Development of Isospora belli in Hct-8, Hep-2, human fibroblast, BEK and Vero culture cells.

The development of Isospora belli, a human coccidian parasite, was studied in different cell lines. Merozoites were observed in all kinds of cells, whereas sporogony was demonstrated only in Hct-8. This implied that not only the human cell line can be infected, but also some animal cell lines. Unizoites could be found in Vero cells. The merozoites were transferred to a new culture cell for three passages and maintained for two weeks, but no oocyst production was observed in any culture cells during cultivation.

Comparison of Cryptosporidium parvum development in various cell lines for screening in vitro drug testing.

This study describes the development of Cryptosporidium parvum in MDCK, MA-104, Hep-2 and Vero cell lines. Differences in susceptibility, infectivity, and the methodology of excystation were determined. Various solutions were considered to determine the factors which enhanced the excystation (eg with and without sodium hypochlorite, trypsin or sodium taurocholate). It was shown that the sporozoites could be excysted in media either with or without trypsin and sodium taurocholate, but the number of sporozoites in the latter solution was less than the former one. Only oocysts digested by sodium hypochlorite and trypsin can enter the culture cells. Numerous meronts and oocysts were demonstrated and persisted for 9 days. Asexual stages were not observed in MA-104. Only few oocysts could be detected 1-3 days post-inoculation. There was a significant difference between the number of oocysts, which invaded MDCK, MA-104, and Hep-2 cells. MDCK gave the highest susceptibility to oocyst invasion among the three cell lines and asexual stages were also found. Among the 25 isolates, which had been cultivated, 23 isolates could infect MDCK and Hep-2. Only 2 isolates could not infect the MDCK cell. These 2 isolates could infect the Vero cell and yielded high numbers of trophozoites. Praziquantel (PZQ), doxycycline, and paromomycin (PRM) were tested on the infecting parasites. The drugs were added either with the inoculum or 24 hours after inoculation. None of them was effective, including PRM, which had been previously reported as effective.

Cyclospora cayetanensis: oocyst characteristics and excystation.

In Thailand in 1999-2000, Cyclospora oocysts from two HIV-infected patients and one patient with prolonged diarrhea were detected by formalin-ether concentration technique. Sporulation was performed by mixing stool samples in 2.5% potassium dichromate solution, sporulated oocysts were then treated with various solutions before mechanical rupturing in order to establish excystation, fewer than 10% of the sporulated oocysts could be excysted. Our techniques provided more details of the characteristic appearance of sporocysts and sporozoites within the oocysts (DMSO-modified acid-fast technique with our modification).