Inactivation of Naegleria fowleri amoebas by copper:silver and chlorine

Abstract

Electrolytically generated copper and silver ions (400:40 and 800:80 μg/L) with and without chlorine (1 mg/L) were evaluated for their efficacy in reducing numbers of viable Naegleria fowleri amoebas in well water (23-25°C and pH 7.3). A 99.9% reduction was achieved by 10 minutes exposure to 1 mg/L free chlorine compared to 8 minutes with chlorine combined with copper:silver (800:80 μg/L). Copper:silver alone showed minimal reduction of N. fowleri after 72 hours exposure. Addition of 1 mg/L free chlorine to copper:silver at concentrations of 400:40 or 800:80 μg/L resulted in significantly enhanced inactivation rates (k = 0.4575 and 0.515 log₁₀ reduction/minute, respectively) than with chlorine alone (k = 0.33). Enhanced inactivation of N. fowleri with combined copper:silver and chlorine may be a consequence of multiple sites of attack on the amoeba membrane by the different disinfectants.