Relevant Criteria for Detecting Microsporidia in Stool Specimens

Abstract

By using different staining techniques, 479 stool specimens from 212 diarrheic patients with AIDS were examined for microsporidian spores. Calcofluor fluorescence staining of 119 specimens revealed fluorescent ovoid structures of microsporidian size. Staining of these samples according to the method of Weber et al. (R. Weber, R. T. Bryan, R. L. Owen, C. M. Wilcox, L. Gorelkin, and G. S. Visvesvara, N. Engl. J. Med. 326:161–166, 1992) with trichrome produced six specimens with pinkish spores containing the characteristic microsporidian belt-like structure. The 6 specimens were processed for transmission electron microscopy, as were another 21 specimens which did not present the belt-like structure after trichrome staining but which looked highly suspicious after fluorescence staining. In these 21 samples, only fungal spores and, particularly, bacterial Clostridium spores were demonstrated, whereas in the 6 samples diagnosed positive after trichrome staining, the existence of microsporidia could be verified by electron microscopy. Based on our observations, we propose that the belt-like structure seen with the Weber stains in microsporidian spores corresponds to structures existing in priming-stage spores. The results suggest that routine microscopical fecal diagnosis for microsporidian infection should include a screening by fluorescence staining and, subsequently, a confirmatory viewing of fluorescence-positive samples after trichrome staining.

Encephalitozoon cuniculi: Grading the Histological Lesions in Brain, Kidney, and Liver during Primoinfection Outbreak in Rabbits

“…In this study, we assessed 80 rabbits from a severe outbreak of E. cuniculi in young rabbits. All our data strongly implicate this pathogen as the causative agent of disease, and the microorganism was identified by (1) the morphological features of the spores in the brain and the kidneys, using different stains [ 20 ]; (2) the histological injuries in the organs sampled [ 4 ]; (3) detection of spores in stools and urine using the MTB and CW staining techniques [ 21 ]; and (4) serological confirmation by CIA testing [ 22 ]. In this study, surprisingly all animals studied showed severe cerebral lesions compatible with E. cuniculi .…”

Practical Guidance for Clinical Microbiology Laboratories: Laboratory Diagnosis of Parasites from the Gastrointestinal Tract

“…Although regarded as a simple test to perform, there are some limitations. In screening 479 fecal specimens, Chioralia et al (133) detected 119 with fluorescent oval structures present, but only six were confirmed as Microsporidia by modified trichrome stain, with yeast cells and bacterial spores accounting for other suspect objects. Didier et al (125) also reported staining of yeasts but noted subtle differences in shape and color, with the cytoplasm in yeast cells staining an orange color.…”

“…Many laboratories still use traditional staining methods, such as the modified trichrome stain, for the detection of Microsporidia (113). These stains are challenging to interpret; therefore, diagnostic criteria have been developed and alternative staining methods (such as calcofluor white) used (133,260,261). Therefore, not surprisingly, a number of PCR-based assays have been developed.…”

Mammalian Microsporidiosis

“…For animals displaying clinical microsporidial disease (e.g., seizures), examination of urine, feces, or cerebrospinal fluid may yield an antemortem diagnosis of encephalitozoonosis. These clinical samples are often screened with a calcofluor white stain for chitin, and Encephalitozoon infection is confirmed with modified trichrome stain, immunofluorescent antibodies, polymerase chain reaction (PCR), transmission electron microscopy, or some combination of methods 23 , 39 , 81 , 93 , 145 . Light microscopic examination of tissue samples and the use of special stains will aid the pathologist in detecting infection and differentiating microsporidial infection from other common protozoal infections of animals (Table 2).…”