Unraveling the Viable Antibiotic Resistome and Their Health Risks on Microplastics in the Aquatic Environment

Microplastics in aquatic environments are ideal carriers for antimicrobial resistance (AMR) and pathogens. However, the viable fractions of microplastics crucial for AMR dissemination remain unknown. Herein, propidium monoazide (PMA) labeling combined with amplicon sequencing and high-throughput quantitative polymerase chain reaction (PCR) were conducted to target the viable microbial communities and associated antibiotic resistome on three typical microplastics from an urban river. Distinct microbial communities and antibiotic resistomes on the microplastics were observed between the viable and total cells. Sixteen viable pathogens, including predominant <i>Vibrio</i> and <i>Aeromonas</i>, were detected on microplastics, and the absolute abundance of antibiotic resistance genes (ARGs) from viable cells was 2-3 orders of magnitude higher than that in surrounding water, suggesting microplastics as new reservoirs for these viable contaminants. The relative abundances of ARGs in viable cells were 1.34-5.41-fold higher than those in total cells, indicating enhanced AMR spread potential. However, viable cells on microplastics harbored lower abundances of high-risk ARGs and risk indices, suggesting that health risks might be overestimated solely on the basis of total ARGs. Elevated risk indices were detected in the viable cell fraction on microplastics compared to those in natural substrates and water. Therefore, this study provides new insights into viable-cell-hosted AMR within the plastisphere, enabling more accurate health risk assessments.