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Bacillus Cereus Selective Agar Base (PEMBA) ISO
For the enumeration and isolation of Bacillus cereus in food
Principles and uses
Bacillus Cereus Selective Agar Base (PEMBA) has been adapted to meet the nutritional needs of Bacillus cereus, and was proposed for the enumeration, detection and isolation of Bacillus cereus in food. This bacterium is resistant to certain concentrations of polymyxin, which inhibits the
accompanying flora, and is effective mainly against Gram-negative organisms. This medium is recommended by ISO 21871 for the determination of low number of Bacillus cereus.
Casein peptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Sodium pyruvate reduces the colony size of the organisms.
Bromothymol blue acts as pH indicator to detect mannitol fermentation. Mannitol is the fermentable carbohydrate providing carbon and energy, Bacillus cereus is mannitol-negative. The Mannitol content allows the identification of the accompanying mannitol positive flora. Sodium chloride maintains the osmotic balance of the medium. Bacteriological agar is the solidifying agent.
Bacillus cereus produces lecithinases. The insoluble degradation products from the lecithin of egg yolk accumulate around the Bacillus cereus colonies, forming a white precipitate. The colonies of Bacillus cereus will appear blue colonies surrounded by a zone of opacity in the medium