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Septata intestinalis frequently isolated from stool of AIDS patients with a new cultivation method
T van Gool1, E U Canning, H Gilis
1Department of Medical Microbiology, University of Amsterdam, The Netherlands.
Abstract:
Two species of microsporidia, Enterocytozoon bieneusi and Septata intestinalis have been reported as intestinal parasites of AIDS patients. In attempts to establish E. bieneusi in vitro, spores were concentrated from stool samples from 4 AIDS patients with biopsy-proven E. bieneusi infections. After sterilization of the concentrate in antibiotic solution, the spores were added to monolayers of RK13 cells grown on the membranes of Transwells. Cultures were established from 7 stool samples from the 4 patients but in every case the species established was S. intestinalis not E. bieneusi. On retrospective examination of the stools, a very small number of spores of a size comparable to that of S. intestinalis was found but this species was not detected in biopsies. Typical septate vacuoles containing Type I tubules were observed in vitro but in contrast to the original description, meronts were intravacuolar 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.
Insights
Researchers attempted to culture Enterocytozoon bieneusi from AIDS patients but unexpectedly established Septata intestinalis in vitro. This novel cultivation method reveals S. intestinalis may be more common than previously thought.
Area of Science:
- Medical Parasitology
- Infectious Diseases
- Cell Biology
Background:
- Enterocytozoon bieneusi and Septata intestinalis are known intestinal microsporidia affecting AIDS patients.
- Previous research has focused on E. bieneusi, with limited understanding of S. intestinalis prevalence.
Purpose of the Study:
- To establish Enterocytozoon bieneusi in vitro from stool samples of AIDS patients.
- To investigate the prevalence and characteristics of microsporidia in immunocompromised individuals using a novel cultivation system.
Main Methods:
- Concentration and sterilization of microsporidia spores from stool samples.
- Inoculation of spores onto RK13 cell monolayers in Transwell cultures.
- Retrospective stool and biopsy examination for microsporidia identification.
Main Results:
- Cultures from 7 stool samples consistently yielded Septata intestinalis, not the intended Enterocytozoon bieneusi.
- S. intestinalis was detected in stool samples but not in patient biopsies.
- In vitro observations revealed intravacuolar meronts and disporoblastic sporogony for S. intestinalis.
Conclusions:
- The novel cultivation system successfully cultured S. intestinalis for the first time.
- This indicates S. intestinalis infections may be more prevalent in AIDS patients than previously recognized.
- The findings challenge existing knowledge of microsporidia lifecycle and diagnosis in immunocompromised hosts.