Tryptone Bile Glucuronic Agar is selective agar for the detection and enumeration of Escherichia coli in foodstuffs and animal feed and water. It differentiates most E.coli species from other coliforms. E.coli absorbs the chromogenic substrate 5-bromo-4-chloro-3-indolyl-ß-D-glucuronide.The enzyme ß-glucorinodase splits the bond between the chromophere 5-bromo-4-chloro-3-indolyl and the ß-D-glucoronide. E.coli colonies appear as blue green coloured colonies.