Salmonella spp. in Sardinian slaughter pigs: prevalence, serotypes and genotypic characterization

In order to further the knowledge about Salmonella prevalence at farm level and pork meat in Sardinia, the prevalence and the sources of Salmonella at 5 pig slaughterhouses (slaughtered pigs and environment) and 2 swine farms (feed and faeces), were investigated and the isolates characterized. Salmonella was isolated from mesenteric lymph nodes (30.5%), colon content (16.4%), carcass and liver (both 14.1%); as regards to the slaughterhouse environment Salmonella prevalence was 37.5% in the any contact surfaces samples and 35.2% in contact surfaces samples. Salmonella could not be isolated in any of the samples taken at farm. N. 31 pigs were carriers of Salmonella in lymph nodes and/or colon content, but among this only 8 were positive at carcasses level. Eight different serotypes were detected; the most common were S. derby (43%) and S. typhimurium (23%). The prevalent S. typhimurium phage type was DT193 (50%). N.32 isolates were found to be resistant to more than one antimicrobial (MDR). Heterogeneous integronassociated resistance genes were present in the isolates. PFGE permitted the resolution of XbaI macrorestriction fragments of the Salmonella strains into 20 distinct pulsetypes. The combinated application of PPA and PFGE gave additional useful information to trace the Salmonella routes in abattoirs. To reduce Salmonella 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).