The 3M Petrifilm Rapid Coliform Count Plate is a ready-made culture medium system which contains Violet Red Bile (VRB) nutrients, a cold-water-soluble gelling agent, a pH indicator to detect acid and a tetrazolium indicator that facilitates colony enumeration.
Petrifilm Rapid Coliform Count Plates are useful for the enumeration of coliform bacteria. Early coliform results may begin to appear as soon as six hours of incubation and appear as discreet, yellow acid zones, with or without colonies. Unlike traditional coliform tests, final coliform results appear as colonies associated with gas bubbles and may begin to appear as early as eight hours of incubation. At any time you see a colony associated with gas within the 24-hour incubation period, it is a confirmed coliform. Continue to incubate plates after each reading to detect confirmed coliform growth. A total coliform count is determined at 24 hours.