Which fungal stain is a fluorescence technique?

• A. PAS reaction
• B. Auramine-rhodamine
• C. Gridley stain
• D. Grocott

Answer: (B)

Fluorescent staining uses dyes that emit light when excited by a specific wavelength, so organisms stand out brightly under a fluorescence microscope. The dye combination auramine-rhodamine is a fluorochrome stain, designed to glow when viewed with the appropriate light, making it the staining method among these options that relies on fluorescence. The PAS reaction is colorimetric, producing a magenta color with Schiff reagent under standard light. Gridley stain is also a color-based stain used in light microscopy, not fluorescence. Grocott’s methenamine silver provides a black deposit on fungal walls with silver staining, again under standard light. So the fluorescent technique in this set is auramine-rhodamine.