Characterization ofSalmonellaResistome and Plasmidome in Pork Production System in Jiangsu, China

The prevalence of antimicrobial resistance in zoonoticSalmonellais a significant ongoing concern over the world. Several reports have investigated the prevalence ofSalmonellainfections in the farm animals in China; however, there is only limited knowledge about theSalmonellacross-contamination in the slaughterhouses. Moreover, the application of genomic approaches for understanding the cross-contamination in the food-animal slaughterhouses is still in its infancy in China. In the present study, we have isolated 105Salmonellastrains from pig carcasses and environment samples collected from four independent slaughterhouses in Jiangsu, China. All theSalmonellaisolates were subjected to whole genome sequencing, bioinformatics analysis for serovar predictions, multi-locus sequence types, antimicrobial resistance genes, and plasmid types by using the in-house Galaxy platform. The antimicrobial resistance ofSalmonellaisolates was determined using a minimal inhibitory concentration assay with 14 antimicrobials. We found that the predominant serovar and serogroup wasS. Derby and O:4(B), with a prevalence of 41.9 and 55%, respectively. All the isolates were multidrug-resistant and the highest resistance was observed against antimicrobials tetracycline (95.4%) and trimethoprim and sulfamethoxazole (90.9%). Additionally, the colistin-resistant determinantmcr-1 gene was detected in five (4.8%) strains. Our study demonstrated the prevalence of antimicrobial resistance inSalmonellastrains isolated from pig slaughterhouses in China and suggested that the genomic platform can serve as routine surveillance along with the food-chain investigation.