Coccidians

Cyclospora cayetanensis. Oocyst in fecal smear (acid-fast stain combined with iron hematoxylin stain, oil immersion). In some laboratories, fecal specimens are fixed in sodium acetate-acetic acid-formalin solution, which does not lend itself well to trichrome staining. With this fixative the stain of choice is iron hematoxylin, and when combined with an acid-fast stain, it is possible to examine smears for the presence of intestinal protozoa and intestinal coccidian oocysts at the same time. In this field, one sees a pink-staining Cyclospora oocyst against the gray-black background of iron hematoxylin.