The Thai Journal of Veterinary Medicine


Escherichia coli strains from dogs with different clinical signs were studied for their antimicrobial sensitivity profiles, extended spectrum beta-lactamase enzymes, and virulent genes. The 364 E. coli isolates originated from the skin (32.48%), urinary tract (31.32%), gastrointestinal tract (16.21%), reproductive system (7.69%), ear (6.05%), respiratory tract (4.94%), and other specimens (1.37%). Using the disk diffusion method, the E. coli were resistant to amoxicillin, amoxicillin-clavulanic acid, azithromycin, cephalexin, ceftriaxone, ciprofloxacin, doxycycline, enrofloxacin, norfloxacin, gentamicin, and sulfamethoxazole/trimethoprim at the rates of 84, 36, 41, 57, 38, 66, 73, 70, 64, 47, and 64%, respectively. Ninety-seven E. coli that were resistant to two or more beta-lactam drugs were chosen for investigation of their ESBL enzymes. Results showed that 36 isolates could produce ESBL enzymes by the combination disk test comprising one set of cefotaxime and cefotaxime-clavulanic acid and another set of ceftazidime and ceftazidime-clavulanic acid. Amplification of the ESBL-encoded genes of the 36 E. coli produced 35 isolates carrying bla CTX-M (543 bp) and 33 isolates harboring bla TEM (863 bp). The genes blaSHV and blaVEB were not found in the tested isolates by PCR. The E. coli-producing ESBL enzymes were further investigated for the virulent factors of Shiga-like toxin E. coli (stx, eae, and hly), Enteropathogenic E. coli (bfp) and Enterotoxigenic E. coli (LT, ST toxin). However, the isolates from the pets in this study did not present any of these virulent genes.



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