USMLE Microbiology Prt 9

23 Questions | Total Attempts: 202

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USMLE Quizzes & Trivia

Questions and Answers
  • 1. 
    A 1-year-old child develops voluminous watery diarrhea and vomiting. She is brought to the pediatrician by her parents and evaluated, then sent home with instructions for the parents to give the child an electrolyte replacement solution. Which of the following viruses is the most likely cause of the child's diarrhea?
    • A. 

      Coronavirus

    • B. 

      Lymphocytic choriomeningitis virus

    • C. 

      Norwalk agent

    • D. 

      Orbivirus

    • E. 

      Rotavirus

  • 2. 
    A 3-year-old child with cystic fibrosis presents with weight loss, irritability, and a chronic productive cough. On physical exam, he is febrile and lung exam reveals intercostal retractions, wheezing, rhonchi, and rales. Chest x-ray demonstrates patchy infiltrates and atelectasis and Gram's stain of the sputum reveals slightly curved, motile gram-negative rods that grow aerobically. The microorganism responsible for this child's pneumonia is also the most common cause of which of the following diseases?
    • A. 

      Croup

    • B. 

      Epiglottitis

    • C. 

      Meningitis

    • D. 

      Otitis externa

    • E. 

      Otitis media

  • 3. 
    A pastry chef cut his finger while slicing a cake. After a week, the site of the injury is warm, red, and swollen, and begins draining pus. While preparing some cream pies, he contaminates the custard with drainage from the lesion. The pies were eaten several days later by patrons of the restaurant. Within 4 hours they developed diarrhea and vomiting with no fever. Which of the following organisms would be most likely to cause these symptoms?
    • A. 

      Bacillus cereus

    • B. 

      Clostridium perfringens

    • C. 

      Escherichia coli

    • D. 

      Shigella sonnei

    • E. 

      Staphylococcus aureus

  • 4. 
    After passing his physical exam, 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. Which of the following is the hepatitis B status of this recruit?
    • A. 

      Asymptomatic carrier

    • B. 

      Chronic active carrier

    • C. 

      Fulminant hepatitis B

    • D. 

      Recovered from acute self-limited HBV

    • E. 

      Vaccinated against HBV

  • 5. 
    A 4-year-old child living in a slum is bitten by a rat while sleeping. Two days later, the child develops a rash characterized by discrete erythematous 1-4 mm macules on the extremities and face, most obvious on the palms and soles. Which of the following organisms is the most likely cause of this child's disease?
    • A. 

      Borrelia burgdorferi

    • B. 

      Pseudomonas mallei

    • C. 

      Pseudomonas pseudomallei

    • D. 

      Spirillium minus

    • E. 

      Streptobacillus moniliformis

  • 6. 
    A 35-y/o man develops hemiparesis, ataxia, homonymous hemianopia, and cognitive deterioration. An MRI of the brain demonstrates widespread areas of abnormal T2 signal in the white matter. An electroencephalogram is remarkable for diffuse slowing over both cerebral hemispheres. Brain biopsy reveals demyelination with abnormal giant oligodendrocytes, some of which contain eosinophilic inclusions. This patient's condition is most closely related to which of the following diseases?
    • A. 

      AIDS

    • B. 

      Chickenpox

    • C. 

      Measles

    • D. 

      Syphilis

    • E. 

      Tuberculosis

  • 7. 
    An otherwise healthy patient who has just received a prosthetic aortic valve develops postoperative fever. Blood cultures are done and she is placed on broad-spectrum antibiotics. Two days later she is still febrile and clinically deteriorating. Which of the following organisms is the most probable etiologic agent?
    • A. 

      Actinomyces israelii

    • B. 

      Candida albicans

    • C. 

      Histoplasma capsulatum

    • D. 

      Nocardia asteroides

    • E. 

      Trichophyton rubrum

  • 8. 
    An 18-year-old college student presents to the student health center complaining of a sore throat and fever. He describes feeling tired for the past few days and reports a loss of appetite. On examination, he has pharyngitis with cervical lymphadenopathy. Blood tests reveal lymphocytosis and the presence of heterophil antibodies. Which of the following best describes the virus responsible for his illness?
    • A. 

      Double-stranded, enveloped DNA virus

    • B. 

