Trypticasein Soy Broth Modified with Novobiocin (mTSB) is recommended by ISO 16654 for the enrichment of E.coli O157:H7. Casein peptone and soy peptone provide nitrogen, vitamins, minerals and amino acids essential for growth. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Dipotassium phosphate acts as a buffer system. Glucose is the fermentable carbohydrate providing carbon and energy. Bile salts and Novobiocin are inhibitors of gram-positive organisms. ISO 16654 recommends preparing the initial suspension and adding a test portion to the 41,5 ºC pre-warmed broth to obtain a ratio of test portion to mTSB + sample of 1/10 (mass to volume, or volume to volume). Incubate for 6 hours then a further 12 hours to 18 hours at 41,5 ºC.
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