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Description:
Voges Proskauer Medium, Modified is recommended for the performance of the Voges - Proskauer test in differentiation of Bacillus cereus in accordance with FDA BAM, 1998. Methyl Red and Voges -Proskauer tests are among the two various tests used in the biochemical id entification of bacterial species. These tests were originally studied by Voges and Proskauer (1) and subsequently by Clark and Lubs (2) to differentiate between members of the coli-aerogens group.
Both the tests are based on the detection of specific bre akdown products of carbohydrate metabolism. In MR-VP Broth, after 18-24 hours of incubation, fermentation produces acidic metabolic byproducts. MR-negative organisms further metabolize the initial fermentation products by decarboxylation to produce neutral acetyl methylcarbinol (acetoin), which results in decreased acidity in the medium and raises the pH towards neutrality (pH 6.0 or above) (3).
In the presence of atmospheric oxygen and alkali, the neutral end products, acetoin and 2, 3-butanediol, are oxidized to diacetyl, which react with creatine to produce a red colour. Inoculate 5 ml medium with 3 mm loopful of culture and incubate tubes 48 ± 2 h at 35°C. Test for production of acetylmethylcarbinol by pipetting 1 ml culture into 16 × 125 mm test tube an d adding 0.6 ml of 5% alpha-naphthol (RM1392) solution and 0.2 ml 40% potassium hydroxide (RM1015). Shake, and add a few crystals of creatine.
Observe results after holding for 1 h at room temperature. Test is positive if pink or violet color develops. Pro teose peptone and dextrose provide necessary growth requirements to the medium and sodium chloride maintains the osmotic equilibrium.
Specification:
100g