Abstract
Metals are widely used in animal feed for their growth-stimulating and antimicrobial effects; yet, there is potential concern that their use can promote antimicrobial resistance through co-selection. However, the prevalence of these metal resistance genes in Salmonella and their impact on the induction of antimicrobial resistance remain unclear. To aid in this understanding, this study investigated of the prevalence of heavy metal resistance genes (HMRGs) and their comparison with antimicrobial resistance genes (ARGs) in Salmonella enterica strains isolated from various sources, across different locations and time periods. Data on stress and AMR genotypes, serovar, source, location, and collection date were retrieved from the NCBI Pathogen Detection Isolate Browser. Isolates from the United States with complete metadata were analyzed using Microsoft Excel and PANDAS (Python Data Analysis Library). Chi-square tests were conducted to assess differences in ARG presence between HMRG-positive and HMRG-negative isolates. Additionally, the co-localization of HMRGs and ARGs on plasmids was examined, and plasmid incompatibility types were assessed. The results show that HMRG prevalence varied significantly across serovars and sources. Certain ARGs occurred at significantly higher frequencies in isolates harboring HMRGs. Co-localization of HMRGs and ARGs on plasmids was frequently observed, although no specific plasmid incompatibility group was uniquely associated with this co-localization. These findings highlight a potential link between metal resistance and antibiotic resistance in S. enterica, reinforcing concerns about the use of heavy metals in agriculture. The results provide important insights for risk assessment and inform strategies aimed at mitigating AMR as a global public health threat.