Mechanisms of resistance to cephalosporin and emergence of O25b-ST131 clone harboring CTX-M-27 ß-lactamase in extraintestinal pathogenic Escherichia coli from dogs and cats in Japan

Thirty-three cefazolin-resistant extraintestinal pathogenic Escherichia coli strains from companion animals were screened for blaCMY-1, blaCMY-2, blaSHV, blaTEM, and blaCTX-M genes. Extended-spectrum beta-lactamase-producing strains were further characterized by O serotyping and multilocus sequence typing. It was found that 20 and 17 isolates harbored TEM-1 and CMY-2 beta-lactamases, respectively, and 13 isolates harbored both beta-lactamases. One isolate harbored DHA-1 beta-lactamase. Eleven isolates were found to possess CTX-M beta-lactamases (CTX-M-27 [n= 6], CTX-M-14 [n= 3], CTX-M-15 [n= 1], and CTX-M-55 [n= 1]). Of 11 CTX-M-positive strains, four strains were O25b-ST131 clones harboring CTX-M-27, and the remaining seven strains belonged to O6-ST127, ONT-ST354, O159-ST539, O1-ST648, O8-ST1642, O25b-ST2042, and ONT-ST2178.