Evaluation of Cysticidal Effects of Contact Lens Disinfectant on Acanthamoeba Isolates

ABSTRACT

PURPOSE: To evaluate the cysticidal effect of 5 kinds of commercially available contact lens disinfectants against 2 clinical isolates of Acanthamoeba. METHODS: Five kinds of commercially available contact lens disinfectants were soaked with cysts of Acanthamoeba ludgdunesis and castellanii at the concentration of 10(3), 10(4), and 10(5) cells/ml for 1 and 4 or 6 hours. Cysts which were not excysted in 7 days after treatment were recognized to be killed. Morphologic changes were evaluated by electron microscopic observation. RESULTS: Contact lens disinfectants which contain myristamidopropyl dimethylamine (MAPD) showed the best cysticidal effect. These disinfectants demonstrated a cysticidal effect on both Acanthamoeba species of all concentrations in 6-hour treatment. Contact lens disinfectants which contain polyhexamethylene biguanide (PHMB) did not demonstrate cysticidal effect, except for Acanthamoeba castellanii at the concentration of 10(3) cells/ml, in either 4- or 6-hour treatment. Separation of plasma membrane from endocyst and damage of organelles were prominent in cases showing a cysticidal effect. CONCLUSIONS: Contact lens disinfectant which contains MAPD may be helpful in preventing the Acanthamoeba keratitis. A higher concentration of PHMB is required to be effective in preventing Acanthamoeba keratitis.