Spread of CTX-Type Extended-Spectrum β-Lactamase-Producing Escherichia coli Isolates of Epidemic Clone B2-O25-ST131 among Dogs and Cats in Japan

This study was performed to investigate the carriage rates of CTX-M-type extended-spectrum β-lactamase (ESBL)-producing Escherichia coli among ill companion animals in Japan. Among the 178 nonrepetitive E. coli isolates, including 131 from dogs and 47 from cats, collected between September and November 2015, 42 (23.6%) isolates from 29 dogs and 13 cats were identified as ESBL producers. The antimicrobial susceptibility, O serotype, phylogenetic group, β-lactamase genotype, plasmid replicon type, and sequence type (ST) of each isolate were analyzed. The major ESBL types were CTX-M-14 (26.8%), CTX-M-15 (24.4%), CTX-M-27 (19.5%), and CTX-M-55 (19.5%); predominant replicon types of bla_CTX-M-carrying plasmid were IncF group and IncI1-Iγ. The most prevalent STs were ST131 (n = 15, 35.7%), followed by ST38, ST10, and ST410. The 15 isolates of ST131 belonged to B2-O25. E. coli B2-O25-ST131 isolates harboring bla_CTX-M-15 or bla_CTX-M-27 were resistant to ceftazidime and ciprofloxacin. In particular, CTX-M-15 producers showed multidrug resistance. Our results demonstrated that the CTX-M-producing pandemic E. coli clone B2-O25-ST131 has already spread in Japanese companion animals as well. Moreover, the similarity of genotypes, serotypes, phylogenetic groups, and STs of the isolates from companion animals to those from humans suggested probable transmission of resistant bacteria between pets and humans.