USMLE Microbiology Prt 6

25 Questions | Total Attempts: 263

SettingsSettingsSettings
USMLE Quizzes & Trivia

Questions and Answers
  • 1. 
    Which of the following is a feature of gram-positive bacteria rather than gram-negative bacteria?
    • A. 

      Lipid A-containing lipopolysaccharide

    • B. 

      Lipoprotein in periplasmic space

    • C. 

      Outer membrane

    • D. 

      Peptidoglycan in periplasmic space

    • E. 

      Thick peptidoglycan cell wall

  • 2. 
    A mailman gets a severe bite wound from a pit bull guarding a junkyard. The wound is cleansed and he receives a booster injection of tetanus toxoid and an injection of penicillin G. Several days later, the wound is inflamed and purulent. The exudate is cultured on blood agar and yields gram-negative rods. Antibiotic sensitivity tests are pending. The most likely agent to be isolated is
    • A. 

      Bartonella henselae

    • B. 

      Brucella canis

    • C. 

      Clostridium tetani

    • D. 

      Pasteurella multocida

    • E. 

      Toxocara canis

  • 3. 
    The World Health Organization identifies an alarming increase in hospital admissions worldwide attributable to a new and unexpected serotype of influenza A virus. The biological attribute of influenza A virus, which allows the sudden appearance of dramatically new genetic variants, is also present in a limited number of other viral families. Which of the following viruses also possesses this biological attribute?
    • A. 

      Coronavirus

    • B. 

      HIV

    • C. 

      Measles virus

    • D. 

      Rabies virus

    • E. 

      Rotavirus

    • F. 

      Rubella virus

    • G. 

      St. Louis encephalitis virus

  • 4. 
    A 1-week-old female infant with symptoms of vomiting and anorexia has a temperature of 102° F. A bulging fontanel is noted on physical examination. The most likely agent is
    • A. 

      Haemophilus influenzae type b

    • B. 

      Listeria monocytogenes

    • C. 

      Neisseria meningitidis

    • D. 

      Staphylococcus aureus

    • E. 

      Streptococcus agalactiae

  • 5. 
    A 7-month-old child presents with a 4-day history of fever, deepening cough, and dyspnea. A chest x-ray 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 culture. The most appropriate therapy includes administration of which of the following drugs?
    • A. 

      Acyclovir

    • B. 

      Ganciclovir

    • C. 

      Ribavirin

    • D. 

      Trifluorothymidine

    • E. 

      Zidovudine

  • 6. 
    A 6-year-old boy presents to the pediatric clinic with fever and earache. He has just finished an unsuccessful course of amoxicillin. On physical exam, his right tympanic membrane appears injected. Which of the following antimicrobials would be most appropriate to prescribe for this patient?
    • A. 

      Amphotericin B

    • B. 

      Bacitracin

    • C. 

      Cefaclor

    • D. 

      Erythromycin

    • E. 

      Sulfamethoxazole

  • 7. 
    A previously healthy 18-month-old girl is brought to the office with 2 days of irritability, poor appetite, and pulling at her left ear. She has no known allergies, and her vaccinations are up-to-date. On examination, the child's temperature is 102.8 F. She is easily consoled by the mother and moves her neck spontaneously without discomfort. There is a clear discharge from the nares. The left tympanic membrane is erythematous, dull, and bulging. Which of the following virulence factors is generally absent in the strains of the causative organism that produce otitis media, compared with those that produce epiglottitis or meningitis?
    • A. 

      β-Lactamase

    • B. 

      IgA protease

    • C. 

      Lipopolysaccharide

    • D. 

      Nonpilus adhesins

    • E. 

      Pili

    • F. 

      Pneumolysin

    • G. 

      Polyribitol phosphate

  • 8. 
    Which of the following organisms is most likely to be implicated as a cause of urethritis that persists after antibiotic therapy for gonorrhea?
    • A. 

      Actinomyces

    • B. 

      Chlamydia

    • C. 

      Mycobacteria

    • D. 

      Nocardia

    • E. 

      Rickettsia

  • 9. 
    Which of the following is more frequently associated with Klebsiella pneumoniae than with Pseudomonas aeruginosa?
    • A. 

