Pre-supplemented Fraser Broth – selective broths for secondary enrichment of Listeria in the analysis of food products according

Fraser broths are used as primary (Half Fraser) and secondary (Fraser) enrichment for the detection of Listeria spp. in food products according to ISO11290. Due to the combined action of lithium chloride, acriflavin and nalidixic acid, these broths inhibit non-Listeria flora. These two broths are slightly buffered so as to slow acidification (acidifying flora), damaging to the growth of Listeria. After enrichment (primary or secondary), the presence of Listeria spp. is detected by the broth turning a yellow to dark brown color (esculin hydrolysis). This color change is not systematic, however, and according to ISO11290 it is imperative to carry out isolation on a selective medium (ALOA, Palcam and/or Oxford). It is possible also to use AFNOR ISO16140 Bio-Rad media RAPID’L.mono, RAPID’Listeria spp. or AL agar. The presence of Listeria in the enriched broth can also be detected via Real-Time PCR using AFNOR ISO16140 certified Bio-Rad iQ-Check kits or Generon PATHfinder kits. SIFIN Fraser broths are available in the most convenient pre-supplemented dehydrated powder format or as the dehydrated base powder to be supplemented.