Mannitol Salt Agar, 500g

Description

Mannitol Salt Agar (MSA) is used as a selective and differential medium for the isolation and identification of Staphylococcus aureus from clinical and non-clinical specimens. It encourages the growth of a group of certain bacteria while inhibiting the growth of others. It is a selective medium prepared according to the recommendations of Chapman for the isolation of presumptive pathogenic staphylococci.

Principle of Mannitol Salt Agar

Mannitol Salt Agar contains peptones and beef extract, which supply nitrogen, vitamins, minerals and amino acids essential for growth. The 7.5% concentration of sodium chloride results in the partial or complete inhibition of bacterial organisms other than staphylococci. Sodium chloride also supplies essential electrolytes for transport and osmotic balance. Mannitol is the fermentable carbohydrate, fermentation of which leads to acid production, detected by phenol red indicator, aids in the differentiation of staphylococcal species. Coagulase positive staphylococci (e.g., Staphylococcus aureus) produce yellow colonies and a surrounding yellow medium while coagulase negative staphylococci produce red colonies and no color change of the phenol red indicator. Agar is the solidifying agent.

Addition of 5% v/v Egg Yolk Emulsion enables the detection of lipase activity of staphylococci along with mannitol fermentation. The salt clears the egg yolk emulsion and lipase production is detected as yellow opaque zone around the colonies.

Uses of Mannitol Salt Agar

1. It is used for the selective isolation and differentiation of Staphylococcus aureus from clinical samples.
2. It is also used for the enumeration of staphylococci in food and dairy products.
3. This medium is also included in the Bacteriological Analytical Manual for cosmetics testing.
4. It is also used in the bacteriological examination of swimming pool water, spas and drinking water using
5. membrane filtration