22. After eating a dinner of leftovers that included rewarmed vegetable fried rice, a 17-year-old boy develops diarrhea and stomach pain. Which of the following is the most likely pathogen?
(A) Bacillus cereus
(B) Campylobacter jejuni
(C) Clostridium botulinum
(D) Clostridium difficile
(E) Escherichia coli
(F) Norwalk agent
(H) Salmonella typhi
(I) Shigella dysenteriae
(J) Vibrio parahaemolyticus (K) Yersinia pestis
23. A 23-year-old woman with a history of sickle cell disease presents with fever and severe bone pain localized to her left tibia. An x-ray film reveals a lytic lesion, and blood cultures reveal infection. A bone culture grows gram-negative rods. Which of the following best describes the infecting organism?
(A) It is comma-shaped and sensitive to acidic pH
(B) It is an obligate intracellular parasite
(C) It is motile and does not ferment lactose
(D) It is motile and oxidase positive
(E) It is a nonmotile facultative anaerobe
24. A 33-year-old HIV-positive man complains of headache and blurred vision. Physical examination reveals papilledema and ataxia. Head CT is normal but CSF obtained by lumbar puncture reveals encapsulated organisms observable with India ink. Which of the following is true concerning this organism?
(A) It can also be identified with methenamine silver stain
(B) It consists of branching septate hyphae
(C) It exists as a mycelial form at room temperature and as yeast at 37 C
(D) It is an encapsulated nondimorphic yeast found worldwide
(E) It is a nonencapsulated dimorphic yeast that reproduces by budding
25. A French exchange student in a town near the Ohio River presents to the local hospital with headache, fever, malaise, and nonproductive cough. He became ill several days after cleaning and moving a chicken coop where hundreds of chickens had roosted for many years. Which of the following microorganisms is most likely responsible for his illness?
(A) Actinomyces israelii
(C) Candida albicans
(D) Coccidioides immitis
(E) Cryptococcus neoformans
(F) Histoplasma capsulatum
(G) Nocardia asteroides
(H) Sporothrix schenckii
26. A 3-year-old girl presents with recurrent subcutaneous abscesses and furuncles. She has a history of pneumonia due to Serratia marcescens. Which of the following enzymes is most likely deficient in her neutrophils?
(A) Aldolase B
(D) Glucose-6-phosphate dehydrogenase
(E) NADPH oxidase
27. An otherwise healthy patient who has just received a prosthetic aortic valve develops postoperative fever. Blood cultures are done, and she is given broad-spec -trum antibiotics. Two days later she is still febrile and clinically deteriorating. Which of the following is the most likely pathogen?
(A) Actinomyces israelii
(B) Candida albicans
(C) Histoplasma capsulatum
(D) Nocardia asteroides
28. After high-dose chemotherapy and irradiation, a 35-year-old woman with acute myeloid leukemia in remission receives a bone marrow transplant from her HLA-matched brother. One week after the graft, the patient develops a fever and a maculopapular rash over her upper extremities and back. She also notes abdominal pain and diarrhea. Laboratory examination is remarkable for elevation of alkaline phosphatase and bilirubin. Which of the following is the most likely cause of this patient's symptoms?
(A) Bacterial infection from the graft
(B) Blast crisis
(C) Graft-vs-host disease
(D) Hyperacute graft rejection
(E) Radiation toxicity
29. A 16-year-old boy with sickle cell disease is hospitalized for a severe infection. His spleen has autosplenec-tomized, and he has had other minor infections in the past. His symptoms include fever, chills, cough, and chest pain. Bacteria from the patient's sputum yield optochin-sensitive organisms with a positive Quellung reaction. Which of the following is the most likely pathogen?
(A) Escherichia coli
(B) Haemophilus influenzae
(C) Klebsiella pneumoniae
(D) Neisseria gonorrhoeae
(E) Streptococci pneumoniae
The figure below represents an Ouchterlony radial immunodiffusion test.
