Bacteriology USMLE Step 1 Practice Question
A 19-year-old college freshman living in dormitory housing presents with fever (39.2°C), severe headache, neck stiffness, and petechial rash. Vital signs show HR 118/min, RR 22/min, BP 105/68 mmHg, SpO2 98% on room air. Cerebrospinal fluid culture grows oxidase-positive gram-negative diplococci; CSF glucose is markedly decreased at 18 mg/dL. He denies recent antibiotic use. Which virulence factor primarily facilitates initial nasopharyngeal colonization by this organism?
Answer choices
- AAlpha toxin
- BExotoxin A
- CProtein A
- DIgA proteaseCorrect answer
- ECord factor
- FLipopolysaccharide (LPS) endotoxin
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.