USMLE Microbiology Prt 5

25 Questions | Total Attempts: 336

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USMLE Microbiology Prt 5 - Quiz

Questions and Answers
  • 1. 
    An 8-year-old boy is taken to a pediatrician because of behavioral changes, mild intellectual deterioration, and "laziness." Over the next several months the boy develops increasing clumsiness and periodic, involuntary, jerky movements every 3 to 6 seconds. Visual deterioration is apparent upon visual field testing, and optic atrophy is evident on funduscopic examination. Cerebrospinal fluid studies do not show significant pleocytosis, but oligoclonal bands of IgG are present on CSF electrophoresis. The electroencephalogram shows periodic discharges that are synchronous with the periods of myoclonus. Computed tomography (CT) of the head shows low-density white matter lesions and cerebral atrophy. At the age of 10, the boy dies. Prior infection with which of the following agents was probably related to the patient's condition?
    • A. 

      Measles virus

    • B. 

      Mumps virus

    • C. 

      Papilloma virus

    • D. 

      Poliovirus

    • E. 

      Varicella

  • 2. 
    A 57-year-old man presents with an episode of shaking chills the previous night. He has now developed right-sided pleuritic chest pain, fever, sweats, malaise, purulent sputum, and mild hemoptysis. On examination, the patient is diaphoretic but alert, with right basilar rales. Chest X-ray films show a right lower lobe infiltrate with blunting of the right costophrenic angle. Why is this patient's sputum filled with pus?
    • A. 

      Teichoic acids and peptidoglycan are chemotactic for neutrophils

    • B. 

      The capsule of the causative agent is chemotactic for neutrophils

    • C. 

      The causative agent is an intracellular organism

    • D. 

      The causative agent is beta hemolytic

    • E. 

      The organism produces an IgA protease

  • 3. 
    A 48-year-old waitress presents to a physician with malaise, loss of appetite, nausea, moderate fever, and jaundice. Laboratory tests indicate a marked increase in serum transaminases. Serology for hepatitis viruses is performed and indicates positive results for the presence of HBsAg, HBc IgM antibody, and HCV antibody. Antibody tests for HBsAb and HAV are negative. The results indicate:
    • A. 

      A dual infection of HBV and HAV

    • B. 

      Chronic hepatitis A infection

    • C. 

      Chronic hepatitis B infection

    • D. 

      Hepatitis C infection

    • E. 

      The presence of an acute HBV infection

  • 4. 
    An 8-year-old girl is brought to the pediatrician for a severe sore throat. The pediatrician prescribes penicillin and sends the girl home. Later that day, she develops a diffuse maculopapular rash, shortness of breath, and wheezing. Her parents take her to the emergency department, where she is diagnosed with anaphylaxis and treated successfully with epinephrine. Three months later, the girl has dysuria and urinary frequency. Urine Gram's stain reveals numerous gram-negative rods. Which of the following antibiotics could be safely given to this patient?
    • A. 

      Ampicillin

    • B. 

      Aztreonam

    • C. 

      Cefoperazone

    • D. 

      Cephalexin

    • E. 

      Methicillin

    • F. 

      Oxacillin

    • G. 

      Ticarcillin

  • 5. 
    A 38-year-old woman with a history of multiple sexual partners is most at risk for which of the following?
    • A. 

      Bladder carcinoma

    • B. 

      Cervical carcinoma

    • C. 

      Endometrial carcinoma

    • D. 

      Ovarian carcinoma

    • E. 

      Rectal carcinoma

  • 6. 
    A psychotic, indigent man with a history of multisubstance abuse has been involuntarily hospitalized for 1 week. Because of persistent diarrhea, stools are sent for ova and parasites, revealing numerous granular, spherical, thin-walled cysts measuring 10-20 μm in diameter. Trichrome stains show up to four nuclei in most of the cysts. These finding are consistent with an infection by which of the following organisms?
    • A. 

      Cryptosporidium parvum

    • B. 

      Dientamoeba fragilis

    • C. 

      Entamoeba histolytica

    • D. 

      Giardia lamblia

    • E. 

      Isospora belli

  • 7. 
    An autopsy is performed on a man who suddenly began vomiting voluminous quantities of blood and exsanguinated. The man's stomach is presented in the accompanying photograph. Which of the following organisms is most likely implicated in the pathogenesis of this disease?
    • A. 

      Cryptosporidium parvum

    • B. 

      Entamoeba histolytica

    • C. 

      Escherichia coli

    • D. 

      Helicobacter pylori

    • E. 

      Mycobacterium tuberculosis

  • 8. 
    A 34-year-old HIV-positive man without previous opportunistic infections presents complaining of dyspnea with daily activity. He states that he has had a mild cough and fever but denies having had chills, sputum production, or chest discomfort. Physical examination is remarkable for oral thrush and a few small, nontender cervical lymph nodes. A chest x-ray film reveals bilateral interstitial infiltrates, and bronchoalveolar lavage reveals small silver-staining cysts. In which other patient population in the U.S. is this organism a frequent cause of a life-threatening pneumonia?
    • A. 

