Lauryl Tryptose Broth and Lauryl Sulfate Broth, which are also known as Lauryl Sulfate Tryptose (LST) Broth, are used for the detection of coliform organisms in materials of sanitary importance.
SUMMARY AND EXPLANATION
Mallmann and Darby developed this medium for the detection of coliform organisms by American Public Health Association (APHA) procedures. They incorporated sodium lauryl sulfate into the formulation since it proved to be selective but not inhibitory for coliforms.
This medium is used for the detection of coliforms in foods and dairy products. It is now the medium of choice for use in the presumptive phase of the Standard Total Coliform Multiple-Tube (MPN) Test for the microbiological examination of water. It is also listed in the Official Methods of Analysis of AOAC International.
Peptone provides essential growth substances, such as nitrogen and carbon compounds, sulfur and trace ingredients. The potassium phosphates provide buffering capacity. Sodium chloride maintains osmotic equilibrium.
Lactose provides a source of fermentable carbohydrate for coliform organisms. The fermentation of lactose with gas formation is a presumptive test for coliforms. Sodium lauryl sulfate inhibits organisms other than coliforms.