Columbia Agar Base 500g is a highly nutritive general-purpose medium for the cultivation of fastidious organisms, especially when used as a base for Blood Chocolate Agar. It is suitable as a selective isolation medium by adding antimicrobial agents and for the isolation and cultivation of a wide variety of microorganisms with difficult growth characteristics. By adding blood, it can be used to determine haemolytic reactions. Most of the common pathogenic bacteria grow well without the addition of blood.

Pancreatic digest of casein, meat peptic digest and Heart pancreatic digest provide nitrogen, vitamins, minerals, and amino acids essential for growth. Yeast extract and maize starch are a source of vitamins, particularly of the B-group essential for bacterial growth. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Bacteriological agar is the solidifying agent. The blood is another source providing growth factors for the microorganisms and is the basis for determining haemolytic reactions. Haemolytic patterns may vary according to the type of blood or base medium used. For example, defibrinated sheep blood gives best results for Group A streptococci.

To make the medium more selective, the following supplements may be added if desired: CNA Staph/Streph Supplement (Cat. CL-6016) for staphylococci, streptococci, and pneumococci isolation. Brucella Supplement (Cat. CL-6017) for Brucella isolation. The European Pharmacopoeia recommends this medium for: “Microbiological examination of non-Sterile products: test for specified microorganisms” for the testing of Clostridia in products.

ISO 10272 indicates that Columbia Agar Base with blood can be used to allow the development of well-isolated colonies, to use these colonies in confirmation tests. With the addition of 5-10% sterile defibrinated blood and, especially with Polyenrichment Supplement (Cat. 6011), Polyenrichment CC Supplement (Cat. CL-6071) and VCN Supplement (Cat. CL-6013), Columbia Agar Base becomes an excellent chocolate agar that can be used to isolate pathogenic Neisseria, gonococci, and meningococci, as good as or better than Thayer-Martin Medium. Depending on the selection of inhibitors, alternative supplements to VCN may be VCNT (Cat. CL-6026) or VCAT (Cat. CL-6014).