Control of Legionella contamination in a hospital water distribution system by monochloramine

Background: We report the results of 1-year application of monochloramine to control Legionella pneumophila contamination in a hospital hot water distribution system. Methods: In the main building of the hospital, a device continuously distributing monochloramine was installed. Legionella pneumophila and Pseudomonas spp contamination was followed in comparison with 2 other water networks in the same building using chlorine dioxide. Results: Monochloramine significantly reduced the number of contaminated sites compared with baseline (from 97.0% to 13.3%, respectively), chlorine dioxide device I (from 100% to 56.7%, respectively), and device II (from 100% to 60.8%, respectively). No positive sample exceeded 104 colony-forming units/L versus 59.4% at baseline. Conclusion: Monochloramine could represent a good alternative to chlorine dioxide in controlling legionellae contamination in public and private buildings.