First Isolation and Molecular Characterization of blaCTX-M-121-producting Escherichia coli O157:H7 from China Cattle
Abstract Background: To study antibiotic resistance and the molecular epidemiology of bovine Escherichia coli (E.coli) O157:H7 and to explore the intrinsic relationship among different isolates, we collected 27 strains of bovine E. coli O157:H7 in Xinjiang from 2012 to 2017 and assessed virulence genes, antibiotic resistance and pulsed-field gel electrophoresis (PFGE) molecular typing. Results: In this study, 21 strains carried at least one virulence gene, and 19 strains carried eae gene (70.4%) including 8 carrying stx1+stx2+eae +hly+tccP. Most strains were sensitive to all antibiotics tested, 4 strains were bacteria-resistant, and 2 strains possessed multi-drug resistance, including one ESBL-producing strain. This is the first report of a blaCTX-M-121 gene in bovine E. coli O157:H7. Moreover, blaCTX-M-121 gene can be transmitted horizontally by plasmid between strains. The PFGE spectral similarity of the 27 strains was between 65.8% and 100%. Two PFGE types including clusters Ⅰ and Ⅱ were obtained through cluster analysis. Conclusions: E. coli O157:H7 may have undergone clonal propagation in cattle farms as well as cross-regional transmission. A horizontal transmission path with E. coli O157:H7 appeared in different areas.