SEPTATA INTESTINALIS FREQUENTLY ISOLATED FROM STOOL OF AIDS PATIENTS WITH A NEW CULTIVATION METHOD

Two species of microsporidia, Enterocytozoon bieneusi and Septata inte stinalis have been reported as intestinal parasites of AIDS patients. In attempts to establish E. bieneusi in vitro, spores were concentrate d from stool samples from 4 AIDS patients with biopsy-proven E. bieneu si infections. After sterilization of the concentrate in antibiotic so lution, the spores were added to monolayers of RK13 cells grown on the membranes of Transwells. Cultures were established from 7 stool sampl es from the 4 patients but in every case the species established was S . intestinalis not E. bieneusi. On retrospective examination of the st ools, a very small number of spores of a size comparable to that of S. intestinalis was found but this species was not detested in biopsies. Typical septate vacuoles containing Type I tubules were observed in v itro but in contrast to the original description, meronts were intrava cuolar and sporogony was mainly disporoblastic. The cultivation system , used for the first time for microsporidia, revealed the presence of unsuspected S. intestinalis infections and indicates that this species may be much more common than hitherto suspected. S. intestinalis has not previously been cultured.