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Control of Legionella in Large Buildings through Community-Wide Introduction of Monochloramine, Page 1 of 2
< Previous page Next page > /docserver/preview/fulltext/10.1128/9781555815660/9781555813901_Chap127-1.gif /docserver/preview/fulltext/10.1128/9781555815660/9781555813901_Chap127-2.gifAbstract:
Monochloramine can be more effective than chlorine at reducing Legionella colonization of potable water systems in large buildings, which are key sources of community-and hospital-acquired Legionnaire's disease. Because monochloramine use is associated with lower concentrations of trihalomethanes, many utilities are converting their residual disinfectant from chlorine to monochloramine. In this chapter, the author observed that monochloramine conversion was associated with decreased Legionella colonization of buildings served by the municipal water system. To determine whether this decreased risk was sustainable over a longer period of time and at a larger number of distal sites, a larger colonization survey was performed in San Francisco before and after conversion to monochloramine. Legionella were isolated from water samples and biofilm swabs, speciated, and serogrouped using standard methods. In the chlorine phase, 29% (45 of 157) of samples collected from water heaters yielded Legionella; fewer than 1% (1 of 159) of water heaters sampled during the monochloramine phase were positive (P<0.001). After controlling for water heater temperature, building height, and disruptions in service, monochloramine use was associated with a 96% reduction in the prevalence of water heater colonization (P<0.001).