Microbiology specialist Lab M is introducing a new medium for the enumeration of presumptive Escherichia coli in milk and milk products.

Modified Lauryl Sulphate Tryptose Broth (ISO) + MUG (mLSTB+MUG) adds 4-methylumbelliferyl-ß-D-glucuronide to the standard Lauryl Tryptose broth formulation. This allows presumptive E. coli to be enumerated from presumptive coliforms in milk and milk products.

Used in conjunction with the Most Probable Numbers (MPN) technique, Modified Lauryl Sulphate Tryptose Broth (ISO) is used as a confirmatory test for lactose fermentation and gas production for presumptive coliforms.

The addition of MUG to the medium allows the positive discrimination of E.coli strains. As the majority of E. coli harbour the glucuronidase enzyme, they can use MUG as a substrate, releasing a fluorogenic compound. Tubes which fluoresce under UV are confirmed for E.coli by a positive indole reaction when Kovac's reagent is added to the tube.