Impact of Urbanization on Antibiotic Resistome in Different Microplastics: Evidence from a Large-Scale Whole River Analysis

Microplastics (MPs) are becoming ubiquitous in environments and viewed as carriers of antibiotic resistance genes (ARGs). Rivers connecting differently urbanized areas contribute a significant input of MPs and ARGs to the environment. However, a systematic study assessing the role of urbanization in shaping antibiotic resistome and mobilome in riverine MPs is lacking. Here, we conducted a large-scale study by placing five types of MPs (polyethylene, polypropylene, polystyrene, polyethylene-fiber, and polyethylene-fiber-polyethylene) into Beilun River with an urbanization gradient. A total of 314 ARGs and 57 mobile genetic elements (MGEs) were detected in MPs by high-throughput quantitative polymerase chain reaction (PCR). The ARGs in MPs showed a clear spatial distribution with the abundance increased by 2 orders of magnitude from rural to urban regions. A holistic analysis of 13 socioeconomic and environmental factors identified that urbanization predominantly contributed to both the abundance and potential MGE-mediated dissemination of ARGs in riverine MPs. Notably, MPs types were found to significantly affect the resistome and dissemination risk of ARGs, with polypropylene being the preferred substrates to acquire and spread ARGs. This work highlights the necessity of controlling MPs and ARGs pollution in urban areas and provides an important guide for the future usage and disposal of plastics.