Thermo Scientific™ MRVP Medium (Dehydrated)

Description

• Differentiate coli-aerogenes group by Methyl-red and Voges-Proskauer tests with Thermo Scientific™ Oxoid™ MRVP Medium (Dehydrated)
• This glucose-phosphate medium is recommended for the Methyl-red and Voges-Proskauer tests, for the differentiation of the coli-aerogenes group 1
• Both of these tests are based on the detection of specific breakdown products of carbohydrate metabolism
• Use MRVP Broth for differentiation of coli-aerogenes group by the Methyl-red and Voges-Proskauer test
• Smith 2 noted the low acid production of Enterobacter aerogenes cultures as compared with those of Escherichia coli
• Clark & Lubs 3 employed methyl-red as a hydrogen-ion concentration indicator in order to differentiate glucose phosphate peptone water cultures of members of the coli-typhoid group
• This test, now known as the Methyl-red test, distinguishes those organisms able to form large amounts of acid from glucose so that the pH falls below 4.4 and those organisms which cannot produce a low pH level
• The difference in pH value is visualised by adding methyl-red to the culture, (<pH 4.4 red: pH 5.0-5.8 orange: >pH 6.0 yellow)
• Voges & Proskauer 4 described a red fluorescent coloration that appeared after the addition of potassium hydroxide to cultures of certain organisms in glucose medium
• The coloration was shown to be due to the oxidation of the acetylmethyl-carbinol producing diacetyl which reacts with the peptone of the medium to give a red colour 5,6
• Durham 7 noted that Enterobacter aerogenes gave a positive reaction but that Escherichia coli produced no coloration, and it later became clear that there was a negative correlation between the Methyl-red and Voges-Proskauer tests 8,9 for lactose-fermenting coliform organisms
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• Remel™ and Oxoid™ products are now part of the Thermo Scientific brand.