Streptococcus agalactiae Selective HiVeg™ Agar Base

Principle and Interpretation

This medium is prepared by completely replacing animal based peptones by vegetable peptones making the medium free of BSE/TSE risks. Streptococcus Agalactiae Selective HiVeg Agar Base is the modification of Streptococcus Agalactiae Selective Agar Base formulated by Hauge and Kohler - Ellingsen (1) for the isolation of Streptococcus agalactiae, the causative agent of mastitis in cattle. Thallous sulphate and crystal violet inhibit the accompanying bacterial flora. Differentiation between Streptococcus species is done on the basis of esculin hydrolysis seen as dark brown colour due to formation of an esculin - thallium complex. Staphylococcus beta- toxin attacks the erythrocytes present in the medium in such a way that they may be completely haemolyzed by Streptococcus agalactiae, though this bacterium is not haemolytic on simple blood agar. Thus Streptococcus agalactiae can be distinguished from obligate, non-haemolyzing colonies. Streptococcus agalactiae forms dove - blue coloured, smooth colonies surrounded by zones of haemolysis. Further identification is done by using biochemical and serological methods, but primarily by using CAMP test (2).