The control of Legionella spp conta

The control of Legionella spp contamination in plumbing
systems of large buildings may be a difficult challenge. This is of
particular concern in hospital settings where contamination of hot
water distribution system actually is the most important risk factor
for nosocomial Legionella pneumonia.1,2 National and international
guidelines aimed at preventing Legionella infection suggest the use
of biocides for the routine treatment of contaminated hot water.3,4
Methods adopted include superheating, ultraviolet light, coppersilver
ionization, ozone, hyperchlorination, chlorine dioxide, and
point-of-use water filters. To date, the best procedure is not
established, but the effectiveness of different systems in terms of
reduction of contamination and related costs has been recently
evaluated.5 Monochloramine is considered more effective than free
chlorine in controlling Legionella contamination of longer distribution
systems for its ability to better penetrate biofilms.6 Indeed,
when adopted for disinfection of municipal water supplies in the
United States, it was associated with a lower prevalence of
Legionella colonization in potable water systems of public and
private buildings6,7 and decreased risk of nosocomial outbreaks of
Legionnaires’ disease.8,9 In this study, we present the preliminary
results of 1-year continuous injection of monochloramine in a hot
water distribution system of a large hospital. A comparison with
chlorine dioxide applied in 2 other water distribution systems of
the same building is also presented.