USMLE Microbiology Prt 7

25 Questions | Total Attempts: 269

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USMLE Quizzes & Trivia

Questions and Answers
  • 1. 
    A 55-year-old man returns from a vacation to the beach. While on vacation, he and his family consumed several meals consisting primarily of seafood, including lobster and raw oysters. Although the other members of his family did not get sick, he developed a bullous rash over his lower extremities, hypotension, and confusion. His past medical history is significant for liver disease and alcoholism. The most likely cause of this man's signs and symptoms is
    • A. 

      Aspergillus fumigatus

    • B. 

      Campylobacter jejuni

    • C. 

      Candida albicans

    • D. 

      Streptococcus (Group A)

    • E. 

      Vibrio vulnificus

  • 2. 
    A 24-year-old female has fever, malaise, and a dry, nonproductive cough. She also complains of headache, muscle aches, and leg pain. Lab 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

  • 3. 
    A Native American man is brought to a rural hospital in New Mexico. On arrival, he is unconscious with severe bronchopneumonia. Family members state that he suffered the sudden onset of chills, fever, and headache several days ago. One day later, the man complained of chest pain and difficulty breathing, and coughed up blood-tinged sputum. Chest x-ray reveals patchy infiltrates and segmental consolidation. Which of the following organisms is the most likely cause of this man's pneumonia?
    • A. 

      Brucella abortus

    • B. 

      Clostridium perfringens

    • C. 

      Francisella tularensis

    • D. 

      Listeria monocytogenes

    • E. 

      Yersinia pestis

  • 4. 
    An elderly patient has pneumococcal pneumonia. She has no known drug allergies. Which of the following antibiotics would be most appropriate?
    • A. 

      Chloramphenicol

    • B. 

      Cefotaxime

    • C. 

      Erythromycin

    • D. 

      Penicillin

    • E. 

      Vancomycin

  • 5. 
    A 30-year-old veterinarian visits her obstetrician for a first-trimester prenatal check-up. She has no complaints. Routine physical exam is significant only for mild cervical lymphadenopathy. She is prescribed spiramycin but is noncompliant. Her baby is born with hydrocephalus and cerebral calcifications. Which of the following organisms is most likely responsible?
    • A. 

      Isospora belli

    • B. 

      Leishmania donovani

    • C. 

      Plasmodium vivax

    • D. 

      Toxoplasma gondii

    • E. 

      Trypanosoma cruzi

  • 6. 
    A 30-year-old veterinarian on a cattle ranch presents with a 1-to-2-month history of malaise, chills, drenching malodorous sweats, fatigue, and weakness. He has anorexia and has lost 15 pounds. He has intermittent fevers that range up to 103 F (39.4 C). He complains of visual blurring. A physical examination reveals mild lymphadenopathy, petechiae, and a cardiac murmur consistent with aortic insufficiency. What is the most likely etiologic agent?
    • A. 

      Bacillus anthracis

    • B. 

      Brucella abortus

    • C. 

      Coccidioides immitis

    • D. 

      Erysipelothrix rhusiopathiae

    • E. 

      Trichinella spiralis

  • 7. 
    Six days after receiving several flea bites in a rat-infested shed in Southeastern New Mexico, a homeless 24-year-old-man develops fever, chills, and a rash that spreads from his abdomen to cover his extremities. He is seen at the hospital emergency department, where blood is drawn for analysis. Eight days later, the public health department reports the presence of antibody to one of the rickettsial group antigens. Which of the following is the most likely diagnosis?
    • A. 

      Endemic typhus

    • B. 

      Epidemic typhus

    • C. 

      Q fever

    • D. 

      Rocky Mountain spotted fever

    • E. 

      Scrub typhus

  • 8. 
    A 54-year-old diabetic patient reports to his physician's office complaining of an unresolved skin lesion on his foot. The lesion began several weeks ago as a blister and has since become a painful, erosive, expanding sore. On examination, the affected site is now 5 cm in diameter, with a black necrotic center and raised red edges. Which of the following toxins has a mechanism of action most similar to the toxin responsible for tissue damage in this patient?
    • A. 

      Anthrax toxin

    • B. 

      Botulinum toxin

    • C. 

      Cholera toxin

    • D. 

      Clostridium perfringens alpha toxin

    • E. 

      Diphtheria toxin

    • F. 

