Microbiology and Parasitology 1. Which of the following characteristics is used to c haracterize Staphylococcus aureus? a.
“Pitting” on sheep blood agar
b. Fermentation of mannitol c.
Positive catalase test
d. Positive coagulase test 2. To differentiate differentiate between a coagulase – negative staphyloccus species and a micrococcus species, which of the following tests can be used? a.
Furazolidone susceptibility
b. Catalase c.
Novoblocin susceptibility
d. Urease 3. A pustule drainage submitted for culture is plated onto primary media. After an 18-h incubation, the sheep blood agar plate reveals a predominance of beta- haemolytic, white porcelain colonies. Gram stain shows gram positive cocci. The colonies test catalase – positive. The most appropriate test for additional identification of the isolate is a.
Bacitracin
b. Bile esculin c.
Bile solubility
d. Coagulase 4. A 43-year-old female patient complains of a very sore throat. The throat swab that is submitted for routine culture grows a variety o f diphtheroids: alpha, beta and nonhemolytic streptococci; staphylococci and Neisseria. The next step is to a.
Report it as normal throat flora
b. Ask for a repeat collection to get a better specimen c.
Identify the beta – haemolytic streptococcus species
d. Identify the neisseria species 5. A nasopharyngeal culture grows a predominance of a beta –hemolytic colony type on sheepbl;ood agar at 18 h. The isolate is susceptible to a 0.04 unit of bacitracin. The most likely identification is beta-hemolytic streptococcus. a.
Group A
b. Group B c.
Group D
d. Not group A, B or D 6. Which of the following is not consistent with streptococcus pneumoniae a.
Alpha hemolysis on sheep blood agar
b. Bile solubility positive c.
Gram positive, oval shaped cocci in pairs
d. Positive catalase test 7. Neisseria species can be identified an differentiated by a. Bile-esculin hydrolysis
b. Carbohydrate utilization c.
Nitrate test
d. Oxidase test 8. A small gram positive rod that causes neonatal meningitis and septicaemia is a.
Escherichia coli
b. C. Diptheriae c.
Listeria monocytogenes
d. S. Agalactiae 9. The X and V factors required for growth of haemophilus influenza are contained in a.
Brain/ heart infusion broth
b. Chocolate agar c.
Sheep – blood agar
d. Thioglycollate broth 10. On a sheep blood agar plate, haemophilus influenza satellites around colonies of a.
Diptheroids
b. S. Pyogenes c.
H. Parainfluenza
d. S. Aureus 11. The specimen of choice for the isolation of Bordetella pertussis from a suspected case of whooping cough is a.
Blood
b. CSF c.
Nasopharyngeal swab
d. Throat swab 12. Family characteristics of enterobacteriaceae include a.
Fermentation of glucose
b. Spore former c.
Formation of indophenols oxidase
d. Failures to reduce nitrates 13. Twenty parents on a surgical ward develop urinary tarct infections after catheterization. In each instance, the isolated organism grows on sheep-blood agar as a large, gray colony, and on MacConkey agar as a large, flat, pink colony. The oxidase-negative, gram negative and produces the same biotype and is resistant only to tet racycline. Additional biochemical results are as follows: Phenylalanine deaminase (PAD): negative
Urease: negative
Hydrogen sulphide (H2S): negative
Omithine decarboxylase: positive
Lysine decarboxylase: positive
Indole: positive
Citrate:Negative. The most probable organism is a.
Escherichia coli
b. Enterobacter cloacae c.
Enterobacter aerogenes
d. Enterobacter vulgaris
14. A mucoid, lactose positive colony type on Macconkey agar that is indole – negative and citrate – positive, and non-motile is a.
Escherichia coli
b. K. Pneumonia c.
Enterobacter cloacae
d. Enterobacter aerogenes 15. Escherichia, Klebsiella, and proteus species are common flora of the a.
Gastrointestinal tract
b. Respiratory tract c.
