Charcoal Selective Medium- Composition, Principle, Preparation, Results, Uses


Charcoal selective medium (CSM) is a complex and selective medium that contains the following ingredients and their quantities per liter of distilled water:

  • Beef extract: 10 g
  • Gelatin peptone: 10 g
  • Casein peptone: 10 g
  • Sodium chloride: 5 g
  • Sodium desoxycholate: 0.1 g
  • Charcoal: 10 g
  • Hematin: 0.005 g
  • Sodium pyruvate: 0.1 g
  • Ferrous sulfate: 0.05 g
  • Cefoperazone: 0.032 g
  • Vancomycin: 0.01 g
  • Cycloheximide: 0.002 g
  • Agar: 15 g

The final pH of the medium is adjusted to 7.4 ± 0.2 at 25°C.

Each ingredient has a specific role in the medium, as explained in the principle section. The medium is prepared by dissolving the components in water, heating to boiling, autoclaving, cooling, and pouring into sterile plates or tubes.

The medium is dark gray to black in color due to the presence of charcoal. The medium should be stored at 2-8°C and used within one month of preparation. The medium should not be used if there are signs of deterioration, such as discoloration, contamination, or changes in physical appearance.

The medium can be supplemented with other antibiotics or substances to enhance its selectivity or specificity for certain Campylobacter species. For example, trimethoprim can be added to inhibit Proteus and Escherichia coli; polymyxin B can be added to inhibit Pseudomonas and Aeromonas; and cefixime can be added to inhibit Salmonella and Shigella.

The composition of charcoal selective medium may vary slightly depending on the manufacturer or the source of the recipe. However, the basic ingredients and their functions remain the same. The medium should be used according to the instructions provided by the manufacturer or the reference method.