DNA technology detects the real E.coli

Researchers from SA Water’s Australian Water Quality Centre (AWQC) laboratories are using DNA technology to differentiate between climate-influenced non-infectious bacterial blooms and potentially dangerous E. coli bacteria.

A common bacterium found in human faeces, E. coli can contaminate waterways and catchments, posing a risk for gastrointestinal illness if not detected and treated effectively; a practice that has become increasingly challenging with the proliferation of a different, possibly climate-evolved bloom E. coli. The thermotolerant bloom E-coli does not pose a risk to human health but can mask its more dangerous counterpart.

The method employed at SA Water uses a unique thermotolerant agar culture developed by AWQC Method Development Coordinator Gary Hallas and the AWQC. Using ION Chef and ION S5 analytical equipment, the sample DNA is placed on a DNA chip with unique barcodes identifying the problematic E. coli found in water samples.

Hallas said developing new methodologies and harnessing progressive technology is vital to staying on top of bacterial evolution.

“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,” he said.

“It is vitally important for health protocols to have an ability to pinpoint between harmful and non-harmful E. coli samples should they ever arise. 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.”

Hallas explained that the findings are groundbreaking for water quality management in Australia, as despite not posing a risk to the human body, non-faecal E. coli has the potential to mask a true contamination event.

“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,” Hallas explained.

“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’s Method Development Coordinator Gary Hallas using the Ion Chef DNA technology. Image credit: SA Water.