy of ti nea ni gra , ha s previ ous l y been known a s Cladosporium werneckii, Exophiala werneckii, a nd Phaeoannellomyces werneckii.
(Courtesy of MG Rinaldi, San Antonio, Texas.)
Parasitology Questions 375. Ba bes i os i s i s a ti ck-borne di s ea s e, ca us ed by i ntra erythrocyti c pa ra s i tes of the genus Babesia, res ul ti ng i n a ffecti ng pers ons wi th ma l a i s e, na us ea , fever, s wea ts , mya l gi a , a nd a rthra l gi a a nd coul d be confus ed wi th Plasmodium falciparum ri ng form i n red cel l s . Infecti on wi th Ba bes i a ha s been mos t commonl y obs erved i n whi ch of the fol l owi ng?
(Reproduced from the Centers for Disease Control and Prevention. http://www.dpd.cdc.gov/dpdx/html/babesiosis.htm.) a . AIDS pa ti ents b. Fores ters c. Spl enectomi zed pa ti ents d. Tra ns fus i on reci pi ents e. Tra ns pl a nt reci pi ents 376. An AIDS pa ti ent (CD4 count < 200/μL) pres ents to hi s pri ma ry ca re phys i ci a n wi th a 2-week hi s tory of wa tery, nonbl oody di a rrhea . Aci d-fa s t s ta i ni ng demons tra tes oocys ts i n fres h s tool s een i n the fi gure bel ow. Whi ch of the fol l owi ng i s the mos t l i kel y di a gnos i s ?
(Reproduced from the Centers for Disease Control and Prevention. Public Health Image Library, ID# 7829. http://phil.cdc.gov/phil/details.asp.) a . Aci d-fa s t ba ci l l i b. Enterocytozoon c. Cryptosporidium d. Entamoeba histolytica e. Yea s t 377. Fl a gel l a te pa ra s i te i s the ca us e of va gi na l i s i n women i n tempera te a rea s . It i s a s exua l l y tra ns mi tta bl e di s ea s e. The promi nent s ymptom i s copi ous fowl -s mel l i ng yel l ow di s cha rge tha t ca n be a ccompa ni ed by cervi ca l l es i ons a nd a bdomi na l pa i n. Wha t pa ra s i te does thi s repres ent? a . Entamoeba histolytica b. Trichomonas vaginalis c. Strongyloides stercoralis d. Schistosoma mansoni e. Balantidium coli 378. A 30-yea r-ol d fema l e s tores her conta ct l ens es i n ta p wa ter. She noti ces deteri ora ti on of vi s i on a nd vi s i ts a n ophtha l mol ogi s t, who di a gnos es her wi th s evere reti ni ti s . Cul ture of the wa ter a s wel l a s vi treous fl ui d woul d mos t l i kel y revea l whi ch of the fol l owi ng? a . Acanthamoeba b. Babesia c. Entamoeba coli d. Naegleria e. Pneumocystis 379. A young nurs e i n a South Ameri ca n ci ty l oca ted i n the tropi cs devel ops cl a s s i ca l s ymptoms of ma l a ri a . An a ccura te di a gnos i s of the Plasmodium s peci es i s neces s a ry to provi de the bes t trea tment to i ns ure recovery a nd prevent rel a ps e. Sporozoi tes from a mos qui to bi te ra pi dl y enter l i ve cel l s where a s exua l merozoi tes enter the bl ood s trea m a nd RBCs a re i nva ded. Thi s erythrocyti c s ta ge provi des a ba s i s for l a bora tory di a gnos i s . Whi ch of the di a gnos ti c cha ra cteri s ti cs of P. falciparum i s bes t des cri bed by the fol l owi ng?
(Reproduced from the Centers for Disease Control and Prevention. http://www.dpd.cdc.gov/dpdx/html/Malaria.htm.) a . An i mporta nt di a gnos ti c fea ture i s the i rregul a r a ppea ra nce of the edges of the i nfected red bl ood cel l b. A peri od of 72 hours i s requi red for the devel opment of the ma ture s chi zont, whi ch res embl es a ros ette wi th onl y 8 to 10 ova l merozoi tes c. Except i n i nfecti ons wi th very hi gh pa ra s i temi a , onl y ri ng forms of ea rl y trophozoi tes a nd the ga metocytes a re s een i n the peri phera l bl ood d. Schüffner dot s ti ppl i ng i s routi nel y s een i n red bl ood cel l s tha t ha rbor pa ra s i tes e. The s i gnet-ri ng-s ha ped trophozoi te i s i rregul a r i n s ha pe wi th a moeboi d extens i ons of the cytopl a s m 380. After returni ng from a wi l dernes s ca mpi ng outi ng, s evera l chi l dren report wa tery, grea s y, a nd foul -s mel l i ng s tool s . The l i fe cycl e of the pa ra s i te res pons i bl e for thi s outbrea k cons i s ts of two s ta ges : the cys t a nd the trophozoi te. Whi ch of the fol l owi ng i s the mos t l i kel y i denti fi ca ti on of thi s orga ni s m?
(A) “Fa ce” a nd (B) “profi l e” of vegeta ti ve forms ; (C, D) cys ts (bi nucl ea te [D] a nd qua dri nucl ea te s ta ges ). 2000×. (Reproduced, with permission, from Brooks GF et al. Ja wetz’s Medi ca l Mi crobi ol ogy. 24th ed. New York, NY: McGraw-Hill; 2007:660.) a . Clonorchis b. Entamoeba c. Giardia d. Pneumocystis e. Trichomonas
381. A worki ng mother ta kes her 4-yea r-ol d chi l d to a da y-ca re center. She ha s noti ced tha t the chi l d’s frequent s tool s a re nonbl oody wi th mucus a nd a re foul s mel l i ng. The chi l d ha s no fever, but does compl a i n of “tummy hurti ng.” The i ncrea s e of fa t i n the s tool di rects the pedi a tri ci a n’s concern towa rd a di a gnos i s of ma l a bs orpti on s yndrome a s s oci a ted wi th whi ch of the fol l owi ng? a . Amebi a s i s b. As ca ri a s i s c. Ba l a nti di a s i s d. Enterobi a s i s e. Gi a rdi a s i s 382. The progl otti d wa s purged from the i ntes ti na l tra ct of a n i ndi vi dua l who recentl y i mmi gra ted to Uni ted Sta tes from Ni ca ra gua . The progl otti d mea s ured 10 mm i n l ength. Wha t s peci es does i t repres ent?
(Reproduced from the Centers for Disease Control and Prevention. Public Health Image Library, ID# 5259. http://phil.cdc.gov/phil/details.asp.) a . Diphyllobothrium latum b. Dipylidium caninum c. Taenia saginata d. Taenia solium e. Echinococcus granulosus 383. Ma ny of the POWs who were hel d ca pti ve i n the Fa r Ea s t duri ng the WWII contra cted va ri ous pa ra s i ti c i nfecti ons , es peci a l l y thos e pri s oners who were forced to work on the i nfa mous Tha i -Burma ra i l wa y. The tropi ca l jungl e envi ronment of the Burma (Mya nma r) ra i l wa y project provi ded perfect condi ti ons for devel opment of the i nfecti ve s ta ge of a pa ra s i te l a rva , whi ch i nfected the POWs through the s ol es of thei r poorl y s hod feet a s they worked. In pa ti ents who ha ve thi s chroni c i nfecti on a nd a re on chroni c corti cos teroi d thera py, a s yndrome ca n occur whi ch res ul ts i n hi gh morta l i ty ra tes . Whi ch of the fol l owi ng pa ra s i tes i s mos t l i kel y to be the cul pri t? a . Ancylostoma duodenale b. Ascaris lumbricoides c. Diphyllobothrium latum d. Strongyloides stercoralis e. Taenia solium 384. Severa l di a gnos ti c tes ts for a nti bodi es to Toxoplasma a re di rectl y compa red for s ens i ti vi ty a nd s peci fi ci ty a ga i ns t the s era of 100 hea l thy a dul ts . Whi l e di fferences a re a ppa rent i n the a ccura cy of the tes ts , i t i s a bl e to concl ude tha t 80% of thos e tes ted ha ve IgG a nti bodi es a ga i ns t Toxoplasma. Whi ch of the fol l owi ng i s mos t compa ti bl e i n hel pi ng to expl a i n thi s fi ndi ng? a . A va ri ety of pa ra s i ti c i nfecti ons i nduce the forma ti on of Toxoplasma a nti body b. The IgM tes t i s more rel i a bl e tha n the IgG tes t for determi na ti on of pa s t i nfecti ons ; retes ti ng for IgM woul d s how tha t mos t peopl e do not ha ve Toxoplasma a nti body c. The potenti a l for Toxoplasma i nfecti on i s wi des prea d, a nd the di s ea s e i s mi l d a nd s el f-l i mi ti ng d. The tes t for Toxoplasma a nti bodi es i s hi ghl y nons peci fi c e. Toxopl a s mos i s i s ca us ed by ea ti ng mea t; therefore, a l l mea t ea ters ha ve ha d toxopl a s mos i s 385. A 32-yea r-ol d homos exua l ma n pres ents to hi s phys i ci a n wi th non-bl oody, foul -s mel l i ng, grea s y s tool s 3 weeks a fter tra vel i ng to Mexi co. Whi l e certa i n enteri c protozoa n a nd hel mi nthi c i nfecti ons ha ve been l ong rel a ted to conta mi na ted food or wa ter, s exua l tra ns mi s s i on of thes e di s ea s es ha s produced a “hyperendemi c” i nfecti on ra te a mong homos exua l ma l es . Whi ch of the fol l owi ng orga ni s ms i s the mos t l i kel y eti ol ogi c ca us e of thi s pa ti ent’s di a rrhea ? a . Amebi a s i s b. As ca ri a s i s c. Enterobi a s i s
d. Gi a rdi a s i s e. Tri churi a s i s 386. Ana l ys i s of a pa ti ent’s s tool revea l s s ma l l s tructures res embl i ng ri ce gra i ns ; mi cros copi c exa mi na ti on s hows thes e to be progl otti ds . Whi ch of the fol l owi ng i s the mos t l i kel y orga ni s m i n thi s pa ti ent’s s tool ? a . Ascaris lumbricoides b. Enterobius vermicularis c. Necator americanus d. Taenia saginata e. Trichuris trichiura 387. An AIDS pa ti ent compl a i ns of hea da ches a nd di s ori enta ti on. A cl i ni ca l di a gnos i s of Toxoplasma encepha l i ti s i s ma de, a nd Toxoplasma cys ts a re obs erved i n a bra i n s ecti on. Whi ch of the fol l owi ng a nti body res ul ts woul d be mos t l i kel y i n thi s pa ti ent?
a . IgM nonrea cti ve, IgG nonrea cti ve b. IgM nonrea cti ve, IgG rea cti ve (l ow ti ter) c. IgM rea cti ve (l ow ti ter), IgG rea cti ve (hi gh ti ter) d. IgM rea cti ve (hi gh ti ter), IgG rea cti ve (hi gh ti ter) e. IgM rea cti ve (hi gh ti ter), IgG nonrea cti ve 388. A young boy from a n i mpoveri s hed a rea i n Argenti na pres ents to a publ i c hea l th cl i ni c wi th Roma na s i gn a nd a cha goma l es i on. Severa l reduvi i d i ns ects from the home a re s hown to the hea l th ca re workers . In the chroni c s ta ge of thi s di s ea s e, where a re the ma i n l es i ons us ua l l y obs erved? a . Di ges ti ve tra ct a nd res pi ra tory tra ct b. Hea rt a nd di ges ti ve tra ct c. Hea rt a nd l i ver d. Li ver a nd s pl een e. Spl een a nd pa ncrea s 389. A woma n who recentl y returned from Afri ca compl a i ns of ha vi ng pa roxys ma l a tta cks of chi l l s , fever, a nd s wea ti ng. Thes e a tta cks l a s t a da y or two a t a ti me a nd recur every 36 to 48 hours . Exa mi na ti on of a s ta i ned bl ood s peci men revea l s ri ngl i ke a nd cres cent-l i ke forms wi thi n red bl ood cel l s . Whi ch of the fol l owi ng i s the mos t l i kel y i nfecti ng orga ni s m? a . Plasmodium falciparum b. Plasmodium vivax c. Schistosoma mansoni d. Trypanosoma gambiense e. Wuchereria bancrofti Questions 390 and 391 390. A young ma n, who recentl y returned to the Uni ted Sta tes from Vi etna m, ha s s evere l i ver di s ea s e. Symptoms i ncl ude ja undi ce, a nemi a , a nd wea knes s . Whi ch of the fol l owi ng i s the mos t l i kel y eti ol ogi c a gent s hown i n the fi gure bel ow?
(Reproduced from the Centers for Disease Control and Prevention. http://www.dpd.cdc.gov/dpdx/html/clonorchiasis.htm.) a . Clonorchis sinensis b. Diphyllobothrium latum c. Plasmodium falciparum d. Taenia saginata e. Taenia solium 391. An i ntermedi a te form of the orga ni s m s hown i n the photomi crogra ph (Ques ti on 390) l i ves i n whi ch of the fol l owi ng? a . Cows b. Mos qui toes c. Pi gs d. Sna i l s e. Ti cks 392. A woma n who recentl y tra vel ed through Centra l Afri ca now compl a i ns of s evere chi l l s a nd fever, a bdomi na l tendernes s , a nd da rkeni ng uri ne. Her febri l e peri ods l a s t for 28 hours a nd recur regul a rl y. Whi ch of the fol l owi ng bl ood s mea rs woul d mos t l i kel y be a s s oci a ted wi th the s ymptoms des cri bed?
a. A b. B c. C d. D e. E 393. A young woma n reports to her phys i ci a n wi th pos s i bl e uri na ry tra ct i nfecti on. The doctor fi nds the va gi na a nd cervi x tender, i nfl a med, a nd covered wi th a frothy yel l ow di s cha rge. Whi ch of the fol l owi ng protozoa des cri bed i n thi s ca s e i s known to exi s t onl y i n the trophozoi te s ta ge? a . Balantidium coli b. Entamoeba histolytica c. Giardia lamblia d. Toxoplasma gondii e. Trichomonas vaginalis 394. An i nterna ti ona l photogra pher returns to the Uni ted Sta tes from a gl oba l pi cture a s s i gnment. He i s s een by hi s phys i ci a n, gi vi ng hi s ma jor compl a i nt a s di a rrhea . Whi ch of the fol l owi ng ca n be rul ed out? a . Echinococcus granulosus b. Dientamoeba fragilis c. Diphyllobothrium latum d. Giardia lamblia e. Leishmania donovani 395. A medi ca l technol ogi s t vi s i ts Sca ndi na vi a a nd cons umes ra w fi s h da i l y for 2 weeks . Si x months a fter her return home, s he ha s a routi ne phys i ca l a nd i s found to be a nemi c. Her vi ta mi n B 12 l evel s were bel ow norma l . Whi ch of the fol l owi ng i s the mos t l i kel y ca us e of her vi ta mi n B 12 defi ci ency a nemi a ? a . Cys ti cercos i s b. Exces s i ve cons umpti on of i ce-col d vodka c. Infecti on wi th Diphyllobothrium latum d. Infecti on wi th Pa rvovi rus B19 e. Infecti on wi th Yersinia 396. A rena l tra ns pl a nt pa ti ent i s a dmi tted for gra ft rejecti on a nd pneumoni a . A routi ne eva l ua ti on of hi s s tool s hows rha bdi ti form l a rva e. Subs equent fol l ow-up revea l s s i mi l a r worms i n hi s s putum. He ha s no eos i nophi l s i n hi s peri phera l ci rcul a ti on. Whi ch of the fol l owi ng i s the mos t l i kel y orga ni s m?
a . Ascaris lumbricoides b. Hymenolepis nana c. Loa loa d. Necator americanus e. Strongyloides stercoralis 397. A 56-yea r-ol d ma l e i mmi gra nt from Bol i vi a compl a i ns of a bdomi na l pa i n a nd cra mpi ng. He comments tha t 2 months previ ous to hi s current probl ems , he ha d numerous bl oody s tool s every da y. Phys i ca l fi ndi ngs i ncl ude ri ght upper qua dra nt pa i n over the l i ver wi th hepa tomega l y, a nd a l i ver bi ops y i s performed. Whi ch of the fol l owi ng pa ra s i tes woul d mos t l i kel y be i denti fi ed i n the l i ver bi ops y? a . Acanthamoeba castellanii b. Ascaris lumbricoides c. Balantidium coli d. Entamoeba histolytica e. Taenia solium 398. Huma n ma l a ri a l i nfecti ons s ta rt wi th the bi te of a mos qui to, a nd pa ti ents ma y experi ence the peri odi c pa roxys ms of thi s i nfecti on due to events tha t occur i n the bl oods trea m. Up to one mi l l i on dea ths worl dwi de ha ve been es ti ma ted a nnua l l y. Whi ch of the fol l owi ng control methods for thi s di s ea s e i s currentl y mos t effecti ve?
a . Anti bi oti cs b. A va cci ne c. Chemoprophyl a xi s d. Ti ck repel l ents e. Whi te cl othi ng 399. An Afri ca n l oca l cl i ni c reports s eei ng i ncrea s ed ca s es of centra l nervous s ys tem (CNS) i nvol vement i n pa ti ents . Geneti ca l l y i nduced cha nges i n the gl ycoprotei n coa t of whi ch one of the fol l owi ng orga ni s ms enha nces i ts es ca pe from the hos t’s i mmune a nti body res pons e by ha vi ng genes tha t encode mul ti pl e, va ri a nt s urfa ce gl ycoprotei ns ? a . Trichinella spiralis b. Trichomonas vaginalis c. Toxoplasma gondii d. Trypanosoma gambiense e. Leishmania donovani
400. Huma n pa ra s i ti c a moeba s a re us ua l l y i nges ted for tra ns mi s s i on. In l es s a cute di s ea s e, pa ti ents ma y experi ence a bdomi na l tendernes s , a bdomi na l cra mps , na us ea , vomi ti ng, a nd di a rrhea . Whi ch of the fol l owi ng bes t des cri bes thes e i ntes ti na l a meba s ? a . Infecti on wi th E. histolytica i s l i mi ted to the i ntes ti na l tra ct b. They a re us ua l l y nonpa thogeni c c. They a re us ua l l y tra ns mi tted a s trophozoi tes d. They ca n ca us e peri toni ti s a nd l i ver a bs ces s es e. They occur mos t a bunda ntl y i n the duodenum 401. Infecti on wi th Schistosoma haematobium, ba s ed on the pres ence of eggs i n uri ne, i s i denti fi ed i n a n Egypti a n fa rmer’s i nfecti on, whi ch ha s ca us ed derma ti ti s , fever, a nd chroni c fi l ero-obs tructi ve di s ea s e. Thes e s ymptoms a re the res ul t of gra nul oma tous rea cti ons to the ova or to products of the pa ra s i te a t the pl a ce of ovi pos i ti on. Whi ch of the fol l owi ng cl i ni ca l ma ni fes ta ti ons ca n be routi nel y obs erved i n thes e i nfecti ons ?
(Reproduced from the Centers for Disease Control and Prevention. http://www.dpd.cdc.gov/dpdx/html/Schistosomiasis.htm.) a . Arthropa thi es b. Bl a dder wa l l hyperpl a s i a c. Ca rdi a c a bnorma l i ti es d. Pul mona ry embol i s m e. Hemorrha gi c cys ti ti s 402. A boy s cout troop goes ca mpi ng i n a New Engl a nd fores t a rea i n the l a te s pri ng. Two weeks l a ter, s evera l of the boys pres ent wi th erythema mi gra ns l es i ons but no other cl i ni ca l ma ni fes ta ti ons . Borrelia burgdorferi, the ca us a ti ve a gent of Lyme di s ea s e, ha s been i s ol a ted from a va ri ety of ti cks s uch a s I. scapularis, Amblyomma, Dermacentor, a nd I. pacificus. Whi ch of the fol l owi ng s ta tements mos t a ccura tel y des cri bes Lyme di s ea s e? a . Dermacentor a nd Amblyomma a re s i gni fi ca nt vectors of B. burgdorferi to huma ns . b. Dogs a nd ca ts a re na tura l l y i mmune to Lyme di s ea s e c. Ixodes scapularis a nd I. dammini a re di fferent types of ti cks d. Onl y a s ma l l percenta ge of peopl e who get bi tten by a ti ck devel op Lyme di s ea s e e. Whi te-ta i l ed deer, a n i mporta nt res ervoi r for I. scapularis, a re dyi ng beca us e of Lyme di s ea s e 403. A ma l e pa ti ent i n a tropi ca l envi ronment ha s eos i nophi l i a duri ng a cute i nfl a mma tory epi s odes of hi s i l l nes s , but thi s i s not cons i dered to be the defi ni ti ve di a gnos ti c fea ture to determi ne wha t i s ca us i ng hi s di s ea s e. Tra ns mi s s i on of huma n pa ra s i tes ma y occur vi a i nges ti on of conta mi na ted food, wa ter, s na i l s , a va ri ety of i ns ects , a nd pos s i bl y even through pets or ra t ectopa ra s i tes . Whi ch of the fol l owi ng requi res a mos qui to for tra ns mi s s i on? a . Ba bes i os i s b. Ba ncrofti a n fi l a ri a s i s c. Dog ta peworm d. Gui nea worm e. Lei s hma ni a s i s 404. A Bra zi l i a n fa rmer pres ents to hi s medi ca l cl i ni c wi th hepa tos pl enomega l y wi th a s ceti c fl ui d i n the peri tonea l ca vi ty. Hi s l i ver i s s tudded wi th whi te gra nul oma s . He i s trea ted wi th pra zi qua ntel . Whi ch of the fol l owi ng orga ni s ms i s endemi c i n Afri ca a nd South/Centra l Ameri ca a nd i s tra ns mi tted by s ki n penetra ti on (by eggs wi th a l a rge l a tera l s pi ne), res ul ti ng i n a derma ti ti s a nd ka ta ya ma fever (s erum s i cknes s -l i ke s yndrome wi th fever, l ympha denopa thy, a nd hepa tos pl enomega l y)? a . Clonorchis sinensis b. Paragonimus westermani c. Schistosoma haematobium d. Schistosoma japonicum e. Schistosoma mansoni 405. The a dul ts i n a vi l l a ge i n s outhern Chi na s uffer from fever, chi l l s , mi l d ja undi ce, eos i nophi l i a , a nd l i ver enl a rgement. Whi ch of the fol l owi ng
orga ni s ms ma y be i nges ted wi th ra w fi s h, often res ul ti ng i n a n a s ymptoma ti c i nfecti on but, wi th a hea vy i nfecti on, ma y ca us e bi l i a ry a nd bi l e duct obs tructi on a nd ha s a n opercul a ted egg? a . Clonorchis sinensis b. Paragonimus westermani c. Schistosoma haematobium d. Schistosoma japonicum e. Schistosoma mansoni 406. Whi ch of the fol l owi ng orga ni s ms i s endemi c i n As i a , a nd ha s a s ma l l l a tera l egg s pi ne, a nd i n chroni c di s ea s e ma y res ul t i n hepa tos pl eni c di s ea s e, porta l hypertens i on, a nd l i ver gra nul oma s ? a . Clonorchis sinensis b. Paragonimus westermani c. Schistosoma haematobium d. Schistosoma japonicum e. Schistosoma mansoni 407. An Afri ca n ri ce fa rmer, who depends on i rri ga ti on wa ter from a regi ona l l a ke, devel ops hema turi a a nd dys uri a s evere enough to ha ve concern for rena l fa i l ure. Whi ch of the fol l owi ng orga ni s ms ha s l a rge termi na l egg s pi nes , ma y ca us e a chroni c gra nul oma tous bl a dder di s ea s e wi th urethra l obs tructi on, chroni c rena l fa i l ure, a nd ma y be detected vi a eggs i n the uri ne? a . Clonorchis sinensis b. Paragonimus westermani c. Schistosoma haematobium d. Schistosoma japonicum e. Schistosoma mansoni 408. Ca mpers i n a Europea n fores t a rea dri nk unfi l tered s trea m wa ter a nd l a ter experi ence a bdomi na l cra mps wi th foul -s mel l i ng a nd grea s y s tool s . Giardia lamblia i nfecti on ca n occur by i nges ti ng a s few a s 10 eggs , res ul ti ng i n a s ymptoma ti c cys t pa s s a ge, s el f-l i mi ted di a rrhea , or chroni c di a rrhea wi th a s s oci a ted ma l a bs orpti on a nd wei ght l os s , Thi s i nfecti on i s bes t di a gnos ed by whi ch of the fol l owi ng? a . Ba erma nn techni que b. Di l uti on fol l owed by egg count c. Enzyme i mmunoa s s a y (EIA) d. Us i ng a s cotch ta pe method e. Si gmoi dos copy a nd a s pi ra ti on of mucos a l l es i ons 409. Pa ti ents wi th E. histolytica ha ve a n a s ymptoma ti c ca rri er ra te grea ter tha n 90%. Chroni c di s ea s e (i ntermi ttent bl oody di a rrhea a nd a bdomi na l pa i n from months to yea rs ) i s often di ffi cul t to di s ti ngui s h from i nfl a mma tory bowel di s ea s e. E. histolytica i nfecti on i s bes t di a gnos ed by whi ch of the fol l owi ng? a . Ba erma nn techni que b. Di l uti on fol l owed by egg count c. EIA d. Exa mi na ti on of a cel l opha ne ta pe s wa b e. Si gmoi dos copy a nd a s pi ra ti on of mucos a l l es i ons 410. Ma ny pa ti ents wi th Strongyloides l ow worm burden a re a s ymptoma ti c. Ini ti a l i nfecti on occurs by s ki n penetra ti on a nd a pul mona ry mi gra ti on occurs . Pa ti ents demons tra te dry cough, wheezi ng, l ow-gra de fever, dys pnea , a nd hemoptys i s . Trea tment i s a va i l a bl e for pa ra s i te era di ca ti on. Whi ch i s the bes t method l i s ted bel ow for detecti ng Strongyloides l a rva e? a . Ba erma nn techni que b. Di l uti on fol l owed by egg count c. EIA d. Exa mi na ti on of a cel l opha ne ta pe s wa b e. Si gmoi dos copy a nd a s pi ra ti on of mucos a l l es i ons 411. Ascaris lumbricoides a re l a rge worms tha t ha ve a compl ex l i fe cycl e i n huma n hos ts i nvol vi ng the di ges ti ve s ys tem, bl oods trea m, hea rt a nd l i ver, pul mona ry ci rcul a ti on, a nd ba ck to the s ma l l i ntes ti ne. Seri ous medi ca l compl i ca ti ons ma y occur i n a ny of thes e s i tes ma ki ng di a gnos i s cri ti ca l . Ascaris i s bes t obs erved i n huma n s peci mens by whi ch one of the fol l owi ng? a . Ba erma nn techni que b. Di l uti on fol l owed by egg count c. EIA d. Exa mi na ti on of a cel l opha ne ta pe s wa b e. Si gmoi dos copy a nd a s pi ra ti on of mucos a l l es i ons 412. A butcher devel ops a ques ti ona bl e ha bi t of ea ti ng va ri ous ki nds of ra w, ground mea t over s evera l yea rs . He eventua l l y s ta rts s ufferi ng from fa ti gue a nd l ympha denopa thy. In hi s extens i ve phys i ca l exa mi na ti on, i ntens el y whi te foca l reti na l l es i ons wi th vi tri ti s a re obs erved. Chori oreti ni ti s i s di a gnos ed, even though a n ol der l a bora tory tes t, the Sa bi n–Fel dma n dye tes t, i s found pos i ti ve. Thi s pa ti ent i s found to be i nfected wi th whi ch of the fol l owi ng? a . Gi a rdi a s i s b. Schi s tos omi a s i s c. Toxopl a s mos i s d. Tri chi nos i s
e. Vi s cera l l a rva mi gra ns 413. One week a fter ea ti ng bea r mea t, a fur tra pper devel ops di a rrhea , na us ea , a nd vomi ti ng. The next week, he experi ences s ys temi c s ymptoms of fever, mya l gi a s , a nd ma l a i s e. Hi s doctor notes peri orbi ta l edema a nd s wol l en eyel i ds , a nd l a bora tory tes ts report a n eos i nophi l i a . He i s di a gnos ed wi th whi ch of the fol l owi ng? a . Gi a rdi a s i s b. Schi s tos omi a s i s c. Toxopl a s mos i s d. Tri chi nos i s e. Vi s cera l l a rva mi gra ns 414. A news pa per corres pondent i s s ent to St Peters burg, Rus s i a , to cover pol i ti ca l events occurri ng there. She dri nks onl y bottl ed wa ter except on a s i de tri p to the countrys i de to vi s i t a n ol d mona s tery. Two weeks l a ter a nd a t home, s he devel ops a chroni c di a rrhea where the s tool s a re wa tery, grea s y, a nd foul s mel l i ng. Whi ch of the fol l owi ng i s the mos t l i kel y di a gnos i s ? a . Gi a rdi a s i s b. Schi s tos omi a s i s c. Toxopl a s mos i s d. Tri chi nos i s e. Vi s cera l l a rva mi gra ns 415. A reti red a i r force col onel ha s ha d a bdomi na l pa i n for 2 yea rs ; he ma kes yea rl y fres hwa ter fi s hi ng tri ps to Puerto Ri co a nd often wa des wi th ba re feet i nto s trea ms . Whi ch of the fol l owi ng s houl d be i ncl uded i n the di fferenti a l di a gnos i s ? a . Gi a rdi a s i s b. Schi s tos omi a s i s c. Toxopl a s mos i s d. Tri chi nos i s e. Vi s cera l l a rva mi gra ns 416. A teena ger who works i n a dog kennel a fter s chool for 2 yea rs ha s ha d a s ki n ra s h, eos i nophi l i a , a nd a n enl a rged l i ver a nd s pl een. Whi ch of the fol l owi ng i s the mos t l i kel y ca us e of thi s i nfecti on? a . Gi a rdi a s i s b. Schi s tos omi a s i s c. Toxopl a s mos i s d. Tri chi nos i s e. Vi s cera l l a rva mi gra ns 417. A young woma n goes to her doctor wi th a va ri ety of medi ca l compl a i nts . Her mucos a l s urfa ces a re tender, i nfl a med, eroded, a nd covered wi th a yel l ow di s cha rge. For one probl em, the l a bora tory reports the i s ol a ti on of a pea r-s ha ped protozoa n wi th a jerky moti l i ty. Thi s orga ni s m i s obs erved i n whi ch of the fol l owi ng? a . Bi ops i ed mus cl e b. Bl ood c. Duodena l contents d. Sputum e. Va gi na l s ecreti ons 418. A hunter, s ucces s ful i n hi s fi rs t bl a ck bea r hunt, ta kes the mea t home to ea t. After cons umi ng mea l s i ncl udi ng bea r mea t over s evera l weeks , two fa mi l y members devel op a fl u-l i ke s yndrome a nd mi l d di a rrhea . Severa l weeks l a ter, two others ha ve fever, GI di s tres s , eos i nophi l i a , mus cl e pa i n, a nd peri orbi ta l edema . Whi ch of the s peci mens l i s ted bel ow woul d mos t ea s i l y detect the orga ni s m res pons i bl e for the cl i ni ca l pres enta ti ons des cri bed? a . Bi ops i ed mus cl e b. Bl ood c. Duodena l contents d. Sputum e. Va gi na l s ecreti ons 419. A fa mi l y of four goes on a va ca ti on for 3 weeks to Centra l a nd South Ameri ca . They cons ume the us ua l di ets i n a l l the a rea s they vi s i t, i ncl udi ng ra w a nd pi ckl ed crus ta cea n. Weeks l a ter, two members produce brown s putum when coughi ng, hemoptys i s , a nd eos i nophi l i a , whi l e the others a re a s ymptoma ti c. A ti s s ue-dwel l i ng trema tode ca us i ng thi s ma y be found i n feces a nd whi ch of the fol l owi ng? a . Bi ops i ed mus cl e b. Bl ood c. Duodena l contents d. Sputum e. Va gi na l s ecreti ons 420. A fores t ra nger who routi nel y dri nks untrea ted s trea m wa ter a nd devel ops mi nor, i ntermi ttent di a rrhea , whi ch becomes chroni c. La bora tory exa mi na ti on of s evera l s tool s fa i l s to determi ne a ny s peci fi c orga ni s m. Her phys i ci a n deci des to us e the Entero-Tes t to try to di s cover the a gent ca us i ng the s ymptoms . Cys ts of a protozoa n a dhere to a pi ece of nyl on ya rn coi l ed i n a gel a ti n ca ps ul e, whi ch i s s wa l l owed. Thes e cys ts a re us ua l l y found i n whi ch of the fol l owi ng? a . Bi ops i ed mus cl e b. Bl ood
c. Duodena l contents d. Sputum e. Va gi na l s ecreti ons 421. A pers on from Na ntucket Is l a nd, Ma s s a chus etts , devel ops fever, fa ti gue, s wea ts , a nd a rthra l gi a a fter hi ki ng wi th fri ends i n a fores t. Hi s phys i ci a n fi nds evi dence of ti ck bi tes tha t ha d not been noti ced. A pa ra s i te res embl i ng ma l a ri a tha t i nfects both a ni ma l s a nd huma ns a nd i s ca rri ed by the s a me ti ck tha t tra ns mi ts B. burgdorferi (the Gra m-nega ti ve s pi rochete tha t ca us es Lyme di s ea s e) woul d mos t l i kel y be obs erved i n whi ch of the fol l owi ng? a . Bi ops i ed mus cl e b. Bl ood c. Duodena l contents d. Sputum e. Va gi na l s ecreti ons 422. A pa ti ent wi th AIDS returns from Ha i ti wi th a cute di a rrhea . The s tool revea l s a n ova l orga ni s m (8-9 μm i n di a meter) tha t i s a ci d-fa s t a nd fl uores ces bl ue under ul tra vi ol et l i ght. The mos t l i kel y i denti fi ca ti on of thi s orga ni s m i s whi ch of the fol l owi ng? a . Cryptosporidium hominis b. Cyclospora cayetanensis c. Enterocytozoon bieneusi d. Giardia lamblia e. Prototheca wickerhamii 423. A 64-yea r-ol d s heepherder from the fa rmi ng regi on of centra l Ca l i forni a i s rus hed to the emergency room i n a na phyl a cti c s hock. The hi s tory, a s tol d by the a mbul a nce medi c, i s tha t the ma n wa s hi t i n the a bdomen duri ng a ba rroom bra wl . Ul tra s ound revea l s a l a rge cys t ma s s i n the l i ver. A ca uti ous needl e a s pi ra ti on of the l i ver ma s s revea l s “hyda ti d s a nd.” Whi ch of the fol l owi ng i s the mos t l i kel y a gent i nvol ved? a . Ascaris lumbricoides b. Clonorchis sinensis c. Echinococcus granulosus d. Fasciolopsis hepatica e. Schistosoma mansoni 424. In a boy from Ira q, a l es i on s hown bel ow wa s found to be i rri ta ted, wi th i ntens e i tchi ng a nd begi ns to enl a rge a nd ul cera te but di d hea l s ponta neous l y. However, a perma nent s ca r wa s l eft a t the s i te. Wha t woul d be your di a gnos i s ?
(Reproduced from the Centers for Disease Control and Prevention. Public Health Image Library, ID# 15069. http://phil.cdc.gov/phil/details.asp.) a . Schistosoma mansoni i nfecti on b. Cuta neous l ei s hma ni a s i s (L. tropica) c. Mucocuta neous l ei s hma ni a s i s (L. braziliensis) d. Ameri ca n trypa nos omi a s i s (T. cruzi) e. Infl a mma ti on due to a ti ck bi te 425. A ti ny worm wa s pa s s ed i n the s tool of a 6-yea r-ol d chi l d. The chi l d reported peri a na l pruri tus , es peci a l l y a t ni ght. The worm mea s ured 10 mm
i n l ength a nd ha d a poi nted ta i l . The eggs recovered by “Scotch ta pe” method. Wha t s peci es does i t repres ent? a . Ascaris lumbricoides b. Enterobius vermicularis c. Necator americanus d. Schistosoma mansoni e. Trichuris trichiura 426. A 12-yea r-ol d boy, a recent i mmi gra nt from Ethi opi a , pres ented wi th a bdomi na l pa i n a s s oci a ted wi th a bdomi na l di s tenti on, na us ea , a nd vomi ti ng. The phys i ci a n noted a n enl a rged l i ver wi th a pa l pa bl e ma s s i n the ri ght upper qua dra nt of a bdomen. Ra di ol ogy wa s ordered; ul tra s onogra phy a nd computed tomogra phy (CT) revea l ed a hepa ti c cys t. Mi cros copi c exa mi na ti on of a bi ops y s peci men confi rmed the di a gnos i s of a pa ra s i ti c i nfecti on. Wha t i s the ca us a ti ve a gent of thi s di s ea s e?
