Lauryl Tryptose (LST) Broth is used for the detection of coliform bacteria in water and wastewater. Lauryl Tryptose Broth is not intended for use in the diagnosis of disease or other conditions in humans.

Lauryl Tryptose Broth is a selective medium for the detection of coliforms in water, dairy products and other foods. The American Public Health Authority (APHA) recommend Lauryl Tryptose Broth for the Most Probable Number Presumptive Test of coliforms in waters, effluent or sewage and as a confirmation test of lactose fermentation with gas production from milk samples and for the detection of coliforms in foods.

Lauryl Tryptose Broth is prepared according to the formulation of Mallmann and Darby. Mallmann and Darby showed that tryptose at a concentration of 2% increased the early logarithmic growth phase when compared to meat peptone. These researchers added phosphate buffers and sodium chloride, which improved gas production by “slow lactose fermenting” organisms. Sodium lauryl sulfate was incorporated as a selective agent for the inhibition of non-coliform organisms.

This medium can also be used with the addition of MUG (4- methylumbelliferyl-β-D-glucuronide) according to the ISO Standard 11866-2 to give enhanced detection of Escherichia coli.