34. Two months after a renal transplant, a 47-year-old 47-year-old man has increasing dyspnea. dyspnea. X-ray X-ray film film of of the the chest shows an interstitial infiltrate. A photomicrograph of lung tissue obtained on biopsy is shown. Which of the following is the most likely causal organism?
A)
Cytomegalovirus
B)
Epstein-Barr Epstein-Barr virus
C)
Hepatitis B virus
D)
HTLV-1
E)
Papillomavirus
F)
Parvovirus B19
15. A 23-year-old 23-year-old woman has a fever fever and and a cough productive of rust-colored rust-colored sputum. sputum. A gram-positive gram-positive coccus isolated from the sputum is sensitive to optochin. Which of the following is the most likely causal organism? A) Enterococcus faecium B)
Streptococcus agalactiae (group B)
C)
Streptococcus pyogenes (group A)
D)
Streptococcus pneumoniae
E)
Streptococcus sanguis
43. A previously healthy 19-year-old woman comes to the medical clinic because of severe abdominal pain for the past 18 hours. She has had increasingly frequent painful urination over the past 24 hours. She is not sexually active. Temperature is 38.5 C (101.3 F), pulse is 90/min, respirations are 14/min, and blood pressure is 115/76 mm Hg. The suprapubic area is tender on palpation. Microscopic examination of urine shows pyuria, hematuria, and bacteriuria. Which of the following organisms is the most likely cause of these symptoms? A)
Chlamydia trachomatis
B)
Escherichia coli
C)
Neisseria gonorrhoeae
D)
Pseudomonas aeruginosa
E)
Staphylococcus aureus
50. Periodic world-wide pandemics of respiratory infections occur because of shifts in the antigenic properties of which of the following viruses? A)
Coronavirus
B)
Influenza A
C)
Influenza B
D)
Influenza C
E)
Parainfluenza virus
F)
Respiratory syncytial virus
G)
Rhinovirus
38. An unimmunized 10-month-old girl is brought to the emergency department because of temperatures to 40 C (104 F) and listlessness for 24 hours. Examination shows a stiff neck. Leukocyte count is 24,000/mm3. Gram's stain of cerebrospinal fluid shows small pleomorphic gram-negative bacteria that require NAD and hemin for growth. A vaccine for which of the following organisms would have prevented this infection? A) B) C) D) E)
Bordetella pertussis Clostridium tetani Corynebacterium diphtheriae Haemophilus influenzae Neisseria meningitidis
F)
Salmonella typhi
G)
Streptococcus pneumoniae
41. Three weeks after being bitten by a friend's puppy in Mexico, a 32-year-old man has tingling at the site of the bite followed by severe agitation and disorientation. The initial wound healed without complications. The puppy died 2 weeks ago. The route by which the infecting virus entered the brain is A)
blood-borne virions infecting cerebral capillary endothelial cells
B)
blood-borne virions infecting choroid plexus cells
C)
blood cells that cross the blood-brain barrier
D)
transport within the axons into the central nervous system
E)
virions carried by lymphatic drainage to the brain
42. A 62-year-old man develops numerous superficial blisters over the scalp, face, groin, and trunk. New lesions develop over areas subjected to minimal trauma. Biopsy of one of the lesions shows an intraepidermal blister with suprabasal acantholysis. Serologic studies are likely to show an autoantibody directed against which of the following? A)
Anchoring filaments
B)
Basement membrane proteins
C)
Desmosomal proteins
D)
Hemidesmosomal proteins
E)
Integrins
6. Which of the following best describes how Clostridium perfringens evades destruction by neutrophils in patients with clostridial myonecrosis? A)
Damaging neutrophil membranes by means of a membrane-damaging toxin
B)
Preventing contact with neutrophils by means of a polysaccharide capsule
C)
Preventing phagocytosis by disruption of neutrophil actin polymerization
D)
Survival in the cytoplasm of a neutrophil
E)
Survival in the phagosome of a macrophage
25.
Picture: a big mass located in the central part of the left hemisphere, mass is encapsulated with 2 different densities, with edema around the mass) A 32-year-old man with AIDS has a 6-week history of progressive weakness of his right hand, expressive aphasia, and a mild headache. A CT scan of the head with contrast is shown. Which of the following is the most likely causal organism? A)
Cryptococcus neoformans
B)
Cytomegalovirus
C)
Pneumocystis carinii
D)
Toxoplasma gondii
E)
Treponema pallidum
33. The presence of which of the following is characteristic of the infectious agent of bovine spongiform encephalopathy? RNA
DNA
Protein
A) + B) + C) + D) + E) F) G) H) -
+ + + + -
+ + + +
43.
Fig.
