Lab M's new Modified Lauryl Sulphate Tryptose Broth with MUG & Tryptophan (ISO) is designed for the presumptive enumeration of Escherichia coli from milk and milk products using the Most Probable Number (MPN) technique according to ISO 11866-1:2005. The key to E. coli enumeration is the addition of 4-methylumbelliferyl-ß-D-glucuronide (MUG) to the standard Lauryl Tryptose broth formulation.

Used in conjunction with the Most Probable Numbers (MPN) technique, Modified Lauryl Sulphate Tryptose Broth with MUG & Tryptophan (ISO) allows presumptive E. coli to be enumerated from presumptive coliforms. The addition of MUG allows the positive discrimination of E. coli strains. The majority of E. coli produce ß-glucuronidase enzyme which enables them to hydrolyse MUG, resulting in the release of a fluorogenic compound. Tubes which fluoresce under UV light are confirmed for E. coli by a positive indole reaction when Kovac's reagent is added to the tube.

Modified Lauryl Sulphate Tryptose Broth with MUG & Tryptophan (ISO) is described in ISO 11866-1:2005 and is used in the HPA National Standard Method D5 for Enumeration of coliforms and presumptive Escherichia coli by the Most Probable Number (MPN) technique.