Extended-Spectrum β-Lactamase and Carbapenemase Genes are Substantially and Sequentially Reduced during Conveyance and Treatment of Urban Sewage

Liguan Li, Joseph Nesme, Marcos Quintela-Baluja, Sabela Balboa, Syed Hashsham, Maggie R Williams, Zhuofeng Yu, Søren J Sørensen, David W Graham, Jesús L Romalde, Arnaud Dechesne, Barth F. Smets*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


Urban wastewater systems (UWSs) are a main receptacle of excreted antibiotic resistance genes (ARGs) and their host microorganisms. However, we lack integrated and quantitative observations of the occurrence of ARGs in the UWS to characterize the sources and identify processes that contribute to their fate. We sampled the UWSs from three medium-size cities in Denmark, Spain, and the United Kingdom and quantified 70 clinically important extended-spectrum β-lactamase and carbapenemase genes along with the mobile genetic elements and microbial communities. Results from all three countries showed that sewage-especially from hospitals-carried substantial loads of ARGs (106-107 copies per person equivalent), but these loads progressively declined along sewers and through sewage treatment plants, resulting in minimal emissions (101-104 copies per person equivalent). Removal was primarily during sewage conveyance (65 ± 36%) rather than within sewage treatment (34 ± 23%). The extended-spectrum β-lactamase and carbapenemase genes were clustered in groups based on their persistence in the UWS compartments. The less-persistent groups were associated to putative host taxa (especially Enterobacteriaceae and Moraxellaceae), while the more persistent groups appeared horizontally transferred and correlated significantly with total cell numbers and mobile genetic elements. This documentation of a substantial ARG reduction during sewage conveyance provides opportunities for antibiotic resistance management and a caution for sewage-based antibiotic resistance surveillance.
Original languageEnglish
JournalEnvironmental Science and Technology
Issue number9
Pages (from-to)5939–5949
Publication statusPublished - 2021


  • Antibiotic resistance
  • Computer simulations
  • Fluxes
  • Bacteria
  • Sewage

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