Antimicrobial resistant and extended‐spectrum β‐lactamase producing Escherichia coli in common wild bird species in Switzerland

A total of 294 fecal swabs from 294 wild birds in Switzerland were cultivated for antimicrobial resistant (AMR) Escherichia coli. Samples were also subcultivated to detect E. coli with extended‐spectrum β‐lactamases (ESBL), carbapenemases, and plasmid‐mediated aminoglycoside or colistin resistance, respectively. Samples from 17 (5.8%) of the birds contained 19 AMR E. coli, whereof 26.3% were multidrug resistant. Five (1.7%) ESBL‐producing E. coli were detected. The isolates harbored blaCTX‐M‐1 (two isolated from carrion crows and from one great spotted woodpecker, respectively), blaCTX‐M‐15 (originating from a grey heron), blaCTX‐M‐55 (from a carrion crow), and blaCTX‐M‐65 (from a common blackbird). Phylogenetic analysis assigned three isolates to commensal phylogroups A and B1, one to extraintestinal pathogenic group B2, and one to phylogroup F. Multilocus sequence typing identified sequence types (STs) that have been found previously in ESBL E. coli in wild birds (ST58, ST205, ST540). One isolate harboring blaCTX‐M‐55 was assigned to the recently emerged fluoroquinolone‐resistant, extraintestinal pathogenic E. coli clone ST1193. Wild birds have the potential to disperse AMR, including clinically important resistance genes, from anthropogenic‐influenced habitats to diverse areas, including vulnerable natural environments such as surface waters or mountain regions. Of 294 fecal samples from resident and short‐distance migratory wild birds, 5.8% contained antimicrobial resistant (AMR) Escherichia coli. Moreover, 1.7% of the samples yielded E. coli producing the extended‐spectrum β‐lactamases CTX‐M‐1, CTX‐M‐15, CTX‐M‐55, or CTX‐M‐65. Wild birds have the potential to disperse AMR bacteria from anthropogenic‐influenced habitats to diverse areas, including vulnerable natural environments such as surface waters or mountain regions.