Survival, biofilm formation, and growth potential of environmental and enteric escherichia coli strains in drinking water microcosms

摘要

E. coli is the most commonly used indicator for faecal contamination in a drinking water distribution system (WDS). The assumption is that E. coli are of enteric origin and cannot persist for long outside their host, therefore acting as indicators of recent contamination events. This study investigates the fate of E. coli in drinking water; specifically addressing survival, biofilm formation under shear stress, and regrowth in a series of laboratory-controlled experiments. We show the extended persistence of three E. coli strains (two enteric and one soil isolate) in sterile and non-sterile drinking water microcosms, at 8 and 17°C, with T90 values ranging from 17.4 ± 1.8 to 149 ± 67.7 days, using standard plate counts and a series of (RT)-Q-PCR assays targeting 16S rRNA, tuf, uidA, and rodA genes and transcripts. Furthermore, each strain was capable of attaching to a surface and replicating to form biofilm in the presence of nutrients under a range of shear stress values (0.6, 2.0, and 4.4 dyn cm-2; BioFlux, Fluxion); however, cell numbers did not increase when drinking water was flowed over (t-test; p > 0.05). Finally, E. coli regrowth within drinking water microcosms containing PE-100 pipe-wall material was not observed in the biofilm or water phase using a combination of culturing and Q-PCR methods for E. coli. The results of this work highlight that when E. coli enters drinking water it has the potential to survive and attach to surfaces but that regrowth within drinking water or biofilm is unlikely.