[beachnet] USGS report on E. coli and pathogen markers

Thank you Jon Dinneen for pointing out this article!

The full article is available for no charge for 30 days following the
date of this summary. View the abstract at
http://jeq.scijournals.org/cgi/content/abstract/38/5/1878.

 

How good are tests for E. coli in streams?


Unexpected research findings show resource managers and researchers may
have to rethink how they determine if water will make people sick


MADISON, WI, AUGUST 22, 2009 - Bacteria commonly used to indicate health
risks in recreational waters might not be so reliable after all.
Pathogenic E. coli were pervasive in stream-water samples with low
concentrations of fecal indicator bacteria. 

This is one of the unexpected findings from recent research that may
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, U.S.
Geological Survey (USGS), Michigan Water Science Center scientist 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," said Duris,
whose study was published in the September-October issue of the Journal
of Environmental Quality.

For this study, scientists collected water samples from 41 river sites
in Michigan and Indiana from 2001-2003 and measured fecal indicator
bacteria concentrations and markers of pathogens. Scientists grouped
samples on whether or not they met recreational water quality criteria.
The frequency of pathogen detection was compared between the sample
groups. 

Among the key findings: 

*	Gene markers for pathogenic E. coli were pervasive in water from
Michigan and Indiana streams even in water with low concentrations of
fecal indicator bacteria. 
*	Water samples exceeding the fecal coliform criteria for
recreational water were significantly more likely to contain two of the
tested pathogen markers. But for the three other tested pathogen
markers, there was no significant difference between the groups. 
*	There was no difference in the frequency of pathogen marker
occurrence between groups based on exceeding the E. coli or enterococci
indicator organism recreational water quality criteria.

In natural waters, low concentrations of fecal indicator bacteria, such
as fecal coliform bacteria, E. coli and enterococci are presumed to
indicate the absence of fecal inputs, and therefore, the absence of
fecally-derived pathogens. However, the distribution of pathogenic
bacteria in river systems and the relation of these bacterial pathogens
to fecal indicator bacteria concentrations is poorly understood. 

"We will need a more intensive study to determine what might be driving
the relationship between fecal indicator organisms and pathogenic E.
coli occurrence," said Duris, whose team of USGS microbiologists
completed the study with funding provided in part by the USGS Toxic
Substances Hydrology Program. 

The USGS Michigan Water Science Center is involved in several other
studies investigating the relation between pathogen occurrence and fecal
indicator bacteria criteria. National studies to assess the impacts of
non-point source pollution are underway. Two regional studies are
ongoing to investigate the occurrence of other bacterial pathogens
including Salmonella, Shigella, and Campylobacter, and the pathogenic
types of E. coli. Factors that could influence the occurrence of these
pathogens in river systems, such as hydrology, season, land-use, and
source are being investigated for relation with pathogen occurrence.

###

The full article is available for no charge for 30 days following the
date of this summary. View the abstract at
http://jeq.scijournals.org/cgi/content/abstract/38/5/1878.

The Journal of Environmental Quality, http://jeq.scijournals.org
<http://jeq.scijournals.org/>  is a peer-reviewed, international journal
of environmental quality in natural and agricultural ecosystems
published six times a year by the American Society of Agronomy (ASA),
Crop Science Society of America (CSSA), and the Soil Science Society of
America (SSSA). The Journal of Environmental Quality covers various
aspects of anthropogenic impacts on the environment, including
terrestrial, atmospheric, and aquatic systems. 

The American Society of Agronomy (ASA) www.agronomy.org
<http://www.agronomy.org/> , is a scientific society helping its 8,000+
members advance the disciplines and practices of agronomy by supporting
professional growth and science policy initiatives, and by providing
quality, research-based publications and a variety of member services.

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