Superficial skin surfaces
d. Urinary tract 16. A discharge from an infected ear grows a colorless colony type of MacConkey agar that swarms on sheep-blood agar. This oxidase-negative, gram-negative rod gives the following biochemical reactions: Phenylalanine deaminase (PAD): positive
Ornithine: positive
Hydrogen sulphide
(H2S)P: positive
Urease: positive
Citrate: positive
Indole: negative
Lysine: negative. The organism described is: a.
Citrobacter freundi
b. Morganella morganii c.
Proteus mirabilis
d. Proteus vulgaris 17. A gram – negative rod biochemically compatible with the genus salmonella fails to ag glutinate in the polyvalent somatic antisera for Salmonella serotyping. What is the next step in the definitive identification of this organism? a.
Report the organism as a Salmonella polyvalent O-positive species and send the isolate elsewhere for additional identification
b. Wash a suspension of the isolate in saline and retest it in the Salmonella polyvalent antiserum c.
Boil a saline suspension of the organism for 15 min, coo l, and retype in Salmonella polyvalent antiserum
d. Retest the isolate using the individual somatic antisera from each se rgroup, A through E 18. A gram-negative rod is isolated from a patient with second- and third-degree burns. The isolate produces a bluish green pigment and a character istic fruity odor. Other characteristic observations are: Triple sugar iron K/K
Motility: positive
Oxidase: positive
Oxidative/fermentation
glucose: oxidative utilization only The most probable genus of this isolate is a.
Acinetobacter
b. Alcaligenes c.
Moraxella
d. Pseudomonas 19. After 48 h of incubation on anaeropbic sheep-blood agar, C lostridium perfringens appears as a
a.
Large, flat colony with a double zone of hemolysis
b. White, butyrous, nonhemolytic colony with a glistening surface c.
Gray, mucoid colony witha zone of alpha hemolysis
d. Colony with a pearllike surface and a single sone of beta hemolysis 20. Isolation of campylobacter jejuni from a patient with gastroenter itis is optimized by a.
iNcubation at 35-37oC
b. Selective enrichment in selenite broth c.
microerophilic environment
d. An anaerobic environment without CO2 21. In the N-acetyl-L-cysteine-alkali method of processing sputum specimens for mycobacterial culture, the N-acetyl-L cysteine serves as a a.
Buffer
b. Decontaminant c.
Digestant
d. pH stabilizer 22. A sputum specimen is submitted to the laboratory accompanied by a re quest for an AFB culture. All of the following are standard protocol for processing this specimen except: a.
Use of a refrigerated centrifuge with bucket covers
b. Use of both liquid and solid media for setup of AFB culture c.
Use of concentrated potassium hydroxide for decontamination procedure
d. Use of a laminar flow biological safety cabinet for processing the specimen 23. Routine sterilization of artificial culture media by autoclaving is recommended at a.
15 psi ast 121oC for 15 min
b. 10 psi at 121oC for 10 min c.
15 psi at 200oF for 15 min
d. 10 psi at 220oF for 10 min 24. When acetone – alcohol is inadvertently omitted from the gram – stain procedure, streptococci and Neisseria will be stained, respectively a.
PUrple and red
b. Purple and purple c.
Red and red
d. Red and purple 25. He color of a non acid fast bacilluys following the acid-alcohol steop and before conterstanding in the acid-fast stain procedure a.
BLUE
b. RED c.
COLORLESS
d. GREEN 26. MacConkey agar is sued for isolation of members of the family enterobacteriaceae because the medium ios a.
Inhibitory and differential
b. Differential and enriched
c.
Enriched and selective
d. Selective and supplemented 27. Ethylhydrocupreine hydrochloride (optochin) is a chemical used to differentiate a.
Catalase-positive Streptococcus species from catalase-negative Staphylococcus species
b. Streptococcus pneumoniae from alpha-hemolytic streptococci c.
