Columbia Agar Base

Columbia Agar Base is a highly nutritive medium used for the growth and isolation of a large variety of microorganisms, particularly very fastidious bacteria: streptococci and pneumococci in animal samples. When blood, selective agents or growth accelerators are added, it becomes possible to prepare a wide variety of media adapted to specific uses.

The typical composition corresponds to that defined in European (EP), United States (UP) and Japanese (JP) Pharmacopeias.

Principles

• Peptones included in the composition of the medium favor the excellent growth of colonies.
• Yeast extract is a source of vitamin B complex.
• Starch is a detoxifying agent and also an energy source.
• Defibrinated sheep blood, which can be added to the medium, favors the detection of hemolytic reactions and supplies X factor (heme) required for the growth of a large number of bacteria, but lacks V factor (nicotinamide adenine dinucleotide) due to the presence of an NADase, which destroys any NAD present. Haemophilus influenzae, which requires both X and V factors, does not grow on agar containing ordinary blood.
• The following media can be prepared with Columbia base:
  • Blood agar: By adding 5 or 10% sterile sheep blood after autoclaving and cooling, the medium is suitable for the growth of Streptococcus, Pneumococcus, Staphylococcus, Listeria and Erysipelothrix. It can be made selective by adding colistin and nalidixic acid to preclude the development of Gram-negative bacteria and Bacillus.
  • Chocolate agar: By adding 10% sheep or horse blood to sterile Colombia Agar and heating to 70°C for 5 minutes until a chocolate color develops, an excellent medium is obtained for growth of Haemophilus, Neisseria, Taylorella or Campylobacter.
  • Base media without enrichment: Columbia Agar can be used to grow Brucella abortus, Yersinia pestis and Clostridium perfringens, as well as all enterobacteria.