[Diarrhea due to microsporidia in a patient with AIDS]

A 26-year-old male AIDS patient with diarrhea of two-months evolution is reported here. The most relevant intestinal pathogens, including Cryptosporidium parvum, were ruled out by routine microbiological tests. Stool samples stained with an "oblong" Ziehl-Neelsen method (fucsin, 7 min instead of 3 min) allowed visualization of organisms resembling microsporidia. Both modified trichrome and calcofluor stains showed organisms compatible with Enterocytozoon bieneusi. Significant titer of antibodies (> or = 1/800) against 4 different microsporidial species were obtained from the serum of the patient by an ELISA test. Clinical improvement was observed after treatment with albendazole, 400 mg twice daily for 4 weeks, even though microsporidial spores were still detected in stool specimens. To our knowledge, this is the first microsporidial infection reported in Argentina.