EDWARD’S MEDIUM BASE, MODIFIED

Streptococci are gram-positive facultatively anaerobic bacteria, which constitute normal commensal flora of mouth, skin, intestine and upper respiratory tract of humans. Group B Streptococci are an important cause of systemic infections in infants and occasionally of bacterial endocarditis. Mastitis is a disease of cattle caused by the organisms Streptococcus agalactiae. It belongs to the Lancefield group B Streptococci. The most common selective agents used for selective isolation of Streptococci are crystal violet and thallium salts. A selective medium containing crystal violet was used by Haxthausen to isolate skin Streptococci. Subsequently it was observed that Streptococci from milk were able to grow on Gentian Violet Blood Agar whereas the other saprophytic milk bacteria were inhibited on this medium. An Esculin Blood Agar containing crystal violet was used by Edwards to isolate the causative agent of mastitis. A similar medium containing thallous acetate was also used to isolate the causative agent of mastitis.

for isolation of Streptococcus agalactiae and other Streptococci associated with bovine mastitis