(Reproduced from the Centers for Disease Control and Prevention. Public Health Image Library, ID# 1452. http://phil.cdc.gov/phil/details.asp.) a . Hymenolepis nana b. Schistosoma haematobium c. Echinococcus granulosus d. Cys ti cercos i s e. Schistosoma japonicum 427. A 23-yea r-ol d woma n who wa s a pi g fa rmer i n Peru but ha d l i ved i n the Uni ted Sta tes for over 15 yea rs pres ented wi th a 2-month hi s tory of l eft-s i de wea knes s a nd ons et of s ei zures . An MRI of the pa ti ent’s hea d revea l ed cys ts i n pa ri eta l l obe. Wha t i s your di a gnos i s ?
(Reproduced from the Centers for Disease Control and Prevention. http://www.cdc.gov/parasites/cysticercosis/.) a . Toxoplasma gondii b. Entamoeba histolytica c. Neurocys ti cercos i s d. Strongyloides stercoralis
e. Acanthamoeba castellanii
Answers 375. The answer is c. (Brooks, p 680. Levinson, pp 355, 371. Murray [2009], pp 840-841. Garcia [2007], pp 180-185.) Babesia i s tra ns mi tted by ti cks of the genus Ixodes. Babesia ca n be mi s ta ken for Plasmodium s pp. (ca us a ti ve orga ni s m of ma l a ri a ) i n a bl ood s mea r. Babesia ha s s evera l di s ti nct cha ra cteri s ti cs i ncl udi ng tha t the pa ra s i tes a re pl eomorphi c, often va cuol a ted, a nd unl i ke ma l a ri a l pa ra s i tes they a re not pi gment-produci ng orga ni s ms . Often a di vi di ng tetra d form a nother di s ti ngui s hi ng fea ture of Babesia ca n a l s o be s een i n the bl ood s mea rs . Pa ti ents become a nemi c a nd devel op hepa tos pl enomega l y, but pa ti ents who a re a s pl eni c a re a t a much grea ter ri s k. Tra ns fus i on reci pi ents , fores ters , i mmunos uppres s ed, a nd el derl y pa ti ents ma y be a t ri s k of a cqui ri ng di s ea s e but not to the s a me extent a s thos e pa ti ents who ha ve been s pl enectomi zed. 376. The answer is c. (Brooks, p 681. Levinson, pp 358-359. Murray [2009], pp 829-830. Ryan, p 702. Garcia [2007], pp 57-73.) The fi gure pres ented i n the ques ti on s hows Cryptosporidium oocys ts s ta i ned wi th a modi fi ed a ci d-fa s t s ta i n a nd they a re not a ci d-fa s t ba ci l l i . Cryptosporidium oocys ts a re rounded a nd mea s ure 4.2 to 5.4 μm i n di a meter. Worl dwi de, the preva l ence of Cryptos pori di os i s i s 1% to 4.5% i n devel oped countri es a nd 3% to 20% i n devel opi ng countri es . Es ti ma ted i nfecti on ra tes i n AIDS pa ti ents ra nge from 3% to 20% i n the Uni ted Sta tes a nd 50% to 60% i n Afri ca a nd Ha i ti . Aci d-fa s t s ta i ni ng methods , wi th or wi thout s tool concentra ti on, a re mos t frequentl y us ed i n cl i ni ca l l a bora tori es . Infecti on wi th Cryptosporidium s p. res ul ts i n a wi de ra nge of ma ni fes ta ti ons , from a s ymptoma ti c i nfecti ons to s evere, l i fe-threa teni ng i l l nes s . Symptoms ca n be chroni c a nd more s evere i n i mmunocompromi s ed pa ti ents , es peci a l l y thos e wi th CD4 counts <200/μL. 377. The answer is b. (Garcia [2007], pp 123-130.) Trichomonas vaginalis i s a n i mporta nt s exua l l y tra ns mi tted fl a gel l a te. An es ti ma ted 250 mi l l i on new ca s es of Tri chomoni a s i s occur a round the worl d wi th ni ne mi l l i on new ca s es i n the Uni ted Sta tes every yea r. The pa ra s i te i nha bi ts predomi na tel y the fema l e l ower geni ta l tra ct a nd ca n a l s o be found i n the ma l e urethra a nd pros ta te. The pa ra s i te di vi des by bi na ry fi s s i on a nd does not ha ve a cys t form a nd i s tra ns mi tted huma n to huma n pri ma ri l y by s exua l i ntercours e. T. vaginalis i nfecti on i n women i s frequentl y s ymptoma ti c. Va gi na l i s wi th a profus e fowl -s mel l i ng yel l ow di s cha rge i s the promi nent s ymptom a nd ca n be a ccompa ni ed by cervi ca l l es i ons a nd a bdomi na l pa i n. Growth of the orga ni s m i s fa vored by hi gh pH >5.9 (norma l pH i n va gi na = 3.5-4.5). In ma l es , the i nfecti on i s often a s ymptoma ti c but urethri ti s , epi di dymi ti s , a nd pros ta ti ti s ca n occur. Thi s i s a ca s e of Trichomonas vaginalis s howi ng a profus e di s cha rge s temmi ng from the cervi ca l os . 378. The answer is a. (Brooks, pp 672, 674. Levinson, pp 355, 371. Murray [2009], pp 803, 844-845. Ryan, p 733.) Acanthamoeba i s a free-l i vi ng a meba , a s i s Naegleria. Naegleria us ua l l y ca us es s evere, often fa ta l , meni ngoencepha l i ti s , whi l e Acanthamoeba i s i s ol a ted from conta ct l ens fl ui d a nd pa ti ents wi th reti ni ti s who do not s tore thei r l ens es under s teri l e condi ti ons . Entry of Acanthamoeba i nto the CNS ca n occur from s ki n ul cers or tra uma ti c penetra ti on. Di a gnos i s i s by exa mi na ti on of the CNS, whi ch conta i ns trophozoi tes a nd RBCs but no ba cteri a . Naegleria, a l s o a free-l i vi ng a moeba , produces a n expl os i ve, ra pi d bra i n i nfecti on. Babesia a re wi des prea d a ni ma l pa ra s i tes , tra ns mi tted by ti cks . Entamoeba coli i s i nges ted a nd i nva de the i ntes ti na l epi thel i um. Pneumocystis jiroveci (not P carinii) ca us es pneumoni a i n i mmunocompromi s ed pa ti ents . Thi s a gent ma y be a n obl i ga te member of the norma l fl ora . 379. The answer is c. (Brooks, pp 674-679. Levinson, pp 361-365. Murray [2009], pp 838-839. Ryan, p 712.) Plasmodium falciparum i nfecti on i s di s ti ngui s hed by the a ppea ra nce of ri ng forms of ea rl y trophozoi tes a nd ga metocytes , both of whi ch ca n be found i n the peri phera l bl ood. The s i ze of the RBC i s us ua l l y norma l . Doubl e dots i n the ri ngs a re common. Irregul a r edges of the i nfected RBC do not a ppea r to be a rel i a bl e or i mporta nt di a gnos ti c fea ture. There a re us ua l l y more tha n 12 merozoi tes i n P. falciparum-i nfected RBCs , a nd thes e a re ra re i n peri phera l bl ood. Schüffner dots a re found i n P. vivax a nd P. ovale i nfecti ons . Plasmodium falciparum peri phera l s mea rs s how s ma l l , del i ca te-a ppea ri ng ri ng trophozoi tes . P. vivax a nd P. ovale produce thi cker a nd l a rger ri ng trophozoi tes .
(A) Ri ng-form trophozoi tes of P. falciparum i n a thi n bl ood s mea r ( B) Ri ng-form trophozoi tes of P. vivax i n a thi n bl ood s mea r. (C) Trophozoi tes of P. ovale i n a thi n bl ood s mea r. (D) Ba nd-form trophozoi tes of P. malariae i n a thi n bl ood s mea r. (E) Schi zont a nd ri ng-form trophozoi te of P. knowlesi i n
a thi n bl ood s mea r. (Reproduced from the Centers for Disease Control and Prevention. http://www.dpd.cdc.gov/dpdx/html/Malaria.htm.) 380. The answer is c. (Brooks, p 660. Levinson, pp 355-358. Murray [2009], pp 824-826. Ryan, pp 745-748.) Giardia exi s ts i n both trophozoi te a nd cys t form. The “trophs ” a re fra gi l e a nd not commonl y s een i n s tool s . The cys ts a re i nfecti ous . Giardia i s the mos t common pa ra s i ti c di s ea s e i n the Uni ted Sta tes . It i s commonl y contra cted from dri nki ng cys t-conta mi na ted wa ter. Chl ori ne does not ki l l Giardia cys ts , but conta mi na ted wa ter ca n be ma de cys t-free by fi l tra ti on. Clonorchis i s a trema tode a nd ha s a s oft-bodi ed s yncyti a l s ha pe (fl a tworms ) a nd a re ca l l ed fl ukes . Clonorchis sinensis i s a l i ver fl uke wi th a s na i l hos t i n i ts l i fe cycl e. Entamoeba a re common pa ra s i tes of the huma n l a rge i ntes ti ne a nd ha ve no fl a gel l a on the a cti ve a moeba . Pneumocystis wa s thought to be a protozoa n but mol ecul a r bi ol ogy s tudi es ha ve proved i t to be a fungus . Trichomonas a re fl a gel l a r protozoa wi th 3 to 5 a nteri or fl a gel l a a nd a n undul a ti ng membra ne. 381. The answer is e. (Brooks, p 660. Levinson, pp 357-358. Murray [2009], pp 824-826. Ryan, pp 745-748.) Giardia lamblia i s the onl y common protozoa n found i n the duodenum a nd jejunum. Trophozoi tes a re commonl y found i n the duodenum a nd do not penetra te the ti s s ues . Four nucl ei cys ts (i nfecti ve s ta ge) ca n rema i n vi a bl e for up to 4 months . Excys ta ti on i s vi a di ges ti ve enzymes . The mecha ni ca l i rri ta ti on to ti s s ues l ea ds to di a rrhea , wi th i ncrea s ed fa t a nd mucus i n the foul -s mel l i ng s tool . Ma l a bs orpti on s yndrome (vi ta mi n A a nd fa ts ) l ea ds to wei ght l os s , a norexi a , el ectrol yte i mba l a nce, a nd a bdomi na l cra mps . Chi l dren a nd i mmunocompromi s ed i ndi vi dua l s a re mos t s i gni fi ca ntl y a ffected. Gi a rdi a s i s s houl d be cons i dered i n the di fferenti a l di a gnos i s of a ny “tra vel er’s di a rrhea .” Entamoeba s peci es a re common pa ra s i tes of the huma n l a rge i ntes ti nes . Mucos a l s urfa ces ha ve di s crete ul cers . Trophozoi tes a nd RBCs a re found i n l i qui d s tool s a nd ca n be i denti fi ed by mi cros copy. Ascaris lumbricoides i s a common roundworm found i n the s ma l l i ntes ti ne wi th l a rva e i n the l ungs . Balantidium coli i s the l a rges t i ntes ti na l protozoa n found i n huma ns . It i s a ci l i a ted, ova l orga ni s m 60 × 45 μm or l a rger. Cys ts a re pa s s ed i n huma n s tool s a nd i nfecti ons occur i n a rea s of poor s a ni ta ti on a nd crowdi ng. Enterobius vermicularis i s the common pi nworm, wi th a n a na l –ora l tra ns mi s s i on (s el f-conta mi na ti on occurs regul a rl y i n chi l dren). 382. The answer is c. (Garcia [2007], pp 357-380.) A number of bra nches i n the uterus a re di a gnos ti c for T. saginata (beef ta peworm) a nd T. solium (pork ta peworm). T. saginata ha s 15 to 20 bra nches on ea ch s i de (A) a nd T. solium ha s 7 to 13 (B). Huma ns a cqui re the T. saginata i nfecti on by i nges ti ng undercooked beef conta i ni ng i nfecti ve l a rva l cys ts (cys ti cerci ). T. solium i nfecti on i s contra cted by huma ns when they ea t undercooked pork conta i ni ng cys ti cerci . Both beef ta peworm a nd pork ta peworm ca n, i n the a dul t form, ca us e di s turba nces of i ntes ti na l functi on. In a ddi ti on, T. saginata, beca us e of i ts l a rge s i ze, ma y produce a cute i ntes ti na l bl ocka ge. Unl i ke T. saginata, T. solium produces cys ti cercos i s , whi ch coul d res ul t i n s eri ous di s ea s e i n huma ns . In T. saginata, the cys ti cercus —encys ted l a rva e s ta ge—devel ops onl y i n ca ttl e.
(Reproduced from the Centers for Disease Control and Prevention. Public Health Image Library, (A) ID# 5259 and (B) ID #4835. http://phil.cdc.gov/phil/details.asp.) 383. The answer is d. (Garcia [2007], pp 271-282.) The tropi ca l jungl e envi ronment of the Burma ra i l wa y project provi ded perfect condi ti ons for devel opment of the fi l a ri form Strongyloides l a rva e, whi ch i nfected the POWs through the s ol es of thei r poorl y s hod feet a s they worked. Thi s roundworm ha s a compl ex l i fe cycl e a nd the pa ra s i te ca n compl ete i ts l i fe cycl e vi a a free-l i vi ng cycl e or one of the two ki nds of pa ra s i ti c cycl es . The pri nci pa l defi ni ti ve hos ts of S. stercoralis a re huma ns but i nfecti on i n dogs ca n a l s o be es ta bl i s hed. As l ong a s the pa ti ent i s i nfected, whi ch ca n be for s evera l deca des , the i nfecti on rema i ns tra ns mi s s i bl e. Tra ns mi s s i on occurs predomi na ntl y i n tropi ca l a nd s ubtropi ca l a rea s but ca n a l s o be found i n countri es wi th tempera te envi ronments i ncl udi ng the Southea s tern Uni ted Sta tes . S. stercoralis i n huma ns us ua l l y produces a n a s ymptoma ti c chroni c i nfecti on of the ga s troi ntes ti na l tra ct tha t ca n rema i n undetected for s evera l deca des . In s ome pa ti ents , a hyperi nfecti on s yndrome ca n devel op wi th the di s s emi na ti on of l a rva e to extra i ntes ti na l orga ns a nd tha t ca n res ul t i n morta l i ty ra tes exceedi ng 80%. Ri s k fa ctors a nd predi s pos i ng condi ti ons i ncl ude: i mmunos uppres s i ve thera pi es wi th corti cos teroi ds , HTLV-1 i nfecti on, orga n tra ns pl a nta ti on, a nd ma l nutri ti on.
(Reproduced from the Centers for Disease Control and Prevention. Public Health Image Library, ID# 1547. http://phil.cdc.gov/phil/details.asp.) 384. The answer is c. (Brooks, pp 682-683. Levinson, pp 365-366, 518. Murray [2009], pp 841-844. Ryan, pp 722-727.) Serol ogi c tes ts , s uch a s the Sa bi n– Fel dma n dye tes t a nd i ndi rect i mmunofl uores cence, ha ve s hown tha t a hi gh percenta ge of the worl d’s popul a ti on ha s been i nfected wi th T. gondii. In a dul ts , cl i ni ca l toxopl a s mos i s us ua l l y pres ents a s a beni gn s yndrome res embl i ng i nfecti ous mononucl eos i s . However, feta l i nfecti ons a re often s evere a nd a s s oci a ted wi th hydrocepha l us , chori oreti ni ti s , convul s i ons , a nd dea th. Acute toxopl a s mos i s i s bes t di a gnos ed by a n IgM ca pture a s s a y. In mos t pa ti ents , s peci fi c IgM a nti body di s a ppea rs wi thi n 3 to 6 months . Obvi ous l y, Toxoplasma i nfecti on i s wi des prea d i n a ni ma l a nd bi rd hos ts but does not a ppea r to ca us e di s ea s e i n them. Congeni ta l i nfecti on occurs onl y when the noni mmune mothers a re i nfected duri ng pregna ncy. Mos t huma n i nfecti ons a re a s ymptoma ti c. Fa ta l i nfecti ons ma y devel op i n AIDS pa ti ents . Toxoplasma a nti gens do not a ppea r to cros s rea ct wi th ma ny of the other pa ra s i tes ’ a nti gens . IgM a nd IgG a nti bodi es ca n be detected wi th equa l rel i a bi l i ty. IgM l evel s drop eventua l l y whi l e IgG a nti bodi es ma y be mea s ured for yea rs . The di a gnos ti c tes t for Toxoplasma, i n order to be a pproved for us e, mus t be hi ghl y s peci fi c a nd s ens i ti ve. There i s no evi dence tha t Toxoplasma i s s prea d by wa ter. 385. The answer is d. (Brooks, p 660. Levinson, pp 357-358. Murray [2009], pp 824-826. Ryan, pp 745-748. Toy, p 314.) The i nfecti on ra te wi th G. lamblia i n ma l e homos exua l s ha s been reported to be from 21% to 40%. Thes e hi gh-preva l ence ra tes a re proba bl y rel a ted to three fa ctors : the endemi c ra te, the s exua l beha vi or tha t fa ci l i ta tes tra ns mi s s i on (the us ua l ba rri ers to s prea d ha ve been i nterrupted), a nd the frequency of expos ure to a n i nfected pers on. Amebi a s i s i s i nfecti on wi th a moeba s a nd a s ymptoma ti c cys t ca rri ers exi s t, formi ng pa rt of a pool tha t potenti a l l y coul d contri bute to thi s probl em. However, the foul -s mel l i ng grea s y s tool s poi nt to Giardia. Ascaris i s a nema tode worm tha t a l s o i nha bi ts the i ntes ti ne of vertebra tes . Thi s l i fe cycl e i ncl udes s wa l l owi ng eggs (from conta mi na ted wa ter), ha tchi ng of eggs i n the i ntes ti ne, mi gra ti on of nema tode to the l ungs , a nd fi na l l y rea chi ng the duodenum. Di a rrhea epi s odes do not a ppea r to be routi nel y reported i n thi s i nfecti on. Enterobius vermicularis i nfecti ons a re noted for peri recta l i rri ta ti on a nd pruri ti s , not di a rrhea epi s odes . Tri churi a s i s (whi pworm) tra ns mi s s i on i s vi a feca l l y conta mi na ted s oi l , not pers on to pers on. 386. The answer is d. (Brooks, pp 686, 690. Levinson, pp 373-376. Murray [2009], pp 881-884. Ryan, pp 793-795. Toy, pp 314, 332.) Enterobius (pi nworm), Ascaris (roundworm), Necator (hookworm), a nd Trichuris (whi pworm) a re roundworms , or nema todes . Taenia saginata (ta peworm), a s egmented fl a tworm, a ffects the s ma l l i ntes ti ne of huma ns . Ta peworm s egments , ca l l ed proglottids, a ppea r i n the s tool of i nfected pers ons . The Taenia group of ta peworms a re cons i dered to be the l a rge (3-10 m i n l ength) ones tha t i nfect huma ns . “Mea s l y pork” conta i ns bl a dderl i ke l a rva e (cys ti cerci ) whi ch a re the s i ze of ri ce gra i ns . Thes e devel op i nto gi a nt ta peworms i n the i ntes ti ne a nd egg-fi l l ed termi na l progl otti ds brea k off a nd a re el i mi na ted i n the feces . Ascaris lumbricoides, the gi a nt roundworm of huma ns , i nfects more tha n one bi l l i on peopl e. Enterobius vermicularis i s the pi nworm, where a na l i rri ta ti on ca us es a na l –ora l tra ns mi s s i on by conta mi na ted fi ngers . Necator s peci es a re hookworms whi ch enter s ki n di rectl y from i nfected s oi l ; the other i mporta nt s peci es of hookworms i s Ancylostoma duodenale. Hookworms i nfect over a bi l l i on peopl e worl dwi de. Iron defi ci ency a nemi a (ca us ed by bl ood l os s a t the s i te of i ntes ti na l a tta chment of the a dul t worms ) i s the mos t common s ymptom of hookworm i nfecti on. Trichuris (whi pworm) a l s o i s tra ns mi tted by i nges ti on of eggs from feces -conta mi na ted s oi l . 387. The answer is b. (Brooks, pp 682-683. Levinson, pp 365-366, 518. Murray [2009], pp 841-844. Ryan, pp 722-727.) One of the l ea di ng ca us es of dea th a mong AIDS pa ti ents i s CNS toxopl a s mos i s . It i s thought tha t Toxo-plasma i nfecti on i s a res ul t of rea cti va ti on of ol d or preexi s ti ng toxopl a s mos i s . Occa s i ona l l y, the i nfecti on ma y be a cqui red by needl e s ha ri ng. Beca us e the di s ea s e i s a rea cti va ti on of ol d or preexi s ti ng toxopl a s mos i s , routi ne qua nti ta ti ve tes ts for IgM a nti body a re us ua l l y nega ti ve, a nd IgG ti ters a re l ow (≤1:256, IFA). More s ophi s ti ca ted methods , s uch a s IgM ca pture or IgG a vi di ty, ma y revea l a n a cute res pons e. 388. The answer is b. (Brooks, pp 663-666. Levinson, pp 366-368. Murray [2009], pp 850-852. Ryan, pp 695, 757-760.) Ameri ca n trypa nos omi a s i s (Cha ga s di s ea s e) i s produced by T. cruzi, whi ch i s tra ns mi tted to huma ns by the bi te of a n i nfected reduvi i d bug. They a re i ntroduced when i nfected bug
feces a re rubbed i nto the conjucti va , the bug bi te, or a brea k i n the s ki n. Infa nts a re often i nfected a nd demons tra te a uni l a tera l s wel l i ng of the eyel i ds (Roma na s i gn). Roma na s i gn i s a ma rker of a cute Cha ga s di s ea s e. The s wel l i ng i s due to bug feces bei ng a cci denta l l y rubbed i nto the eye, or beca us e the bi te wound wa s on the s a me s i de of the chi l d’s fa ce a s the s wel l i ng. After mul ti pl i ca ti on, the ti s s ues mos t l i kel y to be a ffected i n the chroni c s ta ge of the di s ea s e a re the ca rdi a c mus cl e fi bers a nd the di ges ti ve tra ct. A di ffus e i nters ti ti a l fi bros i s of the myoca rdi um res ul ts a nd ma y l ea d to hea rt fa i l ure a nd dea th. The i nfl a mma tory l es i ons i n the di ges ti ve tra ct tha t a re s een i n the es opha gus a nd col on produce cons i dera bl e di l a ta ti on. Cha ga s di s ea s e ha s not been a n i mporta nt di s ea s e i n the Uni ted Sta tes ; mos t ca s es ha ve been i mported, a l though there a re a few reports of endogenous di s ea s e i n the s outhern Uni ted Sta tes . The other orga ns ma y be a ffected, but not a t the ra te the hea rt a nd di ges ti ve tra ct a re i nva ded. 389. The answer is a. (Brooks, pp 674-679. Levinson, pp 361-365. Murray [2009], pp 835-839. Ryan, p 712.) The febri l e pa roxys ms of Plasmodium malariae ma l a ri a occur a t 72-hour i nterva l s ; thos e of P. falciparum a nd P. vivax ma l a ri a occur every 48 hours . The pa roxys ms us ua l l y l a s t 8 to 12 hours wi th P. vivax ma l a ri a but ca n l a s t 16 to 36 hours wi th P. falciparum di s ea s e. In P. vivax, P. ovale, a nd P. malariae i nfecti ons , a l l s ta ges of devel opment of the orga ni s ms ca n be s een i n the peri phera l bl ood; i n ma l i gna nt terti a n (P. falciparum) i nfecti ons , onl y ea rl y ri ng s ta ges a nd ga metocytes a re us ua l l y found. Schistosoma, Trypanosoma, a nd Wucheria i nfecti ons do not pres ent wi th peri odi c s ymptoms i n thei r di s ea s e progres s i ons . 390. The answer is a. (Brooks, pp 692-693. Levinson, p 382. Murray [2009], pp 874-875. Ryan, pp 807-808.) The Chi nes e l i ver fl uke, C. sinensis, i s a pa ra s i te of huma ns tha t i s found i n Ja pa n, Chi na , Korea , Ta i wa n, a nd Indochi na . An es ti ma ted 25 mi l l i on peopl e i n the Fa r Ea s t a re i nfected. Up to one fourth of Chi nes e i mmi gra nts to the Uni ted Sta tes ha rbor thi s fl uke. Inges ti on of conta mi na ted ra w, undercooked, frozen, s a l ted or dri ed fres h wa ter fi s h i s the s ource of i nfecti on—cooki ng conta mi na ted fi s h i s the mos t effecti ve wa y of el i mi na ti ng the pa ra s i te on i ndi vi dua l ba s i s . Mos t pa thol ogi c ma ni fes ta ti ons res ul t from i nfl a mma ti on a nd i ntermi ttent obs tructi on of the bi l i a ry ducts . In the a cute pha s e, a bdomi na l pa i n, na us ea , di a rrhea , a nd eos i nophi l i a ca n occur. In l ong-s ta ndi ng i nfecti ons , ga l l bl a dder/bi l i a ry duct i nvol vement i s common (eg, chol a ngi ti s , chol el i thi a s i s ), pa ncrea ti ti s , a nd chol a ngi oca rci noma ca n devel op, whi ch ma y be fa ta l . Pra zi qua ntel i s the drug of choi ce. Diphyllobothrium latum, the fi s h ta peworm, tra vel s from copepod to frog to wa ter s na i l or rodent to a ca rni vore. D. latum a bs orbs vi ta mi n B 12 , ca us i ng a hos t vi ta mi n defi ci ency. Plasmodium s peci es a re tra ns mi tted vi a a mos qui to vector. Taenia s peci es a re tra ns mi tted by i nges ti on of under-cooked, l a rva e-conta i ni ng beef or pork. 391. The answer is d. (Brooks, pp 692-693. Levinson, p 382. Murray [2009], pp 874-875. Ryan, pp 807-808.) The l i fe cycl e of C. sinensis i s s i mi l a r to tha t of other di geneti c trema todes . A s na i l i s cha ra cteri s ti ca l l y the fi rs t i ntermedi a te hos t of trema todes . Cows a nd pi gs a re i ntermedi a te hos ts for Taenia s peci es . Mos qui toes s erve a s i ntermedi a te hos ts for Plasmodium s peci es . Ti cks a re not i ntermedi a te hos ts for Clonorchis s peci es . 392. The answer is b. (Brooks, pp 674-679. Levinson, pp 361-365. Murray [2009], pp 838-839. Ryan, pp 711-722.) The ca s e hi s tory pres ented i n the ques ti on i s cha ra cteri s ti c of i nfecti on wi th P. falciparum, the ca us a ti ve a gent of ma l i gna nt terti a n ma l a ri a . The l ong dura ti on of the febri l e s ta ge rul es out other forms of ma l a ri a . The pres ence of ri ngl i ke young trophozoi tes a nd cres cent-l i ke ma ture ga metocytes —a s repres ented i n the i l l us tra ti on bel ow—a s wel l a s the a bs ence of s chi zonts i s di a gnos ti c of P. falciparum ma l a ri a . Ans wer opti on A repres ents onl y RBCs a nd C repres ents trypa nos omes a nd RBCs . Choi ce D repres ents a mi crofi l a ri um a nd RBCs whi l e E exhi bi ts crenel l a ted RBCs (round RBCs i nto s hrunken, s ta rry forms ).
(Reproduced from the Centers for Disease Control and Prevention. Public Health Image Library, ID# 5856. http://phil.cdc.gov/phil/details.asp.) 393. The answer is e. (Brooks, pp 661-662. Levinson, pp 356-360. Murray [2009], pp 826-827. Ryan, pp 742-745.) Trichomonas vaginalis i s the onl y protozoa n l i s ted where the trophozoi te i s the di a gnos ti c a nd i nfecti ve s ta ge tha t feeds on the mucos a l s urfa ce of the va gi na (ba cteri a a nd l eukocytes ). The trophozoi te pos s es s es a s hort, undul a ti ng membra ne (one-ha l f of the body) a nd four a nteri or fl a gel l a . No cys t s ta ge exi s ts . A pers i s tent va gi na l i s wi th a frothy a nd foul -s mel l i ng di s cha rge wi th burni ng, i tchi ng, a nd i ncrea s ed frequency of uri na ti on i s common. Balantidium coli i s a l a rge ci l i a ted protozoa n pa ra s i te. Entamoeba histolytica i s a n i ntes ti na l a moeba . Giardia lamblia i s a fl a gel l a ted protozoa n found i n the duodenum a nd jejunum of huma ns . Toxoplasma gondii i s a cocci di a n protozoa n es peci a l l y i mporta nt i n congeni ta l i nfecti ons when the pregna nt woma n becomes i nfected duri ng pregna ncy. 394. The answer is a. (Brooks, pp 686t, 694. Levinson, pp 378-382. Murray [2009], pp 886-887. Ryan, pp 799-801.) Echinococcus granulosus ca us es hyda ti d di s ea s e. The defi ni ti ve hos ts a re dogs . Sheep, ca ttl e, a nd huma ns a re i ntermedi a te hos ts . The a dul t ta peworm does not occur i n huma ns . In the herbi vores (i nfected by gra zi ng where eggs ha ve been depos i ted by ca rni vore feces ) the eggs ha tch a nd rel ea s e hexa ca nths . Thes e penetra te the gut a nd pa s s to other ti s s ues (l i ver, vi s cera , mus cl e, a nd bra i n). Huma ns a re onl y i nfected from dog feces a nd devel op hyda ti d cys ts , a s des cri bed for herbi vores . Di a rrhea , therefore, does not occur wi th E. granulosis huma n i nfecti ons , wherea s the other four choi ces ca n routi nel y pres ent wi th di a rrhea . 395. The answer is c. (Brooks, pp 695. Levinson, pp 376-377. Murray [2009], pp 884-886. Ryan, pp 797-798.) Cons umpti on of ra w fi s h ca us es endemi c di phyl l obothri a s i s i n Sca ndi na vi a a nd the Ba l ti c countri es . Whi l e mos t peopl e do not become i l l , a s ma l l percenta ge (2%) devel ops vi ta mi n B 12 defi ci ency a nemi a . The a dul t fi s h ta peworm ha s a n a ffi ni ty for vi ta mi n B 12 a nd ma y i nduce a s eri ous mega l obl a s ti c a nemi a . Pa rvovi rus B19 ca us es a cute hemol yti c a nemi a pri ma ri l y i n i mmunos uppres s ed pa ti ents . Yersinia i nfecti on i s common i n Sca ndi na vi a but i s not fi s h-borne a nd does not ca us e a nemi a . The l a rva l s ta ge of T. solium i s ca l l ed cysticercus. Huma ns us ua l l y a cqui re cys ti cercos i s by i nges ti on of food a nd wa ter conta mi na ted by i nfected huma n feces . Exces s i ve cons umpti on of i ce-col d vodka ma y l ea d to hea da ches a nd memory l os s , but otherwi s e ha s nothi ng to do wi th pa ra s i temi a . 396. The answer is e. (Brooks, pp 688-691. Levinson, pp 387, 390. Murray [2009], pp 860-862. Ryan, pp 763, 774-777. Toy, p 314.) Strongyl oi di a s i s i s endemi c i n Southea s t As i a , La ti n Ameri ca , s ub-Sa ha ra n Afri ca , a nd pa rts of the s outhea s tern Uni ted Sta tes . Hyperi nfecti on occurs when the rha bdi ti form l a rva e tra ns form i nto fi l a ri form l a rva e i n the ga s troi ntes ti na l tra ct, whi ch then penetra te the peri recta l s ki n or the wa l l of the i ntes ti ne a nd ga i n a cces s to the bl oods trea m. Di s s emi na ti on to the l ungs , l i ver, CNS, a nd other orga ns l ea ds to s evere i nfl a mma ti on a nd orga n dys functi on. The prognos i s for pa ti ents wi th hyperi nfecti on s yndrome i s poor, wi th morta l i ty ra tes exceedi ng >80% i n s ome reports . Defi ni ti ve di a gnos i s depends on the demons tra ti on of S. stercoralis l a rva e i n s tool , duodena l fl ui d, or ti s s ue s peci mens . Gra m s ta i ni ng of s putum a nd/or bronchoa l veol a r l a va ge
fl ui d s a mpl es ma y be us eful for pa ti ents wi th hyperi nfecti on s yndrome. Necator mus t be di s ti ngui s hed from Strongyloides by mi cros copy. Gros s a ppea ra nces a re s i mi l a r. Ascaris i s a common roundworm whi ch ca n be found i n the s ma l l i ntes ti ne a nd l ungs , but not i n a l l body fl ui ds . Hymenolepis s peci es a re ta peworms , found onl y i n the s ma l l i ntes ti ne. Loi a s i s i s a n i nfecti on tra ns mi tted by the bi te of deer fl i es found i n equa tori a l Afri ca . They i nva de s ubcuta neous ti s s ue a nd a re mi gra tory. Mi crofi l a ri a e a re a l s o found i n the bl ood. 397. The answer is d. (Brooks, pp 669-672. Levinson, pp 354-357, 517. Murray [2009], pp 822-824. Toy, p 314.) Entamoeba histolytica i s a pa thogeni c s peci es tha t i s ca pa bl e of ca us i ng di s ea s e, s uch a s col i ti s or l i ver a bs ces s , i n huma ns . Entamoeba dispar i s i ndi s ti ngui s ha bl e from E. histolytica by us ua l l a bora tory tes ts but onl y exi s ts i n huma ns a s a n a s ymptoma ti c ca rri er s ta te a nd does not ca us e col i ti s . Infecti on wi th E. histolytica i s preva l ent i n Centra l a nd South Ameri ca , s outhern a nd wes tern Afri ca , the Fa r Ea s t, a nd Indi a . Poor s a ni ta ti on a nd l ower s oci oeconomi c condi ti ons fa vor the s prea d of the di s ea s e. In the Uni ted Sta tes , thos e who tra vel to endemi c a rea s , homos exua l ma l es , a nd i ns ti tuti ona l i zed pers ons a re a t i ncrea s ed ri s k of i nfecti on. Acanthamoeba s peci es a re free-l i vi ng a meba s i n s oi l a nd wa ter a nd us ua l l y ca us e i nfecti ons of s ki n, encepha l i ti s , a nd keri ti ti s . Ascaris i s a nema tode a nd i s tra ns mi tted by i nges ti on. They ha tch i n the s ma l l i ntes ti ne, a nd l a rva e mi gra te to the pul mona ry a l veol i . From here, they i nduce a cough a nd a re s wa l l owed by the hos t, ma turi ng i n the s ma l l i ntes ti ne. Balantidium coli i s a ci l i a te, i nfecti ng the l i ni ng of the l a rge i ntes ti ne, cecum, a nd termi na l i l i um. Taenia s peci es (beef a nd pork) a re i nges ted i n undercooked mea t. Onl y T. solium (pork) ma y occa s i ona l l y i nvol ve l i ver i f cys ti cercos i s occurs . 398. The answer is c. (Brooks, pp 674-680. Levinson, pp 361-365. Murray [2009], pp 835-838. Ryan, pp 711-722.) Prophyl a xi s for ma l a ri a s houl d be cons i dered whenever a pers on i s tra vel i ng i n a ma l a ri a -endemi c a rea . Mos t drugs us ed i n trea tment a re a cti ve a ga i ns t the pa ra s i te forms i n the bl ood (the form tha t ca us es di s ea s e) a nd i ncl ude: chl oroqui ne, s ul fa doxi nepyri metha mi ne, mefl oqui ne, a tova quone-progua ni l , qui ni ne, a rtemi s i ni n deri va ti ves (not l i cens ed for us e i n the Uni ted Sta tes , but often found overs ea s ). The WHO recommends i ntra venous a rtes una te a s the trea tment of choi ce for s evere ma l a ri a i n a dul ts a nd chi l dren i n a rea s of l ow tra ns mi s s i on. Other control mea s ures s uch a s dra i ni ng s wa mps , protecti ve cl othi ng a nd netti ng, a nd i ns ect repel l ents a re a l s o effecti ve. There i s no currentl y a va i l a bl e va cci ne for ma l a ri a . Ti ck repel l ents woul d not be us eful s i nce onl y mos qui toes a re ma l a ri a l vectors . 399. The answer is d. (Brooks, pp 663-668. Levinson, pp 366-369. Murray [2009], pp 848-852. Ryan, p 902.) Afri ca n trypa nos omi a s i s (s l eepi ng s i cknes s ) i s ca us ed by T. brucei gambiense a nd T. brucei rhodesiense a nd tra ns mi tted by ts ets e fl i es . From the fl y’s s a l i va ry gl a nds , the trypoma s ti gotes enter the hos t’s bl ood a nd l ymph a nd eventua l l y the CNS. The trypoma s ti gotes reproduce by bi na ry fi s s i on a nd a re i nfecti ve for bi ti ng ts ets e fl i es . Duri ng the cours e of trypa nos ome i nfecti on, the number of pa ra s i tes i n the bl ood a nd l ymph ti s s ues fl uctua tes a ccordi ng to the hos t’s i mmune res pons e. An i ncrea s e i n pa ra s i te number i s rel a ted to the prol i fera ti on of pa ra s i te s ub-popul a ti ons tha t expres s a n a nti geni ca l l y new or va ri a nt gl ycoprotei n coa t. Ea ch pa ra s i te ca rri es genes encodi ng mul ti pl e, va ri a nt s urfa ce gl ycoprotei ns (VSG) wi th onl y one VSG bei ng expres s ed a t a ny one ti me. Thes e cha nges l ea d to eva s i on of the i mmune s ys tem a nd produce cha l l enges for va cci ne devel opment. The other pa ra s i tes l i s ted do not exhi bi t thi s a bi l i ty to cha nge s urfa ce gl ycoprotei ns . 400. The answer is d. (Brooks, pp 669-671. Levinson, pp 354-357, 517. Murray [2009], pp 822-824. Ryan, pp 733-738.) Of the i ntes ti na l a meba s , E. hartmanni, E. coli, E. polecki, a nd E. nana a re cons i dered nonpa thogeni c. Entamoeba histolytica i s di s ti ncti vel y cha ra cteri zed by i ts pa thogeni c potenti a l for huma ns , a l though i nfecti on wi th thi s protozoa n i s commonl y a s ymptoma ti c (ca us i ng “hea l thy ca rri ers ”). Symptoma ti c a mebi a s i s a nd dys entery occur when the trophozoi tes i nva de the i ntes ti na l wa l l a nd produce ul cera ti on a nd di a rrhea . Peri toni ti s ca n occur, wi th the l i ver the mos t common s i te of extra i ntes ti na l di s ea s e. The l i fe cycl e of the ameba i s s i mpl e by compa ri s on. There i s encys tment of the troph, fol l owed by excys ta ti on i n the i l eoceca l regi on. The trophs mul ti pl y a nd become es ta bl i s hed i n the cecum, where encys ta ti on ta kes pl a ce a nd res ul ts i n a bunda nt a meba s , cys ts , a nd trophozoi tes . Infecti on i s s prea d by the cys ts , whi ch ca n rema i n for weeks or months i n a ppropri a tel y moi s t s urroundi ngs . 401. The answer is e. (Brooks, pp 665, 688. Levinson, pp 379-382. Murray [2009], pp 876-879. Ryan, pp 803, 808-813.) Three ma jor s peci es of bl ood fl ukes (Schistosoma mansoni, S. japonicum, a nd S. haematobium) ca us e the di s ea s e s chi s tos omi a s i s . The pos i ti on of s pi nes i n thei r eggs i s s peci fi c for ea ch s chi s tos ome s peci es . Thi s di s ea s e i s endemi c i n 74 devel opi ng countri es a nd a n es ti ma ted 200 mi l l i on i nfected a nd 800 mi l l i on peopl e a re a t ri s k of a cqui ri ng s chi s tos omi a s i s . Intes ti na l s chi s tos omi a s i s i s ca us ed by S. mansoni. Ori enta l or As i a ti c i ntes ti na l s chi s tos omi a s i s i s ca us ed by the S. japonicum a nd uri na ry s chi s tos omi a s i s , ca us ed by S. haematobium. Ma jor Pa thol ogy of s chi s tos omi a s i s i s due to i mmunol ogi ca l rea cti ons to Schistosoma eggs tra pped i n ti s s ues . Anti gens rel ea s ed from the egg s ti mul a te a gra nul oma tous rea cti on compri s ed of T cel l s , ma cropha ges , a nd eos i nophi l s tha t res ul ts i n cl i ni ca l di s ea s e. Conti nui ng i nfecti on ma y ca us e gra nul oma tous rea cti ons a nd fi bros i s i n the a ffected orga ns , whi ch ma y res ul t i n ma ni fes ta ti ons tha t i ncl ude: porta l hypertens i on a nd hepa tos pl enomega l y (S. mansoni, S. japonicum). Cys ti ti s a nd urethri ti s (S. haematobium) wi th hema turi a , whi ch ca n progres s to bl a dder ca ncer. Control s tra tegi es for s chi s tos omi a s i s i ncl ude: ma s s trea tment wi th pra zi qua ntel i n the communi ty, i ntroducti on of publ i c hygi ene progra ms (s a fe wa ter s uppl y, s a ni ta ry di s pos a l of excreta , fl us ha bl e toi l ets ) a nd s na i l era di ca ti on progra ms . Currentl y there i s no va cci ne a ga i ns t thi s di s ea s e.
