Phenol Red HiVeg® Agar Base

Principle and Interpretation

These media are prepared by using vegetable peptones in place of animal based peptones that makes the media free of BSE/ TSE risks. Phenol Red HiVeg® Agar media are the modification of Phenol Red Agar media which are recommended (1, 2, 3) for studying the fermentation of various carbohydrates individually by the pure cultures of microorganisms.

HiVeg® peptone No.3 which is free from fermentable carbohydrates is added in the medium thereby preventing the production of false positive reactions. Phenol Red HiVeg® Agar when supplemented with a specific carbohydrate, a positive carbohydrate fermentation reaction is indicated by the production of a yellow colour in agar due to the effect of acid production. Gas production is indicated by the splitting of agar or by the bubbles formation. Plates or tubes may be incubated aerobically or anaerobically depending on the type of the test organism. Addition of some carbohydrates may result in an acid reaction and hence 0.1N sodium hydroxide can be added dropwise to restore the original colour taking care not to obtain too deep red or cerise colour, would prevent fermentation occurring within the usual incubation period.