Enrichment methods for recovery of Yersinia enterocolitica from foods and raw milk.

Modified Rappaport broth used directly and in a two-step procedure with preliminary cold enrichment was evaluated for recovery of Yersinia enterocolitica from laboratory-inoculated samples of ground meat, and naturally-occurring strains from raw milk. The use of modified Rappaport broth generally improved recovery from both inoculated meats and raw milk, but results were not consistent between serotypes used for inoculation and between meat samples. The overall isolation rate for naturally-occurring strains of Y. enterocolitica in producer samples of raw milk was 18.3%. The majority of 98 isolates from milk were indole-positive (98%), lecithinase-positive (87%), hydrolyzed esculin (98%), and fermented salicin (100%) and rhamnose (53%). Thirty-two isolates (33%) were serotypable, representing eleven different serotypes with 0:4 occurring most frequently followed by 0:5 and 0:6,30.