Comparison of chlorhexidine disinfectant in vitro effect on environmental and ocular Acanthamoeba strains, the amoebic agents of human keratitis − an emerging sight-threatening corneal disease in Poland

Abstract

Small amoebae belonging to the Acanthamoeba genus complete their life cycles in different environmental niches as free-living protists however some of them are facultative parasites that can cause severe disease in humans. The sight-threatening Acanthamoeba keratitis develops in immune-competent persons, mainly in contact lens wearers; it is detected with increasing frequency along with the spread of contact lens use. The high abundance of the amoebae in the environment is important for dispersion and transmission of the infections among humans. Emerging threats for the public health generated by these amoebae is the serious medical problem worldwide. Nonspecific symptoms, similar to those occurring in the other eye diseases, diagnostic mistakes, the delay of an appropriate treatment, an exceptional high resistance of the amoebae to chemicals and drugs result in a prolonged course of the disease and often unsuccessful therapeutic management. Thus, different chemicals are still examined for their potential activity in vitro against various species, strains/isolates of Acanthamoeba. As the prolonged therapy often induces encystation subsequently leading to excystment and recurrences of amoebic keratitis, apart from anti-amoebic activity, cysticidal effect of examined agents is desirable. In the present study, results of our comparative investigations showed that cationic antiseptic chlorhexidine digluconate indicated in vitro anti-amoebic effect on environmental Acanthamoeba castellanii Neff strain and pathogenic corneal Acanthamoeba polyphaga T4 genotype. Amoebostatic effect of the disinfectant was expressed in reduced number of surviving amoebae in comparison to the respective control cultures; simultaneously, despite prolonged incubation with the agent no stimulation of encystation was noted. The corneal strain was more resistant to the tested compound than the Neff strain. The cysticidal efficacy of chemicals is very expected, thus further in vitro studies on pathogenic Acanthamoeba strains with different application chemicals pattern are needed.