MICROSPORIDIA IN THE SMALL-INTESTINE OF HIV-INFECTED PATIENTS - A NEWDIAGNOSTIC-TECHNIQUE AND A NEW SPECIES

Objectives: To determine whether microsporidian infections occur in Au stralian patients infected with human Immunodeficiency virus (HIV), to assess the incidence, and to discuss microscopic detection methods. D esign and patients: 180 consecutive HIV-Infected patients (109 with ch ronic diarrhoea and 71 with other indications) underwent upper gastroi ntestinal tract endoscopy and pinch biopsies of the second part of the duodenum. The biopsies were handled by a protocol: four levels, with haematoxylin and eosin stain (H&E) at each level, periodic acid Schiff reagent after diastase (DiPAS) and auramine stain at the second level , and Warthin-Starry (WS) stain and cytomegalovirus early antigen immu noperoxidase study at the third level. Electron microscopy was carried out on samples from the first 95 patients, and thereafter from select ed patients. Setting: The patients came from the HIV Medicine Unit of a teaching hospital and from the practice of a gastroenterologist. Mai n outcome measures: Diagnosis of microsporidia was to be based on the H&E stain, with electron microscopy as the definitive test because the microsporidia are often difficult to see with H&E. Empirically, the W S stain was found to stain the microorganisms and it replaced electron microscopy during the study as the screening diagnostic test. Results : Microsporidia were present in 36 of the 109 patients with diarrhoea (33%) and one of 71 patients without diarrhoea. The WS stain in all ca ses showed developing spores in the enterocytes and in four cases in m acrophages as well. The H&E stain showed non-specific duodenitis and w as not diagnostic in some cases. Electron microscopy on samples from t he first 95 consecutive patients showed 100% concordance with the WS s tain. In 33 cases, electron microscopy showed the multinucleated plasm odia and the spores of Enterocytozoon bieneusi and in the four cases c onfirmed the spores in macrophages and showed a new Encephalitozoon-li ke species with a septate parasitophorous vacuole. Other causes of duo denal infection were sytomegalovirus (11 cases), mycobacteria (8), cry ptosporidia (8) and Giardia lamblia (5). Conclusion: E. bieneusi was t he commonest microorganism found in our series of 180 consecutive pati ents. The actual prevalence of the two microsporidia species within th e HIV-positive population and general community awaits further study. The WS stain provides a sensitive diagnostic test for the presence of E. bieneusi and the new Encephalitozoon-like species, avoiding the cos t and potential sampling error of electron microscopy. The detailed ul trastructure and taxonomy of the new species requires further study.