Molecular epidemiology and serodiversity of Salmonella enterica in a pork chain “from farm to fork” in Northern Thailand

Nowadays, the “One Health Concept” is increasingly applied to attain and to maintain health for humans, animals and the environment by collaboration of institutions locally, nationally and globally. Veterinarians work multidisciplinary on carriers of zoonoses and/or food safety (Veterinary Public Health). Salmonella, one of the most important zoonotic pathogens, is of concern for the safety of food production. The pattern of Salmonella transmission and shedding in swine populations is the result of a variety of factors resulting in a multitude of potential scenarios (Rostagno and Callaway, 2012) and conventional sanitation methods can reduce the microbial load, but cannot eliminate pathogens if present (Olaimat and Holley, 2012). So, control or even elimination of the agent along the production chain is a difficult challenge. Critical points along the chain have been investigated in various studies to trace back the agent for important sources, e. g.: “pre-harvest studies” (Kranker et al., 2003; Lo Fo Wong et al., 2004; Nollet et al., 2004; Dorn-In et al., 2009; Molla et al., 2010; Gotter et al., 2012), studies “from the farm to the abattoir” (Rostagno et al., 2003; Botteldoorn et al., 2004; Sorensen et al., 2004; Bahnson et al., 2006; Vieira-Pinto et al., 2006; Dorr et al., 2009; De Busser et al., 2011; Kich et al., 2011; Visscher et al., 2011; Alban et al., 2012; da Silva et al., 2012) and “post-harvest studies” (Prendergast et al., 2009; Hansen et al., 2010; Gomes-Neves et al., 2012; van Hoek et al., 2012). Although several stages and/or risk factors have been reported as important sources of Salmonella, the lack of consistency, the methodological limitations, as well as the Introduction 2 complex and dynamic epidemiology of Salmonella in swine populations make it difficult to draw definitive conclusions (Rostagno and Callaway, 2012). Moreover, information on the link between living pigs, carcasses and pork pieces is still lacking. So in order to identify possible critical points in the production process, this study was conducted. In a larger framework, 193 live pigs were sampled individually and followed up into an abattoir and further on to cutting and retail- ready pork. 22 cohorts consisting of 7- 10 pigs each were investigated in this study. At the fattening farms, faecal samples were collected just prior to shipment; in addition, samples from the environment were collected in parallel. At slaughter, all pigs in each cohort were sampled (caecal contents and mesenteric lymph nodes). These samples were obtained from 181 pigs. Environmental samples were collected prior, during, and after cleaning and disinfection in addition. 173 freshly cut and transported pork pieces from the same chain were also followed. Finally, pork from retail was sampled. In this study, strains, which have been collected and serotyped, were now genotyped by PFGE to understand the transfer of the agent in the pork chain and in pork products.