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Phage lysis-mediated reduction of antibiotic-resistant bacteria alleviates micro/nanoplastic-driven antimicrobial resistance dissemination in anaerobic digestion
Summary
Researchers used metagenomics to show that micro- and nanoplastics in sewage digesters enrich antibiotic resistance genes by up to 18% and promote the spread of those genes via plasmid transfer, while simultaneously finding that phage viruses — stimulated by plastic stress — kill antibiotic-resistant bacteria and partially offset that resistance buildup.
Micro/nanoplastics (MPs/NPs) prevalent in anaerobic digestion (AD) have posed escalating threats to antimicrobial resistance (AMR) dissemination, yet mechanistic insights remain insufficient. Here we investigated polypropylene (PP)-MPs (200 μm) and PP-NPs (100 nm) at environmentally relevant concentrations (10, 50, and 100 mg/g TS) on antibiotic resistance gene (ARG) dynamics and transfer mechanisms using metagenomics and bioinformatic modeling. PP-MPs/NPs significantly elevated (6.4-17.8 %, p < 0.05) ARG abundance through selective enrichment of aminoglycoside, mupirocin, multidrug, polymyxin, sulfonamide, tetracycline, and novobiocin ARGs. Metagenomic assembly revealed the particle-induced ecological niche specialization of antibiotic-resistant bacteria (ARB), notably the multi-resistant ESKAPE pathogen Enterobacter hormaechei (53.4-69.4 % enrichment, p < 0.05), which harbored mobile aadA, qacEdelta1, and sul1 via conjugative plasmids. Mechanistically, MPs/NPs facilitated horizontal gene transfer (HGT) through synergism of plasmids and phages. The enhanced abundance of conjugation elements, enriched plasmid-borne ARGs, and extensive HGT events promoted plasmid-conjugative transfer, while the strongly correlated ARG-carrying lysogenic phage-host pairs highlighted phage-mediated transfer under MPs/NPs. The significant increase of phage-to-host-ratio (1.0-1.2 folds) revealed the underestimated role of phages lysing ARB under MPs/NPs stress, thereby contributing to ARG load reduction. A novel risk assessment framework prioritizing prevalence, enrichment, mobility, and host pathogenicity identified dfrA3, mefB, OXA-347, and tet44 as high-risk biomarkers and quantified 1.5-9.9 % increased health risks in digestate-exposed scenarios. These findings reveal the neglected role of phage lysis driving ARG reduction, providing actionable targets for mitigating plastic-driven resistance in AD.
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