This Standard sets out a method, using membrane filtration, for enumerating coliforms in water other than packaged water.Where waters are expected to contain low to moderate numbers of background bacteria, use of membrane lauryl sulfate agar (m-LS agar) is recommended as the primary isolation medium. Where waters have a likelihood of containing high numbers of background microorganisms (e.g. some ambient untreated waters, untreated drinking waters), this Standard includes the option to employ an alternative selective agar or broth (m-Endo medium) that is generally more inhibitory and can be expected to a greater extent to restrict the number and size of background colonies.NOTES:1 Membrane filtration is suitable for enumerating microorganisms only when the turbidity of the water is low.2 A flow diagram of the procedure is shown in Appendix A.

DR 06119

AS 4276.5-1995