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Beschreibung

EcoCult(R) Half FRASER (Demi FRASER) broth has high nutrient content and a large buffer capacity that creates optimum growth conditions for Listeria spp. Lithium chloride, nalidixic acid, and acriflavine hydrochloride largely inhibit the growth of accompanying bacteria. The detection of the beta-D-glucosidase activity is possible by the addition of aesculin and ammonium iron (III) citrate, forming a black complex of aesculin with iron (III) ions. A black coloration can develop during incubation, but this reaction is not exclusive to Listeria spp. and cultures that show no blackening cannot be assumed to be free of Listeria spp. According to EN ISO 11290-1, every primary and secondary enrichment in Fraser broth has to be sub-cultured on selective plating media. The EcoCult(R) Half FRASER (Demi FRASER) Broth with antibiotics already contains the antibiotics, so it is only necessary to add the Ammonium iron (III) citrate (1.00092) for the preparation of the primary selective enrichment Half Fraser broth. For the secondary enrichment step, Fraser broth can be prepared by the addition of one additional vial reconstituted FRASER Listeria selective supplements (1.00093) per 500 mL prepared Half Fraser Broth.