Characterization of antimicrobial resistance of Pseudomonas aeruginosa isolated from canine infections

Aims:  To determine the prevalence of Pseudomonas aeruginosa among dogs with suspected soft tissue infections and to characterize these isolates. Methods and Results:  Swabs were taken from infected soft tissues of 402 dogs. Pseudomonas aeruginosa strains were confirmed phenotypically and tested for susceptibility to 11 antimicrobial agents and genotyped by SpeI pulsed-field gel electrophoresis (PFGE). The genetic basis of fluoroquinolone (FQ) resistance and the presence of integrons were also characterized. A total of 27 (6·7%) dogs tested positive for Ps. aeruginosa. Fourteen different SpeI patterns were observed in 25 typeable strains. Among the β-lactams, three isolates presented resistance to ticarcillin and carbenicillin, while only one isolate exhibited resistance to ceftazidime. Among the aminoglycosides (AGs), three strains showed resistance to amikacin, and four strains exhibited resistance to gentamicin and tobramycin. Four strains with mutations that led to the substitution of Thr at position 83 with Ile in GyrA and the exchange of Ser at position 87 with Leu in ParC displayed resistance to all tested FQs. These strains also carried class 1 integrons and showed resistance to between 6 and 10 antimicrobials. These integrons included four different gene cassettes (aacA4-aadA1, blaOXA-31-aadA2, aadA1-arr-3-catB3 and cmlA5-cmlA-aadA1). Conclusions:  A small proportion of infected dogs treated in two animal hospitals in Beijing, China carried Ps. aeruginosa isolates. Low levels of resistance to anti-pseudomonal agents were observed in these strains. Significance and Impact of the Study:  This study is the first report on the antimicrobial resistance profiles of Ps. aeruginosa isolated from infected canine origin in China. Additionally, this is the first report of the oxacillin resistance gene blaOXA-31 in a canine Ps. aeruginosa isolate.