Enterobacteriaceae from non-Enterobacteriaceae
d. Group D enterococci from group-D nonenterococci 28. A lysine-iron agar (LIA) slant shows a red slant ove r a yellow butt. This reaction indicates that the organism a.
Deaminase lysine
b. Decarboxylase lysine c.
Ferments lactose
d. Produce H2S 29. Which of the following statements regarding Simmmon’s citrate agar is incorrect a.
Blue color is an alkaline reaction
b. Citrate is the only source of carbon in the medium c.
Glucose is the carbohydrate in the medium
d. Growth on the slant is interpreted as a positive reaction 30. The reagent(s) used to detect a positive phenylalanine –deaminase reaction is (are) a.
Sulfanilic acid and alpha – napthylamine
b. P-aminodimethylbenzadehyde c.
Alpha-naphthol and potassium hydroxide
d. Ferric chloride 31. To eliminate the antibacterial properties of blood and simultaneously introduce an adequate volume of blood for recovery of microorganisms from septicaemia, the recommended blood-tobroth ratio in the blood-culture bottle is approximately a.
1:2
b. 2:1 c.
1:10
d. 10:1 32. Which of the following specimens is acceptabkle for the evaluation of clinically important anaerobes a.
Feces
b. Sputum c.
Peritoneal fluid
d. Superficial wound 33. A urine is received in the laboratory for culture. If the specimen c annot be oplated immediately, it should be held a.
In the freezer
b. In the refrigerator c.
At room temperature
d. In the 35oC incubator
34. Standardized testing conditions for t he Kirby-Bauer agar-disk diffusion antimicrobial susceptibility test include all of the following except: a.
E of Mueller-hinton media
b. Standard inoculums size c.
Incubation at 35oC
d. Incubation in 8-10% CO2 35. The pair of organisms that would provide a good positive and negative control for phenylethyl – alcohol “(PEA) blood agar is
a.
PSeudomonas aeruginosa and Escherichia coli
b. Haemop-hilus influenzae and Streptococcus pyogenes c.
Eneterococcus and E. Coli
d. Staphylococcus aureus and WS. Pyogenes 36. Which of the following organism will give the appropriate positive and negative reactiosn for quality control of the test listed Positive
Negative
E.coli
Neisseria meningitides
b. Indole
E. Coli
proteus vulgaris
c.
S. Aureus
S. Epidermidis
Pseudomonas aeruginosa
E.coli
a.
Gram stain Catalase
d. Oxidase
37. A fungal colony grows rapidly on Sabouraud’s dextrose agar as a white colony tyope with a dense production of aerial, blue – green spores. On lactopherol cotton blue prparationm, swollen – tipped conidiophores bear sterigmata and conidia in chains. The most likely identification of this isolate is a.
Aspergillus
b. Paeilomyces c.
Penicillium
d. Scopulariopsis 38. A saprobic yeast that inhabits airborne dust, skin, and mucosa grows rapidly and oproduces an orange – to – red color. This isolate most likely belongs to t he genus a.
Cryptococcus
b. Geotrichum c.
Rhodotorula
d. Saccharomyces 39. The function of 10% potassium hydrosxxide in the direct examination of skin, hair and nail scrapings is to a.
Reserve fungal elements
b. Kill contaminating bacteria c.
Clear and dissolve debris
d. Fix preparation for subsequent staining 40. A potentially pathogenic yeast that is normal flora in the oropharyngeal cavity and may produice thrush is a.
Trichosporonm beigelli
b. C. Albicans c.
Cryptococcus neoformans
d. Geotrichum 41. In an iodine preparation of feces, an amoebic cyust appears to have a single nucleus with a large karyosome and chromatin bodies do not appear along the nuclear membrane. A large glycogen mass that stains reddish brown occupies the cytoplasm. The most probable identity of the cyst is a.
Entamoeba histolytica
b. Iodamoeba butschii c.
