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Severe, chronic diarrhea is a frequent complication of human immunodeficiency virus disease, and intestinal microsporidiosis is being recognized with increasing frequency in patients with AIDS. Noninvasive, cost-effective techniques are needed to optimize its diagnosis. Weber's modified trichrome stain (MTS) and the fluorochrome Uvitex 2B stain were used to detect microsporidial spores in smears of stool and duodenal aspirate (DA) samples received from human immunodeficiency virus-infected patients for examination for ova and parasites. Of 305 samples (292 stool and 13 DA samples) from 140 patients examined by MTS, 83 samples from 26 (18.6%) of the patients were positive for microsporidia (23 patients diagnosed initially and 3 diagnosed upon review). A subset of the samples studied by MTS consisting of 108 smears of stool and DA specimens from 60 patients was examined by Uvitex 2B. All 44 samples positive by MTS were also positive by Uvitex 2B. In addition, seven specimens and three patients were initially detected as positive by Uvitex 2B only (all three patients were positive also by MTS upon review). Confirmation of the diagnosis was obtained for 24 of 26 smear-positive patients by duodenal biopsy and/or stool transmission electron microscopy. Of 114 patients with stained smears negative for microsporidia, 23 had duodenal biopsies which showed no microsporidia. For the 43 patients who underwent duodenal biopsy, the sensitivity of both the MTS and the Uvitex 2B methods compared with biopsy results was 100%. Of six patients with negative duodenal biopsies and positive stained smears, four had microsporidia demonstrated by stool transmission electron microscopy. The examination of stool and DA smears stained by Uvitex 2B and/or MTS is a sensitive, noninvasive test for diagnosis of intestinal microsporidiosis which can be successfully implemented in a clinical laboratory. Strict adherence to precise diagnostic criteria is necessary to avoid incorrect results. The simultaneous use of both staining methods enhances performance and may provide greater accuracy, especially for patients with light infections.

Microsporidia are protozoan parasites responsible for significant gastrointestinal disease in patients infected with human immunodeficiency virus. We report the clinical features of 20 patients with chronic diarrhea for whom microsporidian spores were identified by modified trichrome staining of stool smears and confirmed by biopsy and/or electron microscopy of stool. Of the 18 microsporidian protozoa identified to the species level, 14 (78%) were Enterocytozoon bieneusi and four (22%) were Septata intestinalis. The mean CD4 count in these patients was 35 +/- 29 cells/mm3. Parameters of absorption, specifically absorption of fat and D-xylose, and levels of zinc were strikingly abnormal in patients who were tested. Treatment with albendazole led to clinical responses in six of 10 patients, and dietary manipulation resulted in clinical improvement in eight of nine patients. We recommended that patients with chronic, intermittent diarrhea and CD4 counts of < 100 cells/mm3 be further evaluated for microsporidia by modified trichrome staining of stool and light and electron microscopy of small bowel biopsy specimens. Antiprotozoal therapies are currently experimental, but some patients who have been treated with these therapies have dramatic responses. We also recommend that special attention be paid to the measurement of parameters of absorption with appropriate modification of diet.