 Polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH) are gene sequence-based methods currently being used to detect specific strains of indicator bacteria.World Health Organization Guidelines for Drinking Water Quality state that as an indicator organism "Escherichia coli" provides conclusive evidence of recent fecal pollution and should "not" be present in water meant for human consumption.In the U.S., the EPA "Total Coliform Rule" states that a water system is out of compliance if more than 5 percent of its monthly water samples contain coliforms.