(Reproduced from the Centers for Disease Control and Prevention. http://www.dpd.cdc.gov/dpdx/html/Schistosomiasis.htm.) 402. The answer is d. (Brooks, pp 337-339. Levinson, pp 176-177. Murray [2009], pp 411-414. Ryan, pp 434-437.) In the Uni ted Sta tes , B. burgdorferi, the ca us a ti ve a gent of Lyme di s ea s e, ha s two pri nci pa l vectors : I. scapularis i n the ea s tern a nd mi dwes tern Uni ted Sta tes a nd I. pacificus i n the wes tern Uni ted Sta tes . The ti cks a re ti ny a nd ca n ea s i l y be mi s s ed. Fortuna tel y, rel a ti vel y few peopl e who a re bi tten by ti cks devel op Lyme di s ea s e. Lyme di s ea s e, us ua l l y wi th joi nt i nvol vement, i s a l s o s een i n veteri na ry pa ti ents s uch a s dogs , ca ts , a nd hors es . Whi te-ta i l ed deer a nd s ma l l rodents a re a n i mporta nt res ervoi r for thes e ti cks . B. burgdorferi ha s been i s ol a ted from mos qui toes a nd Dermacentor a nd Amblyomma ti cks , a s wel l a s from s evera l Ixodes s peci es . However, the i s ol a ti on of the ba cteri um from thes e ti cks i s not s uffi ci ent evi dence to i ndi ca te tha t they tra ns mi t the di s ea s e to huma ns . 403. The answer is b. (Brooks, pp 687, 692. Levinson, pp 392-393. Murray [2009], pp 863-865. Ryan, pp 695-779, 784-785.) Wuchereria bancrofti i s the ca us e of ba ncrofti a n fi l a ri a s i s or fi l a ri a l el epha nti a s i s . Control of the mos qui to vectors (cul ex, a nophel es , a nd Aedes ) i s the mos t s i gni fi ca nt mecha ni s m to control huma n i nfecti ons . A di s ea s e of the tropi cs a nd s ubtropi cs , a dul ts l i ve i n the l ympha ti cs of a hos t a nd ca us e l ymph bl ocka ge of the feet, a rms , geni ta l s , a nd brea s ts . Enl a rgement of the a ffected body pa rt (el epha nti a s i s ) ca n then occur. Ba bes i os i s i s ca us ed by ti ck-borne Babesia microti. Lei s hma ni a s i s i s s prea d by a s a ndfl y (Phl ebotomus ) vector. Gui nea worms (Dracunculus medinensis) ha s a n a qua ti c l i fe cycl e i nvol vi ng copepods (wa ter fl ea s ). Dog ta peworms woul d routi nel y be tra ns mi tted by feca l conta mi na ti on.
(Reproduced from the Centers for Disease Control and Prevention. Public Health Image Library, ID# 373. http://phil.cdc.gov/phil/details.asp.) 404 to 407. The answers are 404-e, 405-a, 406-d, and 407-c. (Brooks, pp 685, 688, 693. Levinson, pp 379-382. Murray [2009], pp 871-880. Ryan, pp 803, 809-813.) The l i fe cycl e of the medi ca l l y i mporta nt trema todes (or fl ukes ) i nvol ves a s exua l cycl e i n huma ns a nd a n a s exua l cycl e i n s na i l s . The s chi s tos omes ca n penetra te the s ki n, wherea s Clonorchis a nd Paragonimus a re i nges ted, us ua l l y i n fi s h or s ea food. Thes e fl ukes ca n be ea s i l y di fferenti a ted morphol ogi ca l l y by the a ppea ra nce of the egg. Schi s tos ome eggs ha ve a n i denti fi a bl e s pi ne, a nd both Clonorchis a nd Paragonimus eggs a re opercul a ted; tha t i s , they ha ve wha t a ppea rs to be a cover tha t opens . Serol ogi ca l tes ts a re not us eful . Ma ny pa ti ents wi th s chi s tos omi a s i s a re a s ymptoma ti c, but di s ea s e ma y become chroni c, res ul ti ng i n ma l a i s e, di a rrhea , a nd hepa tos pl enomega l y (a n enl a rged l i ver a nd s pl een). Clonorchis i nfecti on us ua l l y ca us es upper a bdomi na l pa i n but ca n a l s o ca us e bi l i a ry tra ct fi bros i s . Pa ra goni mi a s i s i s cha ra cteri zed by a cough, often wi th bl oody s putum, a nd pneumoni a . Pra zi qua ntel i s the trea tment of choi ce for thes e fl ukes . 408 to 411. The answers are 408-c, 409-e, 410-a, and 411-b. (Brooks, pp 660-662, 669-674. Levinson, pp 357-358, 390. Murray [2009], pp 821-826, 853-855, 860862. Ryan, pp 695-696, 733-738, 745-748, 769-771, 774-777. Toy, p 332.) It i s not uncommon tha t repea ted s tool s peci mens do not revea l the s us pected pa ra s i te. Al s o, mi cros copi c a na l ys i s of s tool ma y not revea l pa ra s i te l oa d when s uch da ta a re neces s a ry. For thes e rea s ons , other techni ques a re a va i l a bl e to i denti fy pa ra s i tes a s wel l a s to qua nti ta te them. A Scotch Ta pe method i s us ed for di a gnos i s of Enterobius vermicularis (pi nworms ). The di a gnos i s of gi a rdi a s i s i s us ua l l y ma de by detecti ng trophozoi tes a nd cys ts of G. lamblia i n cons ecuti ve feca l s peci mens . Al terna ti vel y, a gel a ti n ca ps ul e on a s tri ng (enterotes t) ca n be s wa l l owed, pa s s ed to the duodenum, a nd then retri eved a fter 4 hours . The s tri ng i s then exa mi ned for Giardia. A recent i nnova ti on i s the i ntroducti on of a n EIA for G. lamblia. The EIA i s more s ens i ti ve tha n mi cros copy, ca n be performed on a s i ngl e s tool s peci men, a nd does not depend on the pres ence of enti re trophozoi tes a nd cys ts . Duri ng s i gmoi dos copy, a curette or s ucti on devi ce ma y be us ed to s cra pe or a s pi ra te ma teri a l from the mucos a l s urfa ce. A di rect mount of thi s ma teri a l s houl d i mmedi a tel y be exa mi ned for E. histolytica trophozoi tes , a nd then a perma nent s ta i n ma de for s ubs equent exa mi na ti on. The Ba erma nn techni que ma y be hel pful i n recoveri ng Strongyloides l a rva e (See Fi gure on the next pa ge). The pi cture i s of a rha bdi toi d l a rva of S. stercoralis i n a n uns ta i ned wet mount of s tool . Noti ce the rha bdi toi d es opha gus (white arrow) a nd promi nent geni ta l pri mordi um. Es s enti a l l y, feca l ma teri a l i s pl a ced on da mp ga uze on the top of a gl a s s funnel tha t i s three-qua rters fi l l ed wi th wa ter. The l a rva e mi gra te through the da mp ga uze a nd i nto the wa ter. The wa ter ma y then be centri fuged to concentra te the Strongyloides. Worm burdens ma y be es ti ma ted by a number of mi cros copi c methods . Whi l e not often done, s uch procedures ma y provi de da ta on the extent of i nfecti on or the effi ca cy of trea tment of hookworms , Ascaris, or Trichuris. Thi rty thous a nd Trichuris eggs per gra m, 2000 to 5000 hookworm eggs per gra m, a nd one Ascaris egg a re cl i ni ca l l y s i gni fi ca nt a nd s ugges t a hea vy worm burden. A cel l opha ne ta pe s wa b i s us ed to tra p pi nworms cra wl i ng out of the a nus duri ng the ni ght. The ta pe i s then exa mi ned mi cros copi ca l l y for Enterobius.
(Reproduced from the Centers for Disease Control and Prevention. http://www.dpd.cdc.gov/dpdx/html/Strongyloidiasis.htm.) 412. The answer is c. (Brooks, pp 682-684. Levinson, pp 365-366. Murray [2009], pp 841-844. Ryan, pp 695-696, 723-727, 746-748, 779-784, 809-813.) Toxopl a s mos i s i s genera l l y a mi l d, s el f-l i mi ti ng di s ea s e; however, s evere feta l di s ea s e i s pos s i bl e i f pregna nt women i nges t Toxoplasma oocys ts . Cons umpti on of uncooked mea t ma y res ul t i n ei ther a n a cute toxopl a s mos i s or a chroni c toxopl a s mos i s tha t i s a s s oci a ted wi th s eri ous eye di s ea s e. Mos t a dul ts ha ve a nti body ti ters to Toxoplasma, a nd thus woul d ha ve a pos i ti ve Sa bi n–Fel dma n dye tes t. The Sa bi n–Fel dma n dye tes t mea s ures a nti bodi es tha t render the membra ne of l i vi ng T. gondii i mpermea bl e to methyl ene bl ue (no s ta i ni ng occurs ). It i s bei ng repl a ced by IFA a nd ELISA tes ts . Whi l e we us ua l l y thi nk of i n utero i nfecti ons of a devel opi ng fetus a nd the s ubs equent medi ca l di ffi cul ti es of the newborn i nfa nt, a n equa l l y i mporta nt s ource of huma n expos ure i s ra w or undercooked mea t i n whi ch i nfecti ve ti s s ue cys ts a re frequentl y found. When a ti s s ue cys t ruptures , numerous bra dyzoi tes a re rel ea s ed a nd grow, ca us i ng chori oreti ni ti s , myoca rdi ti s , a nd pol ymyos i ti s . Trea tment i s wi th pyri metha mi ne a nd s ul fa di a zi ne. Schi s tos omi a s i s i s ca us ed by bl ood fl ukes whos e cerca ri a e (l a rva e) penetra te s ki n i n s na i l -i nfes ted wa ter. Tri chi nos i s i s ca us ed by the tri chi na worm whos e l a rva e a re found i n uncooked pork. Cuta neous l a rva mi gra ns cons i s ts of s ubcuta neous mi gra ti ng l a rva e of hookworms . Vi s cera l l a rva mi gra ns i s a condi ti on i n huma ns ca us ed by the mi gra tory l a rva e of certa i n nema todes , huma ns bei ng a termi na l hos t. Nema todes ca us i ng s uch zoonoti c i nfecti ons a re Toxocara canis, Toxocara cati, a nd Ascaris suum. La rva currens i s a n i tchy, cuta neous condi ti on ca us ed by i nfecti ons wi th Strongyloides stercoralis tha t i ntermi ttentl y comes a nd goes every few hours . 413 to 416. The answers are 413-d, 414-a, 415-b, and 416-e. (Brooks, pp 660, 685, 687t, 691. Levinson, pp 357-358, 379-382, 390-391. Murray [2009], pp 824-826, 855-856, 862-863, 876-879. Ryan, pp 695-696, 723-727, 746-748, 779-784, 809-813.) Tri chi nos i s mos t often i s ca us ed by i nges ti on of conta mi na ted pork products . However, ea ti ng undercooked bea r, wa l rus , ra ccoon, or pos s um mea t a l s o ma y ca us e thi s di s ea s e. Symptoms of tri chi nos i s i ncl ude mus cl e s orenes s a nd s wol l en eyes . The des cri bed s ymptoms of the fur tra pper woul d not fi t the cl i ni ca l pres enta ti ons of gi a rdi a s i s , s chi s tos omi a s i s , toxopl a s mos i s , or vi s cera l l a rva mi gra ns . Al though gi a rdi a s i s ha s been cl a s s i ca l l y a s s oci a ted wi th tra vel to endemi c a rea s ma ny ca s es of gi a rdi a s i s ca us ed by conta mi na ted wa ter ha ve been reported i n the Uni ted Sta tes a s wel l . Di a gnos i s i s ma de by detecti ng cys ts i n the s tool . In s ome ca s es , di a gnos i s ma y be very di ffi cul t beca us e of the rel a ti vel y s ma l l number of cys ts pres ent. Al terna ti vel y, a n EIA ma y be us ed to detect Giardia a nti gen i n feca l s a mpl es . The s ymptoms tha t were experi enced by the corres pondent woul d not fi t the cl i ni ca l pres enta ti on of s chi s tos omi a s i s , toxopl a s mos i s , tri chi nos a , or vi s cera l l a rva mi gra ns . Schi s tos omi a s i s i s a worl dwi de publ i c hea l th probl em. Control of thi s di s ea s e enta i l s the el i mi na ti on of the i ntermedi a te hos t s na i l a nd remova l of s trea ms i de vegeta ti on. Abdomi na l pa i n i s a s ymptom of s chi s tos omi a s i s . The s ymptoms tha t were experi enced by the col onel woul d not fi t the cl i ni ca l pres enta ti on of gi a rdi a s i s , toxopl a s mos i s , tri chi nos a , or vi s cera l l a rva mi gra ns . Vi s cera l l a rva mi gra ns i s a n occupa ti ona l di s ea s e of peopl e who a re i n cl os e conta ct wi th dogs a nd ca ts . The di s ea s e i s ca us ed by the nema todes Toxocara canis (dogs ) a nd Toxocara cati (ca ts ) a nd ha s been recogni zed i n young chi l dren who ha ve cl os e conta ct wi th pets or who ea t di rt. Symptoms i ncl ude s ki n ra s h, eos i nophi l i a , a nd hepa tos pl enomega l y. The s ymptoms tha t were experi enced by the teena ger woul d not fi t the cl i ni ca l pres enta ti on of gi a rdi a s i s , toxopl a s mos i s , tri chi nos a or s chi s tos omi a s i s . 417 to 421. The answers are 417-e, 418-a, 419-d, 420-c, and 421-b. (Brooks, pp 660-662, 680, 690, 693. Levinson, pp 357-360, 382-383, 390-391. Murray [2009], pp 824-827, 862-863, 875-876. Ryan, pp 695-696, 741-748, 779, 781-784, 803, 805-807.) Trichomonas vaginalis, a n odd-l ooki ng protozoa n, moves wi th a jerky, a l mos t da rti ng moti on. Tri chomoni a s i s , a bothers ome va gi na l i nfecti on, ca n be di a gnos ed by obs ervi ng thi s orga ni s m i n a wet mount of va gi na l s ecreti ons . It ma y be wa s hed out i n the uri ne a s wel l . Trichomonas vaginalis ca n be grown i n s peci a l medi a , a nd there a re now s evera l products a va i l a bl e for di rect detecti on of the orga ni s m. Trichinella spiralis ca us es tri chi nos i s , a pa ra s i ti c di s ea s e tha t i s us ua l l y mi l d a nd res ul ts i n mus cl e pa i n a nd a mi l d febri l e i l l nes s . However, ful mi na nt fa ta l ca s es ha ve been des cri bed. Huma ns , who a re a cci denta l hos ts , become i nfected by i nges ti ng cys ts tha t a re i n the mus cl e of a ni ma l s . Mos t i nfecti ons s ti l l come from pork, a l though regul a ti ons on pi g feedi ng ha ve ma rkedl y reduced the i nci dence. La bora tory di a gnos i s i s
by s erol ogy or demons tra ti on of the l a rva e i n the mus cl e ti s s ue. Paragonimus westermani i s a l ung fl uke. Thi s trema tode i nfects l ung ti s s ue a nd i s s een not onl y i n s putum but a l s o i n feces beca us e i nfected pa ti ents s wa l l ow res pi ra tory s ecreti ons . Pa ra goni mi a s i s i s contra cted by i nges ti ng the meta cerca ri a e tha t a re encys ted i n cra bs or cra yfi s h. Giardia i nfecti on ma y be di ffi cul t to di a gnos e by s tool exa mi na ti on, a s pa ti ents ma y s hed the cys ts i ntermi ttentl y. When s ymptoms pers i s t a nd the s tool exa mi na ti on i s nega ti ve, then duodena l contents ma y be s a mpl ed di rectl y wi th the enterotes t. The pa ti ent s wa l l ows a gel a ti n ca ps ul e tha t conta i ns a coi l ed s tri ng. The other end i s a tta ched to the pa ti ent’s fa ce. The gel a ti n ca ps ul e di s s ol ves , a nd Giardia orga ni s ms , i f pres ent, a dhere to the s tri ng wi thi n a 4-hour peri od. The s tri ng i s retri eved a nd exa mi ned mi cros copi ca l l y. Al terna ti vel y, a n enzyma ti c i mmunoa s s a y ca n detect Giardia a nti gen di rectl y i n a s i ngl e s peci men of feces . Babesia i s a s porozoa n pa ra s i te tra ns mi tted by the bi te of I. scapularis, the s a me ti ck tha t ca rri es B. burgdorferi. Reproducti on of thi s pa ra s i te occurs i n erythrocytes a nd ma y res embl e Plasmodium s peci es when bl ood s mea rs a re exa mi ned. Babesia i s endemi c i n the northea s tern Uni ted Sta tes , pa rti cul a rl y i n the i s l a nds of Ma s s a chus etts . La bora tory di a gnos i s i s ma de by exa mi ni ng bl ood s mea rs for thi s pa ra s i te, or by detecti on of s peci fi c a nti body. Ba bes i os i s cl i ni ca l l y res embl es ma l a ri a . 422. The answer is b. (Brooks, p 680. Levinson, pp 371-372. Murray [2009], pp 830-832.) Cocci di a n-l i ke bodi es ha ve been i denti fi ed i n s tool s of s ome pa ti ents wi th di a rrhea . Thes e orga ni s ms a ppea r to be s i mi l a r to bl ue-green a l ga e a nd were referred to a s Cyanobacterium-l i ke unti l they were recentl y recl a s s i fi ed a s Cyclospora. They a re l a rger tha n the mi cros pori di a a nd res embl e nei ther Giardia nor Prototheca nor other a l ga e-l i ke orga ni s ms . Unl i ke Cryptosporidium (4-5 μm), thes e orga ni s ms fl uores ce under ul tra vi ol et l i ght. The di a rrhea ca n be prol onged a nd rel a ps i ng, a nd the trea tment i s us ua l l y tri methopri m–s ul fa methoxa zol e. See the fi gure for a n i l l us tra ti on of G. lamblia.
Giardia lamblia. (A) “Fa ce” a nd (B) “profi l e” of vegeta ti ve forms ; (C, D) cys ts (bi nucl ea te [D] a nd qua dri nucl ea te s ta ges ). 2000×. (Reproduced, with permission, from Brooks GF et al. Ja wetz’s Medi ca l Mi crobi ol ogy. 24th ed. New York, NY: McGraw-Hill; 2007:660.) 423. The answer is c. (Brooks, p 694. Levinson, p 377. Murray [2009], pp 886-889. Ryan, pp 799-801.) Echinococcus i s a s ma l l , three-s egmented ta peworm found onl y i n the i ntes ti nes of dogs a nd other ca rni vores . Eggs l ea ve thes e hos ts a nd i nfect gra zi ng a ni ma l s . In the herbi vore gut, the eggs ha tch a nd the rel ea s ed forms penetra te the gut. Va ri ous orga ns (es peci a l l y the l i ver) devel op huge, fl ui d-fi l l ed cys ts i n whi ch future s col eces form (hyda ti d s a nd). Dogs become i nfected when they feed on vi s cera of di s ea s ed s heep or cows . Hyda ti d di s ea s e i n huma ns occurs onl y through i nges ti on of dog feces . Huma ns a re onl y a n i ntermedi a te hos t of thi s orga ni s m a nd never the fi na l hos t. None of the other a ns wer opti ons a re ces todes , or ta peworms . 424. The answer is b. (Garcia [2007], pp 190-217.) Lei s hma ni a s i s i s ca us ed by three ma jor s peci es of pa ra s i tes . Cuta neous l ei s hma ni a s i s i s ca us ed by L. tropica (Ba ghda d Sore) i s found i n the Medi terra nea n regi on; mucocuta neous l ei s hma ni a s i s i s ca us ed by L. braziliensis (Ameri ca n l ei s hma ni a s i s ) a nd i s endemi c i n South/Centra l Ameri ca ; vi s cera l l ei s hma ni a s i s i s ca us ed by L. donovani (Ka l a -a za r) a nd i s wi de s prea d i n As i a . In cuta neous di s ea s e, centri fuga l l y growi ng pa pul a r l es i on wi th centra l crus ti ng i s s een whi ch hea l s s ponta neous l y but l ea ves a perma nent s ca r. Mucocuta neous l ei s hma ni a s i s whi ch i nvol ves the s ki n a nd mucoi d ti s s ue, i ni ti a l l y s a me a s cuta neous l es i on but i t does not hea l a nd l ea ds to necros i s of mucoi d ti s s ue, meta s ta s i s to di s ta nt mucoi d ti s s ues a nd i s very di s fi guri ng. Vi s cera l l ei s hma ni a s i s i nvol ves l i ver, s pl een, bone ma rrow, l ymph nodes , s ki n, there i s no bi te rea cti on a nd res ul ts i n l ympha denopa thy, s pl enomega l y a nd hepa tomega l y, chi l l s a nd fever, a nd da rkeni ng of s ki n. Vi s cera l l ei s hma ni a s i s i s becomi ng a n i mporta nt opportuni s ti c i nfecti on i n a rea s where i t coexi s ts wi th HIV. 425. The answer is b. (Garcia 2007, pp 258-260.) The mos t common hel mi nth i nfecti on i n the Uni ted Sta tes (a n es ti ma ted 40 mi l l i on pers ons i nfected). Adul t pi nworms i nha bi t the cecum a nd a dja cent porti ons of the l a rge a nd s ma l l i ntes ti ne. The ma l e worm i s 2 to 5 mm l ong a nd 0.2 mm wi de. The fema l e worm mea s ures 8 to 13 mm i n l ength a nd 0.5 mm i n wi dth. The fema l e i s di s ti ngui s hed by a l ong, thi n s ha rpl y poi nted ta i l . The fema l e when ful l y gra vi d, mi gra te down the i ntes ti na l tra ct to pa s s out the a nus a nd depos i t thei r eggs . Di a gnos i s of Enterobius vermicularis i s ma de by us i ng a Scotch Ta pe Tes t. Eggs a re thi n-wa l l ed eggs a nd mea s ure 50 to 60 mm × 20 to 30 mm a nd a re ovoi d a nd fl a ttened on one s i de. 426. The answer is c. (Garcia 2007, pp 381-410.) The photomi crogra ph i s s howi ng a number of Echinococcus protos col i ces i n a cut s ecti on of a hyda ti d cys t. Hyda ti d di s ea s e i s ca us ed by the l a rva l s ta ges of ces todes of the genus Echinococcus. E. granulosus (dog ta peworm) ca us es cys ti c di s ea s e, the form mos t frequentl y encountered. E. multilocularis (fox ta peworm) ca us es a l veol a r di s ea s e. E. vogeli a nd E. oligarthrus a re the ca us a ti ve a gents of pol ycys ti c hyda ti dos i s . The di a gnos i s of hyda ti d di s ea s e rel i es ma i nl y on fi ndi ngs by ul tra s onogra phy a nd/or other i ma gi ng techni ques s upported by pos i ti ve s erol ogi c tes ts . In E. granulosus i nfecti ons hepa ti c i nvol vement ca n res ul t i n a bdomi na l pa i n, a ma s s i n the hepa ti c a rea , a nd bi l i a ry duct obs tructi on. Mos t i mporta ntl y, the brea k/l ea ka ge from the cys t ca n l ea d to fever, urti ca ri a , eos i nophi l i a , a nd a na phyl a cti c s hock, a s wel l a s s prea di ng of cys ts to other a rea s . Furthermore, other orga ns (l ungs , bra i n, bone, a nd hea rt) ca n a l s o be i nvol ved wi th E. granulosus hyda ti d i nfecti on. Hyda ti dos i s wi th E. multilocularis a ffects the l i ver a s a s l ow growi ng tumor, wi th a bdomi na l pa i n, bi l i a ry obs tructi on often wi th meta s ta ti c l es i ons i nto the l ungs a nd bra i n. E. vogeli cys ts a re norma l l y found i n the l i ver, where i t a cts a s a s l ow growi ng tumor; s econda ry cys ti c devel opment i s a l s o norma l . 427. The answer is c. (Garcia [2007], pp 363-371.) Cys ti cerci cys ts of T. solium (pi g ta peworm) a re l a rva l cys ts tha t i nfect bra i n, mus cl e, or other ti s s ue,
a nd a re a ma jor ca us e of a dul t-ons et s ei zures i n mos t l ow-i ncome countri es . Cys ti cercos i s i s a cqui red by i nges ti ng eggs excreted by a pers on who i s ca rryi ng a n i ntes ti na l pi g ta peworm. In ca s e of neurocys ti cercos i s , CT a nd MRI provi de evi dence on number a nd l oca ti on of cys ti cerci a s wel l a s on thei r vi a bi l i ty a nd the a cutenes s of the hos t i nfl a mma tory res pons e. Neurocys ti cercos i s ca n ca us e a wi de va ri ety of ma ni fes ta ti ons i ncl udi ng s ei zures , menta l di s turba nces , foca l neurol ogi ca l defi ci ts , a nd s i gns of s pa ce-occupyi ng i ntra cerebra l l es i ons .
Immunology Questions Questions 428 to 431 Hypers ens i ti vi ty rea cti ons a re exces s i ve or uncontrol l ed i mmune res pons es tha t ca n s ometi mes res ul t i n da ma ge to the hos t i ns tea d of provi di ng protecti on. The four ma i n types a re repres ented bel ow. Us e thes e rea cti ons to a ns wer the fol l owi ng ques ti ons .
428. A 13-yea r-ol d ma l e wi th cys ti c fi bros i s devel ops repea ted epi s odes of pneumoni a res ul ti ng i n mul ti pl e hos pi ta l i za ti ons . Previ ous a nti bi oti c trea tment res ul ted i n s evere ra s h, fever, a nd s ys temi c a na phyl a xi s a l mos t i mmedi a tel y. A peni ci l l oyl pol yl ys i ne s ki n tes t yi el ds pos i ti ve res ul ts . Whi ch of the fol l owi ng bes t i l l us tra tes the type of hypers ens i ti vi ty rea cti on a s s oci a ted wi th thi s cl i ni ca l s cena ri o? a . Type I b. Type II c. Type III d. Type IV 429. After pl a yi ng i n the bus hes duri ng a ca mpi ng tri p, a 7-yea r-ol d gi rl compl a i ns of i ntens e i tchi ng a nd bl i s teri ng of the ha nds , a rms , a nd l egs . Whi ch of the fol l owi ng a re the mos t l i kel y medi ca l condi ti on a nd the correct hypers ens i ti vi ty di a gra m from thos e pres ented? a . Conta ct derma ti ti s a nd type II b. Conta ct derma ti ti s a nd type III c. Conta ct derma ti ti s a nd type IV d. Arthus rea cti on a nd type I e. Arthus rea cti on a nd type II f. Arthus rea cti on a nd type III 430. Ski n tes ti ng i s us eful i n the di a gnos i s of whi ch of the fol l owi ng? a . Type I a nd II b. Type I a nd III c. Type I a nd IV d. Type II, III, a nd IV 431. Rh di s ea s e a nd Goodpa s ture s yndrome a re bes t repres ented by whi ch of the fol l owi ng? a . Type I a nd II b. Type II a nd III c. Type II a nd IV d. Type II onl y e. Type III onl y
Questions 432 and 433 432. A 7-month-ol d ma l e i nfa nt pres ents to the emergency depa rtment wi th s evere mi ddl e ea r a nd upper res pi ra tory tra ct i nfecti ons , whi ch res pond promptl y to a nti bi oti cs . Two months l a ter he i s a ga i n a dmi tted, thi s ti me wi th Streptococcus pneumoniae pneumoni a . After s evera l more epi s odes of ba cteri a l i nfecti ons , geneti c tes ti ng i s done a nd the pres ence of a defecti ve B-cel l tyros i ne ki na s e gene (btk gene or X-LA gene) i s revea l ed. In a ddi ti on, phys i ca l exa mi na ti on detects very s ma l l tons i l s . Whi ch of the fol l owi ng i s the mos t l i kel y di a gnos i s ? a . Ata xi a -tel a ngi ecta s i a b. Bruton a ga mma gl obul i nemi a c. Chroni c gra nul oma tous di s ea s e d. La te (C5, C6, C7, C8, C9) compl ement defi ci ency e. Thymi c a pl a s i a (Di George s yndrome) 433. Whi ch of the fol l owi ng pa thogens pres ents the mos t s eri ous threa t to thi s chi l d? a . Chlamydia trachomatis b. Mea s l es vi rus c. Mycobacterium tuberculosis d. Va ri cel l a -zos ter vi rus (VZV) Questions 434 and 435 Fl ow cytometry of bl ood from a n HIV-pos i ti ve pa ti ent yi el ded a CD4:CD8 ra ti o l es s tha n 1. 434. Thi s ra ti o bes t repres ents a ma jor decl i ne i n whi ch of the fol l owi ng cel l types a nd i ts a s s oci a ted cel l s urfa ce protei ns ? a . B l ymphocytes ; MHC cl a s s I, IgM, B7, CD19, CD20 b. Cytotoxi c T l ymphocytes ; MHC cl a s s I, TCR, CD3 c. Cytotoxi c T l ymphocytes ; MHC cl a s s I, TCR, CD3, CD28 d. Hel per T l ymphocytes ; MHC cl a s s I, TCR, CD3 e. Hel per T l ymphocytes ; MHC cl a s s I, TCR, CD3, CD28 f. Ma cropha ges ; MHC cl a s s I, MHC cl a s s II, CD14 435. Whi ch of the fol l owi ng bes t repres ents the “cos ti mul a tory s i gna l ” pa i r tha t occurs between cel l ul a r s urfa ce protei ns a s s oci a ted wi th the reduced cel l type repres ented i n the CD4:CD8 ra ti o l es s tha n 1? a . B7 (B cel l ) a nd CD28 (T cel l ) b. B7 (B cel l ) a nd CD4 (T cel l ) c. CD40L (B cel l ) a nd CD40 (T cel l ) d. MHC cl a s s I (B cel l ) a nd CD4 (T cel l ) e. MHC cl a s s II (B cel l ) a nd CD8 (T cel l ) 436. A young gi rl ha s ha d repea ted i nfecti ons wi th Candida albicans a nd res pi ra tory vi rus es s i nce s he wa s 3 months ol d. As pa rt of the cl i ni ca l eva l ua ti on of her i mmune s ta tus , her res pons es to routi ne i mmuni za ti on procedures s houl d be tes ted. In thi s eva l ua ti on, the us e of whi ch of the fol l owi ng va cci nes i s contra i ndi ca ted? a . Ba ci l l us Ca l mette–Gueri n (BCG) b. Bordetel l a pertus s i s va cci ne c. Di phtheri a toxoi d d. Ina cti va ted pol i o e. Teta nus toxoi d 437. A 7-yea r-ol d ma l e devel oped norma l l y unti l 7 yea rs of a ge, a fter whi ch he s uddenl y s ta rts s ufferi ng from progres s i ve pers ona l i ty a nd i ntel l ect deteri ora ti on l ea di ng to dementi a , a nd fi na l l y dea th wi thi n 1 yea r of s ymptoms . Hi s hi s tory revea l s s evere mea s l es a tta ck a t the a ge of 1. La bora tory tes ts i ndi ca te el eva ted mea s l es a nti body l evel s i n both the s erum a nd cerebros pi na l fl ui d (CSF) wi th no a nti body to the M protei n. A l a tent mea s l es -l i ke vi ra l i nfecti on a nd, pres uma bl y, a defect i n cel l ul a r i mmuni ty a re a s s oci a ted wi th whi ch of the fol l owi ng di s ea s es ? a . Creutzfel dt–Ja kob di s ea s e (CJD) b. Eps tei n–Ba rr vi rus (EBV) i nfecti on c. Mul ti pl e s cl eros i s (MS) d. Progres s i ve mul ti foca l l eukoencepha l opa thy (PML) e. Suba cute s cl eros i ng pa nencepha l i ti s (SSPE) 438. A 31-yea r-ol d pa ti ent s ufferi ng from recurrent epi s odi c i ntes ti na l hemorrha ges a ttri buted to a s evere form of Crohn di s ea s e deci des to undergo s urgery to res ect hi s termi na l i l eum. The s urgeon orders two uni ts of bl ood to be pres erved for pos s i bl e us e duri ng the s urgery. The pa ti ent deci des to s tore one uni t of hi s own bl ood a nd one uni t of hi s 35-yea r-ol d brother’s bl ood wi th the bl ood ba nk. Thi s type of dona ti on i s mos t l i kel y whi ch of the fol l owi ng tra ns pl a nta ti on termi nol ogy (pa ti ent’s bl ood:brother’s bl ood)? a . Al l ogra ft:a l l ogra ft b. Al l ogra ft:a utogra ft c. Autogra ft:a l l ogra ft d. Autogra ft:a utogra ft e. Autogra ft:i s ogra ft (s yngenei c gra ft) 439. A 27-yea r-ol d fema l e pres ents to the emergency room wi th a tempera ture of 103°F, s evere fa ti gue, wei ght l os s , a nd joi nt pa i n. Duri ng the hi s tory a nd phys i ca l exa mi na ti on, the pa ti ent reports tha t s he s topped ta ki ng her a s pi ri n a nd corti cos teroi ds to control her condi ti on. A butterfl ytype ra s h over her cheeks , s ens i ti vi ty to l i ght, a nd a hea rt murmur a re a ppa rent. The pa ti ent a l s o reports a hi s tory of a progres s i vel y devel opi ng a rthri ti s a nd gl omerul onephri ti s . La bora tory tes ts further i ndi ca te a nemi a , l eukopeni a , a nd thrombocytopeni a . Thi s condi ti on i s bes t di a gnos ed
by the pres ence of whi ch of the fol l owi ng? a . Anti centromere a nti bodi es b. Anti -ds DNA a nti bodi es c. Anti mi tochondri a l a nti bodi es d. Anti neutrophi l a nti bodi es e. Anti -TSH receptor a nti bodi es 440. A 1-yea r-ol d ma l e pa ti ent pres ents wi th ma rked s us cepti bi l i ty to opportuni s ti c i nfecti ons wi th ba cteri a s uch a s Escherichia coli a nd Staphylococcus aureus a nd funga l Aspergillus. Exa mi na ti on fi ndi ngs revea l gra nul oma tous a bs ces s es i n the l ungs , a ta xi a , nys ta gmus , a nd photophobi a . Bi ochemi ca l a na l ys i s revea l s the defi ci ency of the centra l enzyme i n the res pi ra tory burs t pa thwa y vi a a n i na bi l i ty to reduce ni trobl ue tetra zol i um (NBT) dye. The defi ci ent enzyme a nd rea cti on a re repres ented by whi ch of the fol l owi ng?
