Introduction of Monochloramine into a Municipal Water System: Impact on Colonization of Buildings by Legionella spp

Abstract

Legionnaires' disease (LD) outbreaks are often traced to colonized potable water systems. We collected water samples from potable water systems of 96 buildings in Pinellas County, Florida, between January and April 2002, during a time when chlorine was the primary residual disinfectant, and from the same buildings between June and September 2002, immediately after monochloramine was introduced into the municipal water system. Samples were cultured for legionellae and amoebae using standard methods. We determined predictors of Legionella colonization of individual buildings and of individual sampling sites. During the chlorine phase, 19 (19.8%) buildings were colonized with legionellae in at least one sampling site. During the monochloramine phase, six (6.2%) buildings were colonized. In the chlorine phase, predictors of Legionella colonization included water source (source B compared to all others, adjusted odds ratio [aOR], 6.7; 95% confidence interval [CI], 2.0 to 23) and the presence of a system with continuously circulating hot water (aOR, 9.8; 95% CI, 1.9 to 51). In the monochloramine phase, there were no predictors of individual building colonization, although we observed a trend toward greater effectiveness of monochloramine in hotels and single-family homes than in county government buildings. The presence of amoebae predicted Legionella colonization at individual sampling sites in both phases (OR ranged from 15 to 46, depending on the phase and sampling site). The routine introduction of monochloramine into a municipal drinking water system appears to have reduced colonization by Legionella spp. in buildings served by the system. Monochloramine may hold promise as community-wide intervention for the prevention of LD.

Molecular Survey of the Occurrence of Legionella spp., Mycobacterium spp., Pseudomonas aeruginosa, and Amoeba Hosts in Two Chloraminated Drinking Water Distribution Systems

“…The water sampling procedure was identical to that used for BCV, except that shower water samples were collected when available and biofilm samples were collected from taps and shower heads by swabbing the inner surfaces with sterile cotton. These additional samples facilitated comparison with a previous CDC study (54).…”

“…Details of PCF were reported in a previous U.S. Centers for Disease Control (CDC) study (54), except that the source water has been adjusted to a blend of surface, ground, and desalinated water (at the time of the previous CDC study, the source water was 100% groundwater). Sampling took place in May 2011, targeting eight sites that were positive and seven sites that were negative for Legionella in the previous CDC study (54). Among the eight Legionella-positive sites, three were reported positive only when chlorine was used as the disinfectant and negative following the switch to chloramination.…”

“…were historically reported to be prevalent in the PCF drinking water distribution system (54,61), which serves over 640,000 people. Details of PCF were reported in a previous U.S. Centers for Disease Control (CDC) study (54), except that the source water has been adjusted to a blend of surface, ground, and desalinated water (at the time of the previous CDC study, the source water was 100% groundwater). Sampling took place in May 2011, targeting eight sites that were positive and seven sites that were negative for Legionella in the previous CDC study (54).…”

“…Such a study is of value, considering that the factors that inhibit one pathogen may actually favor the growth of others. For example, in the drinking water distribution system in Pinellas County, FL (PCF), Moore and colleagues (54) previously reported that switching from chlorine to chloramines mitigated Legionella colonization but favored mycobacterial colonization. However, the full extent and implications of such phenomena are unknown.…”

Pyrosequence Analysis of the hsp65 Genes of Nontuberculous Mycobacterium Communities in Unchlorinated Drinking Water in the Netherlands

“…However, since NTM species can grow under oligotrophic conditions (5, 23), distribution of drinking water without a disinfection residual might increase the risk of NTM growth during distribution of the drinking water. On the other hand, studies have demonstrated that certain NTM species are especially resistant to monochloramine and that shifts from chlorine to monochloramine disinfection in drinking water treatment resulted in enhanced numbers of NTM in the drinking water distribution system (24)(25)(26). Research in the 1980s demonstrated the occurrence of M. kansasii in drinking water from the Rotterdam area in the Netherlands (27).…”