      Artificial ventilation

    • B. 

      Cystic fibrosis

    • C. 

      Diabetes mellitus

    • D. 

      Green-colored sputum

    • E. 

      Upper lobe cavitation

  • 10. 
    A 65-year-old man develops a vesicular rash localized to a narrow circumferential band on one side of his chest. The rash is very painful, and the vesicles are confluent with some ulceration. No other significant findings are demonstrated on physical examination. Which of the following diagnoses is most likely to be correct?
    • A. 

      Chicken pox

    • B. 

      Herpes simplex I infection

    • C. 

      Herpes simplex II infection

    • D. 

      Measles

    • E. 

      Shingles

  • 11. 
    A 35-year-old woman presents to her gynecologist because of vaginal itchiness and discharge. Pelvic examination demonstrates abundant white, curdy material in the vagina. Microscopic examination of the material demonstrates fungal hyphae and yeast forms. Which of the following systemic diseases can predispose for this condition?
    • A. 

      Crohn's disease

    • B. 

      Diabetes mellitus

    • C. 

      Disseminated gonococcal infection

    • D. 

      Rheumatoid arthritis

    • E. 

      Systemic lupus erythematosus

  • 12. 
    A 23-year-old woman presents to the emergency room with pelvic pain. A Gram's stain of her cervical discharge reveals multiple polymorphonuclear leukocytes, but none contain gram-negative diplococci. Which of the following statements best describes the two organisms that most commonly cause this disorder?
    • A. 

      Both are unlikely to recur because of acquired cell mediated immunity

    • B. 

      Both are unlikely to recur because of antibody mediated immunity

    • C. 

      Both induce endocytosis by epithelial cells

    • D. 

      Both are obligate intracellular parasites

    • E. 

      Both respond to beta-lactam antibiotics

  • 13. 
    While playing in the park, an 8-year-old girl is bitten in the leg by a neighbor's cat. She presents the next day with fever and bone pain localized to her right calf. X-ray reveals a lytic lesion of the right tibia. Results of the bone culture are pending. You expect the infecting organism to be
    • A. 

      Brucella melitensis

    • B. 

      Eikenella corrodens

    • C. 

      Francisella tularensis

    • D. 

      Pasteurella multocida

    • E. 

      Yersinia pestis

  • 14. 
    A 6-week-old infant is brought to the emergency room with a 10-day history of coughing and choking spells. The white blood cell count is elevated with 80% lymphocytes. The child is gasping for breath, experiencing paroxysms of coughing, and vomits twice in the examination room. Encapsulated, gram-negative rods grow out on Bordet-Gengou media. Which of the following microorganisms is the likely cause of these symptoms?
    • A. 

      Bordetella pertussis

    • B. 

      Haemophilus influenzae type b

    • C. 

      Klebsiella pneumoniae

    • D. 

      Legionella pneumophila

    • E. 

      Mycoplasma pneumoniae

  • 15. 
    A patient is admitted to a psychiatric hospital after having been picked up by the police for making inappropriate sexual advances. A detailed psychiatric interview demonstrates deficits in memory, insight, judgement, personal appearance, and social behavior. The patient is witnessed experiencing a possible epileptic seizure. Over a period of several years, motor findings also develop, including relaxed, but expressionless facies, tremor, dysarthria, and pupillary abnormalities. Which of the following tests performed on his cerebrospinal fluid would most likely be diagnostic?
    • A. 

      CSF glucose

    • B. 

      FTA-ABS

    • C. 

      Gram's stain

    • D. 

      Lymphocyte count

    • E. 

      Neutrophil count

  • 16. 
    The electron transport system of Neisseria is located on which of the following structures?
    • A. 

      Cytoplasmic membrane

    • B. 

      Mesosome

    • C. 

      Mitochondria

    • D. 

      Nuclear membrane

    • E. 

      Polyribosome DNA aggregates

  • 17. 
    A Pap smear from a 30-year-old woman demonstrates protozoal parasites. These organisms are likely to be
    • A. 

      Cryptosporidium parvum

    • B. 

      Entamoeba histolytica

    • C. 

      Giardia lamblia

    • D. 

      Isospora belli

    • E. 

