Assessment of Emerging Pathogens and Antibiotic Resistance Genes in the Biofilm of Microplastics Incubated Under a Wastewater Discharge Simulation.

Microplastics (MPs) are known vectors for the transport of pathogens and antibiotic resistance genes (ARGs), but few studies have examined the long-term (> 30 days) development of MP biofilms. Wastewater Treatment Plant (WWTP) effluents are a significant source of MPs, pathogens, and antibiotics released into the environment. We explored the development of biofilms on high- and low-density polyethylene, polypropylene, and polystyrene incubated in an experimental flow-through stream facility over the course of 10 weeks. Treatments included natural river water (RW) and RW amended with treated wastewater (TWW). Analysis of 16S rRNA amplicon sequencing results revealed that MPs in TWW and RW treatments developed distinct bacterial communities, displaying significant shifts in composition over time. Plastic type had only a minor effect influencing community composition after 10 weeks of incubation. The abundance of the sulfonamide resistance gene sulI, the mobile genetic element intI1, and the emerging pathogens Pseudomonas aeruginosa and Stenotrophomonas maltophilia increased significantly during the same time period. Our results indicate that as MPs persist and disperse in the environment, they may actively contribute to an increase in the risk of human exposure to ARGs and pathogens, especially if the system is impacted by wastewater treatment effluents.