Cryptococcus neoformans produces a unique virulence factor detected by India ink preparation of CSF in meningitis. This virulence factor is also detected serologically by latex agglutination. What is this factor?
- A Polysaccharide capsule (glucuronoxylomannan) ✓
- B Melanin in the cell wall
- C Urease enzyme
- D Phospholipase B
Correct answer: A. Polysaccharide capsule (glucuronoxylomannan)
Explanation
The polysaccharide capsule of Cryptococcus neoformans (composed primarily of glucuronoxylomannan, GXM) creates the characteristic halo/clear zone around the yeast cell in India ink preparations of CSF. Shed capsular antigen (cryptococcal antigen, CrAg) is detected in CSF and serum by latex agglutination or lateral flow assay, which is the most sensitive and specific test for cryptococcal meningitis. Melanin production (via laccase) is another virulence factor but is not the target of diagnostic latex agglutination.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.