In Vitro Amoebicidal Efficiencies of Various Disinfectants Against Four Ocular Isolates of Acanthamoeba Keratitis

ABSTRACT

To evaluate amoebicidal efficacy of various disinfectants, we treated four ocular isolates of Acanthamoeba with three kinds of commercial available contact lens(CL) disinfectants, chlorhexidine, thimerosal, polyhexamethylene biguanide(PHMB) and hexamidine, Acanthamoeba cysts were collected from axenic nonnutrient agar plates from 4-week cultures. Cyst suspension(100microliter) was inoculated on 96-well microplate with concentration of 5x103 cyssts/ml. Each well was treated with three kinds of CL disinfectants(100microliter each, 4, 8, 12, 24hrs) and two-fold diluted chlorhexidine, PHMB and hexamidine(100microliter each, 8 and 48hrs). Only one CL disinfectant containing chlorhexidine(0.005%) and thimerosal(0.001%) showed cysticidal effect. Minimal cysticidal concentration(MCC) of PHMB, chlorhexidine, hexamidine ranged 1.17-3.12microgram/ml, 3.12-12.50microgram/ml, 8.64-52.07microgram/ml respectively with 48hr treatment. In 8hr treatment, MCC of PHMB and chlorhexidine were 4.42-12.50microgram/ml and 9.31-25.0microgram/ml respectively, but hexamidine did not demonstrate cysticidal effect. Therefore for proper sterilzation of contact lens and CL caes, effective disinfectant should be included in the composition of CL cleaning solution. Among the currently used topical amoebicidal agents, PHMB was the most potent cysticidal agent in in vitro study with four ocular stains of Acanthamoeba.