Phenol Red Tartrate HiVeg™ Agar

Principle and Interpretation

Phenol Red Tartrate HiVeg Agar is prepared by using HiVeg peptone which is free of BSE/TSE risks associated with animal based peptones. This medium is the modification of Phenol Red Tartrate Agar which was originally formulated by Brown et al (1) and further modified by Jordon and Harmon (2) for the differentiation of Enterobacteriaceae especially Salmonella species. This medium, like the conventional medium can be used to differentiate Vibrio parahaemolyticus (positive) from Aeromonas species (negative) (3) and also with addition of sodium chloride (25.0 g/l) can differentiate halophilic Vibrio species e.g. Vibrio parahaemolyticus, Vibrio vulnificus, Vibrio aglinolyticus and Vibrio metschnikovii. On this medium, an acidic reaction is produced by Salmonella serotype Enteritidis, Salmonella serotype Cholerasuis, Salmonella serotype Typhi, Salmonella serotype Typhimurium, Escherichia coli, and Proteus vulgaris strains. However the organisms like Salmonella serotype Paratyphi and Salmonella serotype Schottmuelleri produce an alkaline reaction. HiVeg peptone provides the essential growth nutrients like nitrogenous compounds to the organisms. D-Tartaric acid is used most frequently because it is easy to be utilized by the organism. Sodium potassium tartrate corresponds to it in this medium. Tartrate utilization (fermentation) yields an acidic reaction which is indicated by the yellow colour formation at the bottom of the tube. Phenol red acts as the pH indicator while sodium chloride maintains the osmotic balance of the medium. Inoculate cultures isolated on solid medium. Do not take the inoculum from liquid or broth suspension (3).