Extended-Spectrum β-Lactamase–Producing Escherichia coli From Retail Chicken Meat and Humans: Comparison of Strains, Plasmids, Resistance Genes, and Virulence Factors

Background. The worldwide prevalence of extended-spectrum β-lactamase (ESBL)–producing Enterobacteria-ceae is increasing rapidly both in hospitals and in the community. A connection between ESBL-producing bacteria in food animals, retail meat, and humans has been suggested. We previously reported on the genetic composition of a collection of ESBL-producing Escherichia coli (ESBL-EC) from chicken meat and humans from a restricted geographic area. Now, we have extended the analysis with plasmid replicons, virulence factors, and highly discrim-inatory genomic profiling methods. Methods. One hundred forty-five ESBL-EC isolates from retail chicken meat, human rectal carriers, and blood cultures were analyzed using multilocus sequence typing, phylotyping, ESBL genes, plasmid replicons, viru-lence genes, amplified fragment length polymorphism (AFLP), and pulsed-field gel electrophoresis (PFGE). Results. Three source groups overlapped substantially when their genetic composition was compared. A com-bined analysis using all variables yielded the highest resolution (Wilks lambda [Λ]: 0.08). Still, a prediction model based on the combined data classified 40 % of the human isolates as chicken meat isolates. AFLP and PFGE showed that the isolates from humans and chicken meat could not be segregated and identified 1 perfect match between humans and chicken meat. Conclusions. We found significant genetic similarities among ESBL-EC isolates from chicken meat an