Regrowth and survival of opportunistic pathogens, such as Legionella pneumophila, in building water systems are promoted by low disinfectant residual, high surface-to-volume ratio, amenable growth temperatures, water stagnation, and microbial colonization of drinking water (DW) biofilms (BFs). Most of the DW biomass is located within BFs, which provides protection from environmental stresses, access to higher levels of nutrients, and opportunities for symbiotic interactions with other microbes. Disinfectant efficacy information is historically based on the inactivation of pathogens in their planktonic (PL), free-floating forms. However, due to the ecological importance of BFs for pathogen survival, the aim of this study is to determine the effectiveness of free chlorine (FC), monochloramine (MA), and copper/silver ions in the inactivation of BF-associated L. pneumophila developed on copper (Cu) and polyvinylchloride (PVC) surfaces. Ct (disinfectant concentration x time) inactivation values for 2-, 3-, and 4-log10 reduction of PL and BF Lp were determined. L. pneumophila 16S rRNA gene transcript levels were also measured to determine the effect of disinfectant type on bacterial transcription. Results from this study indicate that BF association, disinfectant type, and substratum play an important role in the survival of Legionella pneumophila. Overall, this, and other related research, will provide a better understanding of Legionella ecological stability and survival and aid policy makers in the management of exposure risks to water-based pathogens within building water systems.

Disinfection of Legionella pneumophila within drinking water biofilms using various treatment technologies

2019 Spring National Meeting

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