VRBD Agar Crystal Violet Neutral Red, 500g

Description

Selective agar proposed by DAVIS (1951) for the detection and enumeration of coliform bacteria including E. coli in water, milk, ice-cream, meat and other foodstuffs

This medium complies with the recommendations of the American Public Health Association (1992), the International
Dairy Federation FIL-IDF (Internationaler Milchwirtschaftsverband 1985), the Institute for Food Technology and Packaging (Institut für Lebenmitteltechnologie und Verpackung) (1974) and the EUROGLACE (KLOSE 1968 a, b).

Mode of Action
Crystal violet and bile salts inhibit growth primarily of the Grampositive accompanying bacterial flora. Degradation of lactose to acid is indicated by the pH indicator neutral red, which changes its colour to red, and by precipitation of bile acids.

Typical Composition (g/litre)
Peptone from meat 7.0;

yeast extract 3.0;

sodium chloride 5.0;

lactose 10.0;

neutral red 0.03;

bile salt mixture 1.5;

crystal voilet 0.002;

agar-agar 13.0.

Preparation
Suspend 39.5 g in 1 litre of demin. water and heat to boiling with frequent stirring until completely dissolved. Afterwards do not boil more than 2 minutes.
 Do not autoclave. Do not overheat!
pH: 7.4 ± 0.2 at 25 °C.
The prepared medium is clear and dark-red.

Experimental Procedure and Evaluation
Culture medium is usually inoculated by the pour-plate procedure.
Incubation: 24 ± 2hours at 30 ± 1 °C (IDF-FIL) respectively according to recommended procedures.

Literature
American Public Health Association: Compendium of Methods for the microbiological Examination of Foods. – 3rd ed. (1992).
American Public Health Association: Standard Methods for the Examination of Dairy Products. – 15th ed. (1995).
DAVIS, J.G.: Milk Testing – Dairy Industries Ltd., London, 1951.