Microsporidia are obligate intracellular protozoan parasites that can cause opportunistic infections in AIDS patients. Species from five genera of microsporidia are presently known to infect man. One species, Septata intestinalis originally was detected in stool specimens of individuals with chronic diarrhea and subsequently was found to disseminate to the kidneys, lungs, and nasal sinuses. This organism has since been reclassified as Encephalitozoon and in this study, we report the culture of Encephalitozoon intestinalis from a bronchoalveolar lavage specimen and a nasal mucus aspirate of two AIDS patients living in the USA. The bronchoalveolar and nasal microsporidian isolates grew in several continuous cell lines including RK-13, MDCK, HT-29, Caco-2, Vero, and I047. Transmission electron microscopy of the clinical and cell culture specimens revealed that the new isolates appeared to be E. intestinalis based on morphology and growth of organisms in septated membrane-bound parasitophorous vacuoles. The new E. intestinalis isolates were characterized and compared with the first isolated E. intestinalis that was cultured from stool to confirm their identity and to determine if there existed any minor differences, as seen in the closely related Encephalitozoon cuniculi strains. By the methods of sodium dodecyl sulfate-polyacrylamide gel electrophoresis staining for proteins and carbohydrates, Western blot immunodetection, and polymerase chain reaction-based methods with restriction endonuclease digestion, double-stranded DNA heteroduplex mobility shift analysis, and DNA sequencing of the ribosomal DNA intergenic spacer region, the new isolates were identical to each other and to the reference isolate of E. intestinalis. In addition, with any of these methods, the E. intestinalis organisms could be distinguished from the three E. cuniculi strains, Encephalitozoon hellem, and Vittaforma corneae, which is important for diagnostics, therapeutic strategies, and epidemiology.

The etiologic and clinical features of cholecystisis in infection due to human immunodeficiency virus (HIV) were studies retrospectively. The charts and histopathologic specimens of 136 HIV-infected patients who underwent cholecystectomy between February 1987 and May 1993 at a large tertiary care center were reviewed. Opportunistic pathogens infecting the 107 patients with AIDS included microsporidia (eight cases-- Enterocytozoon bieneusi in six and Septata intestinalis in two); cytomegalovirus alone (six cases); Cryptosporidium alone (eight cases); cytomegalovirus plus Cryptosporidum (15 cases); and Pneumocystis carinii and Isospora belli (one case each). In addition, histopathologic changes characteristic of Kaposi's sarcoma were seen in one case. Thirty-eight patients with AIDS had acalculous cholecystitis for which no etiologic agent was found. Twenty-eight AIDS patients had cholelithiasis, six with coexistent opportunistic gallbladder infection. In the 107 AIDS patients, no specific symptom was found to be predictive of opportunistic infection of the gallbladder, but such infection was significantly associated with an abnormal abdominal ultrasound (P = .017) and with nonvisualization of the gallbladder by radionucleotide biliary scan (P < .001).

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