Distribution patterns and driving mechanisms of antibiotic resistance genes and virulence factor genes under the...

Antibiotic resistance genes (ARGs), as emerging environmental contaminants, have become a global environmental health concern due to their distribution and dissemination across urbanization gradients. This study systematically investigated the diversity, abundance patterns, and driving mechanisms of 173 ARGs, 30 mobile genetic elements (MGEs), and 120 virulence factor genes (VFGs) along a typical urbanization gradient (urban, suburban, and ecological zones) using soil samples collected from Baoding city center to Baiyangdian Lake periphery. High-throughput sequencing and quantitative PCR analyses revealed that suburban areas exhibited significantly higher total relative abundance of ARGs compared to urban and ecological zones (p < 0.05), particularly for aminoglycoside-, fluoroquinolone-, Macrolide-Lincosamide-Streptogramin B-, and multidrug-resistance genes. Suburban soils also showed elevated levels of VFGs associated with Klebsiella pneumoniae, Salmonella enterica, and Escherichia coli (p < 0.05). Notably, significant associations between ARGs and VFGs were observed, with both demonstrating high loads in suburban areas, suggesting these transitional zones may serve as "incubators" for resistant pathogens. Correlation analyses suggest that both biotic (MGEs, microbial communities) and abiotic factors (urbanization, heavy metals, soil properties) may contribute to ARGs and VFGs dissemination, with MGEs appearing to play a central role. Structural equation modeling indicates that urbanization could influence ARGs and VFGs assembly, potentially by altering soil properties, heavy metals, and microbial communities. MGE-mediated horizontal transfer might facilitate ARGs spread, whereas heavy metals and specific microbial taxa may be associated with VFG distribution patterns. These findings provide critical scientific insights into the transmission dynamics of resistance genes during urbanization and offer strategic guidance for developing targeted environmental management policies to mitigate resistance dissemination.