Cryptococcus neoformans is an encapsulated yeast that causes meningitis primarily in immunocompromised patients. Which virulence factor is detected by the India ink preparation and also by the latex agglutination test in CSF?
- A Melanin (produced by laccase enzyme)
- B Glucuronoxylomannan (GXM) polysaccharide capsule ✓
- C Mannoprotein (MP98) surface antigen
- D Phospholipase B (PLB) enzyme
Explanation
The glucuronoxylomannan (GXM) polysaccharide capsule is the major virulence factor of C. neoformans. India ink staining of CSF reveals the large polysaccharide capsule as a negative (unstained) halo around the yeast cell. The latex agglutination test (cryptococcal antigen, CrAg) detects shed GXM antigen in CSF or serum with >95% sensitivity in cryptococcal meningitis; it is the standard diagnostic test. Melanin (produced by laccase from dopamine in CNS) scavenges free radicals but is not detected by these tests. Mannoprotein and PLB are additional virulence factors not used in routine diagnosis.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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