For isoloation and identifiation of yersenia enterocolitica from food and animal feeding stuffs. ISO 10273:1994 Yersinia enterocolitica is a Gram-negative bacillus belonging to the family Enterobacteriaceae. Yersinia enterocolitica is the causative agent of Yersiniosis, a severe form of human gastroenteritis. Bile Esculin Agar is recommended for the isolation and identification of Y. enterocolitica, as per ISO 10273-1994. Bile Esculin Agar containing 4% bile salts was formulated by Swan and modified by Facklam and Moody. Bile Esculin Agar is also recommended by APHA for identification of Group D Streptococci. Peptic digest of animal tissue and beef extract serve as source of carbon, nitrogen and essential growth factors. Enterococci and certain streptococci hydrolyze the glycoside esculin to esculetin and dextrose. Esculin reacts with an iron salt to form a dark brown or black complex. Ferric citrate is incorporated into the medium as an indicator of esculin hydrolysis and resulting esculetin formation. Bile salts are used to inhibit gram-positive bacteria other than Enterococci.