MUG Violet Red Bile Agar, 500 g

Escherichia coli is used as an indicator organism to determine unsanitary conditions. A number of selective media are recommended for use in enrichment, presumptive identification and confirmatory procedures for demonstrating the presence of coliforms. These procedures require longer incubation period. Violet Red Bile Agar is recommended by APHA (1, 2) for the detection and enumeration of coliforms in foods and dairy products. Addition of MUG to this medium permits the rapid detection of E.coli , when the medium is observed for fluorescence under UV light, requiring no further confirmation (3). E.coli possesses the enzyme beta-glucuronidase which specifically cleaves MUG to form a fluorogenic compound 4-methylumbelliferone, which results in visible blue-green fluorescence. MUG Violet Red Bile Agar is therefore recommended for the specific detection of E. coli (1, 2-4). Peptic digest of animal tissue, yeast extract and lactose provide essential nutrients. Crystal violet and bile salts inhibit some gram-positive and gram-negative bacteria. Neutral red acts as a pH indicator and helps to exhibit red colonies in the presence of acid from lactose fermentation. Acidic pH decreases the intensity of fluorescence(8), thus making it difficult to identify fluorescent E.coli . The plates after primary identification i.e. red colonies surrounded by bile precipitate were exposed to ammonia fumes to increase fluorescence as suggested by Freir and Hartman (6) The substrate, MUG is hydrolysed by an enzyme beta-glucuronidase, which is present in most of E. coli and a few strains of Salmonella, Shigella and Yersinia to yield a fluorescent end product, 4-methylumbelliferone (5). Proteus vulgaris in large numbers may suppress gas production by E. coli . Storage and Shelf-life: Store below 30°C in tightly closed container and prepared medium at 2-8° C. Use before expiry period on the label. References: 1. Downes F. P. and Ito K., (Eds.), 2001, Compendium of Methods for the Microbiological Examination of Foods, 4th Ed., APHA, Washington, D.C. 2. Marshall, (Ed.), 1985, Standard Methods for the Examination of Dairy Products, 16th Ed., APHA, Washington, D.C. 3. Feng P. C. S. and Hartman P. A., 1982, Appl. Environ. Microbiol., 43 :1320. 4. FDA Bacteriological Analytical Manual, 8th Edi, AOAC International,Gaithersburg 5. MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. 1, Williams and Wilkins, Baltimore. 6. Freir T.A. and Hartman P.A. (1987) Appl. Env. Microbiol. 53. 1246-1250