Description
Lauryl Tryptose Broth is a standard method medium1 prepared to the formula of Mallmann and Darby2, who demonstrated the value of the medium in the detection of coliforms in water, dairy and other foods, using American Public Health Association Procedures3,4.
Sodium Lauryl Sulphate was incorporated into the medium as a selective but non inhibitory agent for coliforms. The medium is specified for use in the presumptive stage of Standard Total Coliform Multiple Tube – Most Probable Number test for coliforms in the examination of water.
It is also used for the detection of coliforms in foods and milk and is particularly useful in the dairy industry.
The standard medium contains no indicator, but an alternative medium, AM82 Lauryl Tryptose Broth with 0.01 gm of bromocreasol purple per litre is available if preferred. Tubes indicating gas production at 35°C after 24 and 48 hours are subjected to further testing at temperatures of 35°C and 44°C simultaneously in tubes inoculated from the culture tube giving the presumptive positive result.
This medium is suitable for the addition of Kovac’s or Ehrlich’s reagent to detect indole production in tubes indicating gas production at 44°C. This addition may by made as early as 7 hours after incubation if gas production is evident, however, further incubation may be required before considering a tube to have a negative result.
