Which feature aids detection of Cyclospora oocysts in stool due to a fluorescence property?

• A. Autofluorescence under UV light
• B. Gram stain positivity
• C. Acid-fast staining only
• D. Culturing on standard media

Answer: (A)

The feature being tested is the ability to detect Cyclospora oocysts by their inherent fluorescence under ultraviolet light. These oocysts contain substances in their wall that emit light when excited by UV, so they glow with a distinct autofluorescence when examined with a fluorescence microscope. This makes them stand out from debris in the stool without needing a special stain, which is why autofluorescence under UV light is the best clue for identifying them.

Gram staining doesn’t reliably reveal protozoan oocysts and isn’t specific for Cyclospora. Acid-fast staining can be helpful for some coccidia but is not consistently reliable for Cyclospora on its own. Culturing Cyclospora on standard media isn’t feasible, so it wouldn’t aid stool detection.