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Continuous Disinfection by Monochloramine on Domestic Hot Water System of Health-care Facilities for the Control of Legionella Contamination in Italy



Author(s)

Maria Anna Coniglio, Nunzia Andolfi, Giuseppina Faro, Maria Beatrice Pellegrino, Angela Sgalambro, Giuseppe D’Aquila, Alfio Spina and Stefano Melada

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DOI:10.17265/2328-7136/2015.01.002

Backgroud: The prevention of Legionella spp. colonization of water distribution systems is a critical issue in healthcare
settings and only an effective disinfection of water systems and appropriate environmental surveillance strategies allow to prevent nosocomial legionellosis. Methods: Due to the temporary effectiveness (increase of the temperature of water in boilers and shock hyperchlorination), the high costs (point-of-use water filters) or the ineffectiveness (hydrogen peroxide, H2O2) of the previous control procedures, 3 devices (one for each hot water loop) continuously injecting monochloramine have been installed in two different Italian hospitals heavily contaminated by Legionella pneumophila SG3 and SG6. Aim: To evaluate the efficacy of continuous disinfection by monochloramine for control of Legionella on domestic hot water (DHW) distribution system of health-care facilities. Findings: One month after the disinfection of DHW with monochloramine, the load of L. pneumophila SG3 and SG6 (previous mean count ranging from 103 to 105 CFU/L), as well as the Heterotrophic Plate Count (HPC) (previous mean count ranging from > 102 to > 104 CFU/mL), decreased at undetectable levels in 100% of the sampling points in the two hospitals. Conclusion: The results suggest that continuous injection of monochloramine on DHW systems can fully control L. pneumophila and HPC in contaminated hospitals since the beginning of its application.

Hospitals, Legionella, monochloramine.