441. Whi ch of the fol l owi ng s ta tements bes t a ppl i es to the fol l owi ng di a gra m?
(Modified, with permission, from Parslow TG, et al. Medi ca l Immunol ogy. 10th ed. New York, NY: McGraw-Hill; 2001:85.) a . Depi cts the cel l -membra ne MHC product a s s oci a ted wi th na rcol eps y b. Es s enti a l for the tra ns pl a centa l pa s s a ge of a nti body c. Found on T a nd B l ymphocytes a nd a l l nucl ea ted cel l s
d. Pres ent on ma cropha ges but not neutrophi l s e. Repres ents the s ecretory component a s s oci a ted wi th IgA f. Requi red for recogni ti on of proces s ed a nti gen by TH1 a nd TH2 l ymphocytes 442. A 19-yea r-ol d col l ege s tudent devel ops a ra s h. She works pa rt-ti me i n a pedi a tri c AIDS cl i ni c. Her bl ood i s dra wn a nd tes ted for s peci fi c a nti body to the chi cken pox vi rus (va ri cel l a -zos ter). Whi ch of the fol l owi ng a nti body cl a s s es woul d you expect to fi nd i f s he i s i mmune to chi cken pox? a . IgG b. IgA c. IgM d. IgD e. IgE 443. Pa ti ents wi th C5 through C9 compl ement defi ci enci es a re mos t l i kel y to be s us cepti bl e to whi ch of the fol l owi ng i nfecti ons ? a . AIDS b. Gi a rdi a s i s c. Hi s topl a s mos i s d. Nei s s eri a l i nfecti on e. Pneumococca l i nfecti on 444. As pa rt of the ma na gement of a 28-yea r-ol d ma l e wi th a cute ons et of Crohn di s ea s e of the s ma l l bowel , you deci de to trea t hi m wi th a new cockta i l of mous e–huma n chi meri c a nti bodi es to reduce hi s i ntes ti na l i nfl a mma ti on a nd ca chexi a . To whi ch of the fol l owi ng s ets of protei ns a re thes e a nti bodi es di rected? a . IL-1, IL-2, IL-3 b. IL-2, IL-12, TNF-α c. IL-2, TGF-β, TNF-α’ d. IL-1, IL-6, TNF-α’ e. IL-2, IL-3, IL-12 445. A mother a nd newborn a re expos ed to a pa thogen whi l e a t the hos pi ta l for a routi ne checkup a nd brea s tfeedi ng cl i ni c. Thi s s a me pa thogen ha d i nfected the mother a bout a yea r previ ous l y, a nd s he ha d s ucces s ful l y recovered from the s ubs equent i l l nes s . Immuni ty ma y be i nna te or a cqui red. Whi ch of the fol l owi ng bes t des cri bes a cqui red i mmuni ty wi th res pect to the newborn? a . Compl ement ca s ca de b. Increa s e i n C-rea cti ve protei n (CRP) c. Infl a mma tory res pons e d. Ma terna l tra ns fer of a nti body e. Pres ence of na tura l ki l l er (NK) cel l s 446. A 35-yea r-ol d ma l e pa ti ent pres ents wi th numerous s ubcuta neous hemorrha ges . Hi s tory a nd phys i ca l exa mi na ti on revea l tha t he ha s been ta ki ng s edormi d (a s eda ti ve) for the pa s t week. La bora tory tes ts i ndi ca te norma l hemogl obi n a nd whi te bl ood cel l l evel s wi th s i gni fi ca nt thrombocytopeni a (very l ow pl a tel et count). You s us pect tha t he ha s devel oped a drug-i nduced type II hypers ens i ti vi ty rea cti on. Thi s rea cti on ma y occur i f the drug does whi ch of the fol l owi ng? a . Acti va tes T cytotoxi c cel l s b. Acts a s a ha pten c. Induces ma s t cel l degra nul a ti on, rel ea s i ng medi a tors s uch a s hi s ta mi ne, l eukotri enes , a nd pros ta gl a ndi ns d. Induces oxygen ra di ca l producti on through the res pi ra tory burs t pa thwa y e. Pers i s ts i n ma cropha ges 447. After l ea rni ng of a fa mi l y hi s tory of humora l i mmuni ty defi ci ency duri ng a n offi ce vi s i t from a pa ti ent 6 months pregna nt, a ra di a l i mmunodi ffus i on a s s a y i s ordered on feta l s erum. The tes t revea l s no humora l i mmuni ty probl ems a nd norma l res ul ts i n a l l res pects . Accordi ng to thi s tes t, the norma l l evel of whi ch feta l l y ma de i mmunogl obul i n i s the hi ghes t i n the fetus ? a . IgA b. IgD c. IgE d. IgG e. IgM 448. A 31-yea r-ol d ma l e pa ti ent compl a i ns of fa ti gue, yea s t i nfecti on i n hi s mouth, a nd enl a rged l ymph nodes under hi s a rms . He s a ys tha t he wa s i nvol ved i n “hi gh-ri s k” beha vi or 6 yea rs a go whi l e on a tri p to ea s tern a nd s outhern Afri ca . He a l s o i ndi ca tes tha t hi s “HIV tes t” wa s nega ti ve. Whi ch of the fol l owi ng opti ons i s mos t a ppropri a te? a . Ini ti a te trea tment for HIV di s ea s e b. Order a tes t for huma n T-cel l l eukemi a vi rus (HTLV) c. Order a n HIV-1 RNA PCR d. Order a n HIV tes t tha t woul d i ncl ude a nti bodi es to HIV-1 a nd HIV-2 e. Repea t the tes t for HIV-1 449. A l a bora tory a na l ys i s report of a s peci fi c fra cti on of a pa ti ent’s l ymphocytes i ndi ca tes the fol l owi ng: HLA, B, a nd C+, PHA+, CD3–, CD16+, CD11a /CD18+, CD56+, a nd i n vi tro bl a s togenes i s wi th IL-12. Wha t a re the l ymphocytes tha t thi s s et des cri bes ? a . B l ymphocytes b. Cytotoxi c T l ymphocytes
c. NK cel l s d. T hel per 1 (TH1) s ubs et e. T hel per 2 (TH2) s ubs et 450. The compl ement s ys tem pl a ys a key rol e i n the hos t defens e proces s . Whi ch of the fol l owi ng components of thi s s ys tem i s the mos t i mporta nt i n chemota xi s ? a . C1q b. C3a c. C3b d. C4a e. C5a 451. Soon a fter bi rth, a newborn undergoes hea rt tra ns pl a nta ti on s urgery a t a l oca l medi ca l center. Tra ns pl a nta ti on of ti s s ue a nd orga ns i s a common procedure whos e s ucces s depends l a rgel y on the “s el f” vers us “nons el f” i ntera cti ons . Survi va l of a l l ogra fts i s i ncrea s ed by choos i ng donors wi th few ma jor hi s tocompa ti bi l i ty compl ex (MHC) mi s ma tches compa red to reci pi ents a nd by us e of i mmunos uppres s i on i n reci pi ents . Whi ch of the fol l owi ng procedures i s the mos t us eful mea s ure of i mmunos uppres s i on i n reci pi ents ? a . Admi ni s tra ti on of corti cos teroi ds to reci pi ent b. Admi ni s tra ti on of i mmunogl obul i n to reci pi ent c. Des tructi on of donor B cel l s d. Des tructi on of donor T cel l s e. Lymphoi d i rra di a ti on of donor 452. Rel a ti ve to the pri ma ry i mmunol ogi ca l res pons e, s econda ry, a nd l a ter boos ter res pons es to a gi ven ha pten–protei n compl ex ca n be a s s oci a ted wi th whi ch one of the fol l owi ng? a . Anti bodi es tha t a re l es s effi ci ent i n preventi ng s peci fi c di s ea s e b. Decrea s ed a nti body a vi di ty for the ori gi na l ha pten–protei n compl ex c. Increa s ed a nti body a ffi ni ty for ha pten d. Lower ti ters of a nti body e. Ma i ntena nce of the s a me s ubcl a s s , or i di otype, of a nti body produced 453. You a re ma na gi ng a 3-yea r-ol d fema l e pa ti ent wi th a fever of unknown ori gi n. Her s erum i s tes ted for a nti bodi es a ga i ns t Haemophilus influenzae. A preci pi ta ti on tes t conducted by the cl i ni ca l l a bora tory yi el ds the fol l owi ng res ul ts :
From thes e da ta , whi ch of the fol l owi ng ca n be concl uded? a . The nega ti ve rea cti ons a t 1:128 a nd 1:126 a re fa l s e nega ti ves b. The pa ti ent ha s a nti bodi es a ga i ns t H. influenzae, the ti ter i s 64, a nd the di l uti on 1:64 c. The pa ti ent ha s a nti bodi es a ga i ns t H. influenzae, the di l uti on i s 64, a nd the ti ter 1:64 d. The pa ti ent does not ha ve a nti bodi es a ga i ns t H. influenzae s i nce the rea cti on i s nega ti ve wi th undi l uted s erum e. The pa ti ent s houl d be i mmuni zed a ga i ns t H. influenzae 454. Of the fi ve i mmunogl obul i n cl a s s es , IgA i s the ma i n i mmunogl obul i n of s ecreti ons from the geni ta l , res pi ra tory, a nd i ntes ti na l tra cts . As a res ul t, IgA a nti body i s the fi rs t l i ne of defens e a ga i ns t i nfecti ons a t the mucous membra ne. It i s us ua l l y a n ea rl y s peci fi c a nti body. Whi ch of the fol l owi ng s ta tements mos t a ccura tel y des cri bes IgA? a . Compl ement fi xa ti on tes ts for IgA a nti body wi l l be pos i ti ve i f s peci fi c IgA a nti body i s pres ent b. IgA ca n be des troyed by ba cteri a l protea s es c. IgA i s a bs ent i n col os trum d. IgA i s not found i n s a l i va ; therefore, a n IgA di a gnos ti c tes t on s a l i va woul d ha ve no va l ue e. IgA i s a s ma l l mol ecul e wi th a mol ecul a r wei ght of 30,000 kDa 455. A 60-yea r-ol d ma l e pres ents wi th s evere ja undi ce to the l oca l wa l k-i n cl i ni c. Hi s tory a nd phys i ca l exa mi na ti on revea l a 30-yea r hi s tory of a l cohol cons umpti on a nd drug a bus e. Bl ood tes ts revea l el eva ted AST a nd ALT l evel s a nd the pres ence of hepa ti ti s B a nd, a s a res ul t, reduced compl ement l evel s . Compl ement i s a s eri es of i mporta nt hos t protei ns tha t provi de protecti on from i nva s i on by forei gn mi croorga ni s ms . Whi ch of the fol l owi ng bes t des cri bes compl ement? a . Compl ement i nhi bi ts pha gocytos i s b. Compl ement i s a cti va ted by IgE a nti body cl a s s es c. Compl ement pl a ys a mi nor rol e i n the i nfl a mma tory res pons e d. Compl ement protects the hos t from pneumococca l i nfecti on through C1, C2, a nd C4 e. Mi croorga ni s ms a ggl uti na te i n the pres ence of compl ement but do not l ys e
456. Ra di a l i mmunodi ffus i on a nd i mmunoel ectrophores i s i s performed on a young pa ti ent to eva l ua te the functi on of hi s humora l i mmune s ys tem. Whi ch of the fol l owi ng i mmunogl obul i ns ha s no known functi on, i s found i n the s erum i n l ow concentra ti ons , a nd i s pres ent on the s urfa ce of B l ymphocytes (ma y functi on a s a n a nti gen receptor)? a . IgG b. IgA c. IgM d. IgD e. IgE 457. A young pa ti ent wi th s evere recurrent pyogeni c ba cteri a l i nfecti ons , but wi th norma l T-cel l a nd B-cel l numbers , a rri ves a t the hos pi ta l . Tes ti ng revea l s tha t thi s pa ti ent’s CD4 T-hel per cel l s ha ve a defect i n CD40 l i ga nd. As a res ul t, humora l i mmuni ty eva l ua ti on revea l s a s i gni fi ca nt el eva ti on i n the l evel s of whi ch i mmunogl obul i n tha t i s pres ent a s a monomer on B-cel l s urfa ces , a s a penta mer i n s erum, a nd i s i ni ti a l l y s een i n the pri ma ry i mmune res pons e? a . IgG b. IgA c. IgM d. IgD e. IgE 458. A pa ti ent wi th a l ong hi s tory of cons umi ng poorl y cooked pork mea t pres ents wi th genera l i zed mya l gi a a nd a l ow-gra de fever. Stri a ted mus cl e bi ops y revea l s mul ti pl e cys ts . Eos i nophi l i a i s a l s o pres ent wi th el eva ted l evel s of whi ch of the fol l owi ng i mmunogl obul i ns mos t l i kel y i nvol ved i n pa ra s i ti c i nfecti ons ? a . IgG b. IgA c. IgM d. IgD e. IgE 459. A pa ti ent wi th cerebel l a r probl ems a nd s pi der a ngi oma s i s di a gnos ed wi th a combi ned T-cel l a nd B-cel l defi ci ency known a s a ta xi a tel a ngi ecta s i a . In a ddi ti on to a defect i n thi s pa ti ent’s DNA repa i r enzymes , whi ch i mmunogl obul i n i s the pri ma ry a nti body i n s a l i va , tea rs , a nd i ntes ti na l a nd geni ta l s ecreti ons , a nd i s a l s o defi ci ent i n thi s i l l nes s ? a . IgG b. IgA c. IgM d. IgD e. IgE 460. Wi th four s ubcl a s s es , whi ch i mmunogl obul i n i s the predomi na nt a nti body i n the s econda ry i mmune res pons e a nd ha s the grea tes t concentra ti on of the fi ve i mmunogl obul i n cl a s s es i n the fetus ? a . IgG b. IgA c. IgM d. IgD e. IgE 461. A 15-yea r-ol d boy i s bi tten by a n Ixodes ti ck whi l e ca mpi ng wi th hi s pa rents a nd pres ents 1 week l a ter wi th fa ti gue, fever, hea da che, a nd a reddi s h ra s h over hi s trunk a nd extremi ti es . Pos i ti ve IgM a nti body (1:200) to Borrelia burgdorferi i s a s s oci a ted wi th whi ch of the fol l owi ng? a . Acute Lyme di s ea s e b. Fi fth di s ea s e c. Pos s i bl e hepa ti ti s B i nfecti on d. Pos s i bl e s uba cute s cl eros i ng pa nencepha l i ti s (SSPE) e. Sus cepti bi l i ty to chi cken pox 462. A s ma l l chi l d pres ents wi th a l ow-gra de fever, coryza , s ore throa t, a bri ght red ra s h on hi s cheeks , a nd a l es s i ntens e erythema tous ra s h on hi s body. El eva ted IgG a nd IgM a nti body ti ters to pa rvovi rus s ugges t a di a gnos i s of whi ch of the fol l owi ng? a . Acute Lyme di s ea s e b. Fi fth di s ea s e c. Pos s i bl e hepa ti ti s B i nfecti on d. Pos s i bl e s uba cute s cl eros i ng pa nencepha l i ti s (SSPE) e. Sus cepti bi l i ty to chi cken pox 463. Bl ood from a woma n a t a l oca l pregna ncy cl i ni c i s a na l yzed for a nti body ti ters to known pa thogens . A nega ti ve va ri cel l a a nti body ti ter i n thi s young woma n s i gni fi es whi ch of the fol l owi ng? a . Acute Lyme di s ea s e b. Fi fth di s ea s e c. Pos s i bl e hepa ti ti s B i nfecti on d. Pos s i bl e s uba cute s cl eros i ng pa nencepha l i ti s (SSPE) e. Sus cepti bi l i ty to chi cken pox 464. A pa ti ent wi th s evere ja undi ce a nd l i ver fa i l ure ha s a n i ncrea s ed a nti body ti ter to del ta a gent. You s houl d s us pect whi ch of the fol l owi ng?
a . Acute Lyme di s ea s e b. Fi fth di s ea s e c. Pos s i bl e hepa ti ti s B i nfecti on d. Pos s i bl e s uba cute s cl eros i ng pa nencepha l i ti s (SSPE) e. Sus cepti bi l i ty to chi cken pox 465. A pedi a tri c pa ti ent wi th progres s i vel y devel opi ng degenera ti ve neurol ogi c di s ea s e/di s order ha s a n el eva ted CSF a nti body ti ter to mea s l es vi rus . You s houl d s us pect whi ch of the fol l owi ng? a . Acute Lyme di s ea s e b. Fi fth di s ea s e c. Pos s i bl e hepa ti ti s B i nfecti on d. Pos s i bl e s uba cute s cl eros i ng pa nencepha l i ti s (SSPE) e. Sus cepti bi l i ty to chi cken pox 466. A 2-yea r-ol d pa ti ent pres ents to the pedi a tri ci a n for a routi ne vi s i t. Hi s tory a nd phys i ca l exa mi na ti on revea l s recurrent i nfecti ons , a nd enl a rged s ma l l bl ood ves s el s of the s ki n a nd conjuncti va s . In a ddi ti on, the phys i ci a n noti ces i rregul a r movements mos t a ki n to s ta ggeri ng. Sus pecti ng a n i mmune dys functi on, mol ecul a r tes ti ng revea l s a defect i n DNA repa i r enzymes . Thi s a utos oma l reces s i ve i mmune defi ci ency di s order us ua l l y i s a s s oci a ted wi th whi ch of the fol l owi ng?
467. A 10-month-ol d ma l e i nfa nt wi th recurrent H. influenzae i nfecti ons pres ents to the emergency room wi th oti ti s medi a , s i nus i ti s , a nd i n s evere res pi ra tory di s tres s . Immunol ogi ca l a nd geneti c tes ti ng revea l s the a bs ence of B cel l s a nd a des tructi ve muta ti on i n the tyros i ne ki na s e gene. Thi s X-l i nked reces s i ve i mmune di s order i s us ua l l y a s s oci a ted wi th whi ch of the fol l owi ng?
468. Amni ocentes i s conducted duri ng geneti c couns el i ng of a pregna nt woma n revea l s a feta l a denos i ne dea mi na s e defi ci ency. Thi s a utos oma l reces s i ve i mmunodefi ci ency i s us ua l l y a s s oci a ted wi th whi ch of the fol l owi ng?
469. A young chi l d wi th s pa s ti c pa ra l ys i s pres ents to the emergency room. Bl ood tes ts revea l hypoca l cemi a . Thi s i mmune di s order i s us ua l l y a s s oci a ted wi th whi ch of the fol l owi ng?
470. A 10-month-ol d pa ti ent wi th recurrent pyogeni c i nfecti ons , eczema , a nd s evere bl eedi ng (thrombocytopeni a ) i s di a gnos ed wi th Wi s kott– Al dri ch s yndrome. Thi s i mmune di s order i s us ua l l y a s s oci a ted wi th whi ch of the fol l owi ng?
471. An a utogra ft of a burn vi cti m i s bes t des cri bed by whi ch one of the fol l owi ng? a . Tra ns pl a nt from one regi on of a pers on to a nother regi on b. Tra ns pl a nt from one pers on to a geneti ca l l y i denti ca l pers on c. Tra ns pl a nt from one s peci es to the s a me s peci es d. Tra ns pl a nt from one s peci es to a nother s peci es 472. Tra ns pl a nta ti on i nvol vi ng ti s s ue from twi n brothers pos s es s i ng i denti ca l HLA genes i s bes t des cri bed by whi ch one of the fol l owi ng? a . Al l ogra ft: tra ns pl a nt from one s peci es to the s a me s peci es b. Autogra ft: tra ns pl a nt from one regi on of a pers on to a nother regi on c. Is ogra ft: tra ns pl a nt from one pers on to a geneti ca l l y i denti ca l pers on d. Xenogra ft: tra ns pl a nt from one s peci es to a nother s peci es 473. A 21-yea r-ol d pa ti ent i n s evere ki dney fa i l ure recei ves a ki dney from hi s 30-yea r-ol d brother. Thi s type of tra ns pl a nta ti on i s bes t des cri bed by whi ch of the fol l owi ng? a . Al l ogra ft: tra ns pl a nt from one s peci es to the s a me s peci es b. Autogra ft: tra ns pl a nt from one regi on of a pers on to a nother regi on c. Is ogra ft: tra ns pl a nt from one pers on to a geneti ca l l y i denti ca l pers on d. Xenogra ft: tra ns pl a nt from one s peci es to a nother s peci es 474. Duri ng the i nfa ncy da ys of ca rdi a c tra ns pl a nta ti on, nonhuma n pri ma te hea rts were tra ns pl a nted i nto huma ns to s a ve l i ves . Thi s type of tra ns pl a nta ti on i s bes t des cri bed by whi ch one of the fol l owi ng? a . Al l ogra ft: tra ns pl a nt from one s peci es to the s a me s peci es b. Autogra ft: tra ns pl a nt from one regi on of a pers on to a nother regi on c. Is ogra ft: tra ns pl a nt from one pers on to a geneti ca l l y i denti ca l pers on d. Xenogra ft: tra ns pl a nt from one s peci es to a nother s peci es 475. Humora l i mmuni ty eva l ua ti on ma i nl y cons i s ts of mea s uri ng the a mount of IgG, IgM, a nd IgA i n the pa ti ent’s s erum. Thes e three i mmunogl obul i ns repres ent three di s ti nct i s otypes . An i s otype i s cha ra cteri zed by whi ch of the fol l owi ng? a . Determi na nt expos ed a fter pa pa i n cl ea va ge to a n F(a b) fra gment b. Determi na nt from one cl one of cel l s a nd proba bl y l oca ted cl os e to the a nti gen-bi ndi ng s i te of the i mmunogl obul i n c. Determi na nt i nheri ted i n a Mendel i a n fa s hi on a nd recogni zed by cros s -i mmuni za ti on of i ndi vi dua l s i n a s peci es d. Hea vy-cha i n determi na nt recogni zed by heterol ogous a nti s era e. Speci es -s peci fi c ca rbohydra te determi na nt on the hea vy cha i n
476. An a l l otype i s cha ra cteri zed by whi ch of the fol l owi ng? a . Determi na nt expos ed a fter pa pa i n cl ea va ge to a n F(a b) fra gment b. Determi na nt from one cl one of cel l s a nd proba bl y l oca ted cl os e to the a nti gen-bi ndi ng s i te of the i mmunogl obul i n c. Determi na nt i nheri ted i n a Mendel i a n fa s hi on a nd recogni zed by cros s -i mmuni za ti on of i ndi vi dua l s i n a s peci es d. Hea vy-cha i n determi na nt recogni zed by heterol ogous a nti s era e. Speci es -s peci fi c ca rbohydra te determi na nt on the hea vy cha i n 477. Anti bodi es produced from hybri doma s a re extremel y us eful cl i ni ca l l y for thei r monocl ona l properti es . Thes e a nti bodi es ha ve the s a me i di otype. An i di otype i s cha ra cteri zed by whi ch of the fol l owi ng? a . Determi na nt expos ed a fter pa pa i n cl ea va ge to a n F(a b')2 fra gment b. Determi na nt from one cl one of cel l s a nd proba bl y l oca ted cl os e to the a nti gen-bi ndi ng s i te of the i mmunogl obul i n c. Determi na nt i nheri ted i n a Mendel i a n fa s hi on a nd recogni zed by cros s -i mmuni za ti on of i ndi vi dua l s i n a s peci es d. Hea vy-cha i n determi na nt recogni zed by heterol ogous a nti s era e. Speci es -s peci fi c ca rbohydra te determi na nt on the hea vy cha i n 478. A 30-yea r-ol d ma l e pres ents to the emergency room wi th di ffi cul ty i n brea thi ng a nd a bdomi na l pa i n. Upon phys i ca l exa mi na ti on, you noti ce di ffus e a rea s of nondependent, nonpi tti ng s wel l i ng wi thout pruri tus , wi th predi l ecti on for the fa ce, es peci a l l y the peri ora l a nd peri orbi ta l a rea s . You a l s o noti ce s wel l i ng i n the mouth, pha rynx, a nd l a rynx. La bora tory a na l ys i s of bl ood dra wn from thi s pa ti ent i ndi ca tes a compl ement probl em. Whi ch of the fol l owi ng i s mos t l i kel y? a . Hi gh C4, C2, a nd C3 b. Hi gh C1 a nd norma l l evel of C1 es tera s e i nhi bi tor c. Hi gh C1 es tera s e i nhi bi tor a nd hi gh C4 d. Hi gh C1 es tera s e i nhi bi tor a nd l ow C4 e. Low C1 es tera s e i nhi bi tor a nd hi gh C4 f. Low C1 es tera s e i nhi bi tor a nd l ow C4 g. Low C4 a nd hi gh C2 479. A 45-yea r-ol d bus i nes s woma n a rri ves i n your offi ce wi th va gue a bdomi na l compl a i nts . She ha s noti ced mel eni c s tool . Upon performi ng a s i gmoi dos copy, you fi nd a 4-cm ma s s i n the upper col on. You s houl d i mmedi a tel y order a bl ood tes t for whi ch of the fol l owi ng tumor ma rkers ? a . α-Fetoprotei n b. Anti tumor a nti body c. Anti tumor l i ght cha i ns d. Ca rci noembryoni c a nti gen (CEA) e. Huma n chori oni c gona dotropi n f. Pros ta te-s peci fi c a nti gen Questions 480 and 481 480. An 18-yea r-ol d ma l e heroi n a ddi ct, who pra cti ces the s ha ri ng of needl es a t a “s hooti ng ga l l ery,” i s pos i ti ve i n the s creeni ng tes t for AIDS. Thi s pa ti ent i s mos t l i kel y to be i mmunodefi ci ent beca us e of whi ch one of the fol l owi ng? a . A geneti c defect i n chromos ome 14 b. A l ow T-hel per l ymphocyte count c. An a trophi ed thymus d. NADPH enzyme defi ci ency e. Ins uffi ci ent B-cel l ma tura ti on 481. Si nce a fa l s e-pos i ti ve res ul t i s pos s i bl e i n the s creeni ng tes t i n the previ ous vi gnette, the phys i ci a n orders a confi rma tory tes t. Whi ch of the fol l owi ng bes t des cri bes the s ta nda rd confi rma tory tes t, a nd wha t thi s tes t checks for, res pecti vel y? a . Compl ement fi xa ti on tes t; a nti bodi es a ga i ns t the vi rus b. Enzyme-l i nked i mmunos orbent a s s a y (ELISA); a nti gens of the vi rus c. Ra di oi mmunoa s s a y (RIA); s peci fi c a nti bodi es a ga i ns t the vi rus d. Wes tern bl ot; a nti gens of the vi rus e. Wes tern bl ot; s peci fi c a nti bodi es a ga i ns t the vi rus 482. A pregna nt 21-yea r-ol d Rh-nega ti ve fema l e i s a bout to del i ver. The ba by’s fa ther i s determi ned to be Rh-pos i ti ve. To reduce the cha nce for the devel opment of hemol yti c di s ea s e of the newborn, whi ch of the fol l owi ng procedures s houl d you order? a . Admi ni s tra ti on of a nti -Rh a nti bodi es to the fetus pos tdel i very b. Admi ni s tra ti on of a nti -Rh a nti bodi es to the mother pos tdel i very c. Immedi a te bl ood tra ns fus i on of the s us pected fa ther d. Immedi a te bl ood tra ns fus i on of the mother wi th Rh-pos i ti ve bl ood e. Infus i on of i mmune s erum gl obul i n i nto the fetus f. Intra venous i nfus i on of the Rh a nti gen i nto the mother Questions 483 and 484 483. An 8-month-ol d ma l e i nfa nt wi th a hi s tory of chroni c di a rrhea , oti ti s medi a , a nd s evera l epi s odes of pneumoni a pres ents to your cl i ni c wi th gi ngi vos toma ti ti s (due to herpes s i mpl ex vi rus ) a nd ora l ca ndi di a s i s (thrus h). You i mmedi a tel y order a n x-ra y a nd a bl ood workup. X-ra y a nd l a bora tory bl ood a na l ys i s revea l the a bs ence of a thymi c s ha dow a nd a bs ence of B l ymphocytes , res pecti vel y. Hi s tory ta ken from the i nfa nt’s mother revea l s a ra s h evi dent a t bi rth. Whi ch of the fol l owi ng di s ea s es i s mos t l i kel y pres ent i n thi s i nfa nt? a . Ata xi a -tel a ngi ecta s i a
b. Bruton a ga mma gl obul i nemi a c. Chedi a k–Hi ga s hi s yndrome d. Chroni c gra nul oma tous di s ea s e e. Chroni c mucocuta neous ca ndi di a s i s f. Heredi ta ry a ngi oedema g. Severe combi ned i mmunodefi ci ency s yndrome (SCID) h. Thymi c a pl a s i a (Di George s yndrome) i . Wi s kott–Al dri ch s yndrome 484. Whi ch of the fol l owi ng i s the bes t thera py for the i nfa nt i n the previ ous vi gnette? a . Anti funga l a gents b. Bl ood tra ns fus i on c. Bone ma rrow tra ns pl a nt d. IgG from pool ed ra ndom donors e. Immuni za ti on wi th a ttenua ted va cci nes 485. A 5-yea r-ol d chi l d a rri ves a t the emergency depa rtment mi nutes a fter bei ng bi tten by a bl a ck wi dow s pi der. You i mmedi a tel y i nject ga mma gl obul i n i n the form of a n a nti venom. Thi s type of i mmuni za ti on i s referred to a s whi ch of the fol l owi ng? a . Arti fi ci a l a cti ve i mmuni za ti on b. Arti fi ci a l pa s s i ve i mmuni za ti on c. Na tura l a cti ve i mmuni za ti on d. Na tura l pa s s i ve i mmuni za ti on e. Adopti ve i mmuni za ti on 486. A pa ti ent wi th a n i ncrea s ed s us cepti bi l i ty to vi ra l , funga l , a nd protozoa i nfecti on woul d be expected to ha ve a defi ci ency i n whi ch of the fol l owi ng cel l types ? a . B l ymphocytes b. Ma cropha ges c. NK cel l s d. Neutrophi l s e. T l ymphocytes 487. Whi l e wa l ki ng through a fi el d, a 28-yea r-ol d woma n i s s tung by a bee. Wi thi n 10 mi nutes , s he ha s a s thma ti c-l i ke s ymptoms . Thi s type of hypers ens i ti vi ty rea cti on ca n be correctl y cha ra cteri zed by whi ch of the fol l owi ng s equence of s teps ? a . Al l ergen, chemi ca l medi a tors , s ens i ti za ti on, a l l ergen, IgE, s ymptoms b. Al l ergen, IgE, s ens i ti za ti on, a l l ergen, chemi ca l medi a tors , s ymptoms c. Al l ergen, s ens i ti za ti on, IgE, a l l ergen, chemi ca l medi a tors , s ymptoms d. Sens i ti za ti on, a l l ergen, chemi ca l medi a tors , a l l ergen, IgE, s ymptoms e. Sens i ti za ti on, IgE, a l l ergen, s ymptoms , a l l ergen, chemi ca l medi a tors 488. Fi ndi ngs of IgG a nti bodi es to core a nti gen, a nti bodi es to e a nti gen, a nd a nti bodi es to s urfa ce a nti gen i n a hepa ti ti s B pa ti ent refl ects whi ch of the fol l owi ng? a . Acute i nfecti on (i ncuba ti on peri od) b. Acute i nfecti on (a cute pha s e) c. Pos ti nfecti on (a cute pha s e) d. Immuni za ti on e. HBV ca rri er s ta te 489. Fi ndi ngs of HBs Ag-pos i ti ve a nd HBeAg-pos i ti ve tes t res ul ts i n a hepa ti ti s B pa ti ent refl ect whi ch of the fol l owi ng? a . Acute i nfecti on (i ncuba ti on peri od) b. Acute i nfecti on (a cute pha s e) c. Pos ti nfecti on (a cute pha s e) d. Immuni za ti on e. HBV ca rri er s ta te 490. Fi ndi ngs of HBs Ag pos i ti ve, HBeAg pos i ti ve, a nd IgM core a nti body pos i ti ve i n a hepa ti ti s B pa ti ent refl ect whi ch of the fol l owi ng? a . Acute i nfecti on (i ncuba ti on peri od) b. Acute i nfecti on (a cute pha s e) c. Pos ti nfecti on (a cute pha s e) d. Immuni za ti on e. HBV ca rri er s ta te 491. Fi ndi ngs of HBs Ag pos i ti ve, no a nti bodi es to HBs Ag, a nd other tes ts va ri a bl e i n a hepa ti ti s B pa ti ent refl ect whi ch of the fol l owi ng? a . Acute i nfecti on (i ncuba ti on peri od) b. Acute i nfecti on (a cute pha s e) c. Pos ti nfecti on (a cute pha s e) d. Immuni za ti on e. HBV ca rri er s ta te
492. Fi ndi ngs of a nti bodi es to HBs Ag i n a hepa ti ti s B pa ti ent refl ect whi ch of the fol l owi ng? a . Acute i nfecti on (i ncuba ti on peri od) b. Acute i nfecti on (a cute pha s e) c. Pos ti nfecti on (a cute pha s e) d. Immuni za ti on e. HBV ca rri er s ta te 493. A 15-yea r-ol d ma l e i s rus hed to the emergency room wi th a tempera ture of 103°F, s evere hea da che, a nd s ti ff neck. Upon phys i ca l exa mi na ti on, a petechi a l ra s h i s obs erved a l l over hi s body. Sus pecti ng meni ngi ti s , the phys i ci a n orders a l umba r puncture, revea l i ng gra m-nega ti ve di pl ococci (Neisseria meningitidis) on Gra m s ta i n. The phys i ci a n wi s hes to us e a more s ens i ti ve tes t to confi rm thi s a s the ca us a ti ve a gent. Whi ch of the fol l owi ng tes ts combi nes fea tures of gel di ffus i on a nd i mmunoel ectrophores i s a nd i s a ppl i ca bl e onl y to nega ti vel y cha rged a nti gens ? a . Coa ggl uti na ti on (COA) b. Counteri mmunoel ectrophores i s (CIE) c. Enzyme-l i nked i mmunos orbent a s s a y (ELISA) d. La tex a ggl uti na ti on (LA) e. Ra di oi mmunoa s s a y (RIA) 494. A 21-yea r-ol d fema l e pres ents to the emergency room wi th a hi gh fever, hypotens i on, a nd a di ffus e, ma cul a r, s unburn-l i ke ra s h tha t i s des qua ma ti ng. She i s a l s o vomi ti ng, ha s profus e di a rrhea , l eukocytos i s , thrombocytopeni a , a nd el eva ted BUN a nd crea ti ni ne l evel s . Hi s tory from her roomma te revea l s tha t thes e s ymptoms s ta rted s oon a fter the pa ti ent bega n pa cki ng her nos e to s top chroni c nos e bl eeds . Sus pecti ng S. aureus, a na s a l s wa b s peci men i s obta i ned a nd s ent to the l a bora tory. Whi ch of the fol l owi ng ra pi d tes ts wi l l be ordered a nd depends on the pres ence of protei n A on certa i n s tra i ns of S. aureus? a . COA b. CIE c. ELISA d. LA e. RIA 495. A 50-yea r-ol d bui l di ng contra ctor a rri ves i n your offi ce compl a i ni ng of a bdomi na l pa i n tha t ha s i ncrea s ed i n s everi ty over the pa s t 3 months . He ha s noti ced mel eni c s tool . Orderi ng a s i gmoi dos copy, a 10-cm ma s s i s vi s ua l i zed i n the tra ns vers e col on. Surgery i s i mmedi a tel y done a nd the tumor exci s ed. As pa rt of the pa ti ent’s pos ts urgi ca l fol l ow through of thi s res ected ca rci noma of the col on, bl ood i s obta i ned a nd s ent to the l a bora tory to moni tor l evel s of the tumor ma rker known a s CEA. Whi ch of the fol l owi ng tes ts i nvol ves the mea s urement of very s ma l l qua nti ti es of CEA through competi ti on of ra di ol a bel ed a nd unl a bel ed a nti gen for the s a me l i mi ted a mount of a nti body? a . COA b. CIE c. ELISA d. LA e. RIA 496. A 13-yea r-ol d ma l e a rri ves a t hi s doctor’s offi ce wi th a s evere s ore throa t a nd very hi gh fever. On phys i ca l exa mi na ti on, the phys i ci a n obs erves hi s pha rynx to be i nfl a med wi th a s i gni fi ca nt exuda te a l ong wi th tender cervi ca l l ymph nodes . La bora tory tes ts revea l a l eukocytos i s . Sus pecti ng Group A β-hemol yti c Streptococcus pyogenes, a throa t s wa b a nd cul ture a re obta i ned. Us i ng a ra pi d di a gnos ti c ki t recentl y obta i ned, the phys i ci a n deci des to tes t the s peci mens hi ms el f. Thi s tes t i nvol ves i nert pa rti cl es tha t a re s ens i ti zed wi th ei ther a nti gen or a nti body. Whi ch of the fol l owi ng tes ts i s us ed extens i vel y to detect mi crobi a l a nti gens ra pi dl y (5 mi nutes or l es s )? a . COA b. CIE c. ELISA d. LA e. RIA 497. A 7-month-ol d ba by who i s fa i l i ng to thri ve i s brought i nto a nei ghborhood cl i ni c. Hi s tory revea l s tha t the ba by’s mother di ed of AIDS 2 months a go. Bl ood i s obta i ned a nd s ent to the l a bora tory to check for HIV i nfecti on. The phys i ci a n orders a tes t whos e detecti on s ys tem i s ba s ed on enzyma ti c a cti vi ty. Whi ch of the fol l owi ng tes ts i s a heterogeneous i mmunoa s s a y? a . COA b. CIE c. ELISA d. LA e. RIA Questions 498 to 502 A 29-yea r-ol d pregna nt fema l e gi ves bi rth to a s ti l l born chi l d. Hi s tory revea l s tha t the woma n conti nued to ha ve cl os e conta ct wi th her fi ve ca ts , by emptyi ng l i tter boxes a nd feedi ng them ra w mea t, duri ng pregna ncy, a ga i ns t her phys i ci a n’s a dvi ce. An a utops y i s conducted, a nd mul ti pl e cys ts a re found i n the feta l bra i n, l ungs , l i ver, a nd eyes . As a confi rma tory tes t, the pa thol ogi s t orders a n enzyme i mmunoa s s a y to detect the pres ence of Toxoplasma gondii. The di a gra m bel ow pres ents the va ri ous s teps (l a bel ed A-F) of the enzyme i mmunoa s s a y.
