Himedia Phenol Red Lactose Broth

Phenol Red Lactose Broth is recommended for studying lactose fermentation by the pure cultures of microorganisms. Positive reaction is indicated by the change in colour of medium to yellow due to acid production as indicated by phenol red, a pH indicator in the medium. Gas production is indicated by the bubbles formation and entrapped in Durhams tube. Escherichia coli, Enterobacter aerogenes and Klebsiella pneumoniae are known lactose fermentors and gives positive reaction. Proteus vulgaris, Salmonella Typhi, Salmonella Typhimurium and Shigella flexneri do not ferment lactose, hence there is no colour change of the medium.