A 30-year-old woman with type 1 diabetes mellitus has increasing vulvar pruritus and a vaginal discharge. A wet mount preparation of the discharge is shown. Which of the following is the most likely causal organism? A)
Candida albicans
B)
Chlamydia trachomatis
C)
Herpes simplex virus
D)
Human papillomavirus
E)
Trichomonasvaginalis
6. A 50-year-old man who recently immigrated to the USA from Russia develops fever, swelling of the neck, and difficulty swallowing. His vaccination history is uncertain. Examination of the throat shows a gray membrane across the pharynx. The pathogen responsible for this infection most likely acquires its virulence through which of the following genetic events? A)
Acquisition of a transposon
B)
Chromosomal mutation
C)
Conjugation
D)
Recombination
E)
Transduction
7. A 27-year-old woman has a 1-week history of increased urinary frequency, dysuria, and intermittent suprapubic pain that have become worse over the past 3 days. Examination of her urine is most likely to show A) B) C) D) E)
acid-fast organisms budding yeast forms fungal hyphae gram-negative bacilli gram-positive cocci
9. A 23-year-old man who recently emigrated from Costa Rica is admitted to the emergency department with seizures. Findings on examination of his cerebrospinal fluid are within the reference range. A CT scan of the head shows numerous cortical lesions with calcifications; some have surrounding edema. The life cycle of the parasite causing these lesions involves A)
the bite of a blackfly to human
B)
the bite of a mosquito to human
C)
the bite of a sandfly to human
D)
passage through cows
E)
passage through pigs
19. A 5-year-old boy is brought to the physician's office because of pharyngitis. Culture of a swab from the throat grows a β-hemolytic gram-positive coccus in chains. Which of the following components of the microbe is responsible for this organism's shape? A)
Glycoprotein
B)
Lipopolysaccharide
C)
Lipoteichoic acid
D)
Peptidoglycan
E)
Polysaccharide
F)
Teichoic acid
36. A 76-year-old woman has pain on the right side of the trunk. Examination shows a vesicular rash involving the T-10 to T-12 dermatomes. Which of the following is a characteristic of the most likely organism? A)
Absence of an envelope
B)
Double-stranded DNA
C)
Negative-stranded RNA
D)
Positive-stranded RNA
E)
Prion-like structure
F)
Single-stranded DNA
43. A bacterium harboring a 15,000-base pair (bp) plasmid that encodes resistance to tetracycline and ampicillin segregates mutants that lose resistance to either drug. Each independent mutant plasmid appears to increase in size by approximately 5200 bp. Which molecular event best explains these findings? A)
Formation of plasmid concatemers
B)
Formation of pyrimidine dimers
C)
Homologous recombination
D)
Insertion of a transposon
E)
Slip-stranded DNA replication errors
32. Latent infection with which of the following viruses is associated with expression of some (but not all) viral genes in B lymphocytes? A
)
Epstein-Barr virus
B
)
Hepatitis B virus
C
)
Measles virus
D
)
Simian virus 40
E
)
Varicella-zoster virus
45. A 35-year-old man who takes street drugs intravenously develops fever, cough, and hemoptysis. Xray film of the chest shows bilateral infiltrates. Echocardiogram discloses a 1-cm mass that is attached to the tricuspid valve. Blood culture grows yeast. The most likely causal organism is A
)
Aspergillus flavus
B
)
Candida albicans
C
)
Cryptococcus neoformans
D
)
Histoplasma capsulatum
E
)
Mucor species
12. A 60-year-old man develops cirrhosis. He had multiple blood transfusions following severe trauma in 1985. He has no history of jaundice or hepatitis. Serologic tests and polymerase chain reactions on his blood will most likely show evidence of infection with which hepatitis virus? A) A B ) B C ) C D ) D (delta) E ) E
24. A 28-year-old woman develops temperatures to 39.4 C (103 F) and substernal chest pain 3 days after being treated by her dentist for gingivitis. An x-ray film of the chest shows an enlarged cardiac silhouette. On pericardiocentesis, 250 mL of cloudy fluid containing large numbers of neutrophils is removed. Which of the following is most likely on examination of the fluid? A ) Acid-fast bacilli B ) Budding yeast forms C ) DNA virus D ) Gram-negative bacilli E ) Gram-positive cocci
26. A 45-year-old man develops a fever 4 days after an abdominal operation. Blood cultures grow Staphylococcus aureus. Which of the following is the most likely site of infection from which the organism gained access to the blood stream? A ) Anterior nares B ) Sputum C ) Stool D ) Urine E ) Wound
27. An outbreak of acute pneumonia occurs in military recruits living in one barrack and only in those persons located near the air conditioner. Epidemiologic surveillance results in isolation of the causal organism from the patients and from the drip pans of the air conditioner. The organism is resistant to penicillin, susceptible to erythromycin, and weakly gram-negative. The most likely organism is A ) Bordetella pertussis B ) Haemophilus influenzae (nontypeable) C ) Klebsiella pneumoniae D ) Legionella pneumophila E ) Mycobacterium tuberculosis F ) Mycoplasma pneumoniae G ) Staphylococcus aureus H ) Streptococcus agalactiae (group B) I ) Streptococcus pneumoniae J ) Streptococcus pyogenes (group A)
28. A 45-year-old man has fever, chills, cough, and pleuritic chest pain. Culture of a rust-colored sputum specimen yields many α-hemolytic colonies of lancet-shaped, gram-positive cocci in pairs and short chains. The most likely causal organism is A ) Klebsiella pneumoniae B ) Mycobacterium tuberculosis C ) Mycoplasma pneumoniae D ) Staphylococcus aureus E ) Streptococcus pneumoniae F ) Streptococcus pyogenes (group A)
46. A 19-year-old college student develops hematuria and proteinuria. Approximately 3 weeks ago, he had superficial cellulitis of the right proximal thigh and buttocks. His condition is most likely to be secondary to infection with A ) Escherichia coli B ) Pseudomonas aeruginosa C ) Staphylococcus aureus D ) Staphylococcus epidermidis E ) Streptococcus pyogenes (group A)
