The role of Microsporidia in the pathogenesis of HIV-related chronic diarrhea.

Objective: To determine whether infection with Microsporidia leads to diarrhea in patients with human immunodeficiency virus (HIV) infection.

Design: Case-control study.

Setting: Primary care outpatient HIV clinic at a Veterans Affairs medical center.

Patients: One hundred six HIV-infected men, 55 with and 51 without chronic diarrhea.

Measurements: Each patient underwent upper endoscopy and flexible sigmoidoscopy to obtain duodenal, rectal, and sigmoid colonic biopsy specimens. At the time of endoscopy, a fresh stool was obtained for culture, ova and parasite assessment, and Cryptosporidium examination. Biopsy tissue was examined using electron microscopy to detect Microsporidia.

Results: The microsporidian parasite Enterocytozoon bieneusi was detected in the duodenal biopsy specimens of 31 of 106 men (29%); 24 of 106 men (23%) had other enteric pathogens. No significant difference was observed in the occurrence of microsporidiosis in patients with (18 of 55 [33%]) and without (13 of 51 [25%]) chronic diarrhea (odds ratio, 1.42; 95% CI, 0.61 to 3.31). A similar nonsignificant difference was observed after controlling for CD4 count and other enteric pathogens (odds ratio, 1.66; 95% CI, 0.68 to 4.06). Among patients with microsporidiosis, no difference was observed in the intensity of infection (defined by the presence of few, moderate, or abundant organisms) among cases and controls (P > 0.2).

Conclusions: This is the first report to document the presence of E. bieneusi in HIV-positive patients without gastrointestinal symptoms. No significant difference was observed in the occurrence of E. bieneusi infection in HIV-infected patients with or without chronic diarrhea. Thus, the association between microsporidiosis and diarrhea, if one exists, may not be as strong as is currently believed.