Amoebicidal activity of benzothiazole on Acanthamoeba castellanii cysts and trophozoites and its cytotoxic potentials

•Acanthamoeba is free-living amoeba isolated from many ecological areas.•-Granulomatous amebic encephalitis and amebic keratitis, caused by Acanthamoeba spp.•-Usually occurs in chronically ill, debilitated individuals, in immunosuppressed patients and treatment is quite difficult.•This study aimed to determine the effect of benzothiazole on trophozoite and cyst forms of Acanthamoeba castellani.•According to our study results, benzothiazole, due to the effect on cyst and trophozoite could be concluded as a new therapeutic agent against Acanthamoeba spp. Acanthamoeba spp. are free-living amoebae isolated from many ecological areas such as swimming pools, dams and lakes, and soil. Granulomatous amebic encephalitis and amebic keratitis, caused by Acanthamoeba spp., usually occurs in chronically ill, debilitated individuals, in immunosuppressed patients and treatment is quite difficult. This study aimed to determine the effect of benzothiazole on trophozoite and cyst forms of Acanthamoeba castellanii (A.castellanii). Axenic cultures of A. castellanii trophozoites and cysts were prepared to test the amoebicidal activity of benzothiazole. The concentrations of benzothiazole in 24-well plates were prepared as 0.08%, 0.04%, 0.02%, 0.01%, 0.005%, and A. castellanii cysts and trophozoites were added to these cultures. Parasites were counted at 0, ½, 1, 3, 6, 12, 24 and 48 h in the cell counter after staining with trypan blue. Cytotoxicity of benzothiazole on the WI-38 human fibroblast cell line was also tested. Between 0.08% and 0.01% concentrations of benzothiazole showed a strong amoebicidal activity at 24 and 48 h. A significant decrease in 0.005% concentration in the number of live trophozoites and cysts was detected between 6 and 48 h. As a result of the cytotoxicity studies, benzothiazole did not show any cytotoxic effect on the WI-38 human fibroblast cell line even at 1% concentration. Benzothiazole could be concluded as a new therapeutic agent against Acanthamoeba. On the other hand, in vivo studies are needed to confirm the efficacy of the biological effect.