498. Fa i l ure of or i mproper methods for whi ch s tep i n the proces s i s the pri ma ry ca us e of hi gh ba ckground col or? a. A b. B c. C d. D e. E f. F 499. Where i s unl a bel ed a nti body a tta ched i f thi s enzyme i mmunoa s s a y i s i ntended for detecti on of a nti gen? a. A b. B c. C d. D e. E f. F 500. Wha t i s the l oca ti on of the “s ol i d pha s e”? a. A b. B c. C d. D e. E f. F 501. Addi ti on of rea gent a t whi ch s tep wi l l ca us e col or i n the pos i ti ve control wel l a nd rea cti ve pa ti ent s peci mens ? a. A b. B c. C d. D e. E f. F 502. Wha t i s the l oca ti on of the pa ti ent’s s peci men i n the di a gra m? a. A b. B c. C d. D e. E f. F 503. An 18-yea r-ol d ma l e pa ti ent wi th a cute l ymphocyti c l eukemi a fa i l s a l l s ta nda rd chemothera pi es . Cel l s from a n HLA-noni denti ca l donor a re us ed to perform a bone ma rrow tra ns pl a nt. Pri or to tra ns pl a nta ti on, the pa ti ent i s gi ven broa d-s pectrum a nti bi oti cs a nd a n i mmunos uppres s i ve regi men. Wi thi n 2 to 4 weeks , l ymphocyte a nd gra nul ocyte numbers begi n to ri s e, confi rmi ng bone ma rrow cel l engra ftment. However, 1 month l a ter, the pa ti ent devel ops di a rrhea , ja undi ce, a nd a s evere ma cul opa pul a r ra s h. Phys i ca l exa mi na ti on revea l s hepa tos pl enomega l y. Whi ch of the fol l owi ng i s mos t l i kel y occurri ng?
a . Acute rejecti on b. Chroni c rejecti on c. Cycl os pori ne A toxi ci ty d. Gra ft vers us hos t di s ea s e (GVHD) e. Hypera cute rejecti on 504. A 27-yea r-ol d ma l e pa ti ent (bl ood group O) a rri ves a t the emergency room wi th a ma s s i ve i ntes ti na l bl eed (hema tochezi a ). Wi thi n hours he ha s l os t ha l f of hi s bl ood vol ume, a nd you deci de to tra ns fus e. Due to huma n error, you tra ns fus e bl ood group AB i nto hi m a nd wi thi n mi nutes he devel ops a fever, chi l l s , dys pnea , a nd a dra ma ti c drop i n bl ood pres s ure. Thi s rea cti on i s mos t l i kel y due to whi ch of the fol l owi ng? a . A cel l -medi a ted res pons e a ga i ns t AB a nti gens b. IgG producti on by the reci pi ent i n res pons e to AB a nti gens c. Preformed a nti -A a nd a nti -B a nti bodi es i n the reci pi ent d. Preformed a nti -A a nd a nti -B a nti bodi es of the bl ood donor e. Preformed i s ohema ggl uti ni ns of the IgG i s otype 505. Duri ng a cl i ni c offi ce vi s i t, a 35-yea r-ol d ma l e s tockbroker s hows s i gns of exces s i ve nervous nes s a nd i rri ta bi l i ty a nd compl a i ns tha t the offi ce i s too hot. Hi s tory a nd phys i ca l exa mi na ti on revea l s the pres ence of a goi ter a nd exophtha l mi a . La bora tory a na l ys i s of hi s bl ood revea l s hi gh a nti body ti ters a ga i ns t the thyroi d-s ti mul a ti ng hormone (TSH) receptor. Whi ch of the fol l owi ng i s the mos t l i kel y di a gnos i s ? a . Goodpa s ture s yndrome b. Gra ves di s ea s e c. Ha s hi moto di s ea s e d. Juveni l e-ons et di a betes mel l i tus e. Mya s theni a gra vi s f. Perni ci ous a nemi a g. Rheuma toi d a rthri ti s h. Sys temi c l upus erythema tos us (SLE) 506. A 9-yea r-ol d fema l e wi th a recent hi s tory of wei ght l os s a nd vi s i on probl ems a rri ves a t the hos pi ta l . Soon a fter, i t i s determi ned tha t s he ha s l ow bl ood gl ucos e, a nd a utoa nti bodi es a ga i ns t β cel l s a re detected i n her s erum. Whi ch of the fol l owi ng i s the mos t l i kel y di a gnos i s ? a . Goodpa s ture s yndrome b. Gra ves di s ea s e c. Ha s hi moto di s ea s e d. Juveni l e-ons et di a betes mel l i tus e. Mya s theni a gra vi s f. Perni ci ous a nemi a g. Rheuma toi d a rthri ti s h. SLE 507. A 35-yea r-ol d woma n wi th fever, wei ght l os s , fa ti gue, a nd pa i nful joi nts a nd mus cl es pres ents to her phys i ci a n’s offi ce. The phys i ci a n notes tha t s he ha s ma rked photos ens i ti vi ty a nd a ra s h on the cheeks a nd over the bri dge of her nos e. La bora tory tes ts revea l a nemi c condi ti ons a nd the pres ence of a nti -DNA a nti bodi es . Whi ch of the fol l owi ng i s the mos t l i kel y di a gnos i s ? a . Goodpa s ture s yndrome b. Gra ves di s ea s e c. Ha s hi moto di s ea s e d. Juveni l e-ons et di a betes mel l i tus e. Mya s theni a gra vi s f. Perni ci ous a nemi a g. Rheuma toi d a rthri ti s h. SLE Questions 508 to 512
Di a gra m depi cti ng the proces s of T-cell activation by dendritic cells (profes s i ona l a nti gen pres enti ng cel l s , APC). Shown a re a CD4 hel per T cel l (TH), a CD8 cytotoxi c T cel l (CTL), a nd dendri ti c cel l s (DC). Ma jor hi s tocompa ti bi l i ty compl ex (MHC) mol ecul es a re a l s o s hown. CD4 co-receptor i s s hown for TH cel l a cti va ti on, a nd CD8 co-receptor i s s hown for CTL a cti va ti on. There a re 2 zeta cha i ns a nd 4 CD3 compl ex mol ecul es (γ, δ, ε, ε). The recta ngl es a s s oci a ted wi th zeta a nd CD3 a re the ITAMs . Cos ti mul a ti on, s econd s i gna l mol ecul es CD28 a nd B7 a re s hown for both TH a nd CTL a cti va ti on. 508. Whi ch of the fol l owi ng mol ecul es repres ent the pri ma ry or prototypi ca l members i nvol ved i n s i gna l 2 medi a ted a cti va ti on of na ïve T cel l s ? a . CD28, B7-1 or B7-2 b. CTLA-4, CD28, PD-1 c. CTLA-4, B7-1 or B7-2 d. B7-H1, B7-H3, PD-1 509. The fol l owi ng best describes TCR recogni ti on of a nti gen: a . Bi nds to conforma ti ona l determi na nts of whol e protei ns b. Bi nds to l i nea r determi na nts of whol e protei ns c. Bi nds to pepti de i n the context of MHC d. Bi nds to pepti de wi thout MHC e. Bi nds to l a rge gl ycoprotei ns 510. Whi ch of the fol l owi ng best describes the TCR compl ex? a . αβ TCR cova l entl y l i nked wi th CD3 a nd ζ cha i ns b. αβ TCR cova l entl y l i nked wi th CD2 a nd CD28 c. αβ TCR noncova l entl y a s s oci a ted wi th CD3 a nd ζ cha i ns d. αβ TCR noncova l entl y a s s oci a ted wi th CD2 a nd CD28 e. αα TCR noncova l entl y a s s oci a ted wi th CD3 a nd ζ cha i ns 511. The membra ne a s s oci a ted T-l ymphocyte a nti gen receptor or TCR i s bes t des cri bed a s a : a . Heterodi mer cons i s ti ng of cova l entl y l i nked α a nd β cha i ns b. Homodi mer cons i s ti ng of cova l entl y l i nked α a nd β cha i ns c. Homodi mer a s s oci a ted wi th Igα a nd Igβ d. Monomer a s s oci a ted wi th Igα a nd Igβ
e. Hea vy cha i n monomer a s s oci a ted wi th β2m 512. Nea rl y 95% of ma ture T cel l s pos s es s a T-cel l receptor (TCR) compl ex tha t conta i ns : a . Igβ a nd Igα b. CD28 a nd TCR γδ c. A hi ghl y va ri a bl e a nti gen coreceptor a nd TCR γδ d. Four CD3 mol ecul es (γ, δ, ε, ε), ea ch cova l entl y l i nked to the TCR αβ heterodi mer e. Inva ri a bl e ζ cha i n homodi mer noncova l entl y a s s oci a ted wi th the TCR αβ heterodi mer 513. A pres chool boy i s di a gnos ed wi th a n i mmunodefi ci ency cha ra cteri zed by i mpa i red T-cel l a cti va ti on. The defect i s ca us ed by a geneti c a l tera ti on of a membra ne protei n whos e cytopl a s mi c ta i l i s i nvol ved i n s i gna l i ng a s s oci a ted wi th TCR recogni ti on of pepti de a nti gen i n the context of MHC. Whi ch of the fol l owi ng protei ns does NOT fi t thi s des cri pti on? a . CD3γ b. ζ cha i n c. TCRβ d. CD4 e. CD8 514. The germl i ne a nti gen receptor l oci for both a l pha a nd beta cha i ns of the TCR a re found i n: a . Al l nucl ea ted cel l s b. Doubl e pos i ti ve T cel l s onl y c. Na ïve CD4+ T cel l s onl y d. Na ïve CD8+ T cel l s onl y e. Pre-T cel l s onl y 515. The proces s es of nega ti ve s el ecti on for T l ymphocytes el i mi na tes thos e T cel l s wi th TCRs tha t a . Do not recogni ze s el f-pepti de/s el f-MHC b. Recogni ze forei gn-pepti de/s el f-MHC compl exes wi th l ow a vi di ty/a ffi ni ty c. Recogni ze forei gn-pepti de/s el f-MHC compl exes wi th hi gh a vi di ty/a ffi ni ty d. Recogni ze s el f-pepti de/s el f-MHC compl exes wi th l ow a vi di ty/a ffi ni ty e. Recogni ze s el f-pepti de/s el f-MHC compl exes wi th hi gh a vi di ty/a ffi ni ty 516. Cel l s of the i mmune s ys tem a ri s e i n the bone ma rrow. The cel l tha t fi ni s hes i ts ma tura ti on i n the thymus i s the a . Fol l i cul a r B-2 B l ymphocyte b. Ma rgi na l zone B l ymphocyte c. NK cel l d. αβ T l ymphocyte e. Dendri ti c cel l 517. A 1-month-ol d i nfa nt wi th a bri ght red ra s h a nd purul ent conjuncti vi ti s i s a dmi tted to the hos pi ta l . Exa mi na ti on revea l ed eos i nophi l i a , l ow l ymphocyte count, a nd no thymi c s ha dow. Lymphnodes were enl a rged a nd opportuni s ti c i nfecti ons noted. The di a gnos i s wa s a form of SCID termed Omenn s yndrome, a n a utos oma l reces s i ve form of SCID. Muta ti ons i n whi ch of the fol l owi ng woul d expl a i n thi s di s ea s e? a . MHC cl a s s I b. MHC cl a s s II c. CD3 or TCR αβ d. RAG-1 or RAG-2 e. CD4 or CD8 518. Cl a s s -I MHC-res tri cted CD8+ T cel l (CTL) res pons es to tumors ca n be demons tra ted i n pa ti ents wi th va ri ous types of tumors , yet mos t of thes e tumors do not expres s cos ti mul a tory mol ecul es . Whi ch mecha ni s m mos t l i kel y expl a i ns how na ïve CD8+ T cel l s s peci fi c for a nti gens expres s ed by thes e tumors a re a cti va ted a nd di fferenti a te i nto CTLs ? a . Tumor s ecreti on of TGF-β b. Tumor s ecreti on of IL-12 c. Tumor expres s i on of B7 d. Di rect pri mi ng of the CTLs e. Cros s pri mi ng of the CTLs 519. A 47-yea r-ol d woma n ha d a ma s tectomy beca us e s he ha d brea s t ca rci noma tha t wa s previ ous l y di a gnos ed by bi ops y. Pa thol ogi c exa mi na ti on revea l ed tha t s evera l a xi l l a ry l ymph nodes conta i ned meta s ta ti c tumors . A tes t wa s performed on the tumor cel l s extra cted from the ma s tectomy s peci men, whi ch i ndi ca ted tha t the tumor cel l s overexpres s ed a certa i n cel l ul a r proto-oncogene. On the ba s i s of thi s tes t res ul t, the pa ti ent wa s trea ted wi th a n FDA-a pproved monocl ona l a nti body s peci fi c for the protei n encoded by tha t gene. Whi ch of the fol l owi ng wa s mos t l i kel y the protei n ta rget of the FDA-a pproved pa s s i ve a nti body thera py?
a . HPV E6, E7 b. Her2/Neu c. CA-125 d. CD20 e. CEA 520. Whi ch of the fol l owi ng does not des cri be a documented mecha ni s m of tumor-medi a ted i mmune eva s i on? a . Down regul a ti on of cl a s s I MHC b. Secreti on of TGF-β c. Secreti on of decoy mol ecul es d. Anti geni c va ri a ti on 521. Whi ch of the fol l owi ng bes t des cri bes the mecha ni s m(s ) of a cti on of CTLA-4? a . Si gna l 1 a nd cos ti mul a ti on b. Competi ti on a nd i nhi bi ti on c. Acti va ti on a nd prol i fera ti on d. ZAP-70 a nd ITAMs e. PD-1 a nd PD-L1
Answers 428 to 431. The answers are 428-a, 429-c, 430-c, and 431-d. (Kindt, pp 372-396. Parham, pp 365-398.) Rea cti ons to s ma l l a mounts of drugs ca n occur, a s i l l us tra ted i n the s ki n tes t us i ng peni ci l l oyl pol yl ys i ne to revea l a peni ci l l i n a l l ergy or type I hypers ens i ti vi ty rea cti on. In Ques ti on 429, the gi rl wa s l i kel y expos ed to poi s on i vy or poi s on oa k (conta ct derma ti ti s ) whi ch i s a ttri buted to a type IV hypers ens i ti vi ty rea cti on. An Arthus rea cti on i s a l oca l i zed type of rea cti on medi a ted by a ggrega tes of a nti body a nd a nti gen a nd i s cha ra cteri s ti c of type III hypers ens i ti vi ty rea cti ons . In Ques ti on 430, onl y hypers ens i ti vi ty rea cti ons type I a nd IV a re a s s oci a ted wi th s ki n tes ts . Type I i s commonl y referred to a s a cha l l enge i n whi ch a s peci fi c a nti gen i s i njected i ntra derma l l y i nto a s ens i ti zed i ndi vi dua l , crea ti ng a “whea l a nd fl a re” (erythema a nd edema ) rea cti on. Type IV hypers ens i ti vi ty i s commonl y a s s oci a ted wi th tubercul i n i njecti ons to recogni ze the pres ence of del a yed type hypers ens i ti vi ty. In Ques ti on 431, Rh di s ea s e a nd Goodpa s ture s yndrome a re the res ul t of a nti bodi es tha t ha ve formed a ga i ns t norma l l y pres ent hos t a nti gens on red bl ood cel l s a nd the ki dney’s gl omerul a r ba s ement membra ne, res pecti vel y. Thus , thes e two di s ea s es a re a s s oci a ted wi th type II rea cti ons . The ta bl e bel ow des cri bes thes e rea cti ons i n deta i l .
432 and 433. The answers are 432-b and 433-a. (Kindt, pp 284, 498. Parham, pp 170-171, 341-342.) Bruton a ga mma gl obul i nemi a i s a congeni ta l defect tha t becomes a ppa rent a t a pproxi ma tel y 6 months of a ge, when ma terna l IgG i s di mi ni s hed. It occurs i n ma l es a nd i s cha ra cteri zed by a defecti ve btk gene, very s ma l l tons i l s , l ow l evel s of a l l fi ve cl a s s es of i mmunogl obul i ns , a nd no ma ture B cel l s . Thus , the chi l d i s una bl e to produce i mmunogl obul i ns a nd devel ops a s eri es of ba cteri a l i nfecti ons cha ra cteri zed by recurrences a nd progres s i on to more s eri ous i nfecti ons s uch a s s epti cemi a . The mos t common orga ni s ms res pons i bl e for i nfecti on a re H. influenzae a nd S. pneumoniae. Trea tment cons i s ts of pool ed IgG. Cel l medi a ted i mmuni ty i s not a ffected, a nd the chi l d i s a bl e to res pond norma l l y to di s ea s es tha t requi re thi s i mmune res pons e for res ol uti on, s uch a s the mea s l es vi rus , va ri cel l a -zos ter vi rus , a nd M tuberculosis. The other di a gnos es do not des cri be the s peci fi c cl i ni ca l s cena ri o outl i ned i n thi s ca s e. Al s o, i t i s i mporta nt to note tha t s i nce the ma i n defect i n thi s chi l d’s i mmuni ty i s i n the B-cel l l i ne, i n tha t, the chi l d i s una bl e to produce i mmunogl obul i ns . The orga ni s m tha t woul d be mos t da ngerous to the chi l d i s C. trachomatis beca us e the B-cel l l i ne (a nti bodi es ) i s typi ca l l y res pons i bl e for i ts el i mi na ti on from the hos t.
Note: Immunodefi ci ency i s cha ra cteri zed by unus ua l a nd recurrent i nfecti ons : • B-cel l (a nti body) defi ci ency—ba cteri a l i nfecti ons • T-cel l defi ci ency—vi ra l , funga l , a nd protozoa l i nfecti ons • Pha gocyti c cel l defi ci ency—pyogeni c i nfecti ons (ba cteri a l ), s ki n i nfecti ons , s ys temi c ba cteri a l opportuni s ti c i nfecti ons • Compl ement defi ci enci es —pyogeni c i nfecti ons (ba cteri a l ) 434 and 435. The answers are 434-e and 435-a. (Kindt, pp 30-40. Parham, pp 220-230, 352-356.) Cel l s ca n be di fferenti a ted ba s ed on uni que cel l s urfa ce ma rkers (a nti gens ). In thi s ca s e, a CD4:CD8 ra ti o of l es s tha n 1 i ndi ca tes a s i gni fi ca nt reducti on i n the hel per T-l ymphocyte popul a ti on. The s urfa ce protei ns tha t bes t repres ent thi s pool a re MHC I, TCR, CD3, a nd CD28. CD4 i s a l s o a s s oci a ted wi th hel per T l ymphocytes . B l ymphocytes ha ve MHC I, IgM, B7 CD19, a nd CD20. Cytotoxi c T l ymphocytes ha ve MHC I, TCR, CD3, a nd CD8, whi l e ma cropha ges ha ve MHC I, MHC II, a nd CD14. An i mporta nt fa ct to remember i s tha t a l l hea l thy cel l s other tha n ma ture red cel l s ha ve cl a s s I MHC. The B7 s urfa ce protei n on the a nti gen-pres enti ng cel l i s the cos ti mul a tory mol ecul e a nd mus t i ntera ct wi th the CD28 on the hel per T cel l for ful l a cti va ti on to occur (s ee the fol l owi ng fi gures .)
(A) Schema ti c overvi ew of hema topoi es i s , empha s i zi ng the erythroi d, myel oi d, a nd l ymphoi d pa thwa ys . Thi s hi ghl y s i mpl i fi ed depi cti on omi ts ma ny recogni zed i ntermedi a te cel l types i n ea ch pa thwa y. Al l of the cel l s s hown here devel op to ma turi ty i n the bone ma rrow, except T l ymphocytes , whi ch devel op from ma rrow-deri ved progeni tors tha t mi gra te to the thymus . A common l ymphoi d s tem cel l s erves a s the progeni tor of T a nd B l ymphocytes a nd of NK cel l s . Dendri ti c cel l s a ri s e from both the myel oi d a nd l ymphoi d l i nea ges . (Reproduced, with permission, from Parslow TG, et al. Medi ca l Immunol ogy. 10th ed. New York, NY: McGraw-Hill; 2001:3.)
(B) Cl ona l s el ecti on of l ymphocytes by a s peci fi c i mmunogen. Left: The uni mmuni zed l ymphocyte popul a ti on i s compos ed of cel l s from ma ny di fferent cl ones , ea ch wi th i ts own a nti gen s peci fi ci ty, i ndi ca ted here by the di s ti ncti ve s ha pes of the s urfa ce a nti gen receptors . Right: Conta ct wi th a n i mmunogen l ea ds to s el ecti ve prol i fera ti on (pos i ti ve s el ecti on) of a ny cl one or cl ones tha t ca n recogni ze tha t s peci fi c i mmunogen. (Reproduced, with permission, from Parslow TG, et al. Medi ca l Immunol ogy. 10th ed. New York, NY: McGraw-Hill; 2001:62.) 436. The answer is a. (Kindt, pp 2-3, 475-490. Parham, pp 1-7, 437-441.) Recurrent s evere i nfecti on i s a n i ndi ca ti on for cl i ni ca l eva l ua ti on of i mmune s ta tus . Li ve va cci nes , i ncl udi ng BCG a ttenua ted from M. tuberculosis, s houl d not be us ed i n the eva l ua ti on of a pa ti ent’s i mmune competence beca us e pa ti ents wi th s evere i mmunodefi ci enci es ma y devel op a n overwhel mi ng i nfecti on (di s s emi na ted di s ea s e) from the va cci ne. For the s a me rea s on, ora l (Sa bi n) pol i o va cci ne i s not a dvi s a bl e for us e i n s uch pers ons . The other va cci nes l i s ted a re a cel l ul a r a nd s houl d be s a fe to us e i n thi s cl i ni ca l s cena ri o des cri bed. 437. The answer is e. (Kindt, pp 475-484. Parham, pp 24, 437-445.) Mea s l es -l i ke vi rus ha s been i s ol a ted from the bra i n cel l s of pa ti ents wi th SSPE. The rol e of the hos t i mmune res pons e i n the ca us a ti on of SSPE ha s been s upported by s evera l fi ndi ngs i ncl udi ng the fol l owi ng: (1) progres s i on of di s ea s e des pi te hi gh l evel s of humora l a nti body; (2) pres ence of a fa ctor tha t bl ocks l ymphocyte-medi a ted i mmuni ty to SSPE-mea s l es vi rus i n SSPE-CSF; (3) l ys i s of bra i n cel l s from SSPE pa ti ents by SSPE s erum or CSF i n the pres ence of compl ement (a s i mi l a r mecha ni s m coul d ca us e i n vi vo ti s s ue i njury). SSPE i s pa rti cul a rl y common i n thos e who a cqui red mea s l es before 2 yea rs of a ge a nd i s very ra re a fter mea s l es va cci na ti on. Hi gher-tha n-norma l l evel s of s erum a nti bodi es (Ab) to mea s l es vi rus a nd l oca l s ynthes i s of mea s l es Ab i n CSF, a s evi denced by the ol i gocl ona l IgG, i mpl y a connecti on between the vi rus a nd MS. However, the other s tudi es ha ve i mpl i ca ted the other vi rus es . Severa l s tudi es of cel l -medi a ted hypers ens i ti vi ty to mea s l es a nd other vi rus es i n MS ha ve been done, but the res ul ts ha ve been confl i cti ng. Defi ni te concl us i ons rega rdi ng defects i n cel l ul a r i mmuni ty i n thi s di s ea s e ca nnot be rea ched unti l further res ea rch i s compl eted. CJD i s ca us ed by the pri on, whi ch i s a n a l tered hos t protei n tha t becomes i nfecti ous i n na ture. It i s cha ra cteri zed by myocl oni c jerki ng a l ong wi th cha ra cteri s ti c EEG cha nges . PML i s a s s oci a ted wi th the JC vi rus (JCV), whi l e thi s cl i ni ca l s cena ri o i s not cha ra cteri s ti c of EBV i nfecti on. 438. The answer is c. (Kindt, pp 426-440. Parham, pp 455-459.) Tra ns pl a nta ti on termi nol ogy i s bei ng tes ted i n thi s ques ti on. An a utogra ft i s a tra ns fer of a n i ndi vi dua l ’s own ti s s ue to a nother s i te i n the body. An i s o-gra ft (s yngenei c gra ft) i s the tra ns fer of ti s s ue between geneti ca l l y i denti ca l i ndi vi dua l s , s uch a s monozygoti c twi ns . An a l l ogra ft i s the tra ns fer of ti s s ue between geneti ca l l y di fferent members of the s a me s peci es (i e, brother to s i s ter, di zygoti c twi ns , etc), whi l e a xenogra ft i s the tra ns fer of ti s s ue between di fferent s peci es (eg, pi g va l ve to huma n hea rt). In thi s ca s e, one uni t i s the pa ti ent’s own bl ood (a n a utol ogous dona ti on) whi l e the s econd uni t i s hi s ol der brother’s bl ood (mos t l i ke a n a l l ogra ft dona ti on). If hi s brother ha d been a n i denti ca l twi n, then (e) woul d be the correct a ns wer. 439. The answer is b. (Kindt, pp 403, 410-412. Parham, pp 403-416.) Thi s cl i ni ca l ca s e repres ents a pa ti ent s ufferi ng wi th SLE. The di a gnos i s of SLE i s bes t s upported by detecti ng the pres ence of a nti -ds DNA a nd a nti -Smi th (a nti -Sm) a nti bodi es . The pres ence of a nti -ds DNA a nti bodi es a re very s peci fi c for SLE a nd repres ent a poor prognos i s for di s ea s e. Anti nucl ea r a nti bodi es (ANA) ca n a l s o be detected us i ng fl uores cent a nti body tes ts . The other a nti bodi es l i s ted a re rel a ted to other a utoi mmune di s ea s es a s fol l ows : a nti centromere a nti bodi es i n CREST s yndrome a nd occa s i ona l l y i n s ys temi c s cl eroderma , a nti mi tochondri a l a nti bodi es i n pri ma ry bi l i a ry ci rrhos i s , a nti neutrophi l a nti bodi es i n a nti neutrophi l cytopl a s mi c a nti bodi es (ANCA)-a s s oci a ted va s cul i ti s (s ys temi c va s cul i ti s ), a nd a nti -TSH receptor a nti bodi es i n Gra ves di s ea s e (hyperthyroi di s m). 440. The answer is a. (Kindt, pp 66, 495t, 501-503. Parham, pp 57, Ch 13.) The pa ti ent i n thi s ca s e ha s chroni c gra nul oma tous di s ea s e (CGD), a n X-l i nked (65%) or a utos oma l reces s i ve (35%) i nheri ted di s ea s e. Pa ti ents wi th CGD a re not a bl e to genera te a res pi ra tory burs t a fter gra nul ocyte a nd monocyte s ti mul a ti on. Thus , they a re una bl e to ki l l mi croorga ni s ms . Ans wers a , b, a nd c a re a l l i nvol ved i n the res pi ra tory burs t; however, the centra l enzyme i s the NADPH oxi da s e (a ns wer a ). Wi thout thi s enzyme, hydrogen peroxi de (a ns wer b), s uperoxi de (a ns wer c), a nd other mi crobi a l rea cti ve oxygen s peci es woul d not be genera ted. Ans wer d depi cts the s yntheti c pa thwa y for ni tri c oxi de, a potent va s odi l a tor. Ans wers e a nd f a re rea cti ons i nvol vi ng common meta bol i c enzymes i n va ri ous ba cteri a .
