CPC HiVeg™ Agar Base

Principle and Interpretation

This medium is prepared by using HiVeg peptone and HiVeg extract in place of Peptic digest of animal tissue and Beef extract respectively used in the conventional medium, thus making it free from BSE/TSE risks. CPC HiVeg Agar Base is the modification of Cellobiose Polymyxin and Colistin (CPC) Agar Base formulated as per APHA (1) for the cultivation and identification of Vibrio species from foods. CPC HiVeg Agar Base is a selective and differential agar medium, designed to differentiate Vibrio vulnificus from other Vibrios(1). Vibrio cholerae strains except Vibrio cholerae 01-classical biotype grow on CPC HiVeg Agar Base while most Vibrio parahaemolyticus strains do not grow on CPC HiVeg Agar Base.

CPC HiVeg Agar Base contains HiVeg extract and HiVeg peptone which supply the essential nitrogenous compounds to the growing Vibrios. Cellobiose is fermented by some Vibrios and is indicated by the pH indicator bromo thymol blue which turns yellow at acidic pH. Cresol red is the pH indicator of alkaline range which turns red at alkaline pH. Alkaline pH of the medium enhances the recovery of Vibrios.

Prepare dried plates of CPC medium. Transfer a loopful from the surface growth of Alkaline HiVeg Peptone Water (MV618) to the surface of the plate medium by streaking. Incubate CPC HiVeg Agar Base at 40 - 42°C for 18 to 24 hours.

Typical colonies of Vibrio cholerae on CPC HiVeg Agar Base are small, smooth, opaque and green to purple in color as CPC HiVeg medium contains two pH indicators viz. bromo thymol blue and cresol red. A purple background will also develop in the CPC HiVeg Agar upon extended incubation.