      Escherichia coli labile toxin

    • G. 

      Pertussis toxin

    • H. 

      Shigatoxin

    • I. 

      Streptococcal erythrogenic toxins

    • J. 

      Tetanus toxin

    • K. 

      Toxic shock syndrome toxin-1

  • 9. 
    An 18-year-old, previously healthy female 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 your 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 Quellung reaction

  • 10. 
    A 24-year-old woman presents with a 3-day history of fever, chills, chest pain, and cough productive of rust-colored sputum. Past medical history includes a splenectomy 1 year ago. A chest x-ray film indicates consolidation of the right lower lobe. Blood cultures are positive for α-hemolytic gram-positive diplococci. Immunity to the causative organism is based on
    • A. 

      Alternative complement pathway activation

    • B. 

      Antibody to an α-helical coiled fimbria

    • C. 

      IgA antibodies to C carbohydrate

    • D. 

      IgG antibodies to C carbohydrate

    • E. 

      IgG antibodies to a surface acidic polysaccharide

  • 11. 
    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 most likely the causative agent of his diarrhea?
    • A. 

      Chlamydia psittaci

    • B. 

      Entamoeba histolytica

    • C. 

      Salmonella spp.

    • D. 

      Staphylococcus aureus

    • E. 

      Yersinia enterocolitica

  • 12. 
    Bilateral tonsillectomy is performed on an otherwise healthy 11-year-old female with recurrent upper respiratory tract infections. On sectioning the tonsils, numerous small, yellow granules are noted. A granule crushed between two slides has a dense, gram-positive center and numerous branching filaments at the periphery. The granules are most likely composed of which of the following organisms?
    • A. 

      Actinomyces israelii

    • B. 

      Aspergillus fumigatus

    • C. 

      Blastomyces dermatitidis

    • D. 

      Candida albicans

    • E. 

      Corynebacteria diphtheriae

  • 13. 
    A patient with a cavitary lung lesion coughs up sputum that contains thin, acid-fast positive rods. Which of the following features would most likely be associated with these bacteria?
    • A. 

      Nutritional requirement for factors V and X

    • B. 

      Streptokinase

    • C. 

      Toxic shock syndrome toxin

    • D. 

      Visible under dark field illumination

    • E. 

      Waxy envelope

  • 14. 
    An 8-year-old boy is brought to the emergency room with a 3-day history of fever to 102 degrees F and abdominal pain. He also complains of pain in his right knee and right elbow. He was seen four weeks ago because of a sore throat and a rash. A throat culture performed at that time grew gram-positive cocci in chains. Amoxicillin was prescribed, but the boy's mother did not fill the prescription. On physical exam his temp is 101.7F, HR 96, and BP 100/60. Cardiac exam reveals a pansystolic blowing murmur heard best at the apex. His right elbow is tender on extension and flexion with mild swelling. Laboratory tests reveal a positive C-reactive protein, an ESR of 40 and a WBC of 22,000 with a left shift. EKG shows a prolonged PR interval. Which of the following tests would be positive for the microorganism responsible for this patient's illness?
    • A. 

      Catalase test

    • B. 

      Coagulase test

    • C. 

      Sensitivity to bacitracin

    • D. 

      Sensitivity to novobiocin

    • E. 

      Sensitivity to optochin

  • 15. 
    An immigrant from the Far East develops malaise, fever, and rigors, followed by upper right quadrant abdominal pain, vomiting, jaundice, and itching. His urine is dark and his feces are pale. Infestation with which of the following parasites is most strongly suggested by this patient's presentation?
    • A. 

      Clonorchis sinensis

    • B. 

      Enterobius vermicularis

    • C. 

      Plasmodium ovale

    • D. 

      Taenia solium

    • E. 

      Trypanosoma cruzi

  • 16. 
    A 38-year-old woman vacationing in Connecticut is bitten by a tick. She does not seek medical treatment and eventually develops chronic arthritis of the knee and hip joints and paralysis of the left facial muscles. A physical examination during the early stages of the disorder would most likely have revealed
    • A. 

      Aphthous ulcers in the mouth

    • B. 

      Erythema chronicum migrans

    • C. 

      Flaccid paralysis of limb flexors

    • D. 

      Purpuric lesions in a bathing trunk distribution

    • E. 

      Spastic paralysis of limb extensors

  • 17. 
    Global eradication of Lyme disease is unlikely because
    • A. 

