In Vitro Amoebicidal Efficacy of Hexamidine, Polyexamethylene Biguanide and Chlorhexidine on Acanthamoeba Ccular Isolates

ABSTRACT

To evaluate amoebicidal efficacy of various disinfectants, we treated ten ocular isolates of Acanthamoeba with polyhexamethylene biguanide(PHMB), chlorhexidine and hexamidine. Acanthamoeba cysts were collected from axenic nonnutrient agar plates from 4 week culture. Cyst suspension(100microliter) was inoculated on 96-well microplate with concentration of 105 cys/ml. Each well was treated with two-fold diluted hexamidine, PHMB and chlorhexidine(100microliter each, 8 and 48hrs). Each well was examined under the inverted microscope until 7 days after treatment. Minimal cysticidal concentration(MCC) of each disinfectant qas measured after five experiments. MCC of hexamidine, chlorhexidine and PHMB against ten ocular isolates ranged 6.07-500microgram/ml, 3.12-12.50microgram/ml, 1.17-4.68microgram/ml respectively in 48hr treatment. In 8hr treatment, MCC of PHMB and chlorhexidine ranged 4.42-12.50microgram/ml and 4.67-17.71microgram/ml, but hexamidine did not demonstrate cysticidal effect. For proper disinfection of contact lens, disinfectants having cysticidal efficacy should be included in the composition of contact lens solution. Among the currently used topical amoebicidal agents, PHMB showed the greatest cysticidal activity on ten ocular strains of Acanthamoeba in invitro study.