CRITERION™ Tryptose Agar

Cat. no. C7170 CRITERION™ Tryptose Agar 82gm
Cat. no. C7171 CRITERION™ Tryptose Agar 500gm
Cat. no. C7172 CRITERION™ Tryptose Agar 2kg
Cat. no. C7173 CRITERION™ Tryptose Agar 10kg
Cat. no. C7174 CRITERION™ Tryptose Agar 50kg


Hardy Diagnostics CRITERION™ Tryptose Agar is recommended for use in cultivating a wide variety of fastidious microorganisms, particularly Brucella spp., but also streptococci, pneumococci, meningococci, Listeria spp., Pasteurellae and other microorganisms from mixed cultures. Additional enrichment or selective ingredients may be added to the prepared medium, as needed.

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.


Tryptose media prepared with or without meat extract or infusion are commonly recommended for the cultivation and isolation of pathogenic and saprophytic bacteria. It was traditionally considered crucial to include the use of meat extract or infusion as a nutritional supplement in culture media. While studying the growth requirements of Brucella, Huddleson found tryptose media to be equivalent or far better at providing uniformity for the cultivation and differentiation of fastidious microorganisms than meat infusion media.(1) Moreover, Castañeda and McCullough also found media containing tryptose, and supplemented with additional nutrients, particularly useful for isolating Brucella spp. from other cultures.(2,3)

The increased productivity of tryptose media in the isolation and cultivation of fastidious microorganisms, particularly Brucella spp., supports the use of this formulation as a general, all-purpose growth medium; tryptose is also useful when avoiding animal tissue products is desired. Media such as tryptose agar may be further enriched by the addition of 5% sterile, defibrinated sheep, horse or rabbit blood or 5% bovine serum to support the growth of more fastidious microorganisms. Other nutrients to further enrich the medium and selective agents such as crystal violet and varying concentrations of antibiotics may be added to suppress the growth of undesirable microorganisms.(6)

Hardy Diagnostics CRITERION™ Tryptose Agar contains tryptose as the nitrogen and carbon source. Dextrose is the energy source for metabolism. Sodium chloride is added to maintain osmotic balance and agar is the solidifying agent.


Gram weight per liter: 41.0gm/L
Tryptose 20.0gm
Sodium Chloride 5.0gm
Dextrose 1.0gm
Agar 15.0gm

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. Dehydrated culture medium is very hygroscopic. Keep lid tightly sealed. Protect dehydrated culture media from moisture and light. The dehydrated culture media should be discarded if it is not free-flowing or if the color has changed from its original light beige.

Store the prepared culture media at 2-8ºC.



1. Suspend 41gm of the dehydrated culture media in one liter of distilled or deionized water. Stir to mix thoroughly.

2. Heat to boiling for one minute to dissolve completely.

3. Sterilize in the autoclave at 121ºC. for 15 minutes.

4. Cool to 45-50ºC.

Note: Additional nutritional or selective ingredients may be aseptically added prior to dispensing media.

5. Aseptically dispense desired volume into sterile containers.


For information on procedures and interpretation of results, consult listed references.


1. Certain diagnostic tests may be performed directly on this medium. Tryptose Agar is a general, non-selective medium that may support the growth of a wide variety of microorganisms. It is therefore recommended that biochemical and/or serological tests be performed on colonies from pure culture for complete identification.

2. Hemolytic reactions of some strains of group D streptococci may be affected by differences in animal blood. Prior knowledge of these differences may be needed before use, and care should be taken in preparing blood agar from this medium.

3. The atmospheric condition of incubation is known to influence the hemolytic reaction of beta-hemolytic streptococci.(9) Incubate tryptose media supplemented with blood under anaerobic or increased CO2 conditions for best performance.

4. Some organisms may show a decrease in hemolysin production when grown on media containing dextrose.


Standard microbiological supplies and equipment such as autoclaves, incinerators, animal blood, antimicrobial agents, and incubators, etc., are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Bacteroides fragilis
ATCC ® 25285
A 24-72hr 35°C Anaerobic Growth
Clostridium perfringens
ATCC ® 13124
A 24-72hr 35°C Anaerobic Growth
Streptococcus pyogenes
ATCC ® 19615
A 24-72hr 35°C CO2** Growth

User Quality Control

** Atmosphere of incubation is enriched with 5-10% CO2.

Physical Appearance

CRITERION™ Tryptose Agar powder should appear homogeneous, free-flowing, and light beige in color. The prepared media should appear slightly opalescent, and light amber in color.


1. Huddleson, I.F. 1943. Brucellosis in Man and Animals, rev. ed. The Commonwealth Fund, New York, NY.

2. Castañeda, M.R. 1947. A Practical Method for Routine Blood Cultures in Brucellosis. Proc. Soc. Exp. Biol. Med.; 64:114-115.

3. McCullough, W.G., et al. 1947. Studies in the Nutritional Requirements of Brucella suis. J. Bacteriol.; 53:5-15.

4. Vanderzant, C. and D.F. Splittstoesser, (ed.). 1992. Compendium of Methods for the Microbiological Examination of Foods, 3rd ed. APHA, Washington, D.C.

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

6. Moyer, N.P., et al. 1995. Brucella. In Murray, P.R., et al. Manual of Clinical Microbiology, 6th ed. American Society for Microbiology, Washington, D.C.

7. Harmon, S.M., et al. 1995. Bacteriological Analytical Manual, 8th ed. FDA. AOAC International, Washington, D.C.

8. Ruoff, K.L. 1995. Streptococcus. In Murray, P.R., et al. Manual of Clinical Microbiology, 6th ed. American Society for Microbiology, Washington, D.C.; p. 299-305.

9. Atlas, R.M. 1995. Handbook of Microbiology Media for the Examination of Food. CRC Press, Boca Raton, FL; p. 266-268.

10. Marshall, Robert T. 1992. Standard Methods for the Examination of Dairy Products. 16th ed. APHA, Washington, D.C.

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