      Trichomonas vaginalis

  • 18. 
    A previously healthy European child who had been diving into a lake develops meningoencephalitis. The disease is rapidly fatal, despite aggressive medical therapy. Which of the following organisms is most likely to be responsible for this child's illness?
    • A. 

      Acanthamoeba sp.

    • B. 

      Balantidium coli

    • C. 

      Entamoeba histolytica

    • D. 

      Giardia lamblia

    • E. 

      Naegleria fowleri

  • 19. 
    Which of the following microorganisms is an obligate aerobe?
    • A. 

      Bacteroides fragilis

    • B. 

      Clostridium perfringens

    • C. 

      Escherichia coli

    • D. 

      Mycobacterium tuberculosis

    • E. 

      Pseudomonas aeruginosa

  • 20. 
    A sexually active 18-year-old woman presents with a fever of 102 F for the past 24 hours and lower abdominal pain and anorexia for the past 5 days. On physical examination, there is generalized tenderness of the abdomen, and the cervix is erythematous with motion tenderness. There is no rash nor any lesions on the external genitalia.A smear of the odorless cervical discharge contains sloughed epithelial cells and scant neutrophils. Which of thefollowing would likely be found in the exudate?
    • A. 

      A naked, icosahedral double-stranded circular DNA virus

    • B. 

      Iodine-staining intraepithelial inclusion bodies

    • C. 

      Intraneutrophilic gram-negative diplococci

    • D. 

      Intranuclear "owl's eye" inclusion bodies

    • E. 

      Lactose-fermenting gram-negative bacilli

    • F. 

      Pear-shaped flagellated protozoa

    • G. 

      Pleomorphic, gram-negative rods

    • H. 

      Spirochetes on dark-field microscopy

  • 21. 
    Which of the following types of viruses would be most likely to undergo an abrupt, major antigenic shift permitting reinfection of previously exposed individuals?
    • A. 

      Coxsackie viruses

    • B. 

      Hepadna viruses

    • C. 

      Herpesviruses

    • D. 

      Orthomyxoviruses

    • E. 

      Paramyxoviruses

  • 22. 
    A young mother takes her baby to the pediatrician for the first time. The doctor notices the infant's teeth have yellow discolorations. The antibiotic this mother most likely took during pregnancy
    • A. 

      Inhibits aminoacyl-tRNA binding

    • B. 

      Inhibits peptidyl transferase

    • C. 

      Interferes with cell wall synthesis

    • D. 

      Is a large, cyclic, lactone-ring structure

  • 23. 
    A 32-year-old man from Yuma, Arizona presents to a hospital with complaints of a 4-day history of fever, myalgias, and cough. He owns an automobile repair shop and had recently cleaned his garage, which was infested by mice. On physical examination, he is tachypneic and must use accessory respiratory muscles to breathe. Shortly following admission, he is intubated and diagnosed with adult respiratory distress syndrome. What underlying infection should be considered?
    • A. 

      California encephalitis

    • B. 

      Cytomegalovirus

    • C. 

      Hantavirus

    • D. 

      Poliovirus

    • E. 

      Rabies

  • 24. 
    A 27-year-old woman presents to the emergency department complaining of 10-12 episodes of nonbloody diarrhea per day for the past 2 days, along with severe abdominal cramps, nausea, vomiting, and a low-grade fever. She states that she just returned from a vacation to Mexico. While in Mexico, she did not drink any of the local water and ate only cooked foods and a few fresh salads. If fecal leukocytes are present, the patient should most likely be empirically treated with  
    • A. 

      Acyclovir

    • B. 

      Ciprofloxacin

    • C. 

      Mebendazole

    • D. 

      Quinine

    • E. 

      Tetracycline

  • 25. 
    A 7- year-old girl develops behavioral changes, and her performance in school begins to deteriorate. Several months later she develops a seizure disorder, ataxia, and focal neurologic symptoms. She is eventually quadriparetic, spastic, and unresponsive. Death occurs within a year. This patient may have had which of the following viral diseases at 1 year of age?
    • A. 

      Chickenpox

    • B. 

      German measles

    • C. 

      Measles

    • D. 

      Mumps

    • E. 

      Parvovirus B19

Back to Top Back to top