      Double-stranded, nonenveloped DNA virus

    • C. 

      Single-stranded, enveloped RNA virus

    • D. 

      Single-stranded, nonenveloped DNA virus

    • E. 

      Single-stranded, nonenveloped RNA virus

  • 9. 
    A 4-year-old African child develops an infection with Chlamydia trachomatis. How does infection with this organism cause blindness?
    • A. 

      Cataract formation

    • B. 

      Hemorrhage into the anterior chamber

    • C. 

      Hemorrhage into the posterior chamber

    • D. 

      Retinal detachment

    • E. 

      Scarring of the cornea

  • 10. 
    A mother brings her 3-year-old boy into the emergency room because he has developed a harsh, "barking"  cough with hoarseness. The virus responsible for this child's illness belongs to which of the following families?  
    • A. 

      Papovavirus

    • B. 

      Paramyxovirus

    • C. 

      Parvovirus

    • D. 

      Picornavirus

    • E. 

      Poxvirus

  • 11. 
    A 24-year-old man presents with fever, rash, a mild headache, and a sore throat. He denies HIV risk factors, although he is sexually active. On examination, his temperature is 100.8°F and his pulse is 90/min. There is a diffuse, erythematous, maculopapular rash over most of his body. Generalized adenopathy is appreciated, and photophobia is noted when funduscopic examination is attempted. If this man is not treated, which of the following changes in his serologic status will most likely occur?
    • A. 

      The FTA-ABS titer would fall

    • B. 

      The FTA-ABS titer would rise

    • C. 

      The VDRL titer would fall

    • D. 

      The VDRL titer would rise

    • E. 

      Both FTA-ABS and VDRL would fall

    • F. 

      Both FTA-ABS and VDRL would rise

  • 12. 
    A 22-year-old male military recruit complains of a headache and stiff neck. He is examined, blood is drawn, and a lumbar puncture performed. The glucose in the CSF is 100 mg/dL and the serum glucose is 120 mg/dL. The CSF shows 3 lymphocytes and 0 neutrophils/microliter. Which of the following conclusions concerning the interpretation of these findings is most accurate?
    • A. 

      The CSF glucose level suggests bacterial meningitis

    • B. 

      The CSF glucose level suggests viral meningitis

    • C. 

      The lymphocytes suggest bacterial meningitis

    • D. 

      The lymphocytes suggest viral meningitis

    • E. 

      There is no evidence for meningitis

  • 13. 
    Autopsy of a 23-year-old male victim of a motor vehicle accident reveals a small cluster of caseating granulomas in the right lung just above the interlobar fissure and similar granulomas in the hilar lymph nodes. Acid-fast staining demonstrates acid-fast bacilli within these lesions. No other lesions were found in the remaining organs and systems. Which of the following is the most accurate interpretation of these findings?
    • A. 

      Cavitary tuberculosis

    • B. 

      Ghon complex

    • C. 

      Histoplasma infection

    • D. 

      Miliary tuberculosis

    • E. 

      Remote healed tuberculosis

  • 14. 
    A 53-year-old woman with diarrhea and lower abdominal pain of 3 days duration comes to her physician after failing to relieve her symptoms with various home remedies. She denies any recent travel and states that there is blood and pus in her stool. Fecal cultures yield several flagellated, curved, oxidase-positive, gram-negative rods.    The organism isolated is most likely
    • A. 

      Campylobacter jejuni

    • B. 

      Escherichia coli

    • C. 

      Salmonella

    • D. 

      Shigella

    • E. 

      Vibrio cholera

  • 15. 
    A hospitalized patient develops dysuria and suprapubic pain and is treated with ciprofloxacin. What is the mechanism of action of this antibiotic?
    • A. 

      It inhibits dihydrofolate reductase

    • B. 

      It inhibits DNA-dependent RNA polymerase

    • C. 

      It inhibits protein synthesis by binding to the 30s ribosomal subunit

    • D. 

      It inhibits protein synthesis by binding to the 50s ribosomal subunit

    • E. 

      It inhibits topoisomerase II (DNA gyrase)

  • 16. 
    Cefuroxime is believed to exert its antibacterial effect by which of the following mechanisms?
    • A. 

