VIOLET RED BILE GLUCOSE (VRBG) AGAR (ISO)

Violet Red Bile Glucose Agar (VRBGA) (ISO) is for the detection and enumeration of Enterobacteriaceae in food, animal feed and environmental samples. This medium meets the formulation and performance criteria laid down in ISO 21528^1.2 and ISO 11133:2014³.

Directions

Suspend 38.5g of VRBGA (ISO) dehydrated medium in 1 litre of distilled water. Bring to the boil while mixing. Continue to boil for up to 2 minutes or for the minimum time necessary to dissolve completely. DO NOT AUTOCLAVE. Cool to 44-47°C and use within 4 hours. Mix well before pouring.

Description

Various groups of bacteria or individual species are used to provide evidence of poor hygiene, inadequate processing or post-processing contamination of foods. Some bacteria, such as Escherichia coli, are present in the gastrointestinal tract of many animals, including humans, so their presence can be used to indicate potential faecal contamination.

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 gradual 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.

Mossel et al³ modified Violet Red Bile Lactose Agar by adding glucose to improve recovery of all Enterobacteriaceae. Later work by Mossel and Cowell^4,5 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.

Storage conditions and Shelf life

VRBGA (ISO) should be stored in the tightly capped original container at 10-30°C. When stored as directed, the un-opened product will remain stable until the expiry date printed on the packaging.

Locally prepared VRBGA (ISO) plates can be stored for up to 2 weeks when made from CM1082 according to the manufacturer’s instructions and stored at 2-8°C, out of direct sunlight. A longer shelf life may be attainable, but should be validated under the relevant, local manufacturing and storage conditions.

Appearance

Dehydrated medium: Straw-pink, free-flowing powder

Prepared medium: Purple gel

Quality Control

รายละเอียดสินค้า

รหัสสินค้า : CM1082

ยี่ห้อ : Oxoid

Documents & Downloads

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