Prevalence of Salmonella spp and Yersinia enterocolitica in slaughtered pigs: molecular typing, virulence profile and antimicrobial resistance

The prevalence and the sources of <i>Salmonella enterica</i> and <i>Yersinia enterocolitica</i> at slaughterhouse in Sardinia were investigated and the isolates characterized. <i>Salmonella</i> was isolated from colon content (15%), lymph nodes and liver (12.7%) and carcass surface (11%). 28 pigs were <i>Salmonella</i> carriers in lymph nodes and/or colon content and 10 were also positive at carcass level. 69 <i>Salmonella</i> strains were isolated and 7 serovars identified, the most common being Anatum (41%), Rissen, Derby (19.0%), 1,4,[5],12:i:-: (15.9%). N.33 <i>Salmonella</i> strains were found to be resistant to more than one antimicrobial. PFGE permitted the resolution of <i>XbaI</i> macrorestriction fragments of <i>Salmonella</i> strains in 11 pulsetypes. <i>Y. enterocolitica</i> contamination level detected with cultural method in tonsils (3.8x10³CFU/g) represents a possible risk for carcasses and fresh pork meat. The most common <i>Y. enterocolitica</i> bioserotype was 4/O:3 (68.8%). The most common virulence-associated gene in 4/O:3 isolates was the ysta (97.0%,), followed by ail (84.8%) and inv (78.8%,). PFGE performed on <i>Y. enterocolitica</i> strains using the NotI enzyme, yelded 7 different PFGE patterns. To reduce <i>Salmonella</i> and <i>Y. enterocolitica</i> prevalence some preventive measures should be encouraged: the identification of origin of infected slaughtered animals should be performed, and the direct and cross-contamination of carcasses avoided according to HACCP principles in association with good hygiene procedures (GHP).