Electron microscopy as an essential technique for the identification of parasites in aids patients

We use EM with increasing frequency for the identification of opportunistic parasitic infections in HIV-infected individuals. Apart from Pneumocytis carinii, Toxoplasma, Cryptosporidium, and Leishmania, we studied several aspects of microsporidiosis. Infection with the intestinal microsporidian Enterocytozoon was found in as much as 27% of AIDS patients with chronic diarrhoea without other pathogens. EM diagnosis of microsporidiosis is commonly performed on intestinal biopsies, but we have recently demonstrated spores of microsporidium with a non-invasive technique, viz. in faeces (1). However, EM of biopsy material remains the reference technique to distinguish the various species. Combining faeces and biopsy examination, we identified another group of microsporidians, Encephalitozoon sp., in the small intestine of AIDS patients with chronic diarrhoea (Fig. 1). Encephalitozoon sp. with identical ultrastructure was found in urine and sinus discharge, suggesting dissemination of the infection. In the maxillary sinus of one patient, we demonstrated E. bieneusi, a parasite which had previously been found only in small intestine and bile duct epithelium (2) (Fig. 2). After albendazole treatment, Encephalitozoon sp. disappeared from faeces, urine and nasal discharge. Although ultrastructural damage was noted in the developmental cycle of E. bieneusi in biopsies after treatment with albendazole, spores continued to be present in the faeces. These results demonstrate the great value of EM in the diagnosis of several parasitic diseases, especially microsporidiosis.