Well 1 Well 2
Antigen A, B Antigen A, C
Well 1 Well 2
Antigen A, B Antigen A, C
30. The antigen in Well 1 has two different epitopes (antigenic determinant groups), A and B; the antigen in Well 2 also has two epitopes, A and C. Well 3 contains which of the following?
(A) Antibody to A only
(B) Antibodies to A and B
(C) Antibodies to A and C
(D) Antibodies to B and C
31. A 3-year-old boy presents with a 1 -day history of loose stools, fever, abdominal cramping, headache, and myalgia. He has no blood in the stool. A careful history reveals that he has several pet turtles. Which of the following is the most likely pathogen?
(A) Chlamydia psittaci
(B) Entamoeba histolytica
(C) Salmonella spp.
(D) Staphylococcus aureus
(E) Yersinia enterocolitica
32. Which of the following viruses produces disease or sequelae that is/are more severe if the infection occurs at a very young age?
(A) Epstein-Barr virus
(B) Hepatitis B virus
(C) Measles virus
33. A 20-year-old man with stridor is brought to the emergency department by his girlfriend. He had been complaining of abdominal pain earlier in the day. Physical examination is significant for well-demarcated regions of subcutaneous edema. He has had similar episodes before, and his mother and sister have the same condition. Which of the following substances is most likely deficient in this patient?
(A) CI esterase inhibitor
(B) C3b inactivator
34. About a month after being bitten by a bat, a man develops an influenza-like illness. He subsequently develops striking mood changes, pharyngeal spasms with drooling, and seizures, and he falls into a coma. He eventually dies of his illness. This patient's deterioration was most likely caused by a virus from which of the following groups?
35. Which of the following is an example of type II hypersensitivity?
(B) Erythroblastosis fetalis
(C) Food allergy
(D) Serum sickness
36. A 24-year-old woman has fever, malaise, and a dry, nonproductive cough. She also complains of headache, muscle aches, and leg pain. Laboratory values are significant for elevated cold agglutinins. Which of the following microorganisms is responsible for her symptoms?
(A) Haemophilus influenzae
(B) Klebsiella pneumoniae
(C) Legionella pneumophila
(D) Mycoplasma pneumoniae
(E) Streptococcus pneumoniae
37. A 25-year-old woman presents with a confluent macu-lopapular rash that began on her face then spread downward over her trunk. She states that 3 days ago she started having a fever and headache, with bilateral pain associated with the front and back of her neck. She also complains of joint pain. Which of the following diseases does she most likely have?
(A) Infectious mononucleosis
(B) Lyme disease
38. An 18-year-old, previously healthy woman presents to the student health service with fever, vomiting, and diarrhea. On physical examination, she is hypotensive and has an erythematous, red, sunburn-like skin rash. She is currently menstruating and has been using super-absorbent tampons. Which of the following findings from a positive blood culture would confirm the suspected diagnosis?
(A) Organisms are acid-fast
(B) Organisms are coagulase positive
(C) Organisms grow on EMB (eosin-methylene blue) agar
(D) Organisms grow on Thayer-Martin media
(E) Organisms have positive Queilung reaction
39. Following a citywide outbreak of an exanthematous disease, three children at an urban elementary school develop a rash that begins on the face and neck and spreads to the rest of the body. Posterior auricular and posterior cervical lympbadenopathy is present. Distinct, rose-colored spots are seen on the palate, and the pharynx appears red. Which of the following procedures would be recommended for the rest of the students at the school?
(A) A live, attenuated virus vaccine
(B) A live, attenuated virus vaccine plus specific immunoglobulin
(C) An inactivated (killed) virus vaccine
(D) An inactivated (killed) virus vaccine plus specific immunoglobulin
(E) Specific immunoglobulin only
(F) A vaccine with antigen produced by recombinant techniques
40. Global eradication of Lyme disease is unlikely in the foreseeable future because Borrelia burgdorferi
(A) can be maintained in nature indefinitely by a tick vector
(B) has a tough outer coat that is resistant to environmental stresses
(C) has humans as its primary reservoir
(D) is resistant to antibiotics and disinfectants
(E) may reactivate and cause Brill-Zinsser disease
41. A 7-month-old chüd presents with a 4-day history of fever, deepening cough, and dyspnea. A chest x-ray film shows multiple interstitial infiltrates and hyperinflation of the lungs. Multinucleated giant cells with cytoplasmic inclusion bodies are seen when a nasal wash is inoculated into tissue culture. The most appropriate therapy includes administration of which of the following drugs?
