Cytotoxic effect of organic solvents and surfactant agents on Acanthamoeba castellanii cysts

Acanthamoeba castellanii is a protozoan parasite that may cause sight-threatening keratitis in some individuals. Its eradication is difficult because the trophozoites encyst making organisms highly resistant to anti-amoebic drugs. To test new anti-Acanthamoeba agents, usually having low water solubility, organic solvents and surfactant agents should be used. Therefore, the lethal effect of different concentrations of the solvents acetone, methanol, ethanol, and DMSO and surfactant agents Tween 20, Tween 80, and Triton X-100 was tested. The minimal inhibitory concentrations (MIC) were determined against Acanthamoeba cysts. Results of the present study showed that the MIC for ethanol, methanol, acetone and DMSO was 25, 12.5, 12.5, and 10 %, respectively and for Tween 20, Tween 80, and Triton X-100 was 0.25, 0.06, and 0.03 %, respectively. There was no significant inhibitory effect on the multiplication of Acanthamoeba cysts as compared to parasite control when using the concentrations 3.12 % for ethanol, 1.6 % for methanol and acetone, 1.25 % for DMSO, and 0.016 % for Tween 20. On the other hand, both Tween 80 and Triton X-100 showed highly significant difference in comparison to parasite control almost among all the range of concentrations used in this study, and both showed lethal effect of 19 and 27.2 %, respectively at their least concentration.