Entamoeba coli
d. Entamoeba hartmanni 42. The infective stage of this parasite consists of an e gg with a thin hyaline shell, with one flattened side and usually, a fully developed larva within. The parasite is a.
Enterobius vermicularis
b. Hookworm c.
Ascaris lumbricoides
d. Trichuris trichuria 43. The direct iodine preparation is best used to detect protozoan a.
Eggs
b. Trophozoites c.
Cysts
d. Larvae 44. Parasites that are detected by direct visualization in the peripheral blood smear are a.
Ascaris
b. Entamoeba c.
Giardia
d. Plasmodium 45. Chlamydia differ from viruses in that chlamydiae a.
Are true bacteria
b. Are obligate intracellular organisms c.
Produce intracellular inclusions
d. Are isolated in tissue – culture systems 46. A specimen for viral culture is collecte d on a Friday and must be held for processing until the next day. In general, the optimal temperature for holding this specimen is a.
35oC
b. 4oC c.
20oC
d. 70oC 47. Procedure that directly determines beta lactamas eproduction by microorganism is based on detection of a(n) a.
Zone of susceptibiklity around an am picillin disk
b. Zone of inhibition around an o xacillin disk c.
Increased acidity due to the release of penicillin acid
d. Increase in pH due to teh reduction of iodine 48. In a broth-dilution method of antimicrobial susceoptibility testing, the tube with the lowest concentration of antimicrobial in which there is no visible growth is the minimal a.
Antimicrobial concentration
b. Bacteriocidal concentration c.
Inhibitory concentration
d. Lethal concentration 49. This adult disease results from performed neurotoxin that is ingected and causes symptoms of neuromuscular flaccid paralysis. The agent that produces the toxin is a.
Bacillus cereus
b. Clostridium botulinum c.
Clostridium tetani
d. Staphylococcus aureus 50. Two siblings arrive at the emergency room. Both had antecedent sore throats about 2 to 3 weeks earlier that grew beta – haemolytic streptococci; now they present with different clinical symptoms. The brother displays edema and hypertension, and RBC casts are seen in the urine. The sister complains of fever and joint pains and has carditis. The disease that these siblings have are most likely a.
Erysipelas and glomerulonephritis
b. Glomerulonephritis and rheumatic fever c.
Rheumatic fever and scarlet fever
d. Scarlet efever and erysipelas 51. Purulent material is obtained from a carbuncle and submitted for bacter ial cuklture. The direct smear reveals many gram – positive cocci adn WBCs. The c ulture shows growth in the primary broth and on the sheep – blood agar plate and no growth on t eh
Micrococcus sp.
b. S. Aureus c.
S.epidermidis
d. S. Saprophyticus 52. On thiosulfate-citrate-bile-sal;ts-sucrose (TCBS) agar, colonies of Vibrio cholera appear a.
Yellow
b. Colorless c.
Olive green
d. Black 53. A gram-negative coccobacillary organism that is isolated from synovial fluid on chocolate agar resembles either a moraxella species or Neisseria gonorrhoeae. The single best test to distionguish between these organisms is a.
Beta hemolysis
b. Glucose degradation
c.
Motility
d. Oxidas eproduction 54. A lumbar puncture is performed on an 82 -year-old woman who is receiving immunosuppressive therapy. The direct gram’s stain of tyhe CSF reveals small gram positive rods and numerous
WBCs. At 18 h, small translucent colonies with narrow zone of beta hemolysis grow on sheep blood agar. The isolate produces catalase. Identification of this isolate could be made by demonstration of a.
Tumbling motility
b. Metachromatic granulation c.
Hippurate hydrolysis
d. H2S production on TSI agar 55. A dair farmer weho has an intermittent fever, progressive weakness and night sweats is suspected of having undulant fever. Blood cultures from this patient yield an organism that shows the following characteristics: requires an atmosphere of 10% CO2, urease – positive in 1 to 2 h, grows in the presence of thionine dye but not in the presence of fuchsin. Which of the following is described there a.