441. The answer is c. (Kindt, pp 193-195. Parham, pp 133-139.) The fi gure s hown i n the ques ti on i s a s chema ti c repres enta ti on of the MHC cl a s s I mol ecul e, whi ch ha s a CD8 bi ndi ng s i te (α3 ) a nd a pepti de-bi ndi ng s i te (α1 a nd α2 ). MHC cl a s s I i s a cti ve on a l l nucl ea ted cel l s . 442. The answer is a. (Kindt, pp 85-89. Parham, pp 95-105.) The i ni ti a l res pons e to a new i nfecti on i s wi th a n IgM cl a s s a nti body. IgM devel ops qui ckl y a nd us ua l l y di s a ppea rs wi thi n a few months . The s econda ry res pons e i s IgG a nd refl ects the pa ti ent’s i mmune s ta tus or, i n the ca s e of chi cken pox, a va cci na ti on gi ven. 443. The answer is d. (Kindt, pp 168, 185-186, 502. Parham, pp 343-345.) Pa ti ents wi th compl ement defi ci enci es s uch a s C5 through C9, whi ch form the membra ne a tta ck compl ex (MAC), a re predi s pos ed to di s s emi na ted meni ngococca l (nei s s eri a l ) di s ea s e. Thes e pa ti ents ma y a l s o be s us cepti bl e to gonococca l (nei s s eri a l ) i nfecti on. There a ppea rs to be no di s pos i ti on to AIDS or to funga l , pa ra s i ti c, or pneumococca l i nfecti ons . 444. The answer is d. (Kindt, pp 346-347. Parham, pp 58-60.) The a cute-pha s e res pons e i s a pri mi ti ve, nons peci fi c defens e rea cti on, medi a ted by the l i ver, whi ch i ncrea s es i nna te i mmuni ty a nd other protecti ve functi ons i n s tres s ful ti mes . It ca n be tri ggered by chroni c a utoi mmune di s orders s uch a s rheuma toi d a rthri ti s a nd Crohn di s ea s e. Thi s res pons e occurs when hepa tocytes a re expos ed to IL-6 a nd IL-1 or TNF-α. LPS i s a potent i nducer of thes e cytoki nes . They a re res pons i bl e for fever, s omnol ence, l os s of a ppeti te, a nd, i f the res pons e i s prol onged, a nemi a a nd ca chexi a (wa s ti ng). A tra di ti ona l a s s a y known a s the erythrocyte sedimentation rate (ESR) ma y be us ed a s a n i ndi ca tor of a n a cute-pha s e res pons e. The ESR i nvol ves mea s uri ng the ra te a t whi ch the red bl ood cel l s fa l l through pl a s ma , whi ch i ncrea s es a s fi bri nogen concentra ti on ri s es . Currentl y, Crohn di s ea s e ma y be trea ted wi th i nfus i ons of a drug known a s i nfl i xi ma b, whi ch i s a mous e-huma n chi meri c a nti body a ga i ns t huma n TNF-α or a da l i muma b, a ful l y huma ni zed monocl ona l a nti body a ga i ns t huma n TNF-α. The FDA ha s a pproved thes e monocl ona l a nti body drugs i n the trea tment of Crohn di s ea s e, rheuma toi d a nd ps ori a ti c a rthri ti s , a nkyl os i ng s pondyl i ti s , modera te to s evere chroni c ps ori a s i s , a nd juveni l e i di opa thi c a rthri ti s . 445. The answer is d. (Kindt, pp 99-100. Parham, pp 117-118, 267-268.) Ma terna l tra ns fer of a nti body (s ecretory IgA i n the col os trum of brea s t mi l k), however, i s pa s s i ve but s ti l l confers s peci fi c i mmuni ty. It i s termed passive acquired i mmuni ty. Na tura l i mmuni ty i s nons peci fi c. The na tura l i mmune functi ons des cri bed a re not s peci fi c for a certa i n a nti gen. For exa mpl e, certa i n protei ns s uch a s C-rea cti ve protei n (CRP) a re a cute-pha s e rea cta nts . Whi l e el eva ted CRP i s s een i n i nfecti on, i t i s not di s ea s e s peci fi c. 446. The answer is b. (Kindt, pp 77-78.) Ha ptens (i ncompl ete a nti gens ) a re not thems el ves a nti geni c, but when coupl ed to a cel l or ca rri er protei n become a nti geni c a nd i nduce a nti bodi es tha t ca n bi nd the ha pten a l one (i n the a bs ence of the ca rri er protei n). They a re s ma l l mol ecul es tha t a re genera l l y l es s tha n 1000 kDa . Whi l e ha ptens rea ct wi th a nti bodi es , they a re not i mmunogeni c beca us e they do not a cti va te T cel l s a nd ca nnot bi nd the MHC. Ha ptens a re s i gni fi ca nt i n di s ea s e; peni ci l l i n i s a ha pten a nd ca n ca us e s evere l i fe-threa teni ng a l l ergi c rea cti on by des tructi on of erythrocytes . Ca techol s i n the oi l s of poi s on i vy pl a nts a re ha ptens a nd ca us e a s i gni fi ca nt s ki n i nfl a mma tory res pons e. Chl ora mpheni col i s a ha pten tha t ca n l ea d to the des tructi on of l eukocytes a nd ca us e a gra nul ocytos i s . Sedormi d i s a ha pten tha t ca n ca us e thrombocytopeni a a nd purpura (bl eedi ng) through the des tructi on of pl a tel ets . 447. The answer is e. (Kindt, pp 87, 95-100. Parham, pp 115-118.) The ra di a l i mmunodi ffus i on a nd i mmunoel ectrophores i s a re two tes ts us ed to eva l ua te humora l i mmuni ty. Eva l ua ti ng humora l i mmuni ty cons i s ts of mea s uri ng the l evel s of IgM, IgG, a nd IgA i n the pa ti ent’s s erum. Wherea s tota l IgG i s grea ter tha n tota l IgM i n the fetus due to the ma terna l tra ns fer of IgG a nd not IgM a cros s the pl a centa , i t i s i mporta nt to remember tha t IgM i s the a nti body produced i n the grea tes t a mounts by the fetus . The fetus a l s o produces IgG a nd IgA, but the fetus produces grea ter a mounts of IgM tha n thes e other two i mporta nt a nti bodi es . 448. The answer is d. (Kindt, pp 508-509, 512. Parham, pp 25-26, 351-361.) HIV-2 di s ea s e i s very ra re i n the Uni ted Sta tes . However, HIV-2 i s pres ent i n Afri ca , the Fa r Ea s t, a nd s ome pa rts of the Ca ri bbea n. Ma ny of the s creeni ng tes ts for HIV-1 wi l l not detect a nti bodi es to HIV-2. Ei ther a s epa ra te HIV-2 a nti body tes t or a combi na ti on HIV-1/2 i s neces s a ry. Whi l e HTLV di s ea s e i s a l s o s een i n the s a me geogra phi c a rea s , the s ymptoms di s pl a yed by thi s pa ti ent a re more a ki n to HIV di s ea s e. Whi l e a n HIV-1 RNA PCR i s a us eful tes t for moni tori ng the res ul ts of HIV thera py, i t i s not a pproved for di a gnos i s , nor wi l l i t detect HIV-2 nucl ei c a ci d. 449. The answer is c. (Kindt, pp 30, 35-36, 360-363. Parham, pp 16, 65-66.) NK cel l s do not expres s a cel l s urfa ce TCR/CD3 compl ex a nd a re CD4–. About ha l f of huma n NK cel l s a re CD8+. Al s o, mos t NK cel l s expres s a n Fc IgG receptor, known a s CD16, a nd CD56, a neura l cel l a dhes i on mol ecul e va ri a nt. NK cel l s a re genera l l y CD16+, CD56+, a nd CD3–, whi ch contra s ts them wi th T cel l s , whi ch a re CD3+, CD16–, a nd CD56–. In a ddi ti on, B cel l s a re a s s oci a ted wi th CD19 a nd CD20. 450. The answer is e. (Kindt, pp 175-176, 338-339. Parham, pp 39-42.) C3a a nd C5a a re potent medi a tors of i nfl a mma ti on; tha t i s , they ha ve a na phyl a toxi n a cti vi ty. Thi s a cti vi ty i s cha ra cteri zed by s mooth-mus cl e contra cti on a nd the degra nul a ti on of ma s t cel l s a nd ba s ophi l s l ea di ng to the rel ea s e of hi s ta mi ne a nd other va s oa cti ve s ubs ta nces , ca us i ng i ncrea s ed va s cul a r (ca pi l l a ry) permea bi l i ty. C5a i s the mos t potent of thes e a na phyl a toxi ns ; however, i t a l s o s erves a nother rol e a s a potent chemota cti c a gent, a ttra cti ng pol ymorphonucl ea ted neutrophi l s a nd ma cropha ges to the s i te of i nfl a mma ti on. 451. The answer is a. (Kindt, pp 33, 426-440. Parham, pp 460-469.) Al l ogra ft rejecti on i s pri ma ri l y a T-cel l res pons e to forei gn ti s s ue. Ma ny i mmunos uppres s i ve mea s ures exi s t, i ncl udi ng cycl os pori ne, ta crol i mus , s i rol i mus , a za thi opri ne, monocl ona l a nti bodi es , ra di a ti on, a nd corti cos teroi ds . Commonl y us ed, the corti cos teroi ds reduce i nfl a mma tory res pons e a nd a re genera l l y a dmi ni s tered by cytotoxi c drugs , s uch a s cycl os pori ne. Corti cos teroi ds functi on a s i mmunos uppres s i ve a gents by i nhi bi ti ng cytoki ne producti on, s uch a s IL-1 a nd TNF, a nd a l s o by l ys i ng certa i n T-cel l types . Lymphoi d i rra di a ti on i s us ua l l y done s o tha t the bone ma rrow i s s hi el ded. Thi s removes l ymphocytes from l ymph nodes a nd s pl een whi l e a l l owi ng the pa ti ent to ha ve the ca pa ci ty to regenera te new T a nd B cel l s . Li kewi s e, a nti l ymphocyte gl obul i n wi l l des troy the reci pi ent’s l ymphocytes , es peci a l l y T cel l s . Des tructi on of donor B cel l s a nd T cel l s woul d not pl a y a rol e i n the i mmunos uppres s i on of the gra ft reci pi ent. In gra ft cri s es , monocl ona l a nti body to CD3 i s s ometi mes gi ven. Thi s ta rgets ma ture T l ymphocytes for des tructi on. 452. The answer is c. (Kindt, pp 77-78. Parham, pp 115-119.) Wi th repea ted i mmuni za ti on, hi gher ti ters of a l l a nti bodi es a re obs erved, a nd, a s pri mi ng i s repea ted, the i mmune res pons e recrui ts B cel l s of progres s i vel y grea ter a ffi ni ty. The a ffi ni ty of a nti body for a ha pten–protei n compl ex ri s es , pol ycl ona l cros s -rea cti vi ty a l s o ri s es , a nd the res pons e becomes wi der i n s peci fi ci ty. As the number of a nti geni c s i tes detected per rea cti ng pa rti cl e i ncrea s es , the a vi di ty i ncrea s es . In a ddi ti on to s hi fts i n the cl a s s of i mmunogl obul i n s ynthes i zed i n res pons e to a n a nti gen (IgM-IgG), s hi fts a l s o ma y occur i n the i di otype of a nti body. 453. The answer is b. (Kindt, pp 151-153.) In preci pi ta ti on rea cti ons , both the a nti gen a nd the a nti body a re s ol ubl e. The a nti body cros s -l i nks a nti gen mol ecul es , crea ti ng a n i ncrea s i ng l a tti ce tha t eventua l l y forms a n i ns ol ubl e preci pi ta te. The a nti gen mus t be di va l ent, a nd the a nti gen/a nti body proporti on i s cri ti ca l i n order for detecta bl e preci pi ta te to form. The prozone i s the zone of a nti body exces s . The pos tzone i s the zone of a nti gen exces s . The zone of equi va l ence i s the zone where the proporti on of a nti body a nd a nti gen i s opti ma l for preci pi ta te forma ti on. Ti ter i s the
reci proca l of the hi ghes t di l uti on (ra ti o) of a nti body (or a nti gen) a t whi ch there i s s ti l l a detecta bl e rea cti on (s ee fi gure on the next pa ge).
(Modified and reproduced, with permission, from Stites D, Terr A, Parslow T (eds). Ba s i c a nd Cl i ni ca l Immunol ogy. 9th ed. Ori gi na l l y publ i s hed by Appl eton & La nge. Copyright © 1997 by The McGraw-Hill Companies.) 454. The answer is b. (Kindt, pp 96t, 99-100. Parham, pp 117-118.) Ea ch s ecretory IgA mol ecul e ha s a mol ecul a r wei ght of 400,000 a nd cons i s ts of two H2L2 uni ts a nd one mol ecul e ea ch of J cha i n a nd s ecretory component. Some IgA exi s ts i n s erum a s a monomer H2L2 wi th a mol ecul a r wei ght of 160,000. Some ba cteri a , s uch a s Neisseria, ca n des troy IgA-1 by produci ng protea s e. It i s the ma jor i mmunogl obul i n i n mi l k, s a l i va , tea rs , mucus , s wea t, ga s tri c fl ui d, a nd col os trum. IgA does not fi x compl ement, s o one woul d a nti ci pa te tha t a compl ement fi xa ti on tes t woul d not be us eful for IgA a nti body. It i s i mporta nt to remember tha t of the fi ve cl a s s es of i mmunogl obul i ns , onl y IgG a nd IgM a re compl ement-fi xi ng/a cti va ti ng a nti bodi es . 455. The answer is d. (Kindt, pp 9, 55, 168-187. Parham, pp 33-41.) Both IgG a nd IgM a cti va te compl ement by the cl a s s i c pa thwa y, whi l e IgA a cti va tes i t by the a l terna ti ve pa thwa y. IgA, IgD, a nd IgE ca nnot a cti va te compl ement. Compl ement i s a s ys tem of s evera l protei ns tha t i s a cti va ted by ei ther a n i mmune or a noni mmune pa thwa y. Both of thes e pa thwa ys res ul t i n the producti on of ma ny bi ol ogi ca l l y a cti ve components tha t ca us e cel l l ys i s a nd dea th. Thus , i t pl a ys a s i gni fi ca nt rol e i n the i nfl a mma tory proces s . In a ddi ti on, products of the compl ement ca s ca de a re a s s oci a ted wi th enha nci ng ops oni za ti on, neutra l i za ti on of i nva di ng pa thogens , a nd cl ea ra nce of debri s by the CR1 on erythrocytes . In thi s cl i ni ca l ca s e, the pa ti ent i s s ufferi ng from s evere l i ver fa i l ure. Thi s s i gni fi ca nt reducti on i n l i ver functi on ha s l ed to a reduced a bi l i ty by the pa ti ent to produce s uffi ci ent compl ement protei ns , a nd a s a res ul t the pa ti ent i s predi s pos ed to i nfecti ons ca us ed by pyogeni c ba cteri a . See the bel ow fi gure.
The cl a s s i c a nd a l terna ti ve pa thwa ys of the compl ement s ys tem i ndi ca te tha t proteol yti c cl ea va ge of the mol ecul e a t the ti p of the a rrow ha s occurred; a l i ne over a compl ex i ndi ca tes tha t i t i s enzyma ti ca l l y a cti ve. Note tha t the nomencl a ture of the cl ea va ge products of C2 i s undeci ded. Some ca l l the l a rge fra gment C2a a nd others ca l l i t C2b. The C3 converta s e i s depi cted here a s C4b, 2b. Note tha t protea s es a s s oci a ted wi th the ma nnos e-bi ndi ng l ecti n cl ea ve C4 a s wel l a s C2. (Reprinted, with permission, from Levinson W, Jawetz E. Medi ca l Mi crobi ol ogy a nd Immunol ogy. 7th ed. New York, NY: McGraw-Hill; 2002:401.) 456 to 460. The answers are 456-d, 457-c, 458-e, 459-b, and 460-a. (Kindt, pp 95-100, 170-173. Parham, pp 115-120, 264-271.) IgG a nti body provi des a n “i mmune hi s tory.” Tha t i s , IgG a nti body pers i s ts i n mos t peopl e a nd i ndi ca tes the a nti gens to whi ch they ha ve been expos ed. IgG i s not formed ea rl y i n i nfecti on but i s a s econda ry res pons e a ri s i ng weeks to months a fter a nti geni c cha l l enge. IgG a l s o ha s a bui l t-i n memory. Even peopl e wi th very l ow l evel s of s peci fi c IgG wi l l res pond to a n a nti gen cha l l enge wi th a n IgG res pons e. IgM a nti body, i n contra s t, a ri s es ea rl y i n i nfecti on a nd then di s a ppea rs wi thi n a coupl e of months . IgM i s i ntra va s cul a r a nd does not cros s the pl a centa l ba rri er. For thi s rea s on, i nfa nts wi th s peci fi c IgG res pons es to di s ea s e mus t be tes ted for IgM to determi ne whether thei r i mmune s ys tems ha ve produced a nti body or whether the tes t wa s pos i ti ve beca us e of pa s s i vel y tra ns ferred IgG from mother to chi l d. The cl i ni ca l ca s e des cri bed i n Ques ti on 465 i s of a young pa ti ent wi th hyper-IgM s yndrome. Thi s i mmune defi ci ency pres ents ea rl y i n l i fe wi th s evere pyogeni c i nfecti ons , res embl i ng thos e s een i n X-l i nked hypoga mma gl obul i nemi a ; however, unl i ke X-l i nked hypoga mma gl obul i nemi a (very l ow l evel s of a l l i mmunogl obul i ns , vi rtua l a bs ence of B cel l s , found i n young boys wi th fema l e ca rri ers bei ng i mmunol ogi ca l l y norma l ), hyper-IgM s yndrome pa ti ents ha ve a hi gh IgM concentra ti on, l ow IgG, IgA, a nd IgE concentra ti ons , a nd norma l T- a nd B-cel l numbers . The probl em exi s ts i n a muta ti ona l defect i n the CD40 l i ga nd i n CD4-pos i ti ve hel per T cel l s , l ea di ng to fa i l ure of norma l i ntera cti on between thi s l i ga nd on T cel l s a nd CD40 on B-cel l s urfa ces . Thi s fa i l ure l ea ds to a n i na bi l i ty of the B cel l s to cl a s s s wi tch from IgM producti on to other a nti bodi es . Trea tment i ncl udes pool ed ga mma gl obul i n. IgA a nti body i s i nvol ved i n l oca l i mmuni ty a t the l evel of the mucous membra ne. It a l s o a ri s es ea rl y i n di s ea s e, i s s hort l i ved, a nd wi l l di s a ppea r s i mi l a rl y a s IgM. IgE a nti body i s cha ra cteri s ti ca l l y s een i n pa ra s i ti c i nfecti ons , pa rti cul a rl y worm (hel mi nth) i nfecti ons beca us e of the a ttra cti on of eos i nophi l s to
the s i te of the i nfes ta ti on. Certa i n a l l ergi es a re due to exces s i ve producti on of IgE. The pa ti ent i n thi s ca s e ha s i ri chi nos i s a s a res ul t of cons umi ng undercooked pork a nd i nges ti ng the pa ra s i te Trichinella spiralis. IgE s peci fi c for worm protei ns bi nds to receptors on eos i nophi l s , promoti ng the rel ea s e of worm-des troyi ng enzymes i nvol ved i n the a nti body-dependent cel l ul a r cytotoxi ci ty (ADCC) res pons e. IgD a nti body cons i s ts of two l i ght cha i ns a nd two hea vy cha i ns . Its rol e i s not known, but i t ca n be found on the s urfa ce of l ymphocytes , where i t ma y a ct a s a s urfa ce receptor. IgG i s s us cepti bl e to proteol yti c enzymes , whi ch ma y expl a i n why i t i s pres ent i n s uch l ow l evel s i n s erum. In a ddi ti on, the fetus ha s more tota l IgG, tha n IgM, a s a res ul t of ma terna l pl a centa l IgG tra ns fer, even though IgM i s produced i n grea ter a mounts by the fetus . 461 to 465. The answers are 461-a, 462-b, 463-e, 464-c, and 465-d. (Kindt, pp 455-460, 448-454.) Borrelia burgdorferi, the ca us a ti ve a gent of Lyme di s ea s e, el i ci ts a n a cute a nti body res pons e. IgM a ppea rs wi thi n da ys to a few weeks fol l owi ng ti ck bi te, a nd IgG a ppea rs a few weeks l a ter. IgG pers i s ts ; IgM does not. Cros s -rea cti ons occur wi th other treponemes . Fi fth di s ea s e i s a vi ra l exa nthem commonl y s een i n chi l dren 8- to 12-yea r-ol d. Chi l dren a re i l l for a few da ys but recover wi thout i nci dent, us ua l l y wi thi n a bout 1 week. Unfortuna tel y, i f a pregna nt fema l e a cqui res the di s ea s e i n the fi rs t tri mes ter of pregna ncy, the fetus i s a t ri s k. The ca us a ti ve a gent i s thought to be a pa rvovi rus (Pa rvovi rus B19). Fi fth di s ea s e i s a l s o known a s erythema i nfecti os um or s l a pped cheek s yndrome. The four other ma cul opa pul a r or ma cul a r ra s h di s ea s es of chi l dhood a re mea s l es , ros eol a , rubel l a , a nd s ca rl et fever. Adul ts wi th no ti ter to va ri cel l a (VZV) a re a t ri s k for a cqui s i ti on of chi cken pox. If they a re hea l th ca re workers , there i s a ddi ti ona l ri s k of tra ns mi tti ng VZV to i mmunodefi ci ent chi l dren. Anti bodi es to VZV a re rea di l y detected by both enzyme i mmunoa s s a y (EIA) a nd fl uores cent a nti body (FA) techni ques . Del ta a gent i s a recentl y di s covered a nti gen a s s oci a ted wi th HBs Ag. Its pres ence us ua l l y correl a tes wi th HBs Ag chroni c ca rri ers who ha ve chroni c a cti ve hepa ti ti s . EIA a nd RIA tes ts a re a va i l a bl e to detect a nti bodi es to del ta a gent. SSPE i s thought to be ca us ed by a mea s l es -rel a ted vi rus pres ent i n the centra l nervous s ys tem. Mos t SSPE pa ti ents s how el eva ted mea s l es vi rus a nti bodi es i n s erum a nd CSF. In pa ti ents wi th MS, l ower CSF a nti body ti ters ha ve been obs erved, s ugges ti ng a pos s i bl e eti ol ogi c rol e for mea s l es vi rus i n MS. 466 to 470. The answers are 466-d, 467-c, 468-d, 469-b, and 470-d. (Kindt, pp 185-186, 493-504. Parham, pp 403-418.) Immunodefi ci ency di s orders ca n be ca tegori zed a ccordi ng to whether the defect pri ma ri l y i nvol ves humora l i mmuni ty (bone ma rrow deri ved, or B l ymphocytes ) or cel l ul a r i mmuni ty (thymus deri ved, or T l ymphocytes ) or both. Swi s s -type hypoga mma gl obul i nemi a , a ta xi a -tel a ngi ecta s i a , the Wi s kott-Al dri ch s yndrome, a nd s evere combi ned i mmunodefi ci ency di s orders a l l i nvol ve defecti ve B-cel l a nd T-cel l functi on. Infa nti l e X-l i nked a ga mma gl obul i nemi a i s ca us ed chi efl y by defi ci ent B-cel l a cti vi ty, wherea s thymi c hypopl a s i a i s ma i nl y a T-cel l i mmunodefi ci ency di s order. In Ques ti on 466, thi s 2-yea r-ol d pa ti ent ha s a ta xi a (s ta ggeri ng)-tel a ngi ecta s i a (s pi der a ngi oma s ), a n a utos oma l reces s i ve i mmune di s order a s s oci a ted wi th both a l ymphopeni a (cel l ul a r) a nd IgA defi ci ency (humora l ). Ques ti on 467 des cri bes a pa ti ent wi th X-l i nked hypoga mma gl obul i nemi a or Bruton a ga mma gl obul i nemi a , whi ch onl y occurs i n boys a nd i s cha ra cteri zed by l ow l evel s of a l l i mmunogl obul i n cl a s s es a nd the a bs ence of a l mos t a l l B cel l s . Pre-B cel l s a re pres ent; however, they fa i l to di fferenti a te i nto B cel l s . Cel l -medi a ted i mmuni ty i s rel a ti vel y norma l . Recurrent ba cteri a l i nfecti ons occur a fter a bout 6 months of a ge when protecti ve ma terna l IgG a nti body decl i nes . The fetus repres ented i n Ques ti on 468 ha s s evere combi ned i mmunodefi ci ency di s ea s e (SCID) cha ra cteri zed by defects i n ea rl y s tem cel l di fferenti a ti on. As a res ul t, B cel l s a nd T cel l s a re both defecti ve, i mmunogl obul i ns a re very l ow, a nd tons i l s a nd l ymph nodes a re a bs ent. Thymi c a pl a s i a or Di George s yndrome ma rks the young chi l d i n Ques ti on 469. Fa i l ed devel opment of the thymus a nd the pa ra thyroi ds l ea d to hypopa ra thyroi di s m, hypoca l cemi a , a nd ul ti ma tel y a s pa s ti c pa ra l ys i s (s trong mus cl e contra cti ons or teta ny). Fi na l l y, Wi s kott–Al dri ch s yndrome (Ques ti on 470), a n Xl i nked defect, i s a s s oci a ted wi th reduced IgM l evel s a nd va ri a bl e cel l ul a r-medi a ted i mmuni ty. 471 to 474. The answers are 471-a, 472-c, 473-a, and 474-d. (Kindt, pp 33, 426-440, 443-444. Parham, pp 465-475.) Tra ns pl a nta ti on from one regi on of a pers on to a nother regi on of tha t s a me pers on i s a n autograft a nd ha s the bes t cha nce of s ucceedi ng. When a tra ns pl a nt i s done between monozygoti c twi ns , i t i s a n isograft a nd ha s a compl ete MHC compa ti bi l i ty a nd a good cha nce of s ucces s . Allografts a re between members of the s a me s peci es , a nd xenografts a re between members of di fferent s peci es . Both of thes e tra ns pl a nts ha ve a hi gh ra te of rejecti on unl es s i mmunos uppres s i on a ccompa ni es the tra ns pl a nt. 475 to 477. The answers are 475-d, 476-c, and 477-b. (Kindt, pp 101-102.) Is otypes a re determi ned by a nti gens of the i mmunogl obul i n cl a s s es found i n a l l i ndi vi dua l s of one s peci es . In a ddi ti on to hea vy-cha i n i s otypes of IgA, IgD, IgE, IgG, a nd IgM, two l i ght-cha i n i s otypes exi s t for κ a nd λ cha i ns . Al l otypes a re di fferenti a ted by a nti geni c determi na nts tha t va ry a mong i ndi vi dua l s wi thi n a s peci es a nd a re recogni zed by cros s -i mmuni za ti on of i ndi vi dua l s i n a s peci es . Al l otypes i ncl ude the Gm ma rker of IgG a nd the Inv ma rker of l i ght cha i ns . Idi otypes a re a nti geni c determi na nts tha t a ppea r onl y on the F(a b) fra gments of a nti bodi es a nd a ppea r to be l oca l i zed a t the l i ga nd-bi ndi ng s i te; thus , a nti -i di otype a nti s era ma y bl ock rea cti ons wi th the a ppropri a te ha pten. The ca rbohydra te s i de cha i ns of i mmunogl obul i ns a re rel a ti vel y noni mmunogeni c. New determi na nts ma y be expos ed a fter pa pa i n cl ea va ge of i mmunogl obul i ns , but thes e determi na nts a re not i ncl uded i n the cl a s s i fi ca ti on of the na ti ve mol ecul e. 478. The answer is f. (Kindt, pp 186. Parham, pp 33-42, 344.) Thi s pa ti ent ha s a cl a s s i c ca s e of heredi ta ry a ngi oedema . Thi s di s ea s e i s cha ra cteri zed by a defi ci ency of compl ement control protei ns s uch a s C1 es tera s e i nhi bi tor, l ea di ng to overa cti ve compl ement (reduced C4 l evel s ). Uncontrol l ed genera ti on of va s oa cti ve pepti des (C3a a nd C5a ) ca us es i ncrea s ed bl ood ves s el permea bi l i ty, ca us i ng heredi ta ry a ngi oedema . Edema , es peci a l l y of the l a rynx, obs tructs the a i rwa ys . Abdomi na l pa i n ma y i ndi ca te tha t the pa ti ent ha s a ngi oedema of the gut. 479. The answer is d. (Fauci, pp 483, 577-578. Kindt, pp 536-537. Parham, p 503.) The bes t-cha ra cteri zed huma n tumor-a s s oci a ted a nti gens a re the oncofeta l a nti gens . CEA i s a gl ycoprotei n a nd member of the i mmunogl obul i n gene s uperfa mi l y a nd i s el eva ted i n col orecta l ca ncer. α-Fetoprotei n (AFP) i s a na l ogous to a l bumi n a nd el eva ted i n hepa tocel l ul a r ca rci noma . Pros ta te-s peci fi c a nti gen (PSA) i s el eva ted i n pros ta ti c ca ncer. CEA, AFP, a nd PSA a re a l l gl ycoprotei ns . Mel ena refers to a l tered (bl a ck) bl ood per rectum, i ndi ca ti ve of a n upper ga s troi ntes ti na l bl eed. A pa ti ent’s tumor ma rkers a re bes t us ed cl i ni ca l l y i n the moni tori ng of the effi ci ency of the a nti tumor thera py a nd remi s s i on peri ods pos ttrea tment. 480 and 481. The answers are 480-b and 481-e. (Kindt, pp 493-495, 500-502. Parham, pp 350-361.) HIV i nfecti on a ffects ma i nl y the i mmune s ys tem a nd the bra i n. The ma i n i mmunol ogi c fea ture of HIV i nfecti on i s progres s i ve depl eti on of the CD4 s ubs et of T l ymphocytes (T-hel per cel l s ), ca us i ng a revers a l i n the norma l CD4:CD8 ra ti o, l ea di ng to i mmunodefi ci ency. Currentl y, ELISA i s the ba s i c s creeni ng tes t to detect a nti -HIV a nti bodi es . Repea ted rea cti ve ELISA tes ts s houl d be confi rmed us i ng ei ther wes tern bl ot or i mmunofl uores cence. The wes tern bl ot detects s peci fi c a nti bodi es a ga i ns t the va ri ous HIV protei ns (a nti gens ). As s ta ted previ ous l y, the wes tern bl ot i s pos i ti ve when two or more of the p14, gp41, gp120, or gp160 ba nds a re pres ent i n the gel . 482. The answer is b. (Kindt, pp 389-391. Parham, pp 309-310.) Anti -Rh a nti bodi es (IgG a re rea cti ve a t 98.6°F [37°C]) a re the l ea di ng ca us e of hemol yti c
di s ea s e of the newborn (HDN). Currentl y, Rh i mmuni za ti on ca n be s uppres s ed i n a ntepa rtum or pos tpa rtum Rh–women i f hi gh-ti ter a nti -Rh i mmunogl obul i n (RhIg) i s a dmi ni s tered wi thi n 72 hours a fter the potenti a l l y s ens i ti zi ng dos e of Rh+ cel l s (i e, the bi rth of the chi l d). The other choi ces wi l l do nothi ng to prevent the devel opment of HDN i n future pregna nci es . 483 and 484. The answers are 483-g and 484-c. (Kindt, pp 29-30, 440-442, 494-498. Parham, pp 347-350, 476-477.) Immune defi ci ency di s orders occur a s a res ul t of i mpa i red functi on i n one or more of the ma jor i mmune s ys tem components s uch a s B l ymphocytes , T l ymphocytes , B a nd T l ymphocytes , pha gocyti c cel l s , a nd compl ement. Unus ua l a nd recurrent i nfecti ons a re the ha l l ma rk of i mmunodefi ci ency. SCID occurs a s a res ul t of a n ea rl y defect i n s tem cel l di fferenti a ti on a nd ma y be ca us ed a s a res ul t of defecti ve IL-2 receptors , a denos i ne dea mi na s e defi ci ency, or fa i l ure to ma ke MHC cl a s s II a nti gens . Thi s condi ti on i s cha ra cteri zed by B- a nd T-cel l defi ci ency a nd pres ents wi th recurrent i nfecti ons . The other di s orders l i s ted do not ha ve both B- a nd T-cel l defi ci ency wi th a n a bs ence of a thymus gl a nd. Defi ni ti ve trea tment of SCID cons i s ts of s tem cel l tra ns pl a nta ti on, wi th the i dea l donor bei ng a s i bl i ng wi th i denti ca l huma n l eukocyte a nti gens (HLA). 485. The answer is b. (Kindt, pp 95-98, 477-480. Parham, p 272.) There a re three forms of i mmuni ty: a cti ve, pa s s i ve, a nd a dopti ve. Acti ve i mmuni ty i nvol ves a n i ndi vi dua l ma ki ng hi s or her own a nti bodi es , ei ther na tura l l y, by i nfecti on, or a rti fi ci a l l y by i mmuni za ti ons . Pa s s i ve i mmuni ty refers to the tra ns fer of preformed a nti bodi es from one i ndi vi dua l to a nother ei ther na tura l l y (tra ns pl a centa l or enteroma mma ry a nti bodi es from mother to fetus ) or a rti fi ci a l l y through ga mma gl obul i n i njecti ons s uch a s a nti toxi ns , a nti -Rh, a nd a nti venoms (bl a ck wi dow s pi der bi tes a nd the l i ke, etc). Fi na l l y, a dopti ve i mmuni ty refers to the tra ns fer of l ymphoi d cel l s from a n a cti vel y i mmuni zed donor a nd does not i nvol ve a nti body tra ns fer. 486. The answer is e. (Fauci, pp 2054-2058. Kindt, pp 495-500. Parham, pp 346-360.) Pa ti ents wi th T-cel l defects a re genera l l y s us cepti bl e to vi ra l , funga l , a nd protozoa n i nfecti ons . Thi s ca n be es peci a l l y vi s i bl e i n pa ti ents wi th pri ma ry i mmunodefi ci ency di s ea s es s uch a s SCID. For further expl a na ti on of i mmunodefi ci enci es , pl ea s e refer to the a ns wer expl a na ti ons for Ques ti ons 431 a nd 432, 474 to 478, 491 a nd 492. 487. The answer is b. (Kindt, pp 372-388. Parham, pp 367-385.) Thi s i s a n exa mpl e of a type I hypers ens i ti vi ty rea cti on. Type I hypers ens i ti vi ty i s a l s o referred to a s a na phyl a xi s or i mmedi a te-type hypers ens i ti vi ty. Ma jor components i ncl ude IgE, ma s t cel l s /ba s ophi l s , a nd pha rma col ogi ca l l y a cti ve medi a tors . Expos ure to a nti gen ca us es IgE producti on, fol l owed by s ens i ti za ti on of ma s t cel l s a nd ba s ophi l s . Subs equent encounter wi th the s a me a l l ergen (a nti gen) l ea ds to chemi ca l medi a tor rel ea s e (hi s ta mi ne a nd the l i ke, etc) a nd a l s o l ea ds to cl i ni ca l s ymptoms a s s oci a ted wi th a s thma , a l l ergi c rhi ni ti s , a nd s o on. Thi s rea cti on ca n occur wi thi n mi nutes a nd ca n be extremel y s evere a nd l i fe-threa teni ng. 488 to 492. The answers are 488-c, 489-a, 490-b, 491-e, and 492-d. (Kindt, pp 477-479. Parham, pp 243-439.) The fol l owi ng ta bl e pres ents the pa tterns of hepa ti ti s B vi rus (HBV) s erol ogi c ma rkers obs erved i n va ri ous s ta ges of i nfecti on wi th HBV. The di a gnos i s of HBV i nfecti on i s us ua l l y ba s ed on three tes ts : hepa ti ti s B s urfa ce a nti gen (HBs Ag), a nti bodi es to s urfa ce a nti gen (HBs Ag), a nd a nti bodi es to core a nti gen (HBcAg). Tes ts a re a va i l a bl e, however, for e a nti gen a nd a nti bodi es to e a nti gen. A va ri ety of tes ti ng methods a re a va i l a bl e a nd i ncl ude enzyme i mmunoa s s a y, RIA, hem-a ggl uti na ti on, LA, a nd i mmune a dherence. The del ta a gent ha s recentl y been des cri bed. The del ta a gent exa cerba tes i nfecti on wi th HBV, a ppa rentl y i n a s ynergi s ti c ma nner. Commerci a l tes ts a re now a va i l a bl e for the del ta a gent.
493 to 497. The answers are 493-b, 494-a, 495-e, 496-d, and 497-c. (Kindt, pp 145-164.) Of the ma ny methods a va i l a bl e for a nti gen a nd a nti body detecti on, LA, ELISA, RIA, CIE, a nd COA a re the mos t wi del y us ed. LA empl oys l a tex pol ys tyrene pa rti cl es s ens i ti zed by ei ther a nti body or a nti gen. LA i s more s ens i ti ve tha n CIE a nd COA, but s l i ghtl y l es s s ens i ti ve tha n ei ther RIA or EIA. LA ha s been us ed to detect H. influenzae, N. meningitidis, a nd S. pneumoniae a nti gens i n CSF. LA ha s a l s o been us ed for detecti on of cryptococca l a nti gen. Mos t recentl y, LA ha s been wi del y us ed for ra pi d detecti on of group A s treptococca l a nti gen di rectl y from the pha rynx. The tes t i s ra pi d (5 mi nutes ), s ens i ti ve (a pproxi ma tel y 90%), a nd s peci fi c (99%). COA, a l s o a n a ggl uti na ti on tes t, i s s l i ghtl y l es s s ens i ti ve tha n LA but i s l es s s us cepti bl e to cha nges i n the envi ronment (eg, tempera ture). Mos t
s tra i ns of coa gul a s e-pos i ti ve s ta phyl ococci ha ve protei n A i n thei r cel l wa l l . Protei n A bi nds the Fc fra gment of mi crobi a l a nti gens i n body fl ui ds . COA ha s a l s o been us ed to ra pi dl y type or group ba cteri a l i s ol a tes . Enzyme i mmunoa s s a ys (EIAs ) ca n be ei ther homogeneous (EMIT) or heterogeneous (ELISA). EMIT ha s been us ed pri ma ri l y for a s s a ys of l owmol ecul a r-wei ght drugs . Its pri ma ry us e i n mi crobi ol ogy ha s been for a s s a ys of a mi nogl ycos i de a nti bi oti cs . EIAs va ry a s to the s ol i d s upport us ed. A va ri ety of s upports ca n be us ed, s uch a s pol ys tyrene mi crodi l uti on pl a tes , pa ddl es , pl a s ti c bea ds , a nd tubes . The number of l a yers i n the a nti body–a nti gen s a ndwi ch va ri es ; us ua l l y a s a ddi ti ona l l a yers a re a dded, detecti on s ens i ti vi ty i s i ncrea s ed. The two mos t common enzymes a re hors era di s h peroxi da s e (HRP) a nd a l ka l i ne phos pha ta s e (AP). β-Ga l a ctos i da s e ha s a l s o been empl oyed. O-phenyl enedi a mi ne i s the mos t common s ubs tra te for HRP a nd p-ni trophenyl phos pha te for AP. Beca us e EIAs a re us ua l l y rea d i n the vi s i bl e col or ra nge, the tes ts ca n be rea d qua l i ta ti vel y by eye or qua nti ta ti vel y by ma chi ne. CIE wa s ori gi na l l y us ed for “Aus tra l i a a nti gen” (HBs Ag) but wa s s oon repl a ced by RIA. For a deca de, CIE wa s us ed to detect a nti gens i n body fl ui ds . CIE i s not a n ea s y techni que. Its s ucces s depends on the control of ma ny va ri a bl es , i ncl udi ng s ol i d s upport, vol ta ge, current, buffer, a ffi ni ty a nd a vi di ty of a nti bodi es , cha rge on the a nti gen, a nd ti me of el ectrophores i ng. RIA i nvol ves the ra di ol a bel i ng of ei ther a nti body or a nti gen (Ag) us i ng 131 Iodi ne ( 131 I) or 125 I (ra di oi s otopes ). It mea s ures very s ma l l qua nti ti es a nd ca n be us ed to detect hormones , CEA, hepa ti ti s B Ag, s teroi ds , pros ta gl a ndi ns , a nd morphi ne-rel a ted drugs i n pa ti ent s era . 498 to 502. The answers are 498-c, 499-a, 500-f, 501-e, and 502-b. (Kindt, pp 155-158.) The enzyme i mmunoa s s a y (EIA, ELISA) ha s become a common method for the detecti on of ei ther a nti body or a nti gen i n a pa ti ent s peci men. The techni que i s ba s ed on bui l di ng a “s a ndwi ch.” For exa mpl e, the fol l owi ng s a ndwi ch i s ma de on wha t i s ca l l ed the solid phase. The s ol i d pha s e i s us ua l l y a pl a s ti c mi croti ter pl a te but ca n be a pl a s ti c pa ddl e or even a ni trocel l ul os e membra ne. Fi rs t, whol e Toxoplasma orga ni s ms or puri fi ed a nti geni c components of Toxoplasma a re a dded to the pl a te a nd the pl a te i s wa s hed off. Fa i l ure of one or more of the wa s hi ng s teps or i na dequa te wa s hi ng us ua l l y ca us es hi gh ba ckground col or i n the devel oped pl a te. The Toxoplasma a nti gen–a nti body compl ex mus t be detected by the a ddi ti on of a s econd a nti body to whi ch i s l i nked a n enzyme s uch a s hors era di s h peroxi da s e or a l ka l i ne phos pha ta s e. The na ture of thi s s econd a nti body i s dependent on whether one wi s hes to mea s ure IgG or IgM. If the tes t i s for IgG, then the s econd a nti body i s a nti huma n IgG conjuga ted to a n enzyme. Fol l owi ng a nother wa s h cycl e, the enzyme s ubs tra te i s a dded to the pl a te a nd col or devel ops i n thos e wel l s where the s a ndwi ch i s compl ete. If the pa ti ent’s s erum does not conta i n s peci fi c a nti body, then the s a ndwi ch i s not compl eted a nd there i s no devel opment of col or. If the EIA i s for detecti on of a nti gen, then the l a yers of the s a ndwi ch a re a s fol l ows : Speci fi c a nti body Pa ti ent s peci men (conta i n a nti gen) Enzyme-l a bel ed a nti body s peci fi c for the a nti gen enzyme s ubs tra tes There a re ma ny va ri a ti ons of the tes t us i ng a va ri ety of a nti bodi es , i ndi ca tors s uch a s fl uores cence, a nd ma gneti c bea ds a s s ol i d pha s es . EIA i s more s ens i ti ve tha n a ggl uti na ti on methods or compl ement fi xa ti on a nd s l i ghtl y l es s s ens i ti ve tha n RIA. 503. The answer is d. (Kindt, pp 19, 33, 367-368, 441-442. Parham, pp 456, 478-479.) GVHD occurs due to a tta ck by the gra ft a ga i ns t the reci pi ent. There a re three requi rements for GVHD rejecti on: (1) hi s tocompa ti bi l i ty di fferences between the gra ft (donor) a nd hos t (reci pi ent), (2) i mmunocompetent gra ft cel l s , a nd (3) i mmunodefi ci ent hos t cel l . Immunocompetent gra ft cel l s ma y be “pa s s enger” l ymphocytes or ma jor cel l s tra ns pl a nted, a nd mus t be pres ent i n the gra ft. Preventi on of GVHD i s es s enti a l , a s there i s no a dequa te trea tment once i t i s es ta bl i s hed. 504. The answer is c. (Kindt, pp 398-391. Parham, pp 455-458.) Al l bl ood for tra ns fus i on s houl d be ca reful l y ma tched to a voi d tra ns fus i on rea cti on. As s hown i n the ta bl es bel ow, pers ons wi th group O bl ood ha ve no A or B a nti gens on thei r erythrocytes a nd a re thus cons i dered to be uni vers a l donors . In contra s t, pers ons wi th group AB bl ood ha ve nei ther A nor B a nti body a nd thus a re uni vers a l reci pi ents . 505 to 507. The answers are 505-b, 506-d, and 507-h. (Fauci, pp 1960-1967, 2037-2040, 2071-2073. Kindt, pp 403, 408-411, 442-443. Parham, pp 408-413.) Los s of tol era nce by the i mmune s ys tem to certa i n s el f-components ca n l ea d to the forma ti on of a nti bodi es , ca us i ng ti s s ue a nd orga n da ma ge. Such di s ea s es a re referred to a s autoimmune diseases. There a re a hos t of a utoi mmune di s ea s es cha ra cteri zed by the a utoa nti -bodi es . The pres ence of a “butterfl y” ra s h i s a cl a s s i c cuta neous s i gn of SLE a nd i s cha ra cteri zed by a ra s h over the bri dge of the nos e a nd on the cheeks .
