Which organism is demonstrated with Mayer mucicarmine stain?

• A. Cryptococcus neoformans
• B. Candida albicans
• C. Aspergillus fumigatus
• D. Histoplasma capsulatum

Answer: (A)

Mayer mucicarmine highlights polysaccharide capsules that contain acidic mucopolysaccharides. Cryptococcus neoformans has a prominent, mucicarmine-positive capsule, so the capsule stains bright pink/red around a relatively pale yeast cell. This capsule staining pattern is a classic way to identify cryptococcal organisms in tissue and differentiate them from other fungi that lack a mucicarmine-positive capsule. Candida albicans doesn’t have a capsule to highlight with this stain, Aspergillus fumigatus presents as hyphae rather than encapsulated yeast, and Histoplasma capsulatum appears as small intracellular yeasts without a mucicarmine-stained capsule.