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

Abstract

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

Genomic Investigation of Salmonella Isolates Recovered From a Pig Slaughtering Process in Hangzhou, China

“…However, the analysis of coherence between genotypic and phenotypic antimicrobial resistance showed that phenotypic resistance cannot always be linked to the presence of resistance genes. Our results are in agreement with those reported previously in Salmonella isolates, showing a difference between phenotypic and genotypic resistance profiles (Liu et al, 2020(Liu et al, , 2021. Hence, the phenotypic test remains the gold method for the assessment of bacterial behavior toward antimicrobial agents.…”

“…These isolates belong to five different serovars and six MLST patterns, namely, with importance degree, Salmonella Typhimurium ST19, Salmonella Typhimurium ST34, Salmonella London ST155, Salmonella Rissen ST469, Salmonella Goldcoast ST358, and Salmonella Derby ST40. In China, Salmonella Derby was identified as the most isolated serovar from pig slaughterhouse samples (Li et al, 2016(Li et al, , 2019Zhou et al, 2017Zhou et al, , 2018Liu et al, 2020). However, Salmonella Typhimurium has been reported previously as the dominant serovar in Salmonella isolates recovered from pig slaughterhouses in Henan Province (Bai et al, 2015).…”

“…Phenotypical results classified tetracycline and ampicillin as the less effective antimicrobial agents. In fact, the high resistance of Salmonella isolates to tetracycline and ampicillin has been reported over the world in samples collected along the animal food chain (Ed-Dra et al, 2017;Jiang et al, 2019Jiang et al, , 2021Wang et al, 2019;Liu et al, 2020Liu et al, , 2021, since they were frequently used in animal farms (Lekagul et al, 2019). In fact, the abuse and the misuse of antimicrobial drugs in animal livestock for therapeutic, prophylaxis, and growth promotions have led to the development of antimicrobial resistance.…”

“…Recently, whole genome sequencing followed by bioinformatics analysis was considered as a cost-effective method for the diagnosis and characterization of foodborne pathogens (Biswas et al, 2020;Liu et al, 2020Liu et al, , 2021Yu et al, 2020). As proof-of-concept, we conduct a study in a pig slaughterhouse in Hangzhou (Zhejiang Province, China), to obtain Salmonella isolates from different sources.…”

Antimicrobial effect of insect chitosan on Salmonella Typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes survival

“…The common reservoir of Salmonella is the intestinal tract of a wide range of domestic and wild animals, which results in a variety of foodstuffs covering both food of animal and plant origin as sources of infection. Transmission often occurs when organisms are introduced in food preparation areas and are allowed to multiply in food, e.g., owing to inadequate storage temperatures, inadequate cooking, or cross-contamination of ready-to-eat (RTE) food [ 18 , 19 ]. Salmonella enterica subsp.…”