      Bone marrow transplant patients

    • B. 

      Hospitalized adults on antibiotic therapy

    • C. 

      Late-term pregnant women

    • D. 

      Normal adults in periods of stress

    • E. 

      Premature infants

    • F. 

      Preschool children

    • G. 

      Sexually active adolescents

    • H. 

      Third-trimester fetuses

  • 9. 
    A 16-year-old high school cheerleader presents with low grade fever, pleuritic pain and a non-productive cough. Her serum agglutinates Streptococcus salivarius strain MG. Therapy should include which of the following?
    • A. 

      Ampicillin

    • B. 

      Erythromycin

    • C. 

      Oxygen and external cooling

    • D. 

      Penicillin G

    • E. 

      Ribavirin

  • 10. 
    A 24-year-old summer camp counselor complains of a severe headache and weakness. His condition rapidly deteriorates over a period of hours, and he is airlifted to a nearby hospital. A lumbar puncture is performed and a Gram's stain of spinal fluid reveals gram-negative diplococci. Infection with this organism is also associated with which of the following?
    • A. 

      Dysentery

    • B. 

      Erythema chronicum migrans

    • C. 

      Myocarditis

    • D. 

      Ophthalmia neonatorum

    • E. 

      Waterhouse-Friderichsen syndrome

  • 11. 
    A patient is referred to a neurologist because of ataxia. Neurological examination reveals a loss of proprioception and a wide-based, slapping gate. Magnetic resonance imaging reveals degeneration of the dorsal columns and dorsal roots of the spinal cord. Which of the following organisms is most likely to have caused this pattern of damage?
    • A. 

      Haemophilus influenzae

    • B. 

      Herpes simplex I

    • C. 

      Neisseria gonorrhoeae

    • D. 

      Neisseria meningitidis

    • E. 

      Treponema pallidum

  • 12. 
    A 38-year-old AIDS patient presents to the clinic complaining of nausea, occasional vomiting and "bumps" on his groin. On physical examination, multiple, nontender, pedunculated reddish purple nodules in the inguinal and perirectal areas are observed. The patient's liver is palpable 8 cm below the right costal margin. Routine laboratory tests are unremarkable except for an alanine aminotransferase level of 58 and alkaline phosphatase of 90. He denies any foreign travel, but has two pet cats. Which of the following is the most likely cause of this patient's infection?
    • A. 

      Bartonella henselae

    • B. 

      Human papillomavirus

    • C. 

      Molluscum contagiosum virus

    • D. 

      Rickettsia prowazekii

    • E. 

      Treponema pallidum

  • 13. 
    A poor African community is experiencing an epidemic of severe hepatitis. The mortality among pregnant women is particularly high. Which of the following viruses is the most likely cause of the epidemic?
    • A. 

      Cytomegalovirus (CMV)

    • B. 

      Hepatitis A virus (HAV)

    • C. 

      Hepatitis C virus (HCV)

    • D. 

      Herpes simplex I

    • E. 

      Hepatitis E virus (HEV)

  • 14. 
    A medical worker has a needle-stick accident involving an empty syringe that had been previously used on a patient with a known hepatitis B infection. Which of the following is the most probable outcome for the medical worker?
    • A. 

      Acute hepatitis followed by recovery

    • B. 

      "Healthy" carrier

    • C. 

      Persistent infection followed by recovery

    • D. 

      Persistent infection progressing to chronic hepatitis

    • E. 

      Subclinical disease followed by recovery

  • 15. 
    A 2-day-old baby girl suddenly develops abdominal distention, progressive pallid cyanosis, and irregular respirations. The newborn also has "refused" to breast-feed for the past 18 hours. If the mother was treated for a serious infection with antibiotics for 14 days up to and including the day of delivery, which of the following medications did the mother most likely receive?
    • A. 

      Aztreonam

    • B. 

      Chloramphenicol

    • C. 

      Clindamycin

    • D. 

      Metronidazole

    • E. 

      Sulfamethoxazole/trimethoprim

  • 16. 
    A Brazilian immigrant is hired at a meat-packing plant, and undergoes an employment physical. Chest x-ray demonstrates a patchy, bilateral pneumonia and a lung mass, and he is referred to a specialist. Biopsy of the mass demonstrates fungal organisms with a few very distinctive "pilot's wheel" yeast forms. Which of the following is the most likely diagnosis?
    • A. 

      Blastomycosis

    • B. 

      Coccidioidomycosis

    • C. 

      Histoplasmosis

    • D. 

      Paracoccidioidomycosis

    • E. 

      Sporotrichosis

  • 17. 
    A British dairy farmer develops fever with chills, myalgias, headache, skin rash, and vomiting. He is quite ill and is hospitalized. Blood cultures demonstrate tightly coiled, thin, flexible spirochetes shaped like a Shepherd's crook. The spirochetes are easily cultured in serum-enriched nutrient agar. Which of the following organisms should be suspected?
    • A. 

