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Principle
- Listeria identification Agar base (PALCAM) is composed of peptone, starch, dextrose, mannitol, sodium chloride, ammonium ferric citrate, lithium chloride, esculin, phenol red, and agar.
- Peptone provides nitrogen, vitamins, and other essential nutrients. Starch, dextrose and Mannitol are sources of carbon and energy source. Sodium chloride maintains osmatic equilibrium.
- Lithium chloride inhibits gram-negative bacilli. Phenol red is a pH indicator. The combination of mannitol and phenol red helps the detection of mannitol fermentation.
- Esculin is hydrolyzed by Listeria to form esculetin. This esculatin reacts with ammonium ferric citrate to form a brown-black complex seen as a black halo around colonies.
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