Emergence and dissemination of epidemic-causing OXA-244 carbapenemase-producing Escherichia coli ST38 through hospital sewage in Norway, 2020-2022

Background: Population -based sewage surveillance has emerged as a promising approach for studying the prevalence of antibiotic resistance in pathogens. Aim: To determine the temporal prevalence of cefotaxime-resistant Escherichia coli in sewage from five sewage treatment plants located in Bergen city, to determine whether ESBL- and carbapenemase-producing E. coli are consistently disseminated in the receiving environment through sewage. Method: A total of 569 cefotaxime-resistant E. coli were isolated over a period of 19 months (August 2020 to February 2022) using ECC CHROMagarTM plates from 82 samples, antibiotic sensitivity profiles were determined, using SensititreTM plates. The draft genome sequences were determined, using Illumina MiSeq-based sequencing. Complete genome sequences were determined, using Oxford Nanopore-based sequencing. Findings: All 569 strains obtained from influent (N1/4461) and effluent (N1/4108) were multidrug resistant. Most of the sequenced strains (52 of 61) carried blaCTX-M-15 (38.5%) and blaCTX-M-27 (34.6%). The most prevalent sequence types (STs) for ESBL-carrying strains were ST131 (32.8%) and ST38 (21.3%). All CTX-M-27-carrying ST131 strains belonged to clade A or C1, while CTX-M-15-harbouring strains were present in all the clades. Five OXA-244producing ST38 strains, genetically similar to epidemic -causing strains from Western Norway, France and the Netherlands, were isolated only from raw and treated sewage of the treatment plant receiving hospital sewage.