Legionella control by chlorine dioxide in hospital water systems.

This study evaluated the safety and efficacy of chlorine dioxide (ClO₂) fed into the incoming main water line to control Legionella bacteria in two hospital water systems. In both hospitals A and B, positivity of all distal outlets (sinks and showers) for Legionella decreased from 60% to ≤ 10% after the ClO₂ treatment. In hospital B, the heterotrophic plate count bacteria in hot water were reduced from 15,400 cfu/mL to 2,900 cfu/mL after ClO₂ treatment. Mean concentrations of ClO₂ and chlorite (ClO₂^-) in cold and hot water did not exceed the maximum residual disinfection level of 0.8 mg/L and the maximum contaminant level of 1.0 mg/L, respectively. No cases of healthcare acquired legionellosis have been identified in the postdisinfection period in these two hospitals. The study indicates that ClO₂ is a promising disinfectant for controlling not only Legionella, but also other microorganisms in drinking water. [ABSTRACT FROM AUTHOR]