n CRITERION Cooked Meat Medium - a growth medium especially for anaerobic bacteria


Cat. no. C5480 CRITERION™ Cooked Meat Medium 100gm
Cat. no. C5481 CRITERION™ Cooked Meat Medium 500gm
Cat. no. C5482 CRITERION™ Cooked Meat Medium 2kg
Cat. no. C5483 CRITERION™ Cooked Meat Medium 10kg
Cat. no. C5484 CRITERION™ Cooked Meat Medium 50kg


Hardy Diagnostics CRITERION™ Cooked Meat Medium is recommended for the cultivation of aerobic, microaerophilic, and anaerobic microorganisms, especially Clostridium species.

This dehydrated culture medium is a raw material intended to be used in the making of prepared media products, which will require further processing, additional ingredients, or supplements.


The use of animal tissue for culturing anaerobic organisms was first employed by Theobald Smith in 1890.(4) Von Hibler later used brain tissue for cultivating and classifying anaerobic bacilli.(5) Robertson replaced brain tissue with beef heart and used this medium to differentiate putrefactive and saccharolytic species.(4)

The formulation presently used is a modified version of Robertson's formulation. This medium is also referred to as Chopped Meat Medium.(2)

Nutritional requirements needed by most bacteria are provided by beef heart, peptone and dextrose. Dextrose, yeast extract, hemin and vitamin K are added to enhance the growth of anaerobic microorganisms. Amino acids and other nutrients are supplied by the muscle protein in the heart tissue granules. Reducing substances, which permit the growth of strict anaerobes, are supplied by the muscle tissue and the iron filings.(8) It is thought that the meat particles act as a reducing and detoxifying substance, thereby disabling harmful by products that may be produced by the replicating organism.(10) Because reducing substances are more available in denatured protein, the meat particles are cooked before use in the medium.

Growth of spore-forming and non-spore-forming obligate anaerobes is supported by this medium. Cooked Meat Medium is also useful as an enrichment broth for cultivating organisms from a very small inoculum.(2,3,7,8,9) Additionally, researchers have found that Cooked Meat Medium preserves viability of organisms over a long period of time and is useful in maintaining anaerobic stock organisms.(12) The Food and Drug Administration recommends its use in the enumeration and identification of Clostridium perfringens from food.(13)


Gram weight per liter: 33.0gm/L
Beef Heart 454.0gm
Peptic Digest of Animal Tissue 10.0gm
Pancreatic Digest of Casein 10.0gm
Sodium Chloride 5.0gm
Dextrose 2.0gm

Final pH 7.2 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.


Store the sealed bottle(s) containing dehydrated culture medium at 2-30ºC. Keep lid tightly sealed. Protect dehydrated culture media from moisture and light. The dehydrated culture media should be discarded if it is not in pellet form or if the color has changed from its original brown.

Store the prepared culture media at 2-30ºC.



1. Place 1.25gm of meat granules into a test tube and add 10mL of deionized water.

2. Allow to stand for 15 minutes until the meat particles are thoroughly wetted.

3. Autoclave at 121ºC. for 15 minutes. Reduce pressure slowly after sterilization to prevent the medium from expelling from the container.

4. Aseptically add enrichments (vitamin K and hemin) as desired.

5. Cool to 45-50ºC. without agitation.

6. If not used within 24 hours, reheat to 100ºC. prior to use, in order to drive off dissolved oxygen.


For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. K19.


Meat particles in the medium may cause turbidity, which could be misinterpreted as positive growth.

Meat particles blacken only in the presence of alkali, which is a result of ammonia production by proteolytic enzymes.

The reactions observed in the medium are useful for characterization, not speciation, of the organism.


Standard microbiological supplies and equipment such as autoclave, incubators, etc., are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Bacteroides fragilis
ATCC ® 25285
A 24-48hr 35°C Aerobic** Growth
Streptococcus pyogenes
ATCC ® 19615
A 24-48hr 35°C Aerobic Growth
Clostridium perfringens
ATCC ® 13124
A 24-48hr 35°C Aerobic Growth

** Tubes are incubated in an aerobic incubator with the caps screwed down tightly to create an atmosphere of low oxygen tension within the tube.

User Quality Control

** Tubes are incubated in an aerobic incubator with the caps screwed down tightly to create an atmosphere of low oxygen tension within the tube.


CRITERION™ Cooked Meat Medium powder should appear as hard pellets, and brown in color. The prepared media should appear amber with approximately one inch of chopped meat on the bottom.


1. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

2. Jorgensen., et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.

3. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.

4. MacFaddin, J.F. 1985. Media for Isolation, Cultivation, Identification, Maintenance of Bacteria, Vol. I. Williams & Wilkins, Baltimore, MD.

5. Smith, T. 1890. Centr. Bakteriol.; 7:509.

6. Von Hibler, E. 1899. Centr. Bakteriol.; 25:513, 594, 631.

7. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.

8. Robertson, M. 1916. J. Pathol. Bacteriol.; 20:327.

9. Willis. 1977. Anaerobic Bacteriology: Clinical and Laboratory Practice, 3rd ed. Butterworths, London.

10. Quality Assurance for Commercially Prepared Microbiological Culture Media, M22. Clinical and Laboratory Standards Institute (CLSI - formerly NCCLS), Wayne, PA.

11. Dowell, Lombard, Thompson and Armfield. 1979. Media for Isolation, Characterization and Identification of Obligately Anaerobic Bacteria, CDC Laboratory Manual, DHEW Publications No. (CDC) 79-8272. CDC, Atlanta, GA.

12. Holman, W.L. 1919. J. Bacteriol.; 4:149.

13. Claros, M.C., et al. 1995. J. Clin. Micro.; 33; 9:2505-2507. American Society for Microbiology.

14. U.S. Food and Drug Administration. Bacteriological Analytical Manual. AOAC, Arlington, VA.

ATCC is a registered trademark of the American Type Culture Collection.