pathogenic assays of acanthamoeba belonging to the t4 genotype.

background: acanthamoeba genus is introduced as opportunistic and cosmopoli-tan parasite. monkey and wistar rat are appropriate models for experimental study on acanthamoeba infection. in this study acanthamoeba spp. were isolated from hot spring (hs), windows dust (wd) and a corneal sample of keratitis patient (kp) and their pathogenicity surveyed by in vitro and in vivo tests. methods: isolates of acanthamoeba were cultivated axenically for 12 months in pyg medium. overall, 30 wistar rat s, in 6 equal groups were used for developing experimental acanthamoeba keratitis (ak) and granulomatous amoebic encephalitis (gae). the keratitis and granulomatous encephalitis experiments were per-formed by intrastromal and intranasal inoculation of acanthamoeba cysts, respec-tively. pathogenicity of the three isolates was also evaluated by in vitro test using osmotolerance and temperature tolerance assays. identification of genotypes were performed by pcr technique and sequencing. result: none of the isolates could perform ak and gae in wistar rats, although all isolates were described as t4 genotype. isolates obtained from kp and wd could grow only in 30 °c, but not in 37 °c and 40 °c. on the other hand, hs iso-late grew in 30 °c and 37 °c but not in 40 °c. moreover, all of isolate grew in 0.5 m mannitol but not in 1 m and 1.5 m. conclusion: t4 isolates with a long-term axenic culture and different factors re-lated to host and parasite may play role in pathogenicity of these free-living amoebae.