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.