Bile Esculin Agar Iso 10273 1031 Condalab

Bile Esculin Agar is ideal for the isolation and differentiation of intestinal enterococci which is based on esculin hydrolysis in the presence of bile. ISO 10273 recommends it for the fermentation studies of esculin by Yersinia. An esculin test can be carried out to determine presumed pathogenicity since pathogenic Yersinia enterocolitica strains are esculin negative. This test for fermentation of esculin is equivalent to the test for fermentation of salicin.

Organisms positive for esculin hydrolysis hydrolyse the glycoside esculin to esculetin and dextrose. The esculetin reacts with the Ferric citrate to form a dark brown or black colony. Bile Salts do not inhibit enterococci while other Gram-positive bacteria are inhibited. Beef extract and peptone supply the nutrients essential for growth and bacteriological agar is the solidifying agent.

Tolerance to bile and the ability to hydrolyse esculin constitutes a reliable presumptive test for the identification of Enterococci. The brown colour (positive reaction) around the colonies appears after 18-24 hours of incubation at a temperature of 35±2 °C. The presence of intestinal enterococci is an indicator for faecal contamination, especially when the contamination occurred a long before and the less resistant coliform bacteria, including Escherichia coli, may already be dead when the analysis is carried out.