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Principle
- Levin and Cabelli (1972) described M-PA Agar as a selective membrane filter medium for Pseudomonas aeruginosa. The media is composed of L-lysine, yeast extract, xylose, sucrose, lactose, sodium chloride, ferric ammonium citrate, sodium thiosulphate, phenol red, and agar.
- L-lysine is the source of amino acids. Yeast extract provides nitrogen, carbon, vitamins, and other necessary nutrients or growth factors. Xylose, sucrose, and lactose are fermentable carbohydrates. Sodium chloride maintains osmatic balance. Ferric ammonium citrate provides essential ions.
- Sodium thiosulphate is the source of sulfate. Phenol red is a pH indicator, which turns yellow under acidic conditions due to the fermentation of the carbohydrates. Agar is the solidifying agent.
- The selectivity of media can be increased by adding antibiotics like Sulphapyridine, Kanamycin, Nalidixic acid, and Amphotericin B. The sulfonamides are synthetic bacteriostatic antibiotics with a wide spectrum against most gram-positive and many gram-negative organisms.
- Kanamycin inhibits protein synthesis in gram-positive organisms. Nalidixic acid blocks the replication of susceptible gram-negative bacteria. Amphotericin inhibits fungal species.
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