Comparison of pulsed-field gel electrophoresis patterns of antimicrobial-resistant Escherichia coli and enterococci isolates from the feces of livestock and livestock farmers in Japan

Seven hundred thirty-nine animal strains and 662 livestock-farmer strains, consisting of Escherichia coli and enterococci, were examined for their pulsed-field gel electrophoresis (PFGE) and antimicrobial-resistance patterns. Two hundred fifty-eight and 203 PFGE patterns were found among 739 animal strains isolated from animals comprising broilers, pigs and cattle, and 662 human strains isolated from livestock farmers, respectively, from 27 farms in Japan. These results demonstrated that the PFGE patterns found among E. coli and enterococci strains from animals and livestock-farmers were heterogeneous and considerably diverse. The strains having both the identical PFGE pattern and the same drug-resistance pattern were defined as a single clone in this study. Seven types of E. coli and enterococci clones were shared among animals within the same farms and between the different farms housing the same animal species. The 25 strains (3.4%) of 739 E. coli and enterococci animal strains belonged to these seven types of clones. Only three types of E. coli clones were shared among animals between the different farms housing different animal species, but no identical E. faecalis or E. faecium clones were found between different animal species farms. The 15 strains (2.0%) of 739 E. coli and enterococci animal strains belonged to these three types of clones. Additionally, the 11 strains (1.5%) of 739 E. coli and enterococci strains isolated from animals were identical clones to strains isolated from livestock farmers of the same farm. These results suggest that the transmission of animal clones to livestock farmers or vice versa is less common.