E. coli bacteria may not indicate contamination, research shows

Apr. 11, 2011 -- A new study by Georgia Tech researchers has identified sources of Escherichia coli bacteria that might not indicate an environmental hazard...

Apr 11th, 2011
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By identifying strains of E. coli bacteria that might not indicate an environmental hazard, Georgia Tech civil and environmental engineering assistant professor Kostas Konstantinidis (left) and biology graduate student Chengwei Luo have called into question the meaning of the standard fecal coliform test used to monitor water quality. Credit: Georgia Tech/Gary Meek

Apr. 11, 2011 -- A new study by Georgia Tech researchers has identified sources of Escherichia coli bacteria that might not indicate an environmental hazard.

E. coli is believed to live only in the intestines and waste of humans and other warm-blooded animals and quickly die outside its host, characteristics that make it an indicator of fecal pollution of surface waters.

But new analysis identifies nine strains of E. coli that don't fit the current model. These newly sequenced genomes have adapted to survive in the environment -- independent of warm-blooded hosts -- and may not represent a true environmental hazard. However, the standard fecal coliform test used to monitor water quality cannot tell the difference.

According to Kostas Konstantinidis, an assistant professor in the Georgia Tech School of Civil and Environmental Engineering, the environmental E. coli are better at surviving in the external environment but are less effective competitors in the gastrointestinal tract than the type found in the gastrointestinal tract of healthy humans (also called commensal E. coli). This, he said, indicates that the environmental bacteria are highly unlikely to represent a risk to public health.

"These results suggest the need to develop a new culture-independent, genome-based coliform test so that the non-hazardous environmental types of E. coli are not counted as fecal contamination," said Konstantinidis.

His team's research provides a way to start redefining E. coli species and testing for fecal contamination with procedures based on genomics and ecology.

"We are now working to develop a molecular assay that uses the gastrointestinal-specific genes as robust biomarkers to count commensal E. coli cells in environmental samples more accurately than current methods," added Konstantinidis.

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