Product Description

Koch, in 1942, reported that only staphylococci grow on agar media containing 7.5% sodium chloride (4).

Chapman further studied this phenomenon in greater detail and concluded that the addition of 7.5% sodium chloride to phenol red mannitol agar results in an improved medium for the isolation of plasma-coagulating staphylococci(5). Mannitol Salt Agar is listed as one of several media recommended for the enumeration of gram-positive bacteria incosmetics(6), clinical specimens(7-11),  and pharmaceutical products(1).

The USP General Chapter <62> recommends Mannitol Salt Agar as a test medium for isolating Staphylococcus aureus in the Microbiological Examination of Nonsterile Products(1).

Mannitol Salt Agar is a nutritive medium due to its content of peptones and beef extract, which supply essential growth factors, such as nitrogen, carbon, sulfur and trace nutrients. The 7.5% concentration of sodium chloride results in the partial or complete inhibition of bacterial organisms other than staphylococci. Mannitol fermentation, as indicated by a change in the phenol red indicator, aids in the differentiation of staphylococcal species. Agar is a solidifying agent.

References:

1. United States Pharmacopeial Convention, Inc. 2008. The United States pharmacopeia 31/The national formulary 26, Supp. 1, 8-1-08, online. United States Pharmacopeial Convention, Inc., Rockville, Md.
2. European Directorate for the Quality of Medicines and Healthcare. 2008. The European pharmacopoeia, 6th ed., Supp. 1, 4-1-08, online. European Directorate for the Quality of Medicines and Healthcare, Council of Europe, 226 Avenue de Colmar BP907-, F-67029 Strasbourg Cedex 1, France.
3. Japanese Ministry of Health, Labour and Welfare. 2006. The Japanese pharmacopoeia, 15th ed., online. Japanese Ministry of Health, Labour and Welfare. 
4. Koch.  1942.  Zentralbl. Bakteriol. Parasitenkd. Abt. I Orig. 149:122.
5. Chapman. 1945. J. Bacteriol. 50:201.
6. U. S. Food and Drug Administration.  Bacteriological analytical manual, online.  AOAC International, Gaithersburg, Md.
7. Murray, Baron, Jorgensen, Landry and Pfaller (eds).  2007.  Manual of clinical microbiology, 9th ed. American Society for Microbiology, Washington, D.C.
8. Forbes, Sahm and Weissfeld.  2007. Bailey and Scott’s diagnostic microbiology, 12th ed. Mosby, Inc., St. Louis, Mo.
9. MacFaddin. 2000. Biochemical tests for identification of medical bacteria, 3rd ed.  Lippincott Williams & Wilkins, Baltimore, Md.
10. Winn, Koneman, Allen, Janda, Procop, Schreckenberger and Woods (eds.). 2005. Koneman’s Color atlas and textbook of diagnostic microbiology, 6th Ed.  Lippincott Williams & Wilkins, Baltimore, Md.
11. Isenberg and Garcia (Ed). 2004 (update, 2007). Clinical microbiology procedures handbook, 2nd ed. American Society for Microbiology, Washington, D.C.