Topic summary
Indicator organism

Extracted from the Wikipedia article Bioindicator.
Indicator bacteria
Certain bacteria can be used as indicator organisms in particular situations, such as when present in bodies of water. Indicator bacteria themselves may not be pathogenic but their presence in waste may indicate the presence of other pathogens. Similar to how there are various types of indicator organisms, there are also various types of indicator bacteria. The most common indicators are total coliforms, fecal coliforms, E. coli, and enterococci. The presence of bacteria commonly found in human feces, termed coliform bacteria (e.g. E. coli), in surface water is a common indicator of faecal contamination. The means by which pathogens found in fecal matter can enter recreational bodies of water include, but are not limited to, sewage, septic systems, urban runoff, coastal recreational waste, and livestock waste.