Which organism is stained by the Auramine-rhodamine method?

• A. Mycobacterium tuberculosis
• B. Staphylococcus aureus
• C. Candida albicans
• D. Pneumocystis jiroveci

Answer: (A)

This staining method is a fluorochrome acid-fast stain used to detect acid-fast bacilli, particularly mycobacteria. Mycobacteria have a waxy, mycolic-acid–rich cell wall that retains the dye after acid-alcohol decolorization, so they glow brightly under blue (fluorescent) light when stained with Auramine-O and rhodamine. That makes organisms like Mycobacterium tuberculosis stand out as bright, yellow-green rods against a dark background, enabling rapid screening of samples such as sputum. The other organisms listed—Staphylococcus aureus, Candida albicans, and Pneumocystis jiroveci—do not have the same acid-fast cell walls and do not retain this dye, so they do not fluoresce with this method.