Bile Esculin Azide Agar is used for the selective isolation and differentiation of group D streptococci in a laboratory setting. Bile Esculin Azide Agar is not intended for use in the diagnosis of disease or other conditions in humans.
Bile Esculin Azide Agar is a modification of the medium reported by Isenberg and Isenberg, Goldberg, and Sampson. This formula modifies Bile Esculin Agar by adding sodium azide and reducing the concentration of bile. The revised medium is more selective, but still provides rapid growth and efficient recovery of group D streptococci.
Molecular taxonomic studies of the genus Streptococcus have placed enterococci, previously described group D streptococci, in the genus Enterococcus. The ability to hydrolyze esculin in the presence of bile is a characteristic of enterococci and group D streptococci. Swan compared the use of an esculin medium containing 40% bile salts with the Lancefield serological method of grouping and reported that a positive reaction on the bile esculin medium correlated with a serological group D precipitin reaction. Facklam and Moody found that the bile esculin test provided a reliable means of identifying group D streptococci and differentiating them from non-group D streptococci.
Bile Esculin Azide Agar selected for S. bovis, displayed earlier distinctive reactions, and eliminated the requirement for special incubation temperatures.
