Auramine-Rhodamine Fluorescence Technique detects TB or other acid-fast organisms and yields what appearance for the organisms?

• A. Reddish yellow fluorescence
• B. Blue fluorescence
• C. Green fluorescence
• D. No fluorescence

Answer: (A)

Auramine-Rhodamine fluorescence makes acid-fast organisms, like Mycobacterium tuberculosis, stand out with a bright reddish-yellow glow under the fluorescence microscope. The dyes bind to the high mycolic acid content of the cell walls, so the bacilli emit a strong yellow-to-orange fluorescence against a dark background, which also helps screening many fields quickly. Blue fluorescence would not be expected with this stain, and green fluorescence or no fluorescence would indicate different dyes or issues with staining.