This medium is recommended for differentiation of bacteria on the basis of their ability to decarboxylate L-Ornithine hydrochloride. Production of ornithine decarboxylase is a helpful criterion in differentiating Enterobacteriaceae species. Bromocresol purple, BCP and cresol red are the pH indicators in this medium. Positive reaction is indicated by purple colour. Negative reaction is indicated by yellow or olive green colour.