Antimicrobial resistance in wastewater-impacted coastal waters: implications for environmental surveillance and public health
Source: PubMed Central Open Access, NCBI / U.S. National Library of Medicine
Graphical abstract Overview of antimicrobial resistance across wastewater and receiving waters, illustrating changes in bacterial load and antimicrobial-resistant bacteria and gene abundance from upstream freshwater to downstream seawater. graphical Abstract Antimicrobial resistance (AMR) is a global public health concern, and wastewater-impacted aquatic environments are recognized as reservoirs and dissemination pathways for antimicrobial-resistant bacteria () and genes (ARGs). However, harmonized environmental AMR surveillance frameworks that integrate culture-basedenumeration with molecular ARG monitoring across wastewater and receiving surface waters remain limited. This pilot study, conducted in Ireland as part of a European harmonized monitoring initiative, assessedand ARG abundances in wastewaters and surface waters. Wastewater treatment plant influent (=3), effluent (=3) and surface waters upstream and downstream of the discharge point (=3 each) were sampled on three occasions in late 2024. Culture-based methods enumerated total and extended-spectrum-lactamase (ESBL)-producing, while quantitative real-time PCR quantified 16S rRNA and five AMR-associated genes (,,,and). Totalconcentrations were highest in influent (~10–10c.f.u. dl), decreased in effluent (~10–10c.f.u. dl) and lowest in surface waters (~10¹−10² c.f.u. dl). ESBL-producingwere consistently detected in influent (~10c.f.u. dl) and effluent (~10–10c.f.u. dl) but were not recovered from seawater. ARG abundanc
Abstract
Graphical abstract Overview of antimicrobial resistance across wastewater and receiving waters, illustrating changes in bacterial load and antimicrobial-resistant bacteria and gene abundance from upstream freshwater to downstream seawater. graphical Abstract Antimicrobial resistance (AMR) is a global public health concern, and wastewater-impacted aquatic environments are recognized as reservoirs and dissemination pathways for antimicrobial-resistant bacteria () and genes (ARGs). However, harmonized environmental AMR surveillance frameworks that integrate culture-basedenumeration with molecular ARG monitoring across wastewater and receiving surface waters remain limited. This pilot study, conducted in Ireland as part of a European harmonized monitoring initiative, assessedand ARG abundances in wastewaters and surface waters. Wastewater treatment plant influent (=3), effluent (=3) and surface waters upstream and downstream of the discharge point (=3 each) were sampled on three occasions in late 2024. Culture-based methods enumerated total and extended-spectrum-lactamase (ESBL)-producing, while quantitative real-time PCR quantified 16S rRNA and five AMR-associated genes (,,,and). Totalconcentrations were highest in influent (~10–10c.f.u. dl), decreased in effluent (~10–10c.f.u. dl) and lowest in surface waters (~10¹−10² c.f.u. dl). ESBL-producingwere consistently detected in influent (~10c.f.u. dl) and effluent (~10–10c.f.u. dl) but were not recovered from seawater. ARG abundances were highest in influent, reaching up to ~10copies dlfor, remained elevated in effluent (up to ~10copies dl) and were ~2–3 orders of magnitude lower in surface waters relative to effluent. Downstream seawater exhibited higher ARG levels than upstream freshwater despite low culturable. Peak ARG concentrations in effluent and surface waters were observed following a period of heavy rainfall; however, the limited number of sampling events precluded assessment of any statistical association. These findings highlight the impact of wastewater discharges on environmental AMR dissemination and suggest that faecal indicator-based monitoring may underestimate emerging risks, supporting integration of AMR indicators into EU water quality frameworks.