YERSINIA SPP AND NUMBERS, WITH PARTICULAR REFERENCE TO Y-ENTEROCOLITICA BIO SEROTYPES, OCCURRING ON IRISH MEAT AND MEAT-PRODUCTS, AND THE INFLUENCE OF ALKALI TREATMENT ON THEIR ISOLATION/

Samples (n = 340) of Irish meat and meat products were examined to det ermine the incidence and initial numbers of Yersinia spp. present. In cases where no typical Yersinia colonies were observed, samples were c old enriched up to 21 days at 4 degrees C and streaked out on CIN agar with and without post-enrichment alkali treatment. The highest isolat ion rates of Yersinia were found using post-enrichment alkali treatmen t and an incubation temperature of 37 degrees C. All Yersinia isolates were identified to species level and Y. enterocolitica isolates were biotyped and serotyped. Pathogenic isolates (biotypes 1B-5) were exami ned for the presence of a virulence plasmid using dye binding reaction s and agglutination tests. The incidence of Yersinia spp. was high on raw (89%) and cooked meats (49%) obtained from delicatessen counters b ut lower in pre-packaged cooked meats (18.8%). Initial numbers of Yers inia were generally <2.7 log(10)cfu/g on raw meats and <0.7 log(10)cfu /g on cooked meats. Pathogenic Y. enterocolitica were recovered from b oth raw (9%) and cooked meats (2%). Y. enterocolitica serotypes O:3 an d O:5,27 were the most common pathogenic species found on Irish meats.