Selective For: General coliforms
Description: VRB is AOAC approved for the detection of coliform bacteria in dairy products. It is also used for direct count of coliform bacteria in water. This medium is particularly useful to control the pasteurization process of milk. It is possible to determine coliform counts at any stage of the process, thus evaluating the cleanliness of each piece of equipment, as well as finding sources of contamination. This medium promotes growth of E. coli, Enterobacter, Salmonella and inhibits growth of Gram-positive bacteria such as Staphylococcus.
Composition: Peptone, yeast extract, sodium chloride, bile salt mixture, neutral red, lactose and crystal violet. Growth of Gram-positive bacteria and non-coliform bacteria is inhibited by crystal violet and bile salts. The neutral red pH indicator causes lactose-fermenting colonies to turn red.
Procedure: Standard Methodology for product being tested. Incubation times and temperatures:
For general coliforms:
Dairy products: 24 hours at 32°C
Other foods: 24 hours at 35°C
For fecal coliforms:
24 hours at 44.5°C
Interpretation: Coliform bacteria form pink to brick-red colonies about 1 mm in diameter or larger. Non-coliform bacteria, such as Salmonella, Proteus and Shigella are colorless, with no precipitate.
Storage: Room temperature or refrigerate up to 30 days. Freeze if storing more than 30 days.
Shelf Life:1 year
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