508 to 512. The answers are 508-a, 509-c, 510-c, 511-a, and 512-e. (Kindt, pp 254-260. Parham, pp 211-230.) Na ïve T cel l s a re a cti va ted by i ntera cti on wi th dendri ti c cel l s i n l ymphnodes . Acti va ti on requi res s i gna l 1, whi ch i s medi a ted by CD3, zeta cha i ns a nd a co-receptor fol l owi ng i ntera cti on of the TCR wi th MHC a nd pepti de. Si gna l 2 i s cri ti ca l for compl ete a cti va ti on of na ïve T cel l s . The CD28 receptor i s expres s ed by na ïve T cel l s a nd s ends a cti va ti ng s i gna l 2 to the T cel l s a fter i t i s enga ged by ei ther B7-1 (CD80) or B7-2 (CD86). PD-1 a nd CTLA-4 a re i nhi bi tory receptors expres s ed by na ïve T cel l s tha t s end s i gna l s tha t bl ock T cel l a cti va ti on, repres enti ng a key mecha ni s m of peri phera l tol era nce, for exa mpl e, when norma l s el fpepti de a nti gens a re expres s ed i n MHC I or MHC II by dendri ti c cel l s . CTLA-4 competes wi th B7-1 a nd B7-2 for CD28. B7-H1 a nd B7-H3 a re i nhi bi tory l i ga nds expres s ed by dendri ti c cel l s . PD-1 i s bound by B7-H1 (PD-L1). B7-H3 bi nds a di s ti nct receptor on na ïve T cel l s . T cel l s , vi a thei r s urfa ce expres s ed TCR, onl y recogni ze pepti de fra gments of protei ns expres s ed by dendri ti c cel l s i n the context of MHC I (CD8+ T cel l s ) or MHC II (CD4+ T cel l s ). The ma jori ty of TCRs a re compri s ed of a s urfa ce expres s ed, nons ecreted, cova l entl y l i nked a l pha –beta (α, β) heterodi mer. However, a functi ona l TCR compl ex i s ma de up of a n a l pha –beta heterodi mer, noncova l entl y a s s oci a ted wi th the CD3 compl ex (γ, δ, ε, ε) a nd 2 zeta (ζ) cha i ns . 95% of a l l T cel l s expres s a n α, β heterodi mer TCR. Approxi ma tel y 5% of T cel l s expres s a n γ, δ heterodi mer TCR. Thi s ra re s ubs et of T cel l s i s pri ma ri l y a s s oci a ted wi th the gut. Igα a nd Igβ a re a s s oci a ted wi th the B-cel l receptor (BCR). 513. The answer is c. (Kindt, pp 254-259. Parham, pp 222-224.) Al though a nti gen (MHC-pepti de) recogni ti on by T cel l s i s medi a ted by the TCR i t i s i nca pa bl e of s i gna l i ng. Si gna l i ng occurs vi a the CD3 compl ex a nd zeta cha i ns . Si gna l i ng i s a l s o a ugmented by the TCR-co-receptors , CD4 a nd CD8. Therefore, the TCR-β cha i n (a s wel l a s the TCR-α cha i n) i s i nca pa bl e of s i gna l tra ns ducti on. 514. The answer is a. (Kindt, pp 223-232. Parham, pp 125-131.) Li ke a l l genes , TCR genes a re found i n a l l cel l s wi th a nucl eus , a l l cel l s except red bl ood cel l s . 515. The answer is e. (Kindt, pp 245-251. Parham, pp 187-205.) Thymi c s el ecti on s ha pes the peri phera l T cel l repertoi re. The goa l i s to pos i ti vel y s el ect thos e T cel l s expres s i ng TCRs tha t recogni ze pepti des from forei gn protei ns (eg, mi crobi a l pa thogens ). Nega ti ve s el ecti on of T cel l s i n the thymus i s the pri ma ry proces s for preventi ng a utoi mmuni ty a nd i s a key mecha ni s m of centra l tol era nce. T cel l s wi th TCRs tha t pos s es s too hi gh a ffi ni ty for norma l s el f-pepti des a re el i mi na ted by i nhi bi tory s i gna l s tha t res ul ts i n the T cel l s dea th. 516. The answer is d. (Kindt, pp 245-253. Parham, pp 187-197.) T cel l s a l l ma ture i n the thymus a nd B cel l s ma ture i n the bone ma rrow, hence the ori gi n of thei r na mes . It rema i ns uncl ea r where NK cel l s ma ture. Dendri ti c cel l s ma ture i s peri phera l l ymph ti s s ues s uch a s the s pl een a nd l ymph nodes . 517. The answer is d. (Kindt, pp 493-504. Parham, pp 125-128, 347-348.) Thi s i s cha ra cteri zed by the l a ck of a functi ona l TCR a nd BCR. Defects i n recombi na ti on a cti va ti ng genes 1 a nd 2 (RAG-1 a nd RAG-2) woul d res ul t i n the l a ck of TCR a nd BCR gene rea rra ngement a nd s ubs equent protei n expres s i on. The outcome i s T a nd B cel l s a bs ent of a nti gen receptors ma ki ng them a bs ent of i mmune functi on. 518. The answer is e. (Kindt, pp 208-217. Parham, pp 137-145.) Cros s -pri mi ng or cros s -pres enta ti on a l l ows endogenous l y a cqui red a nti gens to be pres ented i n the context of MCH I. Thi s wa s fi rs t des cri bed for pa thogeni c mi crobes but i s now a recogni zed mecha ni s m for a cti va ti ng CD8+ T cel l s a ga i ns t ca ncer cel l -a s s oci a ted a nti gens . Tumor cel l s di rect pri mi ng woul d requi re tha t the tumor cel l expres s es l i ga nds for CD28 for the s econd s i gna l . Tumor cel l s ra rel y expres s B7-1 or B7-2. Tumors a re not commonl y known to expres s IL-12 a s thi s woul d res ul t i n TH1 type cel l -medi a ted i mmuni ty, whi ch woul d res ul t i n el i mi na ti on of the tumor cel l s . Tumors often s ecrete TGF-β1, a potent i mmune s uppres s or. 519. The answer is b. (Kindt, pp 542-543. Parham, pp 502-505.) The i mmune s ys tem i s ca pa bl e of recogni zi ng a nd des troyi ng tumor (ca ncer) cel l s . Ca ncer cel l s expres s protei n a nti gens tha t ra nge i n i mmunogeni ci ty. Some a re of vi ra l ori gi n (though ra re) a nd a re va ry i mmunogeni c others (mos t) a re of s el f-ori gi n a nd much l es s i mmunogeni c. Tumor a nti gens ca n be expres s ed on the tumor cel l s urfa ce or onl y i ntra cel l ul a rl y, thus both humora l (B cel l s ) a nd cel l ul a r (T cel l s ) a re i mporta nt for tumor cel l s ki l l i ng. Li s ted a re exa mpl es of defi ned tumor-a s s oci a ted a nti gens . HPV E6, E7 a re a s s oci a ted wi th cervi ca l ca ncer. CA-125 i s a s s oci a ted wi th ova ri a n ca ncer. CD20 i s a s s oci a ted wi th B-cel l l ymphoma s . CA-125 i s a s s oci a ted wi th col on ca ncer. Her2/neu i s a s urfa ced expres s ed growth fa ctor receptor tha t i s commonl y overexpres s ed i n brea s t ca ncer. Her2/neu overexpres s i ng
brea s t ca ncers a re s ucces s ful l y trea ted wi th pa s s i ve i mmunothera py compri s ed of a dmi ni s tra ti on of a n monocl ona l a nti body (mAb) s peci fi c for Her2/neu. The mAb i s commonl y known a s hercepti n or tra s tuzuma b. 520. The answer is d. (Kindt, p 538. Parham, pp 498-500.) Tumor cel l s ha ve evol ved mecha ni s ms to es ca pe a nd eva de i mmune recogni ti on. Thes e mecha ni s ms i ncl ude va ri ous mol ecul a r geneti c proces s es of el i mi na ti ng MHC I from the tumor cel l s urfa ce. Muta ti ons i nhi bi t effi ci ent a nti gen proces s i ng a nd pres enta ti on. Tumor cel l s a l s o bl ock i mmune cel l s by s ecreti on of s uppres s or protei ns , mos t commonl y TGF-β1, a nd other cytoki ne l i ke “decoy” mol ecul es to confus e the i mmune s ys tem. Anti geni c va ri a ti on i s a n i mmune es ca pe mecha ni s m a s cri bed to pa thogeni c mi crobes s uch a s vi rus es for exa mpl e. 521. The answer is b. (Kindt, pp 259, 406. Parham, pp 220-223, 419-420, 501.) CTLA-4 i s a n a nta goni s ti c/i nhi bi tory receptor norma l l y expres s ed by T cel l s tha t competes wi th CD28 for bi ndi ng of B7-1 a nd B7-2 a nd thus prevents the s econd s i gna l a nd s ubs equent T-cel l a cti va ti on. Thi s i s a key mecha ni s m of peri phera l tol era nce a nd pl a ys rol e i n preventi ng T-cel l a cti va ti on a ga i ns t ca ncer cel l s . Admi ni s tra ti on of a nti bodi es tha t bi nd a nd bl ock CTLA-4 a l l ows CD28 to bi nd B7-1 a nd B7-2 a nd medi a te cos ti mul a ti on res ul ti ng i n the a ugmenta ti on of a nti tumor T-cel l res pons es . Thi s pa s s i ve i mmunothera py a pproa ch ha s been a pproved to trea t a dva nced mel a noma s ki n ca ncers . Si gna l 1 i s TCR compl ex a nd co-receptor medi a ted. Co-s ti mul a ti on (s i gna l 2) i s vi a CD28-B7 enga gement, fol l ows s i gna l 1, a nd res ul ts i n a cti va ti on a nd prol i fera ti on. PD-1/PD-L1 a re a di s ti nct T-cel l i nhi bi tory receptor a nd i ts l i ga nd. ZAP-70 a nd ITAMs a re i nvol ved i n i ntra cel l ul a r T-cel l a cti va ti on s i gna l tra ns ducti on.
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Index Please note that index links point to page beginnings from the print edition. Locations are approximate in e-readers, and you may need to page down one or more times after clicking a link to get to the indexed material. A Absidia, 16 Acanthamoeba, 17, 337, 360, 370 a ci d-fa s t techni que, 50, 76 Actinomyces s peci es A israelii, 186, 209, 230, 247, 252, 253 a cti nomycos i s , 230, 247, 253 a cti ve i mmuni ty, 23, 432 a cute hemorrha gi c conjuncti vi ti s (AHC), 166 a cute i nfecti on, 123, 155, 166, 248, 403, 434 a cute Lyme di s ea s e, 395, 396 a cycl ovi r, 5, 93, 99, 117, 131, 141, 147, 156, 159, 169, 228 a da pti ve i mmuni ty, 21 a denovi rus , 5, 81, 88, 90, 92–98, 102, 104, 110, 115, 116, 121, 127, 134, 140–143, 145–147, 152–154, 160–161, 167–168, 172 a denyl cycl a s e, 187, 221, 234 AHC. See a cute hemorrha gi c conjuncti vi ti s AIDS, 15, 16, 22, 103, 113, 126–127, 144, 150, 153, 156, 160, 165, 171, 196, 217, 244, 292, 308, 320, 322, 323, 336, 342, 355, 359, 365, 366, 389, 400, 406, 422. See also huma n i mmunodefi ci ency vi rus ca ndi di a s i s a nd, 292, 318, 331 Cryptococcus neoformans a nd, 125, 308 Cryptosporidium a nd, 125, 355, 359 M avium compl ex a nd, 175, 217 Pneumocystis jiroveci (carinii) pneumoni a a nd, 81, 320, 322 Strongyloides a nd, 337 tes ti ng a nd, 101, 127, 144 Toxoplasma s peci es a nd, 125, 342, 365, 366 a l l ogra fts , 386, 391, 398, 399, 421, 425, 430 a l l otypes , 399, 431 a l pha vi rus , 104, 154, 155 a ma nta di ne, 84, 107, 115, 156, 158, 166 a mebi a s i s , 365, 372 a mi nogl ycos i des , 52, 54, 58, 59, 69, 71, 74, 226, 231, 286, 435 a moeba s , 17, 348, 360, 361, 365, 369 a moxi ci l l i n, 11, 214, 251 a mphoteri ci n, 47, 70, 71 a mphoteri ci n B, 48, 71, 263, 297, 305, 308, 322, 324, 331, 332 a mpi ci l l i n, 28, 47, 49, 54, 70, 71, 74, 189, 200–202, 229, 235, 237, 247, 248, 251 a na erobes , 54, 219, 226, 227, 230, 252, 253, 259 Ancylostoma duodenale, 19, 366 a nemi a , pa rvovi rus B19 a nd, 147, 165 a ngi oedema , 401, 431 a ni ma l s ources , of ba cteri a , 232 a ns a myci n, 244 a nti bi oti cs , 218, 220. See also specific antibiotics, eg, peni ci l l i n broa d-s pectrum, 93, 141, 202, 208, 216, 408 di a rrhea a nd, 185, 202, 229, 248 di hydrofol i c a ci d reducta s e i nhi bi ti ng, 47 E coli res pons e to, 39 growth curves a nd, 41–42 β-l a cta m, 33, 39, 48, 52, 54, 57, 58, 71, 235, 237 pori ns a nd, 35, 60, 67 res i s ta nce to, 2, 9, 43, 57, 62, 74, 234 50S ri bos ome a nd, 70 toxi ci ty of, 59, 428 tra ns port of, 26 a nti bodi es , 21–24 a nti body tes ts , 79, 91, 102, 111, 123, 126 a nti -ds DNA a nti bodi es , 387, 421 a nti gen detecti on, 123, 174, 230, 255, 407 a nti geni c dri ft, 108, 157
a nti geni c s hi ft, 108, 157 a nti -HAV IgM, 158 a nti -HBc tes ti ng, 136 a nti -HBs Ag tes ti ng, 136–137 a nti mi crobi a l a gents . See a nti bi oti cs a nti vi ra l a gents , 84, 117. See also specific agents, eg, a cycl ovi r a pl a s ti c cri s i s , 147, 161, 165 a rbovi rus es , 66, 94 a rena vi rus , 4, 7, 173, 174 a rthroconi di a , 311, 315, 318, 320, 321, 327–330 a rti fi ci a l pa s s i ve i mmuni za ti on, 402, 432 Ascaris lumbricoides, 19, 340, 341, 346, 352, 356, 357, 362, 366 Ascaris suum, 377 a s epti c meni ngi ti s , 89, 127, 130, 135, 142, 150, 166, 171, 251, 278, 282 a s pergi l l os i s , 48, 71, 296, 306, 321 Aspergillus s peci es , 71, 256, 295, 306, 312, 318–319, 321, 332 A fumigatus, 15, 296, 297, 306, 332 a s trovi rus , 116, 167, 168 a ta xi a , 23, 92, 387, 394, 430 a typi ca l pneumoni a . See pri ma ry a typi ca l pneumoni a a utoa nti bodi es , 23, 409, 437 a utogra fts , 386, 398, 399, 421, 430 a utoi mmune di s ea s es , 228, 421, 437 a zi thromyci n, 13, 274, 279, 287 B B cel l s , 21, 417, 424, 425, 428, 430, 439 ma rkers , 22 Babesia, 335, 359, 360, 374, 379 ba bes i os i s , 279, 335, 374, 379 Ba ci l l us Ca l mette-Guéri n (BCG), 385, 420 Bacillus s peci es , 206, 240 B anthracis, 1, 9, 23, 75, 76, 217, 219, 277 B cereus, 9, 11, 73, 219, 240 ba ci tra ci n, 59, 248 ba cteri a . See also gra m-nega ti ve ba cteri a ; gra m-pos i ti ve ba cteri a ; specific bacteria, eg, Escherichia coli a nti bi oti c meta bol i s m by, 54, 237 cel l wa l l s of, 58 components of, 49, 74–75 entry routes of, 245–246 growth curves of, 2, 33, 41–42 hi gh-yi el d fa cts a bout, 1–3 i ron meta bol i s m by, 26, 52–53 oxygen meta bol i s m by, 28, 54 pori ns of, 35, 52 toxi ns of, 60–62, 64, 67, 73, 75–77, 216, 221, 224, 234, 235, 237–239, 242, 243, 248–249, 254, 256–259 tra ns port methods of, 26, 53 ba cteri a l endotoxi ns , 44, 67, 75, 235, 237 ba cteri a l enterotoxi ns , 67, 73, 149, 218, 221, 234–236, 239, 241 ba cteri a l exotoxi ns , 73–75, 198, 221, 240, 243, 253, 256, 258 ba cteri a l LPS, 2–3, 53, 56, 67, 73, 76, 227 ba cteri a l s pores , 32, 58 ba cteri ol ogy, 217–259 hi gh-yi el d fa cts a bout, 7–12 ba cteri opha ge i nfecti on, 65 Bacteroides fragilis, 54, 183, 226 Ba erma nn techni que, 351, 375 Balantidium coli, 362, 369, 370 ba ncrofti a n fi l a ri a s i s , 349, 374 Bartonella s peci es , 217 B henselae, 153, 218, 243, 246, 284 BCG. See Ba ci l l us Ca l mette-Guéri n bee s ti ngs , 402 Bence Jones protei ns , 21 benza thi ne peni ci l l i n, 196, 244
bi rd, 13, 14, 16, 90, 128, 171, 312, 313, 365 bl a s toconi di a , 13, 301 Blastomyces s peci es , 317, 321, 325 B dermatitidis, 15, 312, 320, 325, 326, 329, 330 bl a s tomycos i s , 302, 313, 314, 316, 325, 326, 329 bl a s tos pores , 328 bl i ndnes s , 12, 146, 281, 287 bl ood a ga r, 218, 230, 251, 273, 286, 287 bl ood s peci mens , for CMV detecti on, 343 bl ood tra ns fus i ons , 129, 130, 155 BMTU. See bone ma rrow tra ns pl a nt uni t bone ma rrow tra ns pl a nt uni t (BMTU), 295, 319 bone ma rrow tra ns pl a nta ti on, 408 Bordetella s peci es , 250, 255 B bronchiseptica, 205, 249, 250 B parapertussis, 253 B pertussis, 10–11, 64, 253 DNA probes for, 13, 165 Borrelia s peci es , 10 B burgdorferi, 23, 36, 60, 164, 243, 248, 281, 349, 355, 373, 379, 429 B recurrentis, 278 botul i s m, 235, 240, 251 bovi ne s pongi form encepha l opa thy (BSE), 67, 129, 139 Branhamella catarrhalis. See Moraxella catarrhalis broa d-s pectrum a nti bi oti cs , 93, 141, 202, 208, 216, 408 Brucella s peci es , 10, 204, 232 B abortus, 204, 217, 221, 249, 250 B melitensis, 187, 232 Bruton a ga mma gl obul i nemi a , 22, 417, 430 BSE. See bovi ne s pongi form encepha l opa thy buboes , 45, 194, 266 buboni c pl a gue, 69, 194, 242 bunya vi rus , 7, 146, 170 Burki tt l ymphoma , 151, 163 C C1 es tera s e i nhi bi tor, 22, 451 C3a compl ement, 391, 424 C5 through C9 compl ement defi ci enci es , 389, 442 C5a compl ement, 391, 424, 431 ca l i ci vi rus , 3, 167 Campylobacter s peci es , 11 C botulinum, 9, 219, 227, 235 C difficile, 9, 229, 230, 239, 246, 248 C jejuni, 189, 220, 232, 235, 236, 249, 257, 259 C perfringens, 9, 73, 219, 234, 239, 240 ca ncer, vi rus es a s s oci a ted wi th, 88, 134, 145, 154, 440 Candida s peci es , 16, 318–320, 327, 328, 332 C albicans, 15, 16, 23, 45, 125, 256, 297, 302, 304, 318, 320, 321, 327, 330–332, 385 C tropicalis, 16 ca ndi di a s i s , 23, 71, 124, 292, 318, 331, 401 vul vova gi na l , 223, 331 Capnocytophaga, 199, 246 ca ps ul a r s wel l i ng, 245 ca ps ul a r vi rul ence fa ctors , 43, 74, 75, 221, 224, 237, 240, 256, 258 ca rbeni ci l l i n, 185 ca rci noembryoni c a nti gen, 400 ca t feces , 17 ca t s cra tch di s ea s e (CSD), 218, 242 ca ta l a s e, 3, 7–9, 28, 54, 74, 75, 207, 230 ca ta l a s e tes t, 185 ca techol s , 423 CD4 l ymphocyte count, 79, 106, 125–126 CD4:CD8 ra ti o, 385, 418, 432 cefota xi me, 69 cefta zi di me, 69, 70
a cti vi ty a ga i ns t H. influenzae, 69 for methi ci l l i n-s us cepti bl e S. aureus s tra i ns , 70 for pl a gue, 69 ceftri a xone, 69, 71, 248 for Lyme di s ea s e, 248 cel l wa l l s , of gra m-nega ti ve vs gra m-pos i ti ve ba cteri a , 59, 67, 218 cel l -medi a ted hypers ens i ti vi ty to mea s l es , 421 i n tubercul os i s , 181, 224 cel l ul i ti s , 75, 195, 253 ca us ed by group A s treptococci , 195, 243 hya l uroni da s e rol e i n, 75 centra l nervous s ys tem (CNS), vi ra l entry i nto, 84, 130, 347, 429 cepha l os pori ns , 11, 52, 54, 71, 74, 237, 280, 286 cerebros pi na l fl ui d (CSF) s peci mens , 35, 83, 89, 118, 131, 386 i n a s epti c meni ngi ti s , 131, 293, 308 for GBS di a gnos i s , 186, 231 cervi ca l ca ncer, 145, 440 cervi ca l ti s s ue s peci mens , for HPV detecti on, 165 cervi cofa ci a l di s ea s e, 208–209 Cestodes, 18, 380, 381 CGD. See chroni c gra nul oma tous di s ea s e Cha ga s di s ea s e, 17, 366 by T. cruzi, 366 tra ns mi tted by ki s s i ng bug, 17 cha ncre, 187, 228, 231, 287 cha ncroi d, 263, 279 Chédi a k-Hi ga s hi di s ea s e, 23 chemoprophyl a xi s , 347, 371 chi cken pox, 238, 279, 422. See also va ri cel l a zos ter vi rus a nti body pres ent, 389 ri s k for a cqui s i ti on, 429 chi l dhood meni ngi ti s , 46, 70 ceftri a xone, 46, 69 Chlamydiae s peci es , 261–289 C pneumoniae, 13, 213, 283, 285–288 C psittaci, 13, 218, 277, 279, 283, 285–288 C trachomatis, 12, 55, 146, 164, 257, 263, 266, 267, 280–288, 418 hi gh-yi el d fa cts a bout, 12–13 vi rus es vs , 277, 283 chl a mydos pores , 315 chl ora mpheni col , 42, 54, 65, 69–71, 74, 247, 279, 423 chol era , 187, 202, 235, 249, 253, 259 cha ra cteri za ti on by, 259 cycl i c AMP a cti va ti on, 235 mode of a cti on of, 234, 253 chol era toxi n, 234, 253 chori oreti ni ti s , 170, 352, 364, 377 chromobl a s tomycos i s i nfecti ons , 299, 325, 327 chroni c gra nul oma tous di s ea s e (CGD), 8, 422 chroni c mucocuta neous ca ndi di a s i s , 23 CID. See cytomega l i c i ncl us i on di s ea s e CIE. See counter i mmunoel ectrophores i s ci profl oxa ci n, 54, 60, 225, 235 for C. jejuni enterocol i ti s , 235 trea tment cours e of, 35 CJD. See Creutzfel dt-Ja kob di s ea s e Cladosporium s peci es , 319 cl i nda myci n, 54, 70, 185, 229, 279, 285 cl ofa zi mi ne, 244 cl oni ng proces s es , 38, 62 Clonorchis s peci es , 20, 361, 368, 374, 375 C sinensis, 18, 343, 349, 350, 356, 361, 367 Clostridium s peci es , 9, 206, 219, 230, 240 C botulinum, 9, 219, 227
C difficile, 9, 229, 230, 239 C perfringens, 9, 73, 219, 239, 240 C tetani, 9, 219, 227, 240, 257 CMV. See cytomega l ovi rus CNS. See centra l nervous s ys tem COA. See coa ggl uti na ti on coa ggl uti na ti on (COA), 404 Coccidioides s peci es , 13, 15, 71, 297, 317, 319, 320, 322, 327, 329, 330 C immitis, 136, 321, 328 cocci di oi domycos i s , 296, 301, 313, 314, 316, 317, 321, 326, 328 col d a ggl uti ni ns , for M pneumoniae di a gnos i s , 174, 255, 270, 272, 286 Col umbi a a ga r, 251 common col d, 84, 108, 129, 130, 133, 134, 138, 143, 158, 159, 171 compl ement, 21, 73, 173, 231, 391, 420, 426, 427, 431, 432, 436 defi ci enci es , 8, 22, 23, 389, 422 compl ement fi xa ti on tes ti ng393, 401, 426, 436 condyl oma a ccumi na tum, 99, 134, 147, 172, 173 conjuga ti on, 1 of DNA, 62, 63, 65 conjuncti vi ti s , 7, 13, 88, 127, 133, 146, 166, 169.257, 274, 281, 413 corona vi rus es , 3, 6, 83, 129, 133, 162, 171 corti cos teroi ds , i mmunos uppres s i on a nd, 16, 293, 308, 340, 364, 387, 425 Corynebacterium s peci es , 63, 228 C diphtheria, 9, 23, 40, 63, 64, 210, 219, 221, 231, 237, 245, 251, 253 counteri mmunoel ectrophores i s (CIE), 207, 404 Coxiella burnetii, 12, 246, 247, 284–286, 288 coxs a cki evi rus A, 6, 129, 132, 142, 166, 172 Creutzfel dt-Ja kob di s ea s e (CJD), 67, 92, 129, 386 Crohn di s ea s e, 386, 389, 423 croup, 7, 134 cryptococcos i s , 293 Cryptococcus s peci es , 298, 312, 330 C neoformans, 16, 125, 308, 311, 332 Cryptosporidium s peci es , 359, 379 C parvum, 17, 125 CSD. See ca t s cra tch di s ea s e CSF s peci mens . See cerebros pi na l fl ui d s peci mens Cyclospora s peci es , 379 C cayetanensis, 355 cys ti cercos i s , 19, 20, 136, 362, 369, 371, 381 cys ti cercus , 19, 362, 369 cys ts of protozoa ns , 355 cytoki nes , 21, 22, 67, 147, 256, 423, 425, 440 cytomega l i c i ncl us i on di s ea s e (CID), 118, 148, 157, 170 cytomega l ovi rus (CMV), 5, 84, 113, 125, 130, 138, 139, 143, 157, 160, 164, 166, 169, 257 D DDI. See di deoxyi nos i ne dea th pha s e, of ba cteri a growth curves , 33–34, 58 del ta a gent, 129, 396, 429, 433 Dengue fever, 6, 114, 151, 162, 165 derma tophytes , 14, 308–311, 317–320, 324, 326, 328, 330 derma tophyti d, 310 DFA mi cros copy. See di rect fl uores cent a nti body mi cros copy di a betes juveni l e ons et, 409 mucormycos i s a nd, 306, 312, 320 di a rrhea a denovi rus a nd, 116 a nti bi oti cs a nd, 45, 185, 189, 202, 229, 248 E coli a nd, 67, 194, 211, 242, 258 rota vi rus es a nd, 7, 115, 134, 161 Di George s yndrome, 22, 430 di hydrofol i c a ci d reducta s e-i nhi bi ti ng a nti bi oti cs , 47 di phtheri a . See Corynebacterium s peci es
di phtheri a toxi n, 64, 220, 253 Diphyllobothrium latum, 19, 367 di pi col i ni c a ci d, 2, 32, 58 di rect fl uores cent a nti body (DFA) mi cros copy, 64, 91, 167 DNA conjuga ti on of, 1, 42, 62, 63, 65 PCR a mpl i fi ca ti on of, 142 tra ns ducti on of, 1, 65, 66 tra ns forma ti on of, 1, 65 DNA gyra s e, i nhi bi ti on of, 57, 70, 225 DNA probes , 13 for M pneumoniae, 61, 165 DNA vi rus es hi gh-yi el d fa cts a bout, 5–6 oncogenes of, 112, 414 doxycycl i ne, 12, 251, 275, 276 ds RNA vi rus es , 4, 7, 152, 154 E e a nti gen, 155, 403, 433 Ea s tern equi ne encepha l i ti s (EEE), 6, 128, 138, 158 EBV. See Eps tei n-Ba rr vi rus Echinococcus granulosis, 369 echovi rus es . See enteri c cytopa thogeni c huma n orpha n vi rus es EDTA. See ethyl enedi a mi netetra a ceti c a ci d EEE. See Ea s tern equi ne encepha l i ti s Ehrlichia s peci es , 12, 265, 283 E chaffeensis, 278, 280, 281, 283, 288 ehrl i chi os i s , 262, 280, 283, 289 EIA. See enzyme i mmunoa s s a y ELISA. See enzyme-l i nked i mmunos orbent a s s a y encepha l i ti s vi rus es ca us i ng, 94, 122, 125, 127, 128, 150–152, 158, 170, 171 endoca rdi ti s , 33, 197, 207, 208, 246, 252, 275, 284 endotoxi ns , 3, 67, 75, 76 enoxa ci n, 225 enoxa ci n, 225 Entamoeba s peci es , 362 E coli, 360 E dispar, 370 E histolytica, 17, 351, 369–371 enteri c cytopa thogeni c huma n orpha n vi rus es (echovi rus es ), 6, 84, 130 enteri c hepa ti ti s C. See hepa ti ti s E vi rus Enterobius vermicularis, 19, 362, 365, 366, 375, 380 Enterococcus s peci es , 190, 236 E faecalis, 8, 47, 70, 236, 237, 245, 256 E faecium, 200, 236, 237 Enterocytozoon, 336, 355 enterotoxi geni c E coli (ETEC), 9, 67 enterotoxi ns , 7, 9, 11, 67, 73, 149, 218, 219, 221, 230, 234–236, 239, 241, 242 enterovi rus , 6, 114, 115, 118, 130, 132, 148, 166, 167, 170, 174 enzyme i mmunoa s s a y (EIA), 56, 60, 308, 406, 407, 429, 433, 435 enzyme-l i nked i mmunos orbent a s s a y (ELISA), 22, 123, 243, 377, 432, 434, 435 a nti gen detecti on a nd, 434 HIV a nti body tes t by, 123, 432 epi demi c typhus , 280, 282 recurrence of, 278 Epidermophyton s peci es , 14, 328 E floccosum, 309, 310, 318, 324, 325 Eps tei n-Ba rr vi rus (EBV), 5, 101, 102, 125–127, 135, 141, 150, 151, 154, 161, 163, 164, 172, 279, 421 l ymphoma a nd, 151, 163 rea cti va ti on or a cqui s i ti on of, 151 s peci fi c a nti bodi es , 164 erythrocyte s edi menta ti on ra te (ESR), 423 erythrogeni c toxi n, 8, 75, 210, 254
erythromyci ns , 11, 13, 69, 215, 235, 248, 257, 280, 283, 285 for C. jejuni enterocol i ti s , 235 for Lyme di s ea s e, 248 a s protei n s ynthes i s i nhi bi tors , 285 Escherichia coli, 8–9, 11, 27, 145, 219, 252, 254, 259, 387 0157/H7 s tra i n, 211, 242, 254 cul ture of, 41, 200 growth curves of, 33, 41 peri pl a s mi c s pa ce i n, 53 ESR. See erythrocyte s edi menta ti on ra te ETEC. See enterotoxi geni c E coli eumycoti c mycetoma , 312 exotoxi ns , 3, 9–11, 73–75, 198, 221, 240, 242, 243, 253, 256, 258 F fa l s e-nega ti ve res ul ts , of PCR, 72 fa l s e-pos i ti ve res ul ts , of PCR, 72 fa mci cl ovi r, 156 Fasciola hepatica, 18 Fasciolopsis buski, 18 fi fth di s ea s e, 123, 429 fi mbri a e, 56, 66, 183, 227 fi mbri a ted (fi m +) s ta te, 56 fi s h, ra w, 345, 350, 369 fi s h fl uke, 297 fl a gel l a , 1, 17, 56, 67, 221, 227, 256, 361, 362, 369 fl a gel l a tes , 17, 140, 337, 359, 369 fl a vi vi rus , 3–4, 6, 122, 151, 155, 174 fl ukes , 18, 20, 361, 367, 372, 374, 375, 377, 378 fl uores cent treponema l a nti body (FTA) tes t, 10, 185, 228 fl uoroqui nol ones , 54, 57, 60, 69, 225, 237, 285 for M. pneumoniae infection, 285 res i s ta nce to, 237 s pectrum of a cti vi ty, 54 fomi tes , 138, 141, 172, 250, 287, 329, 331 food poi s oni ng, 7, 9, 48, 62, 73, 178, 193, 218, 219, 234, 239, 242 Francisella tularensis, 10, 232, 254, 281 FTA tes t. See fl uores cent treponema l a nti body tes t FTA-Abs tes t, 185, 229 fungi . See mycol ogy G ga metocytes , 17, 338, 360, 367, 368 ga nci cl ovi r, 5, 84, 130 Gardnerella vaginalis, 10, 180, 191, 239 GAS. See group A s treptococci ga s tri ti s , 195, 220 ga s troenteri ti s , vi rus es ca us i ng, 58, 115, 133, 148, 149, 159, 161, 167, 168, 215, 230, 234, 241, 249, 257–259 ga s troi ntes ti na l tra ct ba cteri a l entry through, 370 norma l mi crofl ora of, 252 GBS. See group B s treptococci gene cl oni ng, 38, 62 geni ta l wa rts , 134 geni touri na ry tra ct, ba cteri a l entry through, 282, 283 genta mi ci n, 34, 54, 59, 69, 200, 231, 247 res i s ta nce to, 247 Germa n mea s l es , 6, 168 Giardia s peci es , 361, 365, 375, 378, 379 G lamblia, 17, 351, 362, 365, 369, 375, 379 gi a rdi a s i s , 362, 375, 377–378 γ-gl obul i n, 153, 402, 428, 433 gl ucuroni c a ci d, 212 gl ycol i pi ds , of mycoba cteri a , 75, 76 gl ycopepti des , 226 gra ft vers us hos t di s ea s e (GVHD), 436
