Technical Data
Violet Red Bile (Lactose) Agar (Powder)
Microbiological Grade
Storage RT    Shipping RT
Components shown as g/liter
Yeast extract3.0
Sodium chloride5.0
Bile Salts No.31.5
Neutral red0.03
Crystal violet0.002
pH 7.4 0.2
A standard methods, lactose-containing selective medium for selective detection of Coliform in water, dairy products and other food materials. The medium has been used for the determination of the coli-aerogenes content of water, milk and other dairy products, dairy equipment, and food products etc 1,2. Organisms which rapidly attack lactose produce purple colonies surrounded by purple haloes. Non-lactose or late-lactose fermenters produce pale colonies with greenish zones. Other related Gram-negative bacteria may grow but can be suppressed by incubation at >42C or by anaerobic incubation. Druce et al.3 found that Violet Red Bile Lactose Agar was as good an indicator of coli-aerogenes bacteria in milk as MacConkey Broth, and that the medium was suitable for determining the coli-aerogenes content of milk.

Dehydrated Medium: Straw-pink colored, free-flowing powder.
Prepared medium: Dark purple colored gel

Storage conditions and Shelf Life
Store the dehydrated medium at 10-30C. Store the prepared medium at 2-8C and use as freshly as possible.

Suspend 38.5g in 1 liter of distilled water. Bring to the boil. Continue to boil for 2 minutes or for the minimum time necessary to dissolve completely and ensure that there are no remaining flecks of unmelted agar. No further sterilisation is necessary or desirable. Mix well before pouring.

Important Note: This product as supplied is intended for research use only, not for use in human, therapeutic or diagnostic applications without the expressed written authorization of United States Biological.

1. American Public Health Association (1978) Standard Methods for the Examination of Dairy Products. 14th Edn. APHA Inc. Washington DC.
2. American Public Health Association (1992) Compendium of Methods for the Microbiological Examination of Foods 3rd Edition APHA Inc. Washington DC.
3. Druce R. G., Bebbington N. N., Elson K., Harcombe J. M. and Thomas S. B. (1957) J. Appl. Bact. 20. 1-10.
4. Mossel D. A. A. and Vega C. L. (1973) Hlth Lab. Sci. 11. 303-307.