Comparison of two pre-enrichments broths for recovering Listeria spp. fromsalmon (Salmo salar) and salmon-trout (Oncorhynchus mykiss)

Low levels of occurrence of Listeria spp. in fresh salmon (Salmo-salar) and salmon-trout (Oncorhynchus mykiss), may be related to the selectivity of t he pre-enrichment broth recommended by ISO 11290-1. The purpose of this stu dy was to compare the abilities of Fraser base (without supplements) and 0. 1% (w/v) peptone water for recovering Listeria spp. from the fresh fish sam ples. Fifty-six fish were swabbed and the swabs placed in Fraser base and in 0.1% (w/v) peptone water. Samples were analysed 4-6 h later following the ISO 1 1290-1 protocol. A total of fifteen Listeria spp. positive samples were fou nd. Three and twelve samples were found to contain respectively, L. monocyt ogenes and L. innocua. The Fraser base did not detect any of the three L. m onocytogenes positive samples. Only two Listeria spp. positive samples were simultaneously recovered by the two broths. (C) 2001 Elsevier Science Ltd. All rights reserved.