Streptococcus agalactiae is a group B agent when typed using the Lancefield scheme (Oxoid). There is a commercial antibody available: Anti-Streptococcus Group B antibody (ab53584): http://www.abcam.com/Streptococcus-Group-B-antibody-ab53584.html. Phenotypically it give a positive CAMP test with Staphylococcus aureus. It can also be distinguished in a sugar fermentation panel.
Grow your sample on 5-7% horse blood agar (I like Brucella or Columbia base). Any pin-point to small beta-haemolytic colonies, that are catalase-negative, Gram-positive cocci should then be further identified by Lancefield typing (type B). You can also make use of the CAMP test - using sheep red blood cells
We buy the media plate from Biomerieux . It is a chromogenic plate and are only available as plates. All Strep B's have orange to brown colonies. With our evaluation we got a higher % positives as the ones we isolated from bloodagar plates.