Bile Esculin Azide Agar ISO 7899-2 Condalab 1005

Bile Esculin Azide Agar is a modified version of Bile Esculin Agar as it has the addition of sodium azide as an inhibitor and with the reduction of the bile concentration. The resulting medium is more selective yet still provides rapid growth and efficient recovery of enterococci. Organisms positive for esculin hydrolysis hydrolyse, the glycoside esculin to esculetin and dextrose. The esculetin reacts to the Ferric ammonium citrate to form a dark brown or black colony. The ox bile does not inhibit enterococci, but other Gram-positive bacteria are inhibited. Sodium azide inhibits Gram-negative bacteria and tryptone, peptone, and yeast extract supply the nutrients essential for growth. Sodium chloride provides the osmotic balance and the bacteriological agar is the solidifying agent. The presence of intestinal enterococci is an indicator for faecal contamination especially when the contamination has occurred long before and the less resistant coliform bacteria may already be dead when the analysis is carried out. The tolerance to bile and the ability to hydrolyse esculin constitutes a reliable presumptive test for the identification of enterococci as it appears a brown colour (positive reaction) around the colonies.