Auramine-Rhodamine stained sections are typically observed with which microscope?

• A. Brightfield microscope
• B. Polarizing microscope
• C. Fluorescence microscope
• D. Electron microscope

Answer: (C)

Auramine-Rhodamine is a fluorescent fluorochrome stain used to detect acid-fast bacteria, such as Mycobacterium species. When bound to the organisms, the dyes are excited by blue light (or UV) and emit bright fluorescence, best seen with a fluorescence microscope equipped with the appropriate filters. This makes the organisms appear as vivid yellow–orange (often yellow-green) fluorescence against a dark background, which is why fluorescence microscopy is used. A brightfield microscope would not reveal the fluorescence, a polarizing microscope is for substances with birefringence, and an electron microscope is not compatible with fluorescent staining in routine practice.