This study characterized Escherichia coli strains from fresh produce and farm environments in Korea. To characterize Escherichia coli strains and evaluate the spread of antimicrobial resistance, we conducted phenotypic and genetic studies on antimicrobial-resistant strains in isolates from fresh produce and farm environments. We performed a genetic epidemiological characterization of isolates that produced extended-spectrum beta-lactamase (ESBL), and confirmed plasmid transfer in isolates that carried bla CTX-M-type genes. E. coli strains were isolated from eight fresh produce samples and 152 samples from the farm environment from May 2014 to June 2016. Cephalosporin resistance was the most prevalent (61.8%) among the isolates. Five ESBL-producing strains with high genetic homology to E. coli of human- or livestock-origin were identified. There was successful lateral transfer of p lasmids harboring bla CTX-M-type genes to transconjugants . Two isolates from Chinese cabbage and water from a nearby stream harboring the IS Ecp1-bla CTX-M-55 -orf477 operon were confirmed as having sequence type 1196 and the same type of plasmid replicon, suggesting that cross-contamination was highly likely. A high-risk clone ST69 (clonal complex 69) was also observed in the farm environment. This study provides genetic evidence that E. coli antimicrobial resistance factors in farm environments originate in the clinic or in livestock, and suggests that Good Agricultural Practice in farming is important to inhibit the spread of antimicrobial resistance to fresh produce.

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