Researchers at the USGS Michigan Water Science Center said they found pathogenic E.coli were pervasive in stream-water samples, but with low concentrations of fecal indicator bacteria.
The findings, said the scientists, might affect how researchers and resource managers rely on indicator bacteria to determine if water is contaminated with bacteria that can make people sick.
Although harmless themselves, fecal indicator bacteria such as nonpathogenic forms of E.coli, enterococci and fecal coliform bacteria have long been used as an easy-to-measure surrogate to determine if pathogens are present.
"We saw little relation between pathogenic E.coli and fecal indicator bacteria criteria for recreational waters," said Joseph Duris, who led the study. "This is intriguing because we rely on indicator bacteria to tell us whether or not the water could make people sick.
The research is detailed in the Journal of Environmental Quality.
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