Columbia CNA Agar

Columbia CNA Agar is used with blood for the selective isolation of Gram-positive cocci in a laboratory setting. Columbia CNA Agar is not intended for use in the diagnosis of disease or other conditions in humans.

Ellner et al. described Columbia CNA Agar as a variation of Columbia Blood Agar Base that is selective for Gram-positive cocci. Colistin and Nalidixic Acid are added to the formula, selecting for Gram-positive organisms and fungi by suppressing Gram-negative bacteria.


Formula Liter
Enzymatic Digest of Casein 5 g
Enzymatic Digest of Animal Tissue 8 g
Yeast Enriched Peptone 10 g
Corn Starch 1 g
Sodium Chloride 5 g
Colistin 0.015 g
Nalidixic Acid 0.01 g
Agar 14 g

Final pH: 7.3 ± 0.2 at 25°C
Formula may be adjusted and/or supplemented as required to meet performance specifications.


  1. Suspend 43 g of the medium in one liter of purified water.
  2. Heat with frequent agitation and boil for one minute to completely dissolve the medium.
  3. Autoclave at 121°C for 15 minutes. Do not overheat medium.
  4. Prepare 5% blood agar by aseptically adding the appropriate volume of sterile defibrinated blood to melted sterile agar medium, cooled to 45 – 50°C.

Order Details

Product # Product Description
7126A Columbia CNA Agar, 500 g
7126B Columbia CNA Agar, 2 kg
7126T Columbia CNA Agar, 5 kg