MACCONKEY BROTH, USP

Cat. no. U125 MacConkey Broth, USP, 180ml Wide Mouth Polycarbonate Jar, 100ml 12 jars/box

INTENDED USE

Hardy Diagnostics 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 for pre-enrichment of E. coli O157 for toxin testing.

Cat. no. U125 is not intended to be used for the diagnosis of human disease.

SUMMARY

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 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.

FORMULA

Ingredients per liter of water:*

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.

STORAGE AND SHELF LIFE

Storage: Upon receipt store at 2-30ºC. away from direct light. Media should not be used if there are any signs of deterioration, discoloration, contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.

PRECAUTIONS

PROCEDURE

1. Inoculate tubes with the test specimen. Incubate tubes at 42-44ºC. in an aerobic atmosphere with loose caps.

2. For toxin testing procedures, consult the manufacturer's technical insert.

INTERPRETATION OF RESULTS

Lactose-fermenting microorganisms grow well in MacConkey Broth and produce acid, causing the medium to turn yellow. Non-fermenting organisms produce excellent growth but will not produce acid or gas.

LIMITATIONS

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

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as loops, swabs, applicator sticks, other culture media, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
MacConkey Broth (Cat. no. U125):
Escherichia colib
ATCC® 8739
J 18-24hr 42 - 44°C Aerobic Growth; media turns yellow, gas production
Staphylococcus aureusb
ATCC® 6538
B 48hr 42 - 44°C Aerobic Partial to complete inhibition; no color change, no gas production

b Tested in accordance with USP <62>.(14)

USER QUALITY CONTROL

Physical Appearance

Hardy Diagnostics MacConkey Broth should appear clear, and reddish-purple in color.

REFERENCES

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. 2005. 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., 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. American Public Health Association. Standard Methods for the Examination of Water and Wastewater, 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


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