Isolation of an SHV-12 β-Lactamase-Producing Escherichia coli Strain from a Dog with Recurrent Urinary Tract Infections

An Escherichia coli strain (EC98/4153-2) was isolated in 1998 (by the Microbiology and Parasitology Service, Complutense University, Veterinary Hospital, Madrid, Spain) from a urine specimen from a dog with a recurrent urinary tract infection, and this strain was submitted to the Network of Veterinary Antimicrobial Resistance Surveillance (VAV). This strain showed resistance (8) to amoxicillin, cephalothin, cefotaxime, ceftazidime, and aztreonam, but it was susceptible to cefoxitin, imipenem, and amoxicillin-clavulanic acid (Table 1). The same resistance phenotype was detected by the disk diffusion method. Extended-spectrum β-lactamase (ESBL) production was detected in this strain by double-disk synergy tests (with cefotaxime, amoxicillin-clavulanic acid, and ceftazidime disks) (3).Table 1.Antimicrobial susceptibilities of E. coli EC98/4153-2AntimicrobialMIC (μg/ml)IZDa (mm)Amoxicillin>2566cAmoxicillin-clavulanic acidNDb20Cephalothin>2566 Cefoxitin424Cefotaxime6419 Ceftazidime>6413Aztreonam>3213 Imipenem0.0628 Nalidixic acid>2566 Ciprofloxacin811Tetracycline>2566 Chloramphenicol648Trimethoprim>2566 Sulfonamides>5126Gentamicin0.519 Neomycin6410Amikacin419 Apramycin413StreptomycinND6aIZD, inhibition zone diameter, determined by the disk diffusion test.bND, not done.cNo inhibition (diameter of the disk).