Resistome characterisation from catchment to effluent in a treatment plant without hospital inputs: implications for AMR monitoring

Wastewater surveillance is increasingly used to monitor antimicrobial resistance (AMR) at community scales. This study aimed to (1) assess AMR removal across treatment stages, (2) identify persistent versus responsive antimicrobial resistance genes (ARGs), and (3) characterise resistome profile of a wastewater treatment plant (WWTP) in Northeast England with no hospital inputs. Analyses included physicochemical profiling, microbial culturing, and high-throughput quantitative polymerase chain reaction targeting ARGs. Presumptive extended spectrum β-lactamase (ESBL)-producing Escherichia coli were effectively reduced by over two logs in the WWTP, although viable ESBL E. coli was still present in effluent. Comparative analyses revealed significant reductions along treatment stages for most ARGs. However, some ARGs, such as aadA7, blaOXY, and qepA, showed no significant reduction, indicating some ARGs persist through treatment, an important consideration for future monitoring programmes. The resistome profiles from three sub-catchments were similar, with only one ARG (lnuC) showing significant variation. This suggests that domestic-only catchments without hospital inputs may exhibit relatively uniform ARG profiles, although these results are specific to the WWTP studied and requires further validation. Finally, three ARGs, aadA7, sul1_2, and blaOXA48 were identified as potential biomarkers for AMR monitoring in WWTP, based on their abundance, strong correlation patterns, and clinical relevance.