Abstract: In order to investigate the presence,resistant phenotype and molecular characterization of bla_CTX-M gene positive Klebsiella pneumoniae in pet dogs,we isolated ceftaxime-resistant bacteria from anal and nasal swabs of 355 pet dogs and species were further identified by 16S rDNA and MALDI-TOF-MS.We detected bla_CTX-M gene by PCR.All bla_CTX-M gene carrying Klebsiella pneumoniae were subjected to antimicrobial susceptibility testing to observe resistance phenotype,PFGE typing and the whole sequencing to know molecular characterization.The results of PCR showed that 7 bla_CTX-M gene containing Klebsiella pneumoniae were isolated,of which three were from anal swabs and four were from nasal swabs.All strains were resistant to ceftiofur,cefotaxime and amoxicillin-clavulanate,but were susceptible to colistin,meropenem and tigecycline.The results of PFGE patterns indicated that the similarity of three isolates were 100% and the similarity of the other four were <30%.7 isolates belonged to 5 ST types,and 5 were bla_CTX-M-14 gene positive and 2 were bla_CTX-M-3 gene positive.However,some β-lactamase-resistant genes,quinolones-resistant genes and aminoglycosides-resistant genes were co-exist with bla_CTX-M gene in these strains.In summary,we found that the presence of bla_CTX-M gene carrying Klebsiella pneumoniae had a low detection rate,but they were multi-drug resistant,the phenotype of bla_CTX-M and bla_SHV genes in this study were different from the prevalence phenotype at home and abroad.Until now,the usage and control of antibiotics in companion animals still had limitation,we needed pay more attention to antibiotic resistance in companion animals to provide scientific evidence to control in the future.

Key words: pet dogs; Klebsiella pneumoniae; CTX-M