2014 December – Caroline Springs (Victoria) – E.coli

Caroline Springs – Victoria – E.coli
Despite full compliance with the E. coli standard at customer tap supplies throughout 2014-15, a City West Water internal, non-regulatory sampling at a customer tap site on 1 December 2014 resulted in an apparent detection of E. coli (one organism per 100 mL) in the Caroline Springs locality. A re-sample the following day revealed absence of total bacteria, total coliform bacteria and E. coli. The cause of the E. coli detection was concluded to most likely have been due to inadequate aseptic sampling methodology rather than faecal contamination, as indicated by the original result of one E. coli per 100mL and the subsequent totally ‘clear’ resample.

Escherichia coli should not be detected in any 100 mL sample of drinking water. If detected
in drinking water, immediate action should be taken including investigation of potential
sources of faecal contamination.

“Coliforms are Gram-negative, non-spore-forming, rod-shaped bacteria that are capable of aerobic and facultative anaerobic growth in the presence of bile salts or other surface active agents with similar growth-inhibiting properties. They are found in large numbers in the faeces of humans and other warm-blooded animals, but many species also occur in the environment.

Thermotolerant coliforms are a sub-group of coliforms that are able to grow at 44.5 ± 0.2°C. E. coli is the most common thermotolerant coliform present in faeces and is regarded as the most specific indicator of recent faecal contamination because generally it is not capable of growth in the environment. In contrast, some other thermotolerant coliforms (including strains of Klebsiella, Citrobacter and Enterobacter) are able to grow in the environment and their presence is not necessarily related to faecal contamination. While tests for thermotolerant coliforms can be simpler than for E. coli, E. coli is considered a superior indicator for detecting faecal contamination…” ADWG 2011