Autofluorescence, which requires no stain, is recommended for identifying which of the following?

Autofluorescence is a property of certain organisms that allows them to be visualized under fluorescent microscopy without the need for external stains or dyes. Cyclospora cayetanensis, a coccidian parasite, is known for its ability to autofluoresce, which is particularly useful when identifying its oocysts in clinical samples. This characteristic enables microbiologists to detect the organism quickly and efficiently, especially in cases where staining methods may not be applied or might compromise the delicate structure of the oocyst.

In contrast, other options such as Entamoeba histolytica cysts, Toxoplasma gondii tachyzoites, and Dientamoeba fragilis trophozoites typically require specific stains for clear visualization under a microscope. These organisms do not exhibit autofluorescence to the same extent as Cyclospora, making them less suitable for identification via this method. The inability of those parasites to autofluoresce highlights the unique identification potential of Cyclospora cayetanensis through this non-invasive and straightforward approach.