This media is recommended for selective isolation of Yersinia with modification of chromogenic identification. The medium is selective due to the presence of selective mix, which inhibit gram-positive and a number of gram-negative bacteria. Addition of antibiotic supplement makes it highly selective for Yersinia. Thus imparting additional selectivity. One of the chromogen is split by Yersinia species and results in purple coloured colonies. Other organisms are either inhibited or results in colourless colonies.