The most common indicators are Coliforms, E. coli, and Enterococci. The presence of bacteria commonly found in human faeces, termed coliform bacteria (e.g., E. coli), in surface water is a common indicator of faecal contamination.
Related Theory
Indicators of potential human or fecal contamination or of possible presence of pathogens include Staphylococci, Escherichia coli, fecal coliforms, Enterococci and Pseudomonas aeruginosa. Indicator organisms are used to assess overall sanitation or environmental conditions that may signal or indicate the potential presence of pathogens of food safety concern. It is important to note that indicator species are not necessarily pathogenic.