CRITERION™ MANNITOL SALT AGAR (MSA)

Cat. no. C6230 CRITERION™ Mannitol Salt Agar 233.4gm
Cat. no. C6231 CRITERION™ Mannitol Salt Agar 500gm
Cat. no. C6232 CRITERION™ Mannitol Salt Agar 2kg
Cat. no. C6233 CRITERION™ Mannitol Salt Agar 10kg
Cat. no. C6234 CRITERION™ Mannitol Salt Agar 50kg

INTENDED USE

Hardy Diagnostics CRITERION™ Mannitol Salt Agar (MSA) is recommended for use as a selective medium for the isolation of coagulase-positive mannitol-positive Staphylococcus aureus strains.

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.

SUMMARY

Koch reported the use of a medium containing 7.5% sodium chloride as a selective agent for the isolation of staphylococci in 1942.(5) The results were confirmed and improved by Chapman in 1945 by the addition of this salt concentration to phenol red mannitol agar, as Staphylococcus aureus usually ferments mannitol.(3) Non-pathogenic staphylococci usually show less luxuriant growth on this medium after the incubation period.

A sodium chloride concentration of 7.5% is nearly ten times the usual concentration seen in most media. It serves to inhibit most organisms except staphylococci in mixed flora specimens. The beef extract and peptones supply the essential elements carbon, nitrogen, and sulfur. Mannitol is added to show the fermentation capabilities of the organisms. Acid production as the result of fermentation of this sugar results in the formation of colonies with a yellow zone. Those staphylococci that do not ferment mannitol show a purple or red zone around the colonies.

Mannitol Salt Agar (MSA) is recommended by the American Public Health Association for the enumeration of staphylococci in food and dairy products.(9,10)

FORMULA

Gram weight per liter: 116.7g/L
Sodium Chloride 75.0g
Proteose Peptone 10.0g
Mannitol 10.0g
Beef Extract 1.0g
Phenol Red 25.0mg
Agar 15.0g

Final pH 7.4 +/- 0.2 at 25°C.

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

STORAGE AND SHELF LIFE

Store the sealed bottle(s) containing dehydrated culture medium at 2-30°C. 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 pinkish-beige.

Store the prepared plated culture media at 2-8°C. The prepared tubed culture media may be stored at 2-30°C.

PRECAUTIONS

METHOD OF PREPARATION FOR DEHYDRATED CULTURE MEDIA

1. Suspend 116.7g of the dehydrated culture media in 1 liter of distilled or deionized water.

2. Heat to boiling and mix to dissolve completely.

3. Sterilize in the autoclave at 121°C for 15 minutes.

PROCEDURE AND INTERPRETATION OF RESULTS

For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. G40.

LIMITATIONS

Most organisms other than staphylococci are inhibited by the high salt concentration found in Mannitol Salt Agar except for some halophilic marine organisms.

Accurate counting may be difficult with molds or spreading colonies.

Rare, fastidious microorganisms may not grow on selective media formulations.

MATERIALS REQUIRED BUT NOT PROVIDED

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

QUALITY CONTROL

Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Staphylococcus aureus
ATCC® 25923
A 24-48hr 35°C Aerobic Growth; yellow colonies and media at 24-48 hours
Staphylococcus aureus**
ATCC® 6538
J 18-24hr 35°C Aerobic Growth; yellow colonies and media at 18-24 hours
Proteus mirabilis
ATCC® 12453
B 24-48hr 35°C Aerobic Partial to complete inhibition
Escherichia coli**
ATCC® 8739
B 48hr 35°C Aerobic Partial to complete inhibition

** Tested in accordance with USP <61> and <62>.(11,12)

User Quality Control

PHYSICAL APPEARANCE

CRITERION™ Mannitol Salt Agar powder should appear moist, clumpy, and yellow-beige in color. The prepared media should appear clear, slightly opalescent and pinkish-red in color.

REFERENCES

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

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

3. Chapman, G.H. 1945. J. Bacteriol.; 50:201.

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

5. Koch, F.E. 1942. Zentr. Bakt. Labt. Orig.; 149:122.

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

7. Jorgensen, et al. Manual of Clinical Microbiology, 8th ed. American Society for Microbiology, Washington, D.C.

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

9. Standard Methods for the Examination of Dairy Products, APHA, Washington, D.C.

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

11. 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.

12. 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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