      Brucella abortus

    • B. 

      Brucella melitensis

    • C. 

      Leptospira interrogans

    • D. 

      Pseudomonas mallei

    • E. 

      Pseudomonas pseudomallei

  • 18. 
    A patient presents to a physician with jaundice. Physical examination reveals a nodular, enlarged liver. CT of the abdomen shows a cirrhotic liver with a large mass. CT-guided biopsy of the mass demonstrates a malignant tumor derived from hepatic parenchymal cells. Infection with which of the following viruses would most likely be directly related to the development of this tumor?
    • A. 

      Epstein-Barr virus (EBV)

    • B. 

      Hepatitis B virus (HBV)

    • C. 

      Human herpesvirus type 8 (HHV 8)

    • D. 

      Human papillomavirus (HPV)

    • E. 

      Human T-lymphocyte virus (HTLV-1)

  • 19. 
    A 58-year-old alcoholic man with multiple dental caries develops a pulmonary abscess and is treated with antibiotics. Several days later, he develops nausea, vomiting, abdominal pain, and voluminous green diarrhea. Which of the following antibiotics is most likely responsible for this patient's symptoms?
    • A. 

      Chloramphenicol

    • B. 

      Clindamycin

    • C. 

      Gentamicin

    • D. 

      Metronidazole

    • E. 

      Vancomycin

  • 20. 
    A 7-year-old girl develops a fever, conjunctivitis, photophobia, and a cough. Her pediatrician notes white spots on a bright red background on the girl's buccal mucosa. Within days, a rash begins around the hairline, then spreads to the trunk and extremities. One week later, the child suddenly begins to convulse, and loses consciousness. She is taken to the emergency room, where involuntary movements and pupillary abnormalities are noted. Which of the following would most likely be seen on CNS biopsy?
    • A. 

      Demyelination of white matter of cerebral hemispheres with abnormal giant oligodendrocytes

    • B. 

      Perivenous microglial encephalitis with demyelination

    • C. 

      Phagocytosis of motor neurons in the spinal cord

    • D. 

      Severe hemorrhagic and necrotizing encephalitis of the temporal lobe with eosinophilic Cowdry type A inclusion in neurons and glia

    • E. 

      Small granulomas with central caseation in the meninges

  • 21. 
    A 65-year-old man presents with fever, severe headache, and nuchal rigidity. Physical examination in the emergency department shows a Glasgow coma score of 7. Lumbar puncture reveals cloudy cerebrospinal fluid (CSF) with 1200 neutrophils/mm3, elevated protein, and decreased glucose. Which of the following is the most probable etiologic agent of this condition?
    • A. 

      Arbovirus

    • B. 

      Herpesvirus

    • C. 

      Mycobacterium tuberculosis

    • D. 

      Neisseria meningitidis

    • E. 

      Streptococcus pneumoniae

  • 22. 
    A 12-year-old boy has a productive cough characterized by large volumes of foul-smelling sputum. Three years ago, the patient was diagnosed with pancreatic insufficiency, as evidenced by repetitive gastrointestinal symptoms of steatorrhea. After culture of the sputum, colorless, oxidase-positive colonies with a fruity aroma develop on the agar. The function of which of the following proteins is most likely inhibited by the bacteria responsible for this boy's infection?
    • A. 

      A CFTR protein lacking a phenylalanine in exon 10 at position 508

    • B. 

      A GTP-binding protein involved in the elongation step of protein synthesis

    • C. 

      A GTP-binding protein similar to the one coupled with α2-adrenergic receptors

    • D. 

      A GTP-binding protein similar to the one coupled with β-adrenergic receptors

    • E. 

      A phosphorylation-regulated chloride channel in the apical membrane of epithelial cells

  • 23. 
    During the asymptomatic latent phase of AIDS, the virus is actively proliferating, and can be found in association with
    • A. 

      B lymphocytes

    • B. 

      Follicular dendritic cells in lymph nodes

    • C. 

      Ganglion cells

    • D. 

      Oligodendrocytes

    • E. 

      Peripheral nerves

  • 24. 
    A viral organism was isolated from a painful blister on the lip of a teenage girl. The agent was found to double-stranded, linear DNA and was enveloped. The patient had a similar sore approximately 2 months ago. Which of the following is the most likely causative organism?
    • A. 

      Adenovirus

    • B. 

      Coxsackie virus

    • C. 

      Herpes simplex type 1 virus

    • D. 

      Herpes zoster virus

    • E. 

      Papilloma virus

  • 25. 
    A viral organism was isolated from a painful blister on the lip of a teenage girl. The agent was found to double-stranded, linear DNA and was enveloped. The patient had a similar sore approximately 2 months ago. Which of the following is the most likely causative organism?
    • A. 

      Adenovirus

    • B. 

      Coxsackie virus

    • C. 

      Herpes simplex type 1 virus

    • D. 

      Herpes zoster virus

    • E. 

      Papilloma virus

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