Acanthamoeba keratitis is a serious infection of the eye which can result in permanent visual impairment. Therefore this study was performed to evaluate the effectiveness of antimicrobial agents on three Acanthamoeba clinical isolates (HS 6, HKL 95 and HTH 73). Antimicrobial agents used in this study were polyhexamethylene biguanide (PHMB) and chlorhexidine and both were serially diluted. Cyst suspensions from all three strains were tested against the antimicrobial agents, respectively. After 48 h of incubation at 37�C, the suspension was filtered and the filter membrane was placed onto non-nutrient agar plate lawned with heat-killed Escherichia coli. The plates were examined daily under the inverted microscope until day 14 but were negative for Acanthamoeba trophozoites. The presence of trophozoites indicated ineffectiveness of the antimicrobial agents. Both antimicrobial agents used were found to be effective against Acanthamoeba cysts for all the strains tested. PHMB gave minimum cysticidal concentration (MCC) mean value of 4.232 ?g/mL and chlorhexidine showed MCC mean value of 3.906 ?g/mL. So, from this study, it can be concluded that PHMB and chlorhexidine were effective in killing the tested Acanthamoeba cysts.

Introduction: Acanthamoeba spp. are ubiquitous free-living protozoa that are widely distributed in all types of environment throughout the world. Acanthamoeba sp. is the causative agent of two diseases; keratitis and granulomatous amoebic encephalitis. Contaminated contact lenses and corneal lesions are the major risk factors in causing Acanthamoeba keratitis. Objective: The main objective of this study is to isolate Acanthamoeba sp. from contact lens paraphernalia. Materials and Methods: One hundred and seventy five swabs from contact lens paraphernalia were obtained, consisting of 66 swabs of contact lenses, 52 swabs of contact lens storage cases and 57 samples of contact lens disinfecting solutions. Filtration and culture techniques were used to isolate the organism using standard methods. Results: This study successfully isolated Acanthamoeba sp. from contact lenses and contact lens storage cases at 10.6% and 13.5% respectively. However no Acanthamoeba sp. was isolated from the contact lens disinfecting solution. Many of those contact lens wearers whose contact lens paraphernalia were positive for Acanthamoeba showed a deviation from contact lens wear and care procedures recommended by the lens manufacturer and health professionals. Conclusion: The findings that contact lens paraphernalia harbours Acanthamoeba is particularly worrying as the number of cases is increasing. Contact lens wearers should be educated regarding proper hygienic care of their contact lenses. � 2013 Japan International Cultural Exchange Foundation & Japan Health Sciences University.