Mannitol Salt Agar is selective medium for the isolation of pathogenic staphylococci. The medium conforms to the requirements of the Harmonised USP/EP/JP. Chapman showed that adding a high level of sodium chloride to Phenol Red Mannitol Agar allowed for the recovery of pathogenic staphylococci. Pathogenic staphylococci produced yellow colonies whereas non-pathogenic staphylococci produced small red colonies.
Pancreatic digest of casein, peptic digest of animal tissue and beef extract provide the required nitrogen, carbon and vitamins. The high level of sodium chloride inhibits most organisms other than staphylococci. Mannitol is a carbohydrate that is fermented by coagulase positive staphylococci. Phenol red is the pH indicator.
Mannitol Salt Agar
Additional Information
| Shelf Life (days) | |
|---|---|
| Storage Temp (°C) | |
| Dehydrated Medium Appearance | |
| Prepared Medium Appearance | |
| Dehydrated Medium Colour | |
| Prepared Medium Colour | |
| Dehydrated PH | |
| Prepared PH | |
| Recommended Incubation |
Product Description
| Organisms | Ref. No | Result |
| Staphylococcus aureus | NCTC 12981 | Growth, yellow colonies |
| Staphylococcus epidermidis | NCTC 13360 | Growth, pink / red colonies |
| Proteus mirabilis | NCTC 10975 | Inhibited |
Formula*
| g/L | |
| Pancreatic digest of casein | 5.0 |
| Peptic digest of animal tissue | 5.0 |
| Beef extract | 1.0 |
| Sodium chloride | 75.0 |
| Mannitol | 10.0 |
| Phenol red | 0.025 |
| Agar | 15.0 |
| Total | 111.0 |
| *Adjusted/supplemented as required to meet performance requirements |
Preparation
Suspend 111g of the medium in one litre of deionised / purified water. Allow the medium to soak whilst mixing for 10 minutes. Heat with frequent agitation and boil for one minute to completely dissolve the medium. Sterilise at 121°C for 15 minutes. Cool to 45-50°C and aseptically dispense into appropriate sterile containers.