The impact of various microplastics on bacterial community and antimicrobial resistance genes in Norwegian and South African wastewater

Wastewater treatment plants (WWTPs) may serve as hotspots for pathogens and promote antimicrobial resistance (AMR). Plastic debris in wastewater could further contribute to AMR dissemination. The aim of this study is to investigate the impact of various microplastic types on bacterial communities and AMR gene abundance in Norwegian and South African wastewater. Microcosm experiments were designed as follows: Five manufactured microplastic pellet types were used for testing and two rock aggregate types were used as controls. In addition, each material type was subjected to artificial aging treatments using either ultra-violet light or hydrogen peroxide. Each material was incubated in flasks containing inlet/outlet wastewater obtained from Norwegian/South African WWTPs. Nucleic acids were extracted after a one-week incubation period. The detection of the blaFOX and blaMOX genes was performed using quantitative PCR. Extracted DNA was sequenced using a MinION device. Non-metric multi-dimensional scaling plot on full-length 16S sequencing data at the species level showed samples were clustered into distinct material groups. These results were in line with the ANOSIM test showing significant p-values in both Norwegian and South African WWTP settings. Indicator species analysis showed a strong association between many Acinetobacter species with the plastic group than the rock group. Aging treatment using hydrogen peroxide showed some effects on microbial. The abundance of blaFOX and blaMOX genes in the Norwegian wastewater outlet were generally lower compared to those in the inlet, though results were contrary in South African wastewater samples. The relative abundance of AMR genes seemed to be increased on several plastic types (PET, PE, PLA) but decreased on PVC-A. WWTP treatments in this study did not effectively reduce the abundance of AMR genes. In addition, plastic categories were shown to play a pivotal role in developing distinct bacterial communities and AMR profiles.