Microscopy of 4 Pathogenic Enteric Protozoan Parasites: A Review

Abstract

Nonimmunological microscopy procedures for Giardia lamblia, Cryptosporidium species, Cyclospora cayetanensis, and microsporidia are reviewed. In addition to the unstained wet preparation and the routine trichrome stain of the “routine” parasitology, the Gram stain, various modifications of the trichrome stain, the modified carbol fuchsin acid-fast stain, and several fluorescent variations of the acid-fast stain are also covered. The now-extensive literature on the newer techniques of the heated safranin stain, the use of autofluorescence, and the use of fluorescent brighteners, such as calcofluor white and related compounds, are reviewed. Emphasis is placed on the importance of the microscopist being aware of reported variations in both the staining protocols and their results. With increasing use being made of fluorescence microscopy in examination of specimens for the oocysts of cyclospora and the spores of microsporidium, an understanding of the effect of both excitation and barrier filters on the observed results of the procedures is emphasized.