VetBact

Applications:

Violet red bile agar (VRB agar) is a selective medium, which is used for enumeration of coliform bacteria in water, milk and other dairy produts.

The medium contains:

• peptone (contains amino acids and peptides)
• yeast extract (contains peptides, sugars, minerals and B vitamins)
• NaCl (contributes to the osmotic balance)
• bile salts (inhibit gram positive bakteria)
• lactose (carbon source)
• neutral red (pH-indicator)
• crystal violet (inhibit gram positive bakteria)
• agar (gelifying agent)
• water

The final pH of the medium should be 7.4.

Other comments:

VRB agar is often used in combination with TSA (Tryptone Soya Agar) for the detection and enumeration of thermotolerant coliform bacteria (including E. coli). A thin layer of TSA (containing the sample with bacteria) is then molded in the bottom of the plate, which is then incubated for 1-2 h. at ambient temperature. Another layer consisting of VRG-agar is then molded on top on the TSA and the plate is incubated further.

Updated: 2023-05-31.