Resistance induction potency assessment of antibiotic production wastewater and associated resistome shaping mechanisms.

Antibiotic production wastewater (APW) contains multiple substances known to select for and facilitate horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs); however, whether these substances can induce the evolution of antibiotic resistance in real wastewater environments and the fate of such resistance induction potency during the treatment process are poorly understood, nor are its relationship with wastewater quality parameters and function in shaping the antibiotic resistome. In this study, the impacts of filter-sterilized APW and municipal wastewater on the resistance selection of Escherichia coli and the transfer dynamics of conjugative RP4 plasmid-borne ARGs across indigenous sludge communities were evaluated. The resistance development and transfer processes were accelerated in APW owing to enhanced growth inhibition, oxidative stress, and membrane permeability, with antibiotic concentrations much lower than their minimum inhibition concentrations. The effects were reduced simultaneously with the removal of COD and NH3N, but APW effluents still exhibited significant resistance induction potency with wastewater quality parameters meeting discharge standards. In contrast, municipal wastewater did not result in any detectable changes. Based on the metagenomic assembly and binning, stronger resistance induction potency in the antibiotic production wastewater treatment plant endowed indigenous sludge and effluent with greater accumulation, genetic mobility, and pathogenic accessibility of ARGs than in the municipal wastewater treatment plant. Antibiotic resistome assembly was determined primarily by deterministic processes, driven jointly by resistance induction potency, mobilome variance, and microbiome shifts. These results provide novel insights into the application of bioassays to comprehensively evaluate the antibiotic resistance induction effects of APW and their relationships with the resistome to manage risks during the treatment process.