EVALUATION OF SELECTIVE ENRICHMENT AND PLATING MEDIA FOR DETECTION OFSALMONELLA AND YERSINIA-ENTEROCOLITICA ON FRESH DRESSED LAMB CARCASSES

Forty fresh dressed lamb carcasses were tested for Salmonella spp. and Yersinia enterocolitica using various selective enrichment plating me dia. Muller-Kauffmann tetrathionate broth incubated at 43 degrees C fo r 18 h did not recover any strain of Salmonella on three selective pla ting media (XLD, BG and BiS agars). Seven strains of S. typhimurium we re recovered from selenite cystine broth (24 h at 37 degrees C) on the three solid media. The most inhibitory and selective plating medium w as BiS. Most of the non-Salmonella ''suspect'' colonies were identifie d as Escherichia coli (20 on BG, 10 on XLD and 4 on BiS). Cold enrichm ent in PBSSB yielded 22 strains of Y. enterocolitica biotypes 1 and 3, and 3 strains of Yersinia kristensenii on both MacConkey (12 strains) and CIN (10 strains) agars. Pre-enrichment in PBSSB (1 d at 25 degree s C) followed by enrichment in BOS (5 d at 22 degrees C) did not recov er any strain of Yersinia. MacConkey agar was slightly more efficient than CIN agar. Most of the nonyersiniae ''suspect'' colonies were Aero monas hydrophila (GIN agar) and Pseudomonas fluorescens (both solid me dia).