      Competitive inhibition of para-aminobenzoic acid (PABA)

    • B. 

      Inhibition of bacterial cell wall synthesis

    • C. 

      Inhibition of DNA-gyrase

    • D. 

      Irreversible binding to the 30S subunit of bacterial ribosomes

    • E. 

      Irreversible binding to the 50S subunit of bacterial ribosomes

  • 17. 
    A 19-year-old college student presents to the student health clinic complaining of weakness, malaise, and a chronic cough. He has a fever of 100 degrees F and a dry cough; no sputum can be obtained for laboratory analysis, so a bronchial lavage is performed and the washings are submitted to the laboratory. The laboratory reports that the organism is "slow-growing." Serodiagnosis reveals Strep MG agglutinins in the patient's serum. Which of the following organisms is the most likely cause of this student's illness?
    • A. 

      Klebsiella pneumoniae

    • B. 

      Mycoplasma pneumoniae

    • C. 

      Parainfluenza virus

    • D. 

      Respiratory syncytial virus

    • E. 

      Streptococcus pneumoniae

  • 18. 
    An 8-month-old baby presents to the emergency room with a 1-day history of poor feeding and generalized weakness. The mother states that she often feeds the baby honey to pacify her. The toxin responsible for this presentation works by which of the following mechanisms?
    • A. 

      It blocks the release of acetylcholine from the nerve terminal

    • B. 

      It blocks the release of inhibitory neurotransmitters such as glycine and GABA

    • C. 

      It has a subunit that inactivates an elongation factor by ADP-ribosylation

    • D. 

      It is a lecithinase

    • E. 

      It stimulates guanylate cyclase

  • 19. 
    A 7-year-old boy presents to the pediatrician because his mother noticed a "smoky" color to his urine. Upon questioning the mother, it is revealed that the child suffered a sore throat several weeks ago that was left untreated. Physical examination reveals hypertension and mild generalized edema. Urinalysis is significant for red blood cell casts. Which of the following accurately describes the microorganism responsible for this child's illness?
    • A. 

      It causes alpha-hemolysis on blood agar

    • B. 

      It is catalase positive

    • C. 

      It is coagulase positive

    • D. 

      It is sensitive to bacitracin

    • E. 

      It is sensitive to optochin

  • 20. 
    An AIDS patient with clinical pneumonia has a bronchoalveolar lavage that demonstrates small, "hatshaped" structures in alveoli that are about the size of an erythrocyte and stain with silver stains. The microorganism involved is most likely which of the following?
    • A. 

      Aspergillus fumigatus

    • B. 

      Blastomyces dermatitidis

    • C. 

      Mycobacterium avium

    • D. 

      Mycobacterium tuberculosis

    • E. 

      Pneumocystis carinii

  • 21. 
    Which of the following viruses is capable of replication in enucleated cells?
    • A. 

      Adenovirus

    • B. 

      Cytomegalovirus

    • C. 

      Influenza virus

    • D. 

      JC virus

    • E. 

      Poliovirus

  • 22. 
    A 47-year-old man with a history of sickle cell disease has had numerous hospitalizations requiring the placement of intravenous lines. The patient has poor peripheral venous access, and a catheter is placed in the right subclavian vein. The patient subsequently develops right arm discomfort and swelling and a temperature of 40.1 degrees C with chills. Multiple blood cultures are taken, and gram-positive cocci are isolated. The organism is catalase positive and grows on mannitol salt agar, but does not turn the agar yellow; the colonies are gamma-hemolytic on a sheep blood agar plate. Which of the following organisms is the most likely cause of this patient's symptoms?
    • A. 

      Enterococcus faecalis

    • B. 

      Staphylococcus aureus

    • C. 

      Staphylococcus epidermidis

    • D. 

      Streptococcus agalactiae

    • E. 

      Streptococcus pyogenes

  • 23. 
    Microbiologic studies on a gram-positive coccus isolated from a skin abscess demonstrate a positive catalase test and a positive coagulase test. This is most consistent with which of the following organisms?
    • A. 

      S. aureus

    • B. 

      S. epidermidis

    • C. 

      S. pneumoniae

    • D. 

      S. pyogenes

    • E. 

      S. saprophyticus

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