Fecal coliform are the bacteria most commonly found in natural water, says Clemson University Cooperative Extension Service. Most of these bacteria are harmless to humans because they serve as part of a normal, healthy digestive system, but some are pathogenic to humans.
Fecal coliform bacteria live in warm-blooded mammals' digestive tracts, explains Clemson University Cooperative Extension Service. The pathogenic bacteria cause diseases such as ear infections, typhoid, gastroenteritis, dysentery and hepatitis A, as well as cholera in humans. Fecal coliform is found in natural waters such as streams and lakes, primarily due to the waste of farm animals being washed downstream by rain or irrigation runoff. The bacteria from waste can be carried into creeks, storm drains and lakes during storms.
Urban areas can also contribute to the spread of these bacteria because waste from dogs, cats, raccoons and humans additionally spreads them. Illegal or leaky sewer connections, broken septic tanks and poorly functioning wastewater treatment plants also contribute to the spread of the bacteria, reports Clemson University Cooperative Extension Service.
Scientists test levels of fecal coliform in water by collecting a sample from a natural body of water in a sterile container. The water sample is then filtered, placed in a special solution and incubated for 24 hours without changing temperatures. Experts then count the number of fecal coliform colonies and report the numbers as number of colonies per 100 ml of water, notes Clemson University Cooperative Extension Service.