Selective Streptococcus Agar Selective Streptococcus Agar is a medium used with the addition of blood to isolate and detect pathogenic Streptococci, especially those from Group A. The antimicrobial additions increase the selectivity of this medium by suppressing common bacteria detected from a throat swab. Casein Digest Peptone and Beef Extract provide nitrogenous compounds. Maltose is the fermentable carbohydrate. Together with Nucleic Acid, it promotes the production of hemolysis. Sodium Chloride maintains the osmotic balance. Neomycin and Polymyxin B are selective agents against coliforms, Staphylococci, Micrococcus spp., Haemophilus spp., and Neisseria spp., among others. Agar is the gelifying agent. Data-sheet.pdf S19-106.pdf