COMPARISON OF EB AND FRASER ENRICHMENT BROTHS FOR THE DETECTION OF LISTERIA SPP AND LISTERIA-MONOCYTOGENES IN RAW-MILK DAIRY-PRODUCTS AND ENVIRONMENTAL-SAMPLES

This study is a comparison of the isolation frequency of Listeria spp, and Listeria monocytogenes from selected naturally contaminated dairy products, especially soft smear-ripened cheeses from raw milk and sam ples of feces and rinse samples from the udder taken on the farm, by u sing an enrichment broth (EB) recommended by the International Dairy F ederation and the U.S. Food and Drug Administration (IDF and FDA) or F raser broth as the selective enrichment. Detection and identification were carried out according to the IDF protocols and a polymerase chain reaction technique. Listeria spp, were detected in 39.8% of the 570 s amples while 15.3% were positive for L. monocytogenes. For cheese and curd samples, Fraser enrichment broth gave a statistically significant higher recovery for all Listeria spp. (26 to 21%) as well as for L. m onocytogenes in particular (9 to 1.4%). For raw milk and samples taken from feces and the udder rinse no significant difference was found be tween EB and Fraser broth. A combination of both enrichments resulted in an increase of recovery over all matrices by 15%.