CRITERION™ MacConkey Broth

Cat. no. C6140 CRITERION™ MacConkey Broth 70gm
Cat. no. C6141 CRITERION™ MacConkey Broth 500gm
Cat. no. C6142 CRITERION™ MacConkey Broth 2kg
Cat. no. C6143 CRITERION™ MacConkey Broth 10kg
Cat. no. C6144 CRITERION™ MacConkey Broth 50kg


Hardy Diagnostics CRITERION™ MacConkey Broth is recommended for cultivating gram-negative, lactose- fermenting bacilli from water and foods as a presumptive test for coliforms. MacConkey Broth can also be used pre-enrichment of E. coli O157 for toxin testing.

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.


Hardy Diagnostics CRITERION™ MacConkey Broth is a modification of the original bile salt broth recommended by MacConkey, which contained 0.5% sodium taurocholate and litmus as an indicator.(1) MacConkey later suggested variations of this formulation using neutral red as an indicator instead of litmus.(2,3) Consequently, Childs and Allen demonstrated the inhibitory effect of neutral red and further revised the formula to include the less inhibitory bromcresol purple.(4) Bile salts in the growth medium replaced the original sodium taurocholate.

Gelatin peptone provides CRITERION™ MacConkey Broth with nitrogen and vitamins to promote growth. Lactose is utilized by lactose-fermenting bacilli. Bile salts inhibit the growth of gram-positive microorganisms, and bromcresol purple acts as the pH indicator.


Gram weight per liter: 35.0gm/L
Gelatin Peptone 20.0gm
Lactose 10.0gm
Bile Salts 5.0gm
Bromcresol Purple 0.01gm

Final pH 7.3 +/- 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 35gm of the dehydrated culture medium in one liter of distilled or deionized water. Stir to mix thoroughly.

2. Heat as necessary to dissolve completely.

3. Dispense as desired into tubes containing inverted Durham tubes. Loosen caps prior to autoclaving.

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

5. Cool to 45-50ºC. Tighten caps and store appropriately until use.


For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. K194 or U125.


Due to nutritional variation, some strains encountered may grow poorly or fail to grow on this medium.


Standard microbiological supplies and equipment such as loops, tubes, autoclaves, incinerators, and incubators, etc., are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Escherichia coli
ATCC ® 8739**
J 18-24hrs 35°C Aerobic Growth; media turns yellow, gas production
Staphylococcus aureus
ATCC ® 6538**
B 18-24hrs 35°C Aerobic Partial to complete inhibition; no color change in media, no gas production

** Recommended QC strains for User Quality Control according to the CLSI document M22 when applicable.

Tested in accordance with USP <61> and <62>.(13,14)

User Quality Control

Physical Appearance

CRITERION™ MacConkey Broth powder should appear homogeneous, free-flowing, and light beige in color. The prepared medium should appear clear and reddish-purple in color.


1. MacConkey. 1901. Zentralbl. Bakteriol.; 29:740.

2. MacConkey, A.T. 1905. Lactose-fermenting bacteria in faeces. J. Hyg.; 5:333-379.

3. MacConkey. 1908. J. Hyg.; 8:322.

4. Childs, Eileen and Allen, L.A. 1953. Improved methods for determining the most probable number of Bacterium coli and of Streptococcus faecalis. J. Hyg.; 51:468-477.

5. 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.

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

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

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

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

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

11. American Public Health Association. Standard Methods for the Examination of Dairy Products, APHA, Washington, D.C.

12. Greenberg, A.E., et al. (ed.). 1992. Standard Methods for the Examination of Water and Wastewater, 18th ed. APHA, Washington, D.C.

13. The Official Compendia of Standards. USP General Chapter <61> Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests. USP-NF. United States Pharmacopeial Convention Inc., Rockville, MD.

14. The Official Compendia of Standards. USP General Chapter <62> Microbiological Examination of Nonsterile Products: Tests for Specified Microorganisms. USP-NF. United States Pharmacopeial Convention Inc., Rockville, MD.

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