Legionella control by chlorine dioxide in hospital water systems

egionnaires’ disease is caused by Legionella bacteria, which colonize 12–70% of hospital water systems (Lin et al, 1998b). Of the Legionnaires’ disease cases reported to the Centers for Disease Control and Prevention (CDC), 25–45% were hospital-acquired (Benin et al, 2002). Legionella and other opportunistic pathogens colonize water systems; cause pneumonia, wound, and bloodstream infections in hospitalized patients; and cause approximately 25% of all hospital-acquired infections (Anaisse et al, 2002). These infections could be prevented through active and supplemental disinfection of hospital water systems. Disinfection methods that have been used by hospital water systems to control Legionella include thermal eradication, hyperchlorination, copper–silver ionization, and point-of-use (POU) filters. Thermal eradication is a short term solution that is time-consuming and labor-intensive to implement. High levels of free chlorine in distribution systems from hyperchlorination will cause excessive pipe corrosion problems. Although copper–silver ionization has been an effective disinfection method, a recent study showed that Legionella could develop resistance to copper and silver ions (Mietzner et al, 2005). POU filters do not provide disinfectant residual protection for the entire water distribution system. Chlorine dioxide (ClO2) is a promising alternative disinfectant for hospital water systems to prevent Legionnaires’ disease. Chlorine dioxide has been effectively used to control Legionella in European hospitals (Hill et al, 2000; Hood et al, 2000; Hamilton, et al,1996). However, chlorine dioxide has not been extensively evaluated in the United States for its disinfection efficacy and safety to control hospital-acquired Legionnaires’ disease (Bova et al, 2004; Sidari et al, 2004; Srinivasan et al, 2003). Chlorine dioxide has long been considered an alternative drinking water disinfectant in the United States (Aieta & Berg, 1986). BY ZHE ZHANG,