      Borrelia burgdorferi can be maintained in nature indefinitely by a tick vector

    • B. 

      Borrelia burgdorferi is resistant to antibiotics and disinfectants

    • C. 

      Borrelia burgdorferi is resistant to environmental stresses

    • D. 

      Human disease may reactivate after the primary infection (Brill-Zinsser disease)

    • E. 

      Humans are the primary reservoir for Borrelia burgdorferi

    • F. 

      Because then nobody would be able to drink tequilla

  • 18. 
    A 54-year-old farmer in rural Pennsylvania presents to his physician with chronic cough. Chest x-ray demonstrates a mass lesion with hilar lymphadenopathy. Biopsy of the mass demonstrates multiple, tiny yeast forms within macrophages. Which of the following is the most likely diagnosis?
    • A. 

      Blastomycosis

    • B. 

      Coccidioidomycosis

    • C. 

      Histoplasmosis

    • D. 

      Paracoccidioidomycosis

    • E. 

      Sporotrichosis

  • 19. 
    Two weeks after birth, a neonate develops sepsis, skin vesicles, and conjunctivitis. Over the next several days, the baby's condition deteriorates with development of seizures, cranial nerve palsies, and lethargy. The baby dies approximately one week after onset of symptoms. Which of the following infectious agents would most likely cause this clinical presentation?
    • A. 

      Cytomegalovirus

    • B. 

      Herpes simplex

    • C. 

      Rubella

    • D. 

      Syphilis

    • E. 

      Toxoplasmosis

  • 20. 
    A one-week-old baby develops nuchal rigidity and fever. A lumbar puncture is performed and the cerebrospinal fluid demonstrates large numbers of neutrophils. Which of the following is the most likely causative agent?
    • A. 

      Coxsackievirus

    • B. 

      Escherichia coli

    • C. 

      Herpes virus

    • D. 

      Mycobacterium tuberculosis

    • E. 

      Neisseria meningitidis

  • 21. 
    A patient presents to a physician because of pain during defecation accompanied by blood in the stool. Physical examination demonstrates a large perianal mass. Pathologic examination of the rectal mass following resection demonstrates a condyloma in which transformation to frank carcinoma has occurred. Which of the following viruses would most likely be associated with these lesions?
    • A. 

      Epstein-Barr virus (EBV)

    • B. 

      Hepatitis B virus (HBV)

    • C. 

      Human herpesvirus type 8 (HHV8)

    • D. 

      Human papilloma virus (HPV)

    • E. 

      Human T-cell leukemia virus (HTLV-1)

  • 22. 
    A 23-year-old woman with a history of sickle cell disease presents with fever and severe bone pain localized to her left tibia. X-ray 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 a facultative intracellular parasite

    • B. 

      It is a nonmotile facultative anaerobe

    • C. 

      It is comma-shaped and sensitive to acidic pH

    • D. 

      It is motile and does not ferment lactose

    • E. 

      It is motile and oxidase positive

  • 23. 
    A 42-year-old Hispanic man is brought to the emergency room by ambulance after suffering a grand mal seizure at home. There is no history of recent illness, fever, headache, seizures, or head trauma. He drinks alcohol occasionally and denies any other drug use. The patient has been a resident of the United States for 15 years, but occasionally travels to his previous home in Honduras. Neurologic exam shows the patient to be alert and oriented. No focal abnormalities are noted. A CT scan of the head reveals multiple punctate calcifications, and two enhancing cystic lesions with surrounding edema. What is the most likely diagnosis?
    • A. 

      Amebiasis

    • B. 

      Cytomegalovirus infection

    • C. 

      Echinococcosis

    • D. 

      Neurocysticercosis

    • E. 

      Toxoplasmosis

  • 24. 
    Which of the following viruses produce 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

    • D. 

      Poliovirus

    • E. 

      Varicella zoster virus

  • 25. 
    A 40-year-old otherwise healthy gardener presents with several subcutaneous nodules on his right hand, where he had cut himself on rose thorns. Physical exam reveals several erythematous fluctuant lesions. Which of the following organisms is most likely responsible for his condition?
    • A. 

      Aspergillus

    • B. 

      Malassezia

    • C. 

      Onchocerca

    • D. 

      Rhizopus

    • E. 

      Sporothrix

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