gra m s ta i n, 1, 26, 28, 30, 35, 39, 40, 43, 45, 49, 59, 61, 63, 64, 175, 176, 180, 182, 183, 185–187, 197, 201, 217, 218, 251, 255, 273, 280, 282, 286, 370, 404 procedura l s teps for, 35 gra m-nega ti ve ba cteri a , 27, 53, 59, 67, 76, 177, 181, 218, 225, 237, 269, 283, 286 cel l wa l l s of, 56, 59, 67 gra m-pos i ti ve ba cteri a , 59, 63, 67, 72–74, 76, 225 cel l wa l l s of, 56, 59, 67 Gra ves di s ea s e, 409, 422 group A s treptococci (GAS), 179, 231, 236, 239, 243, 248, 253, 285 group B s treptococci (GBS), 8, 183, 231, 236, 257 growth curves , 2, 33, 41–42 a nti bi oti cs a nd, 41 of i ncuba ti ng cul tures , 41 GVHD. See gra ft vers us hos t di s ea s e H HAART. See hi ghl y a cti ve a nti retrovi ra l thera py Haemophilus s peci es , 146, 226, 255 H ducreyi, 10, 54, 55, 279 H influenzae, 10, 69, 145, 146, 192, 197, 216, 221, 222, 230, 236, 259, 392, 397, 418, 434 ha nta vi rus pul mona ry s yndrome (HPS), 146, 150, 151, 174 ha ptens , 392, 423, 425, 431 HAV. See hepa ti ti s A vi rus HBcAg tes ti ng, 89, 160, 433 HBeAg tes ti ng, 93, 117, 136, 141, 160, 403 HBs Ag tes ti ng, 89, 141, 158, 403, 433 HBV. See hepa ti ti s B vi rus HCV. See hepa ti ti s C vi rus HDV. See hepa ti ti s D vi rus Helicobacter pylori, 10, 220, 243, 256 hema ggl uti na ti ng a nti body res pons es , 104 hema tochezi a , 408 hema topoi es i s , 419 α-hemol yti c s treptococci , 244, 252, 254, 255 hepa ti ti s , hi gh-yi el d fa cts a bout, 4 hepa ti ti s A vi rus (HAV), 4, 6, 89, 103, 130, 135, 145, 152–153, 155, 158, 168, 174 hepa ti ti s B vi rus (HBV), 4, 68–69, 73, 83, 89, 105, 110, 129, 130, 136, 137, 142, 145, 152–155, 160, 169, 172, 174, 433 s erol ogi c ma rkers of, 105, 137, 155, 433, 434 hepa ti ti s C vi rus (HCV), 4, 102, 142, 152, 153, 155, 157, 159, 167, 169, 172, 174 hepa ti ti s D vi rus (HDV), 4, 89, 129, 130, 136, 155, 174 hepa ti ti s E vi rus (HEV), 4, 130, 134, 135, 155, 167, 174 herpes s i mpl ex vi rus (HSV), 5, 29, 79, 82, 124, 131–134, 138, 139, 141, 142, 146–148, 152–153, 156, 159, 164, 166, 169, 171, 172, 228 a cycl ovi r a nd, 5, 131, 147, 156, 159, 169, 228 i n HIV pa ti ents , 156–157, 169 type 1, 124, 131–133, 138–139, 141, 142, 146, 156, 169, 172 type 2, 5, 29, 79, 124, 131, 132, 148 herpes vi rus es , 3, 5 heterophi l a nti body tes t, EBV, 5, 102, 111, 126, 127, 152, 164 HEV. See hepa ti ti s E vi rus HGE. See huma n gra nul ocyti c ehrl i chi os i s hi ghl y a cti ve a nti retrovi ra l thera py (HAART), 124, 125 Histoplasma s peci es , 15, 317, 321 H capsulatum, 14, 306, 312–314, 316, 320, 327, 329 hi s topl a s mos i s , 295, 306, 313–314, 316, 326, 327 tes ti ng for, 293, 300 HIV. See huma n i mmunodefi ci ency vi rus HIV RNA vi ra l l oa d, 81, 123, 126 HME. See huma n monocyti c ehrl i chi os i s Hortaea werneckii, 319, 320, 333 HPS. See ha nta vi rus pul mona ry s yndrome HPV. See huma n pa pi l l oma vi rus HSV. See herpes s i mpl ex vi rus HTLV. See huma n T-cel l l ymphotrophi c/l eukemi a vi rus huma n gra nul ocyti c ehrl i chi os i s (HGE), 12, 265, 280, 281 huma n i mmunodefi ci ency vi rus (HIV), 22, 79–82, 95, 101, 113, 123–127, 135, 143, 144, 150, 151, 157, 166, 169, 171, 206, 225, 298, 322, 324, 380, 385, 390, 406, 431, 432. See also AIDS
di a gnos i s of, 22, 79, 123 i mmunol ogi c fea ture of, 432 ri s k for, 95, 143 tes ti ng a nd, 126, 127, 144, 390, 424 trea tment s tra tegi es for, 322 huma n monocyti c ehrl i chi os i s (HME), 263, 278–280, 288 huma n pa pi l l oma vi rus (HPV), 5, 88, 111, 113, 134, 145, 147, 153–154, 160–161, 165, 166, 172, 440 huma n T-cel l l ymphotrophi c/l eukemi a vi rus (HTLV), 6, 153, 156, 364, 394, 399, 424 hya l uroni c a ci d ca ps ul es , 8, 75–77 hyda ti d di s ea s e, 369, 380, 381 hydrol yti c enzymes , of ba cteri a , 1, 67 hydronephros i s , 47 Hymenolepis s peci es , 370 hypers ens i ti vi ty rea cti ons , 383, 390, 402, 416, 417, 433 i n tubercul os i s , 22 types of, 383 hypha e, 13–16, 295, 299, 300, 305, 306, 312, 315, 318, 320, 321, 324–332 I i di otypes , 399, 425, 431 IFN. See i nterferon IFN-α. See i nterferon-α IgA a nti body, 131, 393, 426, 428 ma terna l tra ns fer of, 423 IgD a nti body, 21, 426, 429, 431 IgE a nti body, 21–23, 426, 428, 431, 433 IgG a nti body, 17, 21, 23, 36, 60, 68, 123, 131, 136, 137, 155, 158, 159, 164, 169, 173, 243, 341, 365, 366, 395, 403, 417, 418, 421–422, 424–426, 428–432, 436 IgM a nti body, 10, 21, 23, 60, 89, 131, 136, 137, 155, 158, 164, 169, 243, 364–366, 395, 399, 403, 424–426, 428–431, 434–436 fetus a nd, 390, 424 i mi da zol e, 14, 306, 324 i mmune res pons es , 67, 77, 121, 135, 235, 383 i mmune s erum gl obul i n (ISG), 137 i mmuni ty, types of, 21, 23–24 i mmuni za ti on, 40, 46, 68, 104, 140, 159, 162, 167, 173, 180, 182, 210, 255, 385, 402, 425, 431, 432 a rti fi ci a l a cti ve/pa s s i ve, 402 i mmunodefi ci ency, 23, 182, 397, 412, 418 i mmunodefi ci ency di s orders , 22, 429, 430, 433 i mmunogl obul i ns , 68, 141, 159, 173, 390, 393–395, 399, 417, 418, 425, 426, 428, 430–432 i mmunol ogy, 383–440 hi gh-yi el d fa cts a bout, 20–24 i mmunos uppres s i on corti cos teroi ds a nd, 425 gra fts a nd, 391, 425 i nfa nti l e meni ngi ti s , 31, 46, 48, 57, 70 i nfa rcti on, 321 i nfecti ous mononucl eos i s , 5, 126, 151, 152, 161, 163, 164, 228, 279, 364 i nfl uenza , 4, 7, 90, 97, 104, 108, 109, 112, 115, 122, 135, 145, 146, 154, 159, 166, 171, 174, 199, 246, 261, 282, 297, 308 pneumoni a a fter, 384 i nha l a ti on a nthra x. See wool s orter’s di s ea s e i nna te i mmuni ty, 21, 147, 173, 422 i nterferon (IFN), 152, 153 i nterferon-α (IFN-α), 22, 102, 103, 117, 142, 147, 152, 153, 169, 173 i ntes ti na l tra ct. See ga s troi ntes ti na l tra ct i nvers i on muta ti ons , 68 i odi ne trea tment s tep, of gra m s ta i ns , 35, 59 i ron meta bol i s m, 53 ISG. See i mmune s erum gl obul i n i s ogra ft, 421, 430 i s oni a zi d, 44, 244 i s otypes , 21, 399, 430, 431 J JC vi rus , 5, 171, 172, 421 juveni l e ons et di a betes mel l i tus , 409 K
Ka pos i s a rcoma , i n HIV pa ti ents , 5, 6, 153 katG, 44 KDO. See ketodeoxyoctul ona te Klebsiella, 10 K granulomatis, 55 K pneumoniae, 145, 218, 236, 245, 259 Koch pos tul a tes , 1 Kopl i k s pots , 7, 133, 134, 169 Kuru, 92, 139, 140 L LA. See l a tex a ggl uti na ti on β-l a cta m a nti bi oti cs , 1, 33, 57 a l l ergy to, 71 res i s ta nce to, 33 β-l a cta m ri ng, 52, 234, 235 β-l a cta ma s e, 1, 27, 52–54, 74, 190, 225, 234, 235, 237, 246, 248 Lactobacillus s peci es , 207, 208 l a g pha s e, of ba cteri a growth curves , 33, 58 La s s a fever, 122, 142, 160, 169, 174 l a tent i nfecti on of a denovi rus , 104, 153 of HSV, 104, 133 l a tex a ggl uti na ti on (LA), 16, 185, 308, 404 Legi onna i res di s ea s e, 10, 64, 177, 213, 218, 255 Leishmania, 17, 18, 374, 380 Lei s hma ni a s i s , 374, 380 Leptospira interrogans, 233 l eptos pi ros i s , 207, 233, 251 LGV. See l ymphogra nul oma venereum l i ce, 12, 177, 218, 267, 269, 281, 282, 289 l i nezol i d, 11 Listeria monocytogenes, 9, 94, 97, 142, 146, 180 l i ver a bs ces s es , 348 loa loa, 19 Loeffl er medi um, 12, 251 l og pha s e, of ba cteri a growth curves , 33, 58 l omefl oxa ci n, 225 Löwens tei n-Jens en medi um, 10, 12 LPS, ba cteri a l , 2–3, 11, 22, 53, 56, 57, 67, 73, 75, 76, 227, 240, 254, 423 Lyme di s ea s e, 10, 36, 60, 243, 248, 278, 281, 349, 355, 373, 429 a cute, 395, 396 l ymphogra nul oma venereum (LGV), 13, 55, 263 l ymphoma Burki tt, 101, 151, 163 M ma d cow di s ea s e, 139 Ma dura foot, 312 ma jor hi s tocompa ti bi l i ty compl ex (MHC), 22, 391, 410 ma l a bs orpti on s yndrome, 339, 362 ma l a ri a , 17, 18, 112, 338, 347, 355, 359, 361, 367, 368, 371, 379 control methods for, 347 Malassezia furfur, 294, 317 ma terna l tra ns fer of a nti body, 389, 423 M bovis, 23 mea s l es , 6, 7, 79, 109, 121, 133, 134, 143, 145, 148, 150, 154, 159, 160, 165, 168, 169, 172, 173, 386, 396, 418, 420, 421, 429 mea t, ra w, 406 medi a l i mi ti ng fa ctors of ba cteri a l growth i n, 34 s el ecti ve, 11–12 meni ngi ti s , 6–10, 16, 23, 31, 35, 46, 48, 49, 54, 69–72, 74, 75, 95, 125, 127, 129–131, 135, 136, 142, 150, 166, 171, 212, 228 a s epti c, 6, 7, 89, 127, 130, 135, 142, 150, 166, 171, 251, 278, 282 chi l dhood, 46, 70 cul ture of ba cteri a ca us i ng, 64 i nfa nti l e, 171
meta bol i s m, ba cteri a l , 53, 237 meta bol i te detecti on, 307 methi ci l l i n-res i s ta nt S aureus (MRSA), 11, 46, 69, 70, 72, 74 metroni da zol e, 11, 18, 54 MHC. See ma jor hi s tocompa ti bi l i ty compl ex mi cona zol e, 306, 307 mi crobi ol ogy. See mol ecul a r mi crobi ol ogy Microsporum s peci es , 4, 292, 294, 309, 317, 318, 324 M audouini, 292, 309, 311, 324 M canis, 309, 310, 329 mi nocycl i ne, 248 mi s s ens e muta ti on, 68 mi togens , 22, 76 mol ecul a r mi crobi ol ogy, 25–77 hi gh-yi el d fa cts a bout, 1–3 mol l us cum conta gi os um, 6, 172 monol a cta ms , 237 mononucl eos i s , 5, 126, 143, 151, 152, 161, 163, 164, 228, 279, 364 Moraxella catarrhalis, 49, 74, 216, 246, 259 mos qui toes , 17, 19, 82, 94, 105, 112, 114, 118, 122, 138, 142, 155, 171, 174, 338, 347, 367, 368, 371, 373, 374 EEEV a nd, 138 mouth, norma l mi crofl ora of, 246, 252, 327 MRSA. See methi ci l l i n-res i s ta nt S aureus Mucor s peci es , 13, 16, 328 mucormycos i s , 306, 312, 320 mumps , 7, 96, 100, 133, 145, 150, 157, 158, 165 Mycobacterium s peci es , 217 i n HIV pa ti ents , 6 M avium compl ex, 6, 175, 196, 217, 244 M leprae, 10, 217 M tuberculosis, 10, 11, 22, 44, 54, 75, 76, 125, 217, 218, 237, 246, 250, 418, 420 mycol ogy, 13, 291–305 hi gh-yi el d fa cts a bout, 13 Mycoplasma s peci es , 12–13 hi gh-yi el d fa cts a bout, 12 M fermentans, 262, 267, 268, 278, 283 M hominis, 283 M orale, 283 M pneumoniae, 255, 282, 286 M salivarium, 283 N Naegleria, 17, 360 na fci l l i n, 226 na l i di xi c a ci d, 225 na tura l ki l l er cel l s , 21, 121, 173 Necator s peci es , 366 N americanus, 19, 346, 357 nega ti ve s s RNA vi rus es , hi gh-yi el d fa cts a bout, 7 Negri bodi es , 7, 114, 138, 139, 166 Neisseria s peci es , 190, 235, 236 N gonorrhoeae, 57, 73–75, 227, 232, 246 N meningitidis, 8, 23, 69, 75, 212, 227, 235, 245, 254, 434 nema todes , 19, 20, 365, 370, 377, 378 NGU. See nongonococca l urethri ti s Nocardia s peci es , 321 nonfi mbri a ted (fi m–) s ta te, 56 nongonococca l urethri ti s (NGU), 262, 266, 267, 272, 278, 282, 285 nons ens e muta ti on, 45, 68 norfl oxa ci n, 225 NPV. See nega ti ve predi cti ve va l ue nucl ei c a ci d a mpl i fi ca ti on tes ts , 22, 29, 55, 144, 152 nucl ei c a ci d probes , 22, 29 nys ta ti n, 250, 307, 318 O
obl i ga te i ntra cel l ul a r pa ra s i te, 4, 12, 262, 266, 283 ofl oxa ci n, 225 Onchocerca volvulus, 19 opportuni s ti c fungi , hi gh-yi el d fa cts a bout, 73 opportuni s ti c i nfecti ons , i n HIV pa ti ents , 81, 124 ora l ca ndi di a s i s , 401 orchi ti s , 7, 87, 133, 166 orni thos i s , 262, 277 orthomyxovi rus es , 4, 7 os teomyel i ti s , 8, 190, 224, 232, 237, 253, 283 oxa ci l l i n, 70, 74, 241 P PAP. See pri ma ry a typi ca l pneumoni a pa pi l l oma vi rus , 3, 5, 88, 110, 154, 160. See also huma n pa pi l l oma vi rus Paracoccidioides brasiliensis, 312, 314, 329, 330 pa ra cocci di oi domycos i s , 293, 300, 314, 316, 317, 326 Paragonimus s peci es , 375 P westermani, 349, 350, 378 pa ra i nfl uenza vi rus , 7, 88, 90, 95, 134, 143 pa ra myxovi rus es , 4, 7 pa ra s i tol ogy, 16–17 hi gh-yi el d fa cts a bout, 1–24 pa rvovi rus , 3, 5, 123, 135, 138, 141, 142, 147, 148, 152, 154, 161, 369, 395, 429 pa rvovi rus B19, 5, 123, 135, 138, 147, 148, 152, 154, 161, 165, 369, 429 pa s s i ve i mmuni ty, 432 Pasteurella multocida, 10, 68, 181, 205, 224, 232, 250 PBPs . See peni ci l l i n-bi ndi ng protei ns PCP. See Pneumocystis carinii pneumoni a PCR. See pol ymera s e cha i n rea cti on PCR-res tri cti on fra gment l ength pol ymorphi s m a s s a ys , 44 peni ci l l i n, 10, 11, 25, 41, 52, 54, 57, 59, 63, 64, 69–71, 74, 177, 179, 182, 186, 188, 218, 224–226, 230, 231, 233–237, 244, 246–248, 273, 275, 277, 280, 284, 286, 288, 294, 318, 416, 423 a l l ergi es a nd, 416 growth curves a nd, 41 res i s ta nce to, 248 for wool s orter’s di s ea s e, 278 peni ci l l i n G, 10, 186, 233, 248 peni ci l l i na s e, 52, 70, 180, 218, 234, 235 peni ci l l i n-bi ndi ng protei ns (PBPs ), 31, 57, 70, 235 pepti c ul cer, 118, 220 pepti dogl yca ns , 1, 2, 70, 71, 75, 76, 227 pepti dyl tra ns fera s e, i nhi bi ti on of, 253 Pepto-Bi s mol , 11, 235 peri pl a s mi c s pa ce, 1, 53, 67 peri toni ti s , 283, 372 peroxi da s e, 3, 28, 54, 435, 436 pertus s i s toxi n, 253 phys i ol ogy, 1–3, 25–77 hi gh-yi el d fa cts a bout, 1–24 pi corna vi rus es , 3, 6 pi l i , 1, 3, 8, 10, 56, 66, 67, 73, 75, 212, 227, 254 pi nworm, 19, 362, 365, 366, 375, 376, 380 pl a gue buboni c, 69, 194, 242 pneumoni c, 242 pl a s mi ds , 2, 43, 62, 63, 234, 248 Plasmodium s peci es , 17, 338, 359, 367, 368, 379 P falciparum, 17, 338, 360, 361, 367, 368 P malariae, 17, 361, 367 P ovale, 17, 360, 361, 367 P vivax, 17, 360, 361, 367 PML. See progres s i ve mul ti foca l l eukoencepha l opa thy pneumococca l pneumoni a , i n HIV pa ti ents , 182, 255 Pneumocystis carinii pneumoni a (PCP), 323
Pneumocystis s peci es , 323 P carinii, 16, 322, 323, 360 P jiroveci, 16, 322, 323 pneumoni a , 7, 8, 10–13, 15, 16, 35, 138, 143, 145, 159 i n HIV pa ti ents , 135 P jiroveci, 16, 322, 323 PCP, 323 pos ti nfl uenza l , 145 pri ma ry a typi ca l , 267 RSV, 90, 143 vi ra l , 97, 159, 171 pneumoni c pl a gue, 242 pol y-D -gl uta mi c a ci d, 76 pol ymera s e cha i n rea cti on (PCR), 37, 61, 79 for determi ni ng HIV progres s i on, 123, 390 for HSV meni ngi ti s , 82, 131 preventi on of conta mi na ti on of, 72 proces s of, 61, 62 pol yoma vi rus , 3, 5, 99, 100, 148, 150, 154, 171 pori ns , 35, 44, 52, 60, 67 pos a cona zol e, 45, 307 pos i ti ve s s RNA vi rus es , hi gh-yi el d fa cts a bout, 6 pos ti nfecti on, 123, 403 poxvi rus , 3–5, 140, 172 PPV. See pos i ti ve predi cti ve va l ue pregna ncy GBS a nd, 231 rubel l a i nfecti on i n, 96, 124 pri ma ry a typi ca l pneumoni a (PAP), 267, 278, 282 pri mers , for PCR, 37, 49, 61, 74 pri ons , 67, 68, 92, 119, 139, 140, 172, 421 progres s i ve mul ti foca l l eukoencepha l opa thy (PML), 171, 172, 386, 421 Propionibacterium, 186, 252 protea s e i nhi bi tors , 124 protozoa , 16, 18, 22, 23, 322, 323, 341, 345, 354, 355, 362, 369, 371, 378, 402, 418, 433 Pseudallescheria s peci es , 313 P boydii, 313 ps eudohypha e, 15, 80, 221, 223, 318, 320, 321, 331, 332 ps eudomembra nous enterocol i ti s , 185, 229, 230, 248 ps eudomona ds , 240 Pseudomonas aeruginosa, 9, 43, 67, 221, 256, 258 Q Q fever, 12, 24, 247, 262, 265, 277, 278, 280, 281, 284–286, 288 quel l ung tes t, 197, 245 qui nol ones , 182, 225, 235 qui nupri s ti n-da l fopri s ti n, 11 R ra bi es , 7, 45, 68, 92, 108, 138–141, 154, 157, 158, 166, 170, 171 ra di oi mmunoa s s a y (RIA), 401, 404 ra pi d pl a s ma rea gi n (RPR) tes t, for s yphi l i s , 184 ra w fi s h, 345, 350, 369 ra w mea t, 406 rea cti ve oxygen s peci es , 28, 74, 422 rea l -ti me pol ymera s e cha i n rea cti on, 37, 48, 61, 72, 74 reovi rus es , 4 res pi ra tory burs t pa thwa y, 387, 390 res pi ra tory di s ea s es , 110, 134, 146, 160, 236, 250, 255, 286, 287 gra m-nega ti ve rods a s s oci a ted wi th, 221, 222, 232 ha nta vi rus , 7, 146, 147, 150, 151, 155, 162, 174 res pi ra tory s yncyti a l vi rus (RSV), 7, 90, 121, 130, 138, 142, 143, 157, 160, 166, 169 res pi ra tory tra ct, 84, 95, 130, 133, 134, 138, 143, 160, 166, 189, 205, 221, 222, 235, 245–247, 261, 284, 287, 288, 384 ba cteri a l entry through, 189 reti ni ti s , 5, 165, 337, 360 revers e tra ns cri pta s e, 4, 6, 57, 101, 123, 124, 130, 151, 157, 169, 225 revers e tra ns cri pta s e i nhi bi tors , 124, 151, 169
Rh a nti bodi es , 401, 432 rha bdovi rus , 4, 7, 140 rheuma ti c fever, 8, 75, 240, 244, 275 rhi nocerebra l i nfecti ons , 16 rhi novi rus es , 6, 129, 133, 138, 158 Rhizopus s peci es , 320, 328 R arrhizus, 297, 305 RIA. See ra di oi mmunoa s s a y ri ba vi ri n, 7, 84, 93, 94, 102, 107, 115, 130, 141, 142, 152, 153, 157, 158, 160, 166, 169, 173 50S ri bos ome, a nti bi oti cs bi ndi ng to, 70 Rickettsiae s peci es , 12, 261–289 hi gh-yi el d fa cts a bout, 12 R australis, 280 R conorii, 280 R prowazekii, 277, 281, 282 R rickettsii, 277, 278, 280, 281 R sibirica, 265, 280 R typhi, 277 ri fa mpi n, 11, 190, 222, 248 ri ma nta di ne, 166 RNA probes , 3, 4 RNA vi rus es , hi gh-yi el d fa cts a bout, 3–4, 6–7 Rocky Mounta i n s potted fever, 12, 54, 284, 285, 287, 289 rota vi rus es , 7, 73, 115, 116, 134, 145, 148, 149, 154, 159–161, 167, 168 RPR tes t. See ra pi d pl a s ma rea gi n tes t RSV. See res pi ra tory s yncyti a l vi rus RT PCR, for determi ni ng HIV progres s i on, 123 rubel l a . See Germa n mea s l es rubeol a . See mea s l es S Sa bi n-Fel dma n dye tes t, 352, 364, 377 Sa i nt Loui s encepha l i ti s (SLE), 23, 156, 409, 421, 437 Salmonella s peci es , 12, 38, 56 S enteritidis, 232 S typhi, 24 SARS. See s evere a cute res pi ra tory s yndrome SBE. See s uba cute ba cteri a l endoca rdi ti s Schistosoma s peci es , 18, 348, 367 S haematobium, 18, 372 S japonicum, 18, 372 S mansoni, 18, 372 s chi s tos omi a s i s , 352, 353, 372, 375, 377, 378 SCID. See s evere combi ned i mmunodefi ci ency di s ea s e s crub typhus , 12, 262, 266, 278, 281, 289 s edormi d, 390, 423 s el ecti ve medi a , 7, 11, 32, 58, 60, 241, 250, 332, 420 s ens i ti vi ty, 10, 55, 61, 62, 64, 72, 127, 182, 192, 234, 239, 240, 247, 250, 255, 341, 387, 435 of ba cteri a l tes ts , 10, 234 s erol ogi c ma rkers , 433, 434 s evere a cute res pi ra tory s yndrome (SARS), 6, 83, 162 s evere combi ned i mmunodefi ci ency di s ea s e (SCID), 22, 413, 430, 432, 433 s exua l l y tra ns mi tted di s ea s es , 5, 17, 262, 266, 332 Shi ga -l i ke toxi n, 210–212, 242 Shigella, 9, 12, 34, 58–60, 246, 257, 259 s i ckl e cel l di s ea s e, 147 s i derophores , 26, 52 s i gmoi dos copy, 351, 352, 375, 400, 405 s i mpl e di ffus i on, 52, 404 s ki n norma l mi crofl ora of, 252 a s porta l of entry, 198, 245, 246, 317 s peci mens of, 324 tes ti ng a nd, 384 s l a pped cheek ra s h, 123, 143
SLE. See Sa i nt Loui s encepha l i ti s ; s ys temi c l upus erythema tos us s ma l l pox, 5, 6, 92, 140 s na i l s , 344, 349, 374 Southern bl ot, 37, 38, 61, 62 s peci fi ci ty, 21, 56, 75, 192, 228, 239 of ba cteri a l tes ts , 56, s pheropl a s ts , 2, 39, 63 s pherul es , 13, 15, 294, 300, 301, 316, 319, 320, 327, 328 s pi der bi tes , 433 s pi rochetes , medi ca l l y i mporta nt, 241 s pora ngi ophores , 328 s pora ngi os pores , 13, 301, 328 s pores , 2, 13, 16, 58, 72, 73, 76, 219, 241, 254, 312, 323, 333 Sporothrix s peci es , 14, 294 S schenckii, 317 s porozoa ns , 379 s potted fevers , 12, 54, 262, 265, 266, 280, 281, 284, 287, 289 s putum s peci mens , 182, 226, 273 SSPE. See s uba cute s cl eros i ng pa nencepha l i ti s s s RNA vi rus es , hi gh-yi el d fa cts a bout, 4, 6 Stachybotrys chartarum, 294, 317 Staphylococcus s peci es , 2, 8, 73, 74 medi ca l l y i mporta nt, 241 S aureus, 2, 7, 11, 12, 43, 46, 57, 67, 69, 70, 72–74, 145, 146, 149, 153, 182, 188, 195, 218, 221, 224, 226, 230, 231, 234, 235, 237, 239, 241, 243, 245, 256, 258, 404 methi ci l l i n-res i s ta nt, 11, 46, 69, 70, 72, 74 va ncomyci n-i ndetermi na te, 11, 182 S epidermidis, 49, 52, 74, 178, 190, 207, 208, 218, 239, 241, 245, 252, 256 S saprophyticus, 8, 181, 224, 241 tes ti ng for, 49 s ta ti ona ry pha s e, of ba cteri a growth curves , 33, 58, 65 s tem cel l tra ns pl a nta ti on, 432 s tool s peci es , a denovi rus detecti on i n, 167, 168 Streptococcus s peci es group A s treptococci , 179, 195, 231, 236, 239, 243, 248, 253, 285 group B s treptococci , 8, 183 α-hemol yti c, 8, 197, 201, 207, 244, 245, 252 S agalactiae, 8 S mutans, 67, 208, 252 S pneumoniae, 8, 11, 35, 42, 51, 57, 69, 77, 145, 146, 218, 224, 228, 236, 237, 245, 248, 286, 384, 418, 434 S pyogenes, 2, 8, 74–77, 212, 236, 244, 248, 253, 258, 405 S salivarius, 209, 252, 253 S viridans, 197, 245 s treptomyci n, 69, 244 Strongyloides stercoralis, 19, 377 s uba cute ba cteri a l endoca rdi ti s (SBE), 8, 197, 275 s uba cute s cl eros i ng pa nencepha l i ti s (SSPE), 7, 100, 150, 154, 165, 172, 420, 421, 429 s ul fa drugs , 12, 70 s ul fona mi des , growth curves a nd, 42, 65, 279 s uperoxi de di s muta s e, 3, 9, 28, 54, 387 s wi ne fl u, 204, 250, 251 Synerci d, 237 s yphi l i s , 10, 184, 185, 228, 229, 231, 232, 279, 287 s ys temi c l upus erythema tos us (SLE), 23, 156, 409, 421 T T cel l s , 22, 24, 154, 410, 411, 438–440 B7-1 (CD80)/B7-2 (CD86), 438 cytotoxi c, 173 defects , 163, 433 ma rkers , 17 wi th TCRs , 412 T pallidum hema ggl uti na ti on tes t (TPHA), 184, 228 T pallidum i mmobi l i za ti on (TPI) tes t, 185, 228 Taenia s peci es , 277, 367, 368, 370
T saginata, 19, 362 T solium, 19, 362, 369, 371, 381 ta peworms , 19, 349, 362, 365–367, 369, 370, 374, 380, 381 tetra cycl i nes , 11–13, 39, 71, 74, 233, 234, 243, 247, 248, 263, 267, 268, 277–280, 282, 283, 285 Tha yer-Ma rti n a ga r, 8, 12 thi ck-wa l l ed s pores , 316, 325 thi os ul fa te ci tra te bi l e s a l ts s ucros e medi um, 205, 206, 250 thrombos i s , 321 thrus h, 16, 124, 125, 318, 401 ti ck-borne di s ea s es , 279, 335 ba bes i os i s , 263, 279, 335, 349, 374, 379 Borrelia burgdorferi a nd, 23, 36, 60, 112, 164, 233, 349, 395, 429 ehrl i chi os i s , 12, 262, 263, 265, 280, 283, 289 Lyme di s ea s e, 10, 36, 60, 233, 243, 248, 278, 281, 349, 355, 373, 395, 396, 429 RMSF, 277–281, 285 ti nea i nfecti ons ti nea ba rba e, 310 ti nea ca pi ti s , 292, 295, 300, 309, 311, 319 ti nea corpori s , 295, 300, 301, 309, 310, 317, 319, 329 ti nea cruri s , 309, 324 ti nea ni gra , 295, 319, 320, 330, 333 ti nea pedi s , 292, 294, 295, 300, 310, 311, 318, 319 ti nea ungui um, 300, 310, 326 ti nea vers i col or, 14 TMP. See tri methopri m tobra myci n, 46, 69, 70, 185 toga vi rus , 3, 6, 154 toxi c s hock s yndrome (TSS), 7, 75, 191, 238 toxi ns , ba cteri a l , 253. See also endotoxi ns ; exotoxi ns Toxocara s peci es Toxocara canis, 377, 378 Toxocara cati, 377, 378 Toxoplasma s peci es T gondii, 17, 125, 345, 347, 358, 364, 369, 377, 406 tes ti ng for, 341 toxopl a s mos i s , 341, 352, 353, 364, 366, 374, 376–378 TPHA. See T pallidum hema ggl uti na ti on tes t TPI tes t. See T pallidum i mmobi l i za ti on tra ns ducti on, of DNA, 1, 65, 66 tra ns forma ti on, of DNA, 1, 42, 65 tra ns i ti on muta ti on, 68 tra ns pl a nta ti on termi nol ogy, 386, 421 tra ns vers i on muta ti ons , 68 tra vel ers di a rrhea , 9, 242 trema todes , 20, 354, 361, 367, 374, 378 Treponema pallidum, 10, 29, 55, 184, 185, 233, 270, 274, 285 Trichinella spiralis, 19, 347, 378, 428 tri chi nos i s , 352, 353, 377, 378 Trichomonas s peci es , 378 T vaginalis, 17, 180, 337, 345, 347, 359, 360, 369, 378 tri chomoni a s i s , 223, 304, 332, 359, 378 Trichophyton s peci es , 14, 318 T mentagrophytes, 309–310 T rubrum, 292, 299, 309–311, 328 T tonsurans, 292, 299, 309, 311 Trichosporon s peci es , 301 Trichuris trichiura, 19, 341, 357 tri methopri m (TMP), 47, 70, 74, 250, 379 tri methopri m-s ul fa drugs , 379 trophozoi tes , 16, 17, 323, 332, 338, 339, 345, 360–362, 368, 369, 372, 375 Trypanosoma s peci es , 17, 18, 347, 367 T cruzi, 17, 356, 366 T gambiense, 343, 347, 371 trypoma s ti gotes , 371 TSS. See toxi c s hock s yndrome
tubercul os i s , 10, 11, 22, 24, 44, 54, 75, 76, 125, 217, 218, 224, 237, 246, 250, 321, 418, 420 tul a remi a . See Francisella tularensis typhus , 12, 24, 262, 266, 277, 278, 280–282, 284, 285, 289 U Ureaplasma urealyticum, 10, 13, 262, 267, 268, 272, 278, 282, 285 urethri ti s , nongonococca l , 8, 13, 18, 30, 49, 257, 262, 266, 360, 372 uri na ry s tone, 47 uri na ry tra ct i nfecti on, 8, 27, 200, 241, 252, 281 V va cci na ti on for, 45, 96, 107 common col d, 108 HAV, 4, 96, 145, 153 HBV, 145, 153, 160 HPV, 5, 96 i nfl uenza , 97, 108 mea s l es , 421 meni ngi ti s , 197 ra bi es , 93, 141, 158 rota vi rus es , 7, 161 rubel l a , 96, 145, 148, 170 s ma l l pox, 140 va gi na va gi ni ti s , 8, 10, 17, 85, 124, 180, 208, 212, 224, 231, 236, 239, 252, 304, 318, 331, 332, 337, 345, 359, 360, 369, 378 va gi nos i s , ba cteri a l , 223, 304 va ncomyci n, 7, 11, 45, 59, 69–71, 82, 190, 193, 200, 226, 237, 247, 248, 250 res i s ta nce to, 71 va ncomyci n-i ndetermi na te S aureus (VISA), 7, 11, 182, 225, 226 va ncomyci n-res i s ta nt enterococci (VRE), 11, 71, 237 va ri a nt s urfa ce gl ycoprotei ns (VSG), 347, 371 va ri cel l a zos ter vi rus (VZV), 5, 79, 385, 418 i mmune s ta tus a nd, 144, 385, 420, 422 rea cti va ti on of, 107, 279 va ri ol a , 5, 92, 133, 140 VDRL tes t. See Venerea l Di s ea s e Res ea rch La bora tory tes t Venerea l Di s ea s e Res ea rch La bora tory (VDRL) tes t, 110, 184, 187, 228, 229, 231 verotoxi n. See Shi ga -l i ke toxi n Vibrio s peci es , 59 V cholerae, 11, 24, 206, 221, 234, 249, 257, 259 V parahaemolyticus, 203, 250, 257, 258 V vulnificus, 249, 258, 259 vi ra l pneumoni a , 97, 159, 171 vi rol ogy, 2–4, 165 hi gh-yi el d fa cts a bout, 1–3 vi rul ence fa ctors , 26, 43, 74–76, 180, 191, 216, 221, 224, 237, 240, 256, 258 vi rus . See also specific viruses, eg, herpes s i mpl ex vi rus ca ncer a nd, 6, 18, 88, 96, 104, 134, 145, 154, 160, 173, 214, 372, 414, 431, 439, 440 Chlamydiae vs , 12, 135, 261, 264, 277, 283 entry routes of, 198, 249 ga s troenteri ti s ca us ed by, 5, 58, 115, 116, 133, 148, 159, 161, 167, 168, 202, 215, 257–259 pri ons vs , 67, 68, 92, 139, 140 VISA. See va ncomyci n-i ndetermi na te S aureus vi s cera l l a rva mi gra ns , 352, 353, 377, 378 VRE. See va ncomyci n-res i s ta nt enterococci VSG. See va ri a nt s urfa ce gl ycoprotei ns VZV. See va ri cel l a zos ter vi rus W wa l ki ng pneumoni a . See pri ma ry a typi ca l pneumoni a wa rts , geni ta l , 134 Wes t Ni l e vi rus , 6, 82, 128 Wes tern bl ot a na l ys i s , 22, 36, 60, 123, 126, 127, 401, 432 Wes tern equi ne encepha l i ti s , 6, 94, 100, 122, 141, 150, 174 Wi s kott Al dri ch s yndrome, 23, 398, 401, 430 wool s orter’s di s ea s e, 278
Wuchereria s peci es W bancrofti, 19, 343, 374 X xenogra ft, 421, 430 Y yea s ts , 13, 320 Yersinia s peci es , 243 Y enterocolitica, 249 Y pestis, 24 Z zygomycos i s , 320
