Immunology USMLE Step 1 Practice Question
A 42-year-old man with AIDS (CD4 count 35 cells/μL) presents with progressive headache, fever (38.9°C), and blurred vision for 2 weeks. Vital signs show BP 118/76, HR 98, RR 16, SpO2 98% on room air. Lumbar puncture reveals opening pressure 32 cm H₂O with elevated protein (180 mg/dL) and normal glucose. India ink staining of cerebrospinal fluid demonstrates round budding yeast with thick polysaccharide capsule. No focal neurologic deficits noted. Which virulence factor most directly contributes to this organism's pathogenicity?
Answer choices
- ADimorphic growth in soil and tissue
- BProduction of diphtheria like exotoxin
- CAntigenic variation of surface glycoproteins
- DPolysaccharide capsuleCorrect answer
- EActin based intracellular motility
- FMelanin production by laccase enzyme protecting against oxidative killing
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