Which stain is frequently used to highlight the capsule of certain encapsulated fungi?

• A. Mucicarmine
• B. Gram
• C. Giemsa
• D. PAS

Answer: (A)

The capsule of encapsulated fungi is made of polysaccharides, so a stain that binds acidic polysaccharides will highlight that capsule. Mucicarmine specifically binds the capsule’s polysaccharides and stains it a distinct pinkish-red, causing the capsule to stand out clearly around the fungal cell in tissue sections. This makes it especially useful for identifying organisms like Cryptococcus neoformans, where the capsule is a key diagnostic feature. Other stains have different targets—Gram stains bacteria and general cell walls, Giemsa highlights cytoplasm and nuclei, and PAS stains broad polysaccharides but isn’t as capsule-specific as mucicarmine.