Characterization of extended-spectrum β-lactamase-producing Escherichia coli isolated from municipal and hospital wastewater in Japan

Objectives: The purpose of this study was to characterize the strains of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (ESBL-EC) isolated from municipal and hospital wastewater by detecting antibiotic resistance genes (ARGs) as well as antibiotic susceptibility. To identify the source of ESBL-EC, multi-locus sequence typing and typing plasmids that may carry ESBL-producing genes were conducted. Methods: Wastewater was sampled twice a month from February 2019 to February 2020 from a municipal wastewater treatment plant and hospital located in a city in northeastern Japan. Throughout the study period, 279 and 37 strains of ESBL-EC were isolated from municipal and hospital wastewater, respectively. Results: All 316 isolates were resistant to ampicillin and cefotaxime and susceptible to imipenem and tigecycline. Almost all (98.1%) of the ESBL-EC isolates possessed bla(CTX-M), and the bla(CTX-M-9) group was detected most frequently (62.3%). Multi-locus sequence typing revealed a higher diversity of sequence types (STs) in the isolates from municipal wastewater than in those from hospital wastewater; although ST131, which recently caused nosocomial-and community-associated infections worldwide, was dominant in both types of wastewater. All ST131 isolates possessed the IncFII plasmid, which is often reported to carry bla(CTX-M). Conclusions: These results demonstrated that healthy people carry clinically important antibiotic-resistant bacteria and ARGs, motivating routine monitoring of municipal wastewater to detect such antibiotic-resistant bacteria and ARGs from a variety of sources supported by the high diversity of STs in the present study. (c) 2023 The Author(s). Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )