Effect of Monochloramine Treatment on Colonization of a Hospital Water Distribution System by Legionella spp.: A 1 Year Experience Study

Abstract

Contamination of hot water distribution systems by Legionella represents a great challenge due to difficulties associated with inactivating microorganisms, preserving the water characteristics. The aim of this study was to examine over the course of 1 year in 11 fixed sites, the impact of monochloramine disinfection on Legionella, heterotrophic bacteria (36 °C), Pseudomonas aeruginosa contamination, and chemical parameters of a plumbing system in an Italian hospital. Three days after installation (T0), in the presence of monochloramine concentration between 1.5 and 2 mg/L, 10/11 sites (91%) were contaminated by L. pneumophila serogroups 3 and 10. After these results, the disinfectant dosage was increased to between 6 and 10 mg/L, reducing the level of Legionella by three logarithmic unit by 2 months postinstallation (T2) until 6 months later (T3). One year later (T4), there was a significant reduction (p = 0.0002) at 8/11 (73%) sites. Our data showed also a significant reduction of heterotrophic bacteria (36 °C) in 6/11 (55%) sites at T4 (p = 0.0004), by contrast the contamination of P. aeruginosa found at T0 in two sites persisted up until T4. The results of the present study show that monochloramine is a promising disinfectant that can prevent Legionella contamination of hospital water supplies.

Legionella Diversity and Spatiotemporal Variation in the Occurrence of Opportunistic Pathogens within a Large Building Water System

“…After conversion to monochloramine disinfection within BWSs, there were reductions in the number of distal sites testing positive for Legionella (39–100% to 0–18% positivity); however, there was a large range in the log reduction of Legionella levels (0.2 to 3 log 10 CFU L −1 ) with one study reporting no changes in levels post-conversion during the one- to three-year monitoring period [ 58 , 59 , 60 ]. Control of biofilm-associated Legionella was also observed [ 58 , 61 ], most likely due to the better penetration of monochloramine into biofilms compared to chlorine [ 62 ]; however, control of biofilm-associated L. pneumophila (Lp) was previously reported to be pipe material specific during chlorine and monochloramine treatment [ 63 ].…”

Combining Traditional and Molecular Techniques Supports the Discovery of a Novel Legionella Species During Environmental Surveillance in a Healthcare Facility

“…Moreover, to achieve control of Legionella proliferation, the national and international directives point out several disinfection strategies, based on chemical disinfectants (i.e., chlorine dioxide, monochloramines, and hydrogen peroxide) and physical treatments [i.e., ultraviolet (UV) light and hot temperature treatments]. All of them have shown some advantages and disadvantages (Mcdonnell and Russell, 1999 ; Richardson et al, 2007 ; Lin et al, 2011 ; Mancini et al, 2015 ; Girolamini et al, 2019 ). However, some authors have shown how these treatments, especially the use of chemical disinfectants, could select resistant strains and introduce some changes in the bacterial genome.…”