Thermo Scientific™ MR-VP Medium (Dehydrated)

Description

• Help identify enteric gram-negative bacilli using Thermo Scientific™ Remel™ MR-VP Medium (Dehydrated)
• In 1898, Voges and Proskauer reported the production of a red color after the addition of potassium hydroxide to cultures grown on an appropriate medium 1
• Later Barret made the VP test more sensitive by the addition of alpha naphthol to the medium 2
• In 1915, Clarke and Lubs first described the methyl red test in differentiating between the coli-aerogenes group of enteric bacteria 3
• MR-VP medium was developed further to permit both tests to be performed using the same medium
• Differentiate microorganisms on the basis of acid or acetylmethyl carbinol production (MR-VP Reaction)
• Both MR and VP tests can be performed using the same medium
• Ease of Differentiation: MR positive organisms produce a red color, while VP positive organisms produce a pink-red color
• MR and VP negative organisms produce a yellow color on the surface of the medium
• The medium requires the addition of Methyl Red Reagent (R21236) and VP A 5% (R21200) and VP B (R21281) reagents
• The MR test is based on the use of a pH indicator, methyl red, to determine the hydrogen ion concentration present when an organism ferments glucose 4
• MR-positive organisms continue to produce acids, overcoming the phosphate buffer and resulting in a low pH and a red color development
• MR-negative organisms further metabolize the initial fermentation products by decarboxylation to produce neutral acetyl methyl carbinol (acetoin), which results in a neutral pH
• The VP test is based on the detection of acetylmethylcarbinol derived from glucose metabolism and is used primarily to separate Escherichia coli (VP negative) from the Klebsiella-Enterobacter group (VP positive)
• Acetylmethylcarbinol is a precursor to 2,3-butanediol are oxidized to diacetyl which is the reactant for the pink-red color produced in the VP test 5
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• Remel™ and Oxoid™ products are now part of the Thermo Scientific brand.