Chocolate Agar

Chocolate Agar is an alternative medium for the isolation of fastidious organisms from clinical specimens. In 1945, Johnston reported a medium which produced Neisseria gonorrhoeae colonies within 24 hours1 whose recovery time was further reduced by Carpenter and Morton formulation that is enriched with hemoglobin and yeast extract giving the Chocolate Agar formulation2.

Fastidious organisms such as Haemophilus and Neisseria require specially enriched culture media and conditions. The red blood cells from the blood in chocolate agar have been heated until they are lysed, giving the medium its 'chocolate' appearance. This provides the medium heat-labile X factor (heme/hemin) and the V factor (nicotinamide adenine dinucleotide, NAD) necessary for the growth of Haemophilus influenzae in addition to other nutrients. Further incorporation of pyridoxal into chocolate medium resulted in a medium that useful in the recovery of nutritionally deficient Streptococcus species.

Chocolate agar, however, does not reveal hemolysis data, so species differentiation among the members of Haemophilus must be performed in another manner.

Product NameCatalog #Quantity
Chocolate Agar mono plate, 90 x 15 mm CC9230P 10/pk
Chocolate Slant CC9230S 10/pk
Chocolate Broth CC9230B 10/pk

Quality Control

The following organisms are routinely used for testing for this medium.
Test OrganismsResults
Chocolate Agar:  
  Neisseria gonorrhoeae ATCC® 43069 Growth
  Haemophilus influenzaATCC® 10211 Growth
Chocolate Agar with Pyridoxal:  
  Neisseria gonorrhoeaeATCC® 43069 Growth
  Haemophilus influenza ATCC® 10211 Growth
  Streptococcus mitis ATCC® 6249 Growth

User Quality Control

Check for signs of contamination and deterioration. Users of commercially prepared media may be required to perform quality control testing with at least one known organism to demonstrate growth or a positive reaction; and at least one organism to demonstrate inhibition or a negative reaction (where applicable).

Ingredients g/L

(Final pH 7.2 +/- 0.2 at 25°C)
Proteose Peptone 20.0
Sodium Chloride 5.0
Dipotassium Phosphate 0.50
Dextros 0.50
Agar 15.0
Chocolate Agar with Pyridoxal contains:  
Pyridoxal 0.01
2 total citations

  1. Johnston, et al. 1945. J. Ven. Dis. Inf.; 26:239.
  2. Carpenter, C.M. and H.E. Morton. 1947. Proc. N.Y. State Assoc. Public Health Labs; 27:58-60.
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