Fluorescence techniques for diagnosing intestinal microsporidiosis in stool, enteric fluid, and biopsy specimens from acquired immunodeficiency syndrome patients with chronic diarrhea.

OBJECTIVE: To evaluate three fluorescent chitin stains for detecting microsporidia spores in specimens from acquired immunodeficiency syndrome (AIDS) patients with chronic diarrhea.
METHODS: We compared the Fungifluor, Calcofluor White, and Fungiqual A fluorochrome stains for identifying Enterocytozoon bieneusi and Septata intestinalis spores in stool, intestinal fluid, biopsy imprints, and paraffin biopsy sections. The modified chromotrope trichrome stain was used as the standard light microscopic technique for stool and fluid specimens. Stained and unstained paraffin sections and fluid preparations were also evaluated. Multiple specimens from 50 consecutive symptomatic AIDS patients and archival material from known microsporidia-positive AIDS patients were analyzed.
RESULTS: Spores of E bieneusi and S intestinalis fluoresce brightly with all three fluorochrome stains in all of the types of diagnostic specimens. Fluorescing debris and the much larger fungal forms were readily distinguished. Spores were equally well detected in unfixed and formalin-fixed stool specimens, but were not as well detected after sodium acetate-acetic acid, polyvinyl acetate, and ethanol fixation. Bouin's tissue fixative gave a higher background staining than formalin. Spores were readily detected in archival paraffin sections and stool preparations, even when the specimens had been stained previously. Repeat fluorochrome staining was possible. The methods also could detect extraintestinal parasites in paraffin sections.
CONCLUSION: The three fluorescent chitin stains are sensitive and rapid methods for detecting microsporidia spores in stool, intestinal fluid, biopsy imprint, and tissue specimens, even from archived material.