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Chloraminated drinking water systems commonly use free chlorine conversions (FCCs) to prevent or control nitrification, but unintended water quality changes may occur, including increased disinfection by‐product and metal concentrations. This study evaluated water quality in a chloraminated drinking water system and residential locations before, during, and after their annual, planned FCC. Water quality alternated between relatively consistent and variable periods when switching disinfectants. During the FCC, regulated four trihalomethane and five haloacetic acid concentrations increased by four and seven times, respectively, and exceeded corresponding maximum contaminant levels. Implications of disinfection by‐product sampling during an FCC were assessed, and an approach to account for increased FCC disinfection by‐product concentrations was proposed. For metals, the FCC had minor impacts on distribution system concentrations and did not appear to impact residential concentrations. Overall, observed variable water quality appeared primarily associated with switching disinfectants and depended on distribution system hydraulics. [ABSTRACT FROM AUTHOR]

Building water systems promote the regrowth and survival of opportunistic pathogens, such as Legionella pneumophila, especially within biofilms, where most drinking water microbes reside. However, compared to their planktonic form, disinfection efficacy for the biofilm-associated forms of water-based pathogens is unclear. The aim of this study was to determine the effectiveness of free chlorine and monochloramine in the inactivation of biofilm-associated L. pneumophila strain Philadelphia-1 serogroup 1 (Lp). Mature (1.5-2 y old) drinking water biofilms were developed on copper (Cu) and polyvinylchloride (PVC) slides within biofilm annular reactors, then colonized with Lp at approximately 4 log10 CFU cm-2 and exposed to 2 mg L-1 of free chlorine or monochloramine. Ct (disinfectant concentration x time, expressed as mg min L-1) inactivation values for 2-, 3-, and 4-log10 reduction of planktonic and biofilm Lp were determined. For planktonic Lp, free chlorine was more effective at inactivation compared to monochloramine treatment and for biofilm-associated Lp, monochloramine was more effective on Cu biofilms, while free chlorine was more effective on PVC biofilms. In contrast to monochloramine, free chlorine treatment of Cu and PVC biofilms, negatively impacted Lp 16S rRNA gene transcript levels, and may act synergistically with Cu surfaces to further reduce transcript levels. Moreover, Lp cells shed from biofilms into the bulk water, were more resistant to disinfection compared to prepared planktonic Lp cells. Results from this study indicate that biofilm association, disinfectant type, and substratum play an important role in the survival of Legionella pneumophila in building water systems. [ABSTRACT FROM AUTHOR]

A quantitative polymerase chain reaction assay (115 bp amplicon) specific to Escherichia coli K12 with an ABI™ internal control was developed based on sequence data encoding the rfb gene cluster. Assay specificity was evaluated using three E. coli K12 strains (ATCC W3110, MG1655 & DH1), 24 non-K12 E. coli and 23 bacterial genera. The biofilm detection limit was 10³ colony-forming units (CFU) E. coli K12 ml-1, but required a modified protocol, which included a bio-blocker Pseudomonas aeruginosa with ethylenediaminetetraacetic acid buffered to pH 5 prior to cell lysis/DNA extraction. The novel protocol yielded the same sensitivity for drinking water biofilms associated with Fe3O4 (magnetite)-coated SiO2 (quartz) grains and biofilm-surface iron corrosion products from a drinking water distribution system. The novel DNA extraction protocol and specific E. coli K12 assay are sensitive and robust enough for detection and quantification within iron drinking water pipe biofilms, and are particularly well suited for studying enteric bacterial interactions within biofilms. [ABSTRACT FROM AUTHOR]

Drinking water ( DW) biofilm communities influence the survival of opportunistic pathogens, yet knowledge about the microbial composition of DW biofilms developed on common in-premise plumbing material is limited. Utilizing 16 S and 18 S rRNA gene pyrosequencing, this study characterized the microbial community structure within DW biofilms established on unplasticized polyvinyl chloride ( uPVC) and copper (Cu) surfaces and the impact of introducing Legionella pneumophila (Lp) and Acanthamoeba polyphaga. Mature (> 1 year old) biofilms were developed before inoculation with sterilized DW (control, Con), Lp, or Lp and A. polyphaga (LpAp). Comparison of uPVC and Cu biofilms indicated significant differences between bacterial ( P = 0.001) and eukaryotic ( P < 0.01) members attributable to the unique presence of several family taxa: Burkholderiaceae, Characeae, Epistylidae, Goniomonadaceae, Paramoebidae, Plasmodiophoridae, Plectidae, Sphenomonadidae, and Toxariaceae within uPVC biofilms; and Enterobacteriaceae, Erythrobacteraceae, Methylophilaceae, Acanthamoebidae, and Chlamydomonadaceae within Cu biofilms. Introduction of Lp alone or with A. polyphaga had no effect on bacterial community profiles ( P > 0.05) but did affect eukaryotic members ( uPVC, P < 0.01; Cu, P = 0.001). Thus, established DW biofilms host complex communities that may vary based on substratum matrix and maintain consistent bacterial communities despite introduction of Lp , an environmental pathogen. [ABSTRACT FROM AUTHOR]

Transmission of Francisella tularensis, the etiologic agent of tularemia, has been associated with various water sources. Survival of many waterborne pathogens within free-living amoeba (FLA) is well documented; however, the role of amoebae in the environmental persistence of F. tularensis is unclear. In this study, axenic FLA cultures of Acanthamoeba castellanii, Acanthamoeba polyphaga, and Vermamoeba vermiformis were each inoculated with virulent strains of F. tularensis (Types A and B), the attenuated live vaccine strain, and Francisella novicida. Experimental parameters included low and high multiplicity of infection and incubation temperatures of 25 and 30 °C for 0-10 days. Francisella spp. survival was enhanced by the presence of FLA; however, bacterial growth and protozoa infectivity were not observed. In contrast, co-infections of A. polyphaga and Legionella pneumophila, used as an amoeba pathogen control, resulted in bacterial proliferation, cytopathic effects, and amoebal lysis. Collectively, even though short-term incubation with FLA was beneficial, the long-term effects on Francisella survival are unknown, especially given the expenditure of available amoebal derived nutrients and the fastidious nature of Francisella spp. These factors have clear implications for the role of FLA in Francisella environmental persistence.