What are indicator bacteria and where do they come from?
Public health agencies use measurements of fecal indicator bacteria such as E. coli or enterococci to determine the potential for fecal contamination and to compare to public health-based thresholds. Like the pathogens they represent, fecal indicator bacteria are found in feces of both human sources (e.g. sewer discharges, and failing septic systems) and non-human sources (e.g. pets, waterfowl, and farm animals). Indicator bacteria are used because it is difficult to measure the actual pathogens themselves.
