A Representative Collection of Commensal Extended-Spectrum- and AmpC-β-Lactamase- Producing Escherichia coli of Animal Origin for Phage Sensitivity Studies

Introduction: Extended-spectrum beta-lactamase (ESBL)- and AmpC beta-lactamase (AmpC)-producing Escherichia coli from livestock and meat represent a zoonotic risk and biocontrol solutions are needed to prevent transmission to humans. Methods: In this study, we established a representative collection of animal-origin ESBL/AmpC E. coli as target to test the antimicrobial potential of bacteriophages. Results: Bioinformatic analysis of whole-genome sequence data of 198 ESBL/AmpC E. coli from pigs, broilers, and broiler meat identified strains belonging to all known E. coli phylogroups and 65 multilocus sequence types. Various ESBL/AmpC genes and plasmid types were detected with expected source-specific patterns. Plaque assay using 15 phages previously isolated using the E. coli reference collection demonstrated that Warwickvirus phages showed the broadest host range, killing up to 26 strains. Conclusions: 154/198 strains were resistant to infection by all phages tested, suggesting a need for isolating phages specific for ESBL/AmpC E. coli. The strain collection described in this study is a useful resource fulfilling such need.