Integron-associated genes are reliable indicators of antibiotic resistance in wastewater despite treatment- and seasonality-driven fluctuations

• Published in: Water research (Oxford) 2024-07, Vol.258, p.121784, Article 121784
• Main Authors: Tavares, Rafael D.S., Fidalgo, Cátia, Rodrigues, Elsa T., Tacão, Marta, Henriques, Isabel
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Bacteria - drug effects; Bacteria - genetics; Drug Resistance, Microbial - genetics; Environmental health indicators; Genes, Bacterial; Integrons; Integrons - genetics; Resistome; RNA, Ribosomal, 16S - genetics; Seasons; Waste Disposal, Fluid; Wastewater; Wastewater-based surveillance
• ISSN: 0043-1354; 1879-2448; 1879-2448
• DOI: 10.1016/j.watres.2024.121784

•Antimicrobial resistance indicators were evaluated in a WWTP over 1 year.•Treatment and seasonality influenced the bacterial community and resistome.•intI1, blaGES and qacE∆1 genes correlated with the total concentration of ARGs.•blaGES and blaVIM genes correlated with the concentration of several ARGs’ classes.•Integron-related genes are good indicators of antibiotic resistance in wastewater. The present study aims to characterize the bacterial community, resistome and integron abundance of a municipal wastewater treatment plant (WWTP) over the course of 12 months and evaluate the year-long performance of integron-related genes as potential indicators of antibiotic resistance mechanisms in influents and effluents. For that, total DNA was extracted and subjected to 16S rRNA-targeted metabarcoding, high-throughput (HT) qPCR (48 targets) and standard qPCR (5 targets). Targets included integrase genes, antibiotic resistance genes (ARGs) and putative pathogenic groups. A total of 16 physicochemical parameters determined in the wastewater samples were also considered. Results revealed that the WWTP treatment significantly impacted the bacterial community, as well as the content in ARGs and integrase genes. Indeed, there was a relative enrichment from influent to effluent of 13 pathogenic groups (e.g., Legionella and Mycobacterium) and genes conferring resistance to sulphonamides, aminoglycosides and disinfectants. Effluent samples (n = 25) also presented seasonal differences, with an increase of the total ARGs’ concentration in summer, and differences between winter and summer on relative abundance of sulphonamide and disinfectant resistance mechanisms. From the eight putative integron-related genes selected, all were positively correlated with the total ARGs’ content in wastewater and the relative abundance of resistance to most of the specific antibiotic classes. The genes intI1, blaGES and qacE∆1 were the most strongly correlated with the total concentration of ARGs. Genes blaGES and blaVIM, were better correlated to resistance to beta-lactams, aminoglycosides and tetracyclines. This study supports the use of integron-related genes as powerful indicators of antibiotic resistance in wastewater, being robust despite the variability caused by wastewater treatment and seasonality. [Display omitted]