Multidrug-resistant bacteria contribute to core bacterial community and ARGs persistence during full-scale pharmaceutical wastewater treatment.

Pharmaceutical wastewater treatment plants (WWTPs) are confronted with a wide range of contaminants, resulting in the accumulation of antibiotic resistance genes (ARGs) and the evolution of multidrug-resistant (MDR) bacteria. However, the ecological roles of these MDR residents during full-scale wastewater treatment remain unclear. In this study, the core bacterial communities as well as potential MDR bacteria for industrial WWTPs were firstly categorized out. Taxa belonging to MDR bacteria were frequently detected to persist with low relative abundance across different treatment units, even in the effluent. Then, the occurrence and health risk of ARGs were evaluated. Certain abundant and prevalent ARGs, such as fabG, macB, and adeF, were found to exhibit high prevalence. Some pivotal mobile genetic elements, acting as key network hubs, can link MDR bacteria with a broad range of ARGs. Finally, the result showed that several metagenome-assembled genomes recovered from the effluents were not only classified as MDR bacteria harboring ARGs with high risk, but also served as important members of the core bacterial community. These findings provide critical insights into the ecological roles of MDR bacteria during the full-scale pharmaceutical wastewater treatment, and emphasize the urgent need for real-time monitoring of wastewater-borne MDR bacteria for ecological health.