42. A formula-fed, 1-month-old boy is exposed to his sister, who has chickenpox. He does not develop signs of varicella. His mother had the infection 5 years ago. Which class of immunoglobulins did he acquire from his mother in utero that protected him from this virus?
43. After passing his physical examination, a 19-year-old army recruit gives urine and blood samples for further testing. Serum analysis yields elevated ALT, HBsAg, Anti-HBc, HBeAg, and bilirubin. All other values are normal. What is the hepatitis B status of this recruit?
(A) Asymptomatic carrier
(B) Active carrier
(C) Fulminant hepatitis B
(D) Recovered from acute self-limited HBV
(E) Vaccinated against HBV
44. A 65-year-old man undergoes coronary artery bypass surgery that entails grafting the left internal mammary artery to the left main coronary arteiy to form an alternative conduit for blood flow. This patient received a(n)
(B) autograft (E) horoograft (D) isograft
45. Following a barbecue hosted by a hunter who served "bear hamburgers," several guests develop abdominal pain and diarrhea; their condition progresses about a week later to fever, myalgia, periorbital edema, and petechial hemorrhages in the conjunctiva. A peripheral blood smear shows an increased eosinophil count. Which of the following is the most likely cause of these symptoms?
(B) Bacillus cereus food poisoning
(D) Escherichia coli gastroenteritis
46. A patient presents with right lower-quadrant pain, fever, and diarrhea. Physical examination reveals diffuse abdominal tenderness; laboratory examination shows a moderate leukocytosis, leading to a presumptive diagnosis of acute appendicitis. Surgical exploration of the abdomen reveals mesenteric adenitis, but the appendix is normal. Which of the following organisms is most likely responsible for these signs and symptoms?
(A) Clostridium difficile
(B) Enterohemorrhagic Escherichia coli
(C) En tero invasive E. coli
(D) Enteropathogenic E. coli
(E) Enterotoxigenic E. coli
(F) Mycobacterium tuberculosis
(I) Vibrio cholerae
(J) Yersinia enterocolitica
47. A 68-year-old patient with alcoholic cirrhosis is hospitalized with ascites and esophageal varices. The patient's temperature is 38.3 C (101 F). Paracentesis reveals a polymorphonuclear cell count of 300/mm3. Which of the following is the most likely infecting organism?
(A) Bacillus cereus
(B) Clostridium difficile
(C) Escherichia coli
(D) Entamoeba histolytica
(E) Giardia lamblia
48. A 4-year-old child who has had repeated infections with staphylococci and streptococci has normal phagocytic function and delayed hypersensitivity responses. Lymph node biopsy would most likely reveal
(A) absence of postcapillary venules
(B) absence of germinal centers
(C) defective chemotactic response of neutrophils
(D) depletion of paracortical areas
(E) depletion of thymus-dependent areas
49. A 47-year-old man presents with a nonproductive cough and rales on his chest examination. A chest x-ray film suggests atypical pneumonia. The pneumonia resolves after treatment with azithromycin. A diagnosis of psittacosis is established by the presence of complement fixing antibodies against Chlamydia psiltaci in the convalescent serum. Which of the following is the most likely occupation of this patient?
(A) Cat breeder
(C) Homeless shelter worker
(D) Poultry farmer
(E) Slaughter house worker
50. A 20-year-old college student presents to the university health clinic with sore throat, fever, and fatigue. Physical exam is significant for cervical lymphadenopa-thy and mild hepatomegaly. Heterophile antibody tests are negative. Microscopic examination of an epithelial cell would be expected to reveal
an enlarged nucleus with peripherally displaced chromatin conidia and septate hyphae
(C) a giant nucleus surrounded by a clear zone
(D) a multinucleated giant cell
(E) staining with India ink
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