Characterization of Salmonella Resistome and Plasmidome in Pork Production System in Jiangsu, China

Abstract

The prevalence of antimicrobial resistance in zoonotic <i>Salmonella</i> is a significant ongoing concern over the world. Several reports have investigated the prevalence of <i>Salmonella</i> infections in the farm animals in China; however, there is only limited knowledge about the <i>Salmonella</i> cross-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 105 <i>Salmonella</i> strains from pig carcasses and environment samples collected from four independent slaughterhouses in Jiangsu, China. All the <i>Salmonella</i> isolates 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 of <i>Salmonella</i> isolates was determined using a minimal inhibitory concentration assay with 14 antimicrobials. We found that the predominant serovar and serogroup was <i>S</i>. 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 determinant <i>mcr</i>-1 gene was detected in five (4.8%) strains. Our study demonstrated the prevalence of antimicrobial resistance in <i>Salmonella</i> strains isolated from pig slaughterhouses in China and suggested that the genomic platform can serve as routine surveillance along with the food-chain investigation.