Does the presence of Escherichia coli and enterococci bacteria actually pose a threat to human health?

By Sharon Moen, Minnesota Sea Grant

“Hooray for Michael Sadowsky and all others involved in revealing the truth about beach closures and E. coli,” said Carlos Fetterolf, retired executive secretary of the Canada/U.S. Great Lakes Fishery Commission. “Finally, some 40 plus years after the Academy published National Water Quality Criteria 1972 there’s a breakthrough.”

In 1970 the National Academy of Sciences asked Fetterolf to be the science coordinator for developing national water quality criteria. “We recognized the weaknesses of using E. coli as a contamination proxy,” said this former National Sea Grant Advisory Board member, “but wouldn’t go as far as Sadowsky has.” 

Michael Sadowsky, Professor in the University of Minnesota’s Department of Soil, Water and Climate, and Director of the University’s BioTechnology Institute, is a world leader in microbial source tracking, or in other words, “figuring out the sources of fecal contamination.” How far has he gone?

Backed by Sea Grant’s commitment to research, Sadowsky and his colleagues have gone far enough to show that Escherichia coli and enterococci, the bacteria responsible for “Water Contact Not Recommended” beach advisories, can often be traced back to waterfowl and other animals¹. Water sullied by waterfowl might be nasty, but it is not a serious human health concern. They and others have also revealed populations of E. coli living the good life in sand and sediments throughout the world ^1,2,3,4.

Sadowsky said, “The presence of E. coli or enterococci doesn’t mean you are going to get sick. The nation’s beach standards err on the side of caution with the consequence being that beaches will be closed more often. At this time, beach monitoring programs lump bacteria together without knowing where the bacteria came from. Once we are better able to determine the sources of contamination, we’ll be better able to determine the risk to human health.”

The Environmental Protection Agency‘s (EPA) recommended standards for beach bacteria focus on E. coli and enterococci because these bacterial proxies meet the important criteria of being cheap, easy and quick to find in 100 ml of water. Tracy Bone, Environmental Scientist with the EPA’s Office of Science and Technology said the EPA hoped that research would have yielded a better way to determine health risks on beaches, but for now—and into the foreseeable future—E. coli and enterococci will have to suffice.

The EPA issues beach monitoring recommendations under the authority of the Clean Water Act as amended by the Beaches Environmental Assessment and Coastal Health (BEACH) Act of 2000. The recommendations, which were developed in 1986 and updated last year, are designed to protect swimmers, surfers, divers and others recreating along the nation’s coastlines⁵. 

The EPA Office of Water estimates that 36 out of 1000 people ingesting water at advisory-prompting bacteria levels could experience the unfortunate effects of diarrhea, vomiting, nausea and stomachache⁵. This risk assessment assumes the people swallowed bacteria that came from a human’s intestinal track. Mounting evidence is making that assumption obsolete. 

Pursuing microbial source-tracking techniques is one way Sea Grant is working to ensure the economic and environmental success of the nation’s coastal communities. Knowing the origin of fecal bacteria could make the difference between a “Water Contact Not Recommended” sign and a spectacular day of beach fun. 

 

Useful Beach Bacteria Monitoring Links

 

• U.S. Geological Survey Great Lakes Beach Health Initiative
• Environmental Protection Agency, Beaches

References

¹ JR548. Ishii, S., Sadowsky, M.J. 2008. Escherichia coli in the environment: Implications for water quality and human health. Microbes and Environments. 23(2): 101-108.

² Bauer, L. and Alm, E. 2012. Escherichia coli toxin and attachment genes in sand at Great Lakes recreational beaches. J. Great Lakes Research 38(1): 129–133.

³ JR606. Eichmiller, J.J., Hicks, R.E., and Sadowsky, M.J. 2013. Distribution of genetic markers of fecal pollution on a freshwater sandy shoreline in proximity to wastewater effluent. Environmental Sci. and Tech. 47: 3395-3402.

⁴ JR604. Ran, Q., Badgley, B.D., Dillon, N., Dunny, G.M., and Sadowsky, M. 2013. Occurrence, genetic diversity, and persistence of enterococci in a Lake Superior watershed. Applied and Environmental Microbiology. 79(9): 3067-3075.

⁵ U.S. EPA Office of Water. 2012. Recreational Water Quality Criteria. 820-F-12-058.