A selective medium for the isolation of presumptive pathogenic staphylococci. Most other bacteria are inhibited, with the exception of a few halophilic species. Directions Suspend g in 1 litre of distilled water and bring to the boil to dissolve completely. Description A selective medium prepared according to the recommendations of Chapman 1 for the isolation of presumptive pathogenic staphylococci. Most other bacteria are inhibited by the high salt concentration with the exception of some halophilic marine organisms.
Presumptive coagulase-positive staphylococci produce colonies surrounded by bright yellow zones whilst non- pathogenic staphylococci produce colonies with reddish purple zones. Mannitol Salt Agar is recommended for the detection and enumeration of coagulase-positive staphylococci in milk 2 , in food 3 and other specimens 4. The high concentration of salt in the medium clears the egg yolk emulsion and lipase production is detected as a yellow opaque zone around colonies of staphylococci which produce this enzyme.
Presumptive coagulase-positive staphylococci produce colonies with bright yellow zones whilst coagulase-negative staphylococci are surrounded by a red or purple zone.
Pick off suspect colonies and subculture in a medium not containing an excess of salt e. Nutrient Broth No. Appearance Dehydrated medium: Straw-pink coloured, free-flowing powder Prepared medium: Red coloured gel. Precautions A few strains of Staphylococcus aureus may exhibit a delayed fermentation of mannitol. Negative plates should be re-incubated overnight before discarding. It is a selective medium prepared according to the recommendations of Chapman for the isolation of presumptive pathogenic staphylococci.
Mannitol Salt Agar contains peptones and beef extract, which supply nitrogen, vitamins, minerals and amino acids essential for growth. The 7. 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.
Agar is the solidifying agent. The salt clears the egg yolk emulsion and lipase production is detected as yellow opaque zone around the colonies.
Hallo, My respected sir, You please tell me… How process can I measurements the antimicrobial sensitivity test of Staphylococcus aureus??? Which process or method can I following for the sensitivity test of Staphylococcus aureus?????? I kindly requested to you, please you response me. With my respect. If the organism in MSA ferments mannitol and forms yellow colonies, can we directly assume it as S. What is the ideal method? Please explain this.
If you find the MSA turned yellow, S. Aureus is there, but it is regarded as presumptive test; one should perform coagulase test too. Streak on NA to adopt pure culture and then perform coagulase test. Save my name and email in this browser for the next time I comment. Principle of Mannitol Salt Agar Mannitol Salt Agar contains peptones and beef extract, which supply nitrogen, vitamins, minerals and amino acids essential for growth.
Uses of Mannitol Salt Agar It is used for the selective isolation and differentiation of Staphylococcus aureus from clinical samples. It is also used for the enumeration of staphylococci in food and dairy products.
This medium is also included in the Bacteriological Analytical Manual for cosmetics testing. It is also used in the bacteriological examination of swimming pool water, spas and drinking water using membrane filtration Preparation of Mannitol Salt Agar Suspend Boil to dissolve the media completely.
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