DNA technology used to detect E. coli in our water

Tuesday, 14 May, 2019 | Supplied by: SA Water


SA Water scientists from the Australian Water Quality Centre (AWQC) are using cutting-edge DNA technology to quickly differentiate between climate-influenced non-infectious bacterial blooms and potentially dangerous E. coli bacteria, in order to help maintain public health and safeguard Australia’s water supplies.

A common bacterium found in human faeces, E. coli has long been a potential contaminant to waterways and catchments, posing a risk for gastrointestinal illness if not detected and treated by SA Water and other utilities. This practice has been made more challenging for water treatment operators over recent years with the proliferation of a different, potentially climate-evolved bloom E. coli, which does not pose a risk to human health but can mask its more dangerous counterpart.

“The prevalence of thermotolerant bloom E. coli has been an increased issue for water utilities across Australia, which we speculate is potentially due to Australia’s changing climate and water conditions, allowing for an evolution link and gene transference mechanism between common bacteria in our open water sources and our indicator organism for risk management,” said AWQC’s Method Development Coordinator, Gary Hallas.

“Through a new thermotolerant culturing process and then identifying the unique E. coli DNA sequence-types, we can clearly differentiate the make-up of both naturally blooming and potentially pathogenic faecal E. coli within just a few hours and, most importantly, if any samples are of human health concern.”

The new method utilises a unique thermotolerant agar culture developed by Hallas and the AWQC. Using the Ion Chef and the Ion S5 analytical equipment from Thermo Fisher Scientific, the DNA from the samples is placed on a DNA chip with unique barcodes identifying the problematic E. coli found in water samples. This is said to provide more detailed and reliable information than ever provided before in routine use by water laboratories around Australia.

“This is groundbreaking research for water quality management in Australia, as despite not posing risk to the human body, non-faecal E. coli has the potential to mask a true contamination event should it ever arise,” said Hallas.

“Much like tracing a DNA fingerprint, we can also use the Ion Chef and Ion S5 to identify unique characteristics in the water samples, which allows us to track and monitor its presence over time at a single location or its movement through the network.

“We are the only water utility in the country regularly using this software to sequence specific E. coli DNA, and SA Water is at the forefront in helping other utilities across the water industry to identify and manage blooms in their water sources to prevent potential waterborne illness.”

Image caption: AWQC Method Development Coordinator Gary Hallas using the Ion Chef DNA technology. Image credit: SA Water.

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