The auramine-rhodamine technique will demonstrate which organism?

• A. Mycobacterium tuberculosis
• B. Streptococcus pneumoniae
• C. Escherichia coli
• D. Pseudomonas aeruginosa

Answer: (A)

Auramine-rhodamine is a fluorescent acid-fast stain used to detect bacteria that have waxy, mycolic-acid–rich cell walls. These walls resist decolorization by acid alcohol, so acid-fast organisms glow brightly under a fluorescence microscope. Mycobacterium tuberculosis is demonstrated because it is acid-fast and will produce a strong fluorescent signal with this stain, making it a sensitive method for screening specimens like sputum for tuberculosis.

The other organisms listed do not have the same waxy cell-wall properties, so they are not acid-fast and will not fluoresce with this technique in the same way. They would be identified by other staining methods (for example, Gram staining) rather than auramine-rhodamine.