A hidden reservoir of antibiotic resistance genes: transferable plasmids in community air and wastewater

TL;DR

This study finds antibiotic resistance genes in community air and wastewater, showing they can spread and pose public health risks.

Contribution

The study identifies transferable plasmids in non-clinical environments that carry clinically relevant antibiotic resistance genes.

Findings

33 out of 160 environmental samples yielded transferable plasmids conferring resistance to multiple antibiotics.

Plasmid peccDNA113 from air contained the carbapenemase gene blaNDM-5 and showed similarity to clinical plasmids.

aac(3)-IId was the most prevalent antibiotic resistance gene among the 150 identified.

Abstract

Plasmid-mediated dissemination of antibiotic resistance genes (ARGs) poses a major public health threat. In contrast to the well-studied resistance plasmids within pathogens, those from non-pathogenic environmental reservoirs remain underexplored. Here, we characterized transferable multidrug-resistant plasmids captured from community air and wastewater via conjugation assays. Transconjugants obtained from these environmental samples were profiled phenotypically against 17 antibiotics and genetically via short- and long-read sequencing. Conjugative plasmid transfer was successfully captured from 33 (20.6%) of 160 environmental samples, yielding 78 transconjugant isolates and 40 plasmid types. The captured plasmids conferred resistance to 4–18 antibiotics, with near-universal resistance to ampicillin (98.7%) and retained susceptibility to polymyxin B (84.6%). Among 150 ARG instances identified across 19 classes, aac(3)-IId was the most prevalent. The dominant plasmids ps15D023_8 (wastewater) and peccDNA113 (airborne) were particularly notable; peccDNA113 carried 4 ARGs, 9 virulence factors (including fimH and AcrB), and confers resistance to at least 7 antibiotics. Critically, the carbapenemase gene blaNDM-5 was detected, and peccDNA113 shows homology to clinical plasmids, indicating a high risk of clinical–environmental exchange. These findings highlight community environments as crucial reservoirs for mobile, high-risk resistance plasmids and underscore the urgent need for expanded surveillance beyond clinical settings.

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