Thermo Scientific™

Violet Red Bile Glucose (VRBG) Agar (ISO) (Dehydrated)

Related applications:

Industrial Microbiology

Selectively enumerate Enterobacteriaceae in food, animal feed, and environmental samples with Thermo Scientific™ Oxoid™ Violet Red Bile Glucose (VRBG) Agar (ISO) (Dehydrated) while adhering to ISO 21528 and ISO 11133:2014. Due to the careful addition of selective inhibitory components, neutral red, crystal violet, and bile salts, the medium provides selectivity against non-target Gram-positive bacteria.
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Use Violet Red Bile Glucose (VRBG) Agar for examination of food, animal feed, and environmental samples, for the presence of indicator groups such as coliforms. As well as providing evidence of food hygiene and safety, indicator groups provide a measure of food quality and spoilage potential. One of the most common groups of bacteria employed as indicator organisms by the food industry are the coliforms, which can be regarded as a subgroup within the Enterobacteriaceae. However, in an attempt to improve assessment of food safety and quality by the food industry, there has been a move towards testing for total Enterobacteriaceae rather than limiting testing to coliforms.

In processed foods, particularly foods subjected to heat treatment, these organisms can provide a reliable indication of process failure, under-processing, or post-processing contamination.
  • Easy-to-read results: due to inclusion of neutral red indicator and crystal violet in the medium Enterobacteriaceae form purple pink colored colonies.
  • Adheres to ISO 21528 and ISO 11133:2014 standards.
Mossel 1 modified Violet Red Bile Lactose Agar by adding glucose to improve recovery of all Enterobacteriaceae. Later work by Mossel and Cowell;2,3 demonstrated that lactose could be omitted, resulting in the formulation known as VRBGA.

Enterobacteriaceae rapidly ferment glucose and so reduce the pH of the medium, which produces purple/pink coloured colonies due to the inclusion of the neutral red indicator and crystal violet in the medium. These colonies are usually surrounded by purple halos of precipitated bile salts. Crystal violet and bile salts inhibit the growth of Gram-positive flora.

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1. ISO 11133:2014 Microbiology of food, animal feed and water - Preparation, production, storage and performance testing of culture media.
2. Mossel, Eelderink, Koopmans and van Rossem. 1978. Lab Practice 27:1049.
3. Mossel, Eelderink, Koopmans and van Rossem. 1979. J. Food Protect. 42:470.