Water Resources--Office of Water Quality
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Fecal indicator bacteria are used to assess the quality of water because they are not typically disease causing, but are correlated to the presence of several waterborne disease-causing organisms (pathogens). The concentration of indicator bacteria (the term "indicator bacteria" is used synonymously with fecal indicator bacteria in this section) is a measure of water safety for body-contact recreation or for consumption.
|Wastes from warm-blooded animals contribute a variety of intestinal bacteria that are pathogenic to humans.|
|Body contact with water that contains pathogens of the genera Salmonella, Shigella, and Vibrio can result in several types of disease in humans, including gastroenteritis and bacillary dysentery, typhoid fever, and cholera.|
|The presence of Escherichia coli (E. coli) in water is direct evidence of fecal contamination from warm-blooded animals and indicates the possible presence of pathogens (Dufour, 1977).|
Water-quality criteria have been developed by the U.S. Environmental Protection Agency (USEPA) for concentrations of indicator bacteria in recreational, shellfish growing, ambient, and potable waters.
|Typical concentrations of indicator bacteria in contaminated and uncontaminated surface waters (table 7.1-1) are often much higher than water-quality criteria established as safe levels by USEPA. For bathing water, the geometric mean concentration established by the U.S. Environmental Protection Agency (1976) for fecal coliform bacteria is 200 col/100 mL (colonies per 100 milliliters). In 1986, the USEPA modified the Federal criteria so that E. coli and enterococci bacteria are now the recommended indicator bacteria (U.S. Environmental Protection Agency, 1986).|
|Ground water typically contains lower concentrations of indicator bacteria than surface water.|