Cysticidal Effect of Chlorine Against Environmental and Clinical Isolates of Acanthamoeba

Acanthamoeba is a free-living amoeba that has been identified to cause Acanthamoeba keratitis and granulomatous amoebic encephalitis. Their physiological characteristics can be related to pathogenic potential which have a medical importance. This study was carried out to investigate the value of minimum cysticidal concentration of chlorine against them. Acanthamoeba strains tested were from clinical isolates from hospitals (HSB 1, HKL 48 and HKL 95) and environmental isolates (PHS 2, PHS 11 and PHS 15). The minimum cysticidal concentration of chlorine was determined by dilution process using 12 wells microtitre plate starting with 2500 ppm. 100 µl cyst suspensions standardized at 105/ml were pipetted into all wells and incubated overnight at 30°C. Cysts were then washed using Page saline and cultured on non nutrient agar overlaid with Escherichia coli. The presence of trophozoites was then observed. The lowest concentration able to prevent trophozoites formation was noted as the minimum cysticidal concentration. Minimum cysticidal concentration test showed the same concentration of 156 ppm (156 µg/ml) chlorine solution was needed to kill all cysts of Acanthamoeba isolates. This indicates that the physiological traits of environmental and clinical isolates are the same. Isolates from the environmental specimens are also able to show the pathogenic potential similar to clinical specimens, thus capable of causing disease to human.