SGrade/USMLE Step 1/Bacteriology
Bacteriology Practice Questions
Staph, strep, clostridia, enterics, Pseudomonas, zoonoses, STIs, intracellular organisms, and resistance mechanisms.
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A 7-month-old infant is brought to the clinic with a history of fever, irritability, and decreased oral intake. Physical examination reveals bulging fontanelle and nuchal rigidity. Lumbar puncture shows Gram-positive lancet-shaped diplococci. The most important virulence factor contributing to this organism's ability to cause invasive disease is its:
Examiner's Design Intent
The NBME designed this question to test a student's ability to: 1) Identify a common, high-yield pathogen (*Streptococcus pneumoniae*) from a classic clinical vignette and Gram stain morphology. 2) Recall the *most impor…
A 72-year-old man with a history of diabetes and an indwelling urinary catheter develops a fever and chills. Blood cultures are drawn and grow Gram-positive cocci in clusters that are catalase-positive but coagulase-negative. The organism is sensitive to vancomycin. Which of the following virulence factors is most important for the pathogenesis of this infection in this patient?
Examiner's Design Intent
The NBME designed this question to test the precise identification of a common nosocomial pathogen (*S. epidermidis*) based on key laboratory results and to link that organism to its most important virulence factor in a …
A 45-year-old man presents with a painful abscess on his leg. Culture of the purulent material grows Gram-positive cocci in clusters that are catalase-positive and coagulase-positive. The isolate is found to be resistant to oxacillin and methicillin. Which of the following genetic mechanisms is primarily responsible for the antibiotic resistance observed in this organism?
Examiner's Design Intent
The NBME designed this question to test a student's ability to identify a high-yield pathogen (*Staphylococcus aureus*), recognize its specific resistance pattern (MRSA), and recall the precise genetic mechanism responsi…
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