Plastics as a potential vector for spread of antimicrobial resistance and pathogens from wastewater discharge in the marine environment

Antimicrobial resistance and marine plastic pollution are major global health and environmental challenges. Despite this, there is limited knowledge about the occurrence of pathogenic and antibiotic-resistant bacteria (ARB) in wastewater from Norwegian treatment plants and how these discharges affect coastal marine environments. Bacteria from wastewater can develop biofilms on plastic particles in the ocean. Therefore, PlastiSpread will investigate whether marine plastic pollution can be a potential transmission route for pathogens, ARB, and antibiotic resistance genes (ARG) from wastewater into the marine environment, including the seafood value chain. The PlastiSpread project has been endorsed as part of the UN Ocean Decade Action No. 6. PlastiSpread uses an innovative experimental approach that includes both field- and lab-scale plastic model systems, where biofilm formation on different materials (plastics, wood, and glass) is studied under exposure to wastewater from three different treatment plants (primary or primary and secondary treatment). In addition, the composition and concentration of microorganisms, ARB, ARG, antibiotics, and potentially toxic metals (PTMs) in the wastewater are characterised. Two of the treatment plants are located in Trondheim, while the third is in Greece. The field model system is established at selected exposed and unexposed locations in the Trondheim Fjord. In addition to studying biofilm formation on the same materials used in the laboratory experiments, mussels are used as indicators of effects on marine organisms. The project has established knowledge about the presence of antibiotics, PTMs, ARB, and ARG in wastewater and how their occurrence and distribution are affected by primary and secondary treatment in the plants. Untreated wastewater contains a range of antibiotics; however, only secondary treatment reduces their concentrations. Primary treatment does not contribute to reducing the levels of ARB and ARG. The biofilm experiments, both in the laboratory and in the field, are currently under analysis.

Antimicrobial resistance (AMR) and marine plastic pollution are major global health and environmental concerns. Despite this, there is limited knowledge concerning the occurrence of pathogens and antibiotic resistant bacteria (ARB) in Norwegian wastewater (WW) effluents from urban areas and in the coastal marine environments into which they are discharged. Furthermore, the potential role of plastics as a vector for the transmission of pathogens, ARB and antibiotic resistant genes (ARG) throughout the marine environment is poorly understood. PlastiSpread will provide important new knowledge about the microbial community in biofilms associated with marine plastics, and how they are influenced by variations in urban WW discharges. Such findings will help evaluate the potential role of marine (micro)plastic litter to act as a reservoir and vector for the development and spread of AMR and pathogenic bacteria in marine environments and more widely into the human food chain. A novel approach, integrating field- and lab-scale plastic model systems will be used to investigate the influence of WW effluent composition and polymer type on the bacterial community composition in plastic-associated biofilms, including occurrence of potential pathogens, ARB and ARGs. The field model system will be situated at selected exposed and non-exposed sites in Trondheim Fjord, where marine bivalve mollusks will also be used as indicators for exploring effects on marine organisms present at the same sites. A highly novel aspect of PlastiSpread will be to determine experimentally the process of horizontal gene transfer of ARGs from WW to susceptible plastic-associated biofilm bacteria. Greece has the highest consumption of antibiotics in Europe (double that of Norway). PlastiSpread investigates how this influences the occurrence of ARB and ARGs in local effluent WW through a set of complementary studies conducted in Greece using the same plastic materials and methods.