Evaluation of Fraser broth to isolate Listeria from poultry

The detection of Listeria spp. from food samples without the need for subcu lture to agar plates means a big saving in lime and money for routine monit oring of food products. The efficiency of the differential system (esculin- ferric ammonium citrate) of Fraser broth as a screening test for the presen ce of Listeria spp. in raw chicken meat was investigated. The study uas car ried out on 100 eviscerated and refrigerated chicken carcasses:for isolatio n the USDA-FSIS method was used. One case (1 % of positive samples) was fal se negative and three (60 % of negative samples) false positives. Thus. the ability of the differential system to detect positive samples (sensitivity ) was 98.95 % and the ability to detect negative samples (specificity) was 40 %. These data do not make this system very efficient as a screening test when working with food highly contaminated with other esculin positive mic roorganisms, as is the case with raw poultry meat. (C) 2000 Academic Press.