Background: Fluoroquinolone agents, such as enrofloxacin and marbofloxacin, are commonly used in for pseudomonal infection in veterinary medicine. However, the rate of resistance rate to fluoroquinolone s is rapidly increasing , according to multiple studies in various countries. The p P oint mutation s in the quinolone resistance - determining region (QRDR) is are closely related to the increased fluoroquinolone resistance of Pseudomonas aeruginosa . The aim of this study was to investigate current antimicrobial susceptibility and fluoroquinolone resistance in P. aeruginosa strains isolated from dogs. The presence of the point mutations in the QRDR was confirmed by gyrA and parC polymerase chain reaction and nucleotide sequencing analysis.
Results: A total of 84 nonduplicated P. aeruginosa strains were obtained from 228 healthy dogs (healthy group) and 260 dogs with clinical signs (infected group). From Of Among these isolates , 38 strains from the healthy group were detected in several sample type s, whereas 46 strains from the infected group were mostly obtained mostly from dogs’ ears with otitis externa (41/260, 15.8%). All strains were resistant to nalidixic acid, while some were also resistant to enrofloxacin (23/84, 27.4%), marbofloxacin (17/84, 20.2%), levofloxacin (12/84, 14.3%), or ciprofloxacin (11/84, 13.1%). Enrofloxacin resistance was significantly higher in strains from the infected group than in th ose at of from the healthy group ( p <0.05). Among the 23 fluoroquinolone-resistant strains, 8 and 4 different mutations were detected in the gyrA and parC genes, respectively. Mutations in gyrA were significantly common in the infected group ( p <0.05). Hotspots for the gyrA and parC mutations were Thr83 (34.8%, 8/23) and Pro116 (91.3%, 21/23), respectively. Double and triple mutations were also found in 5 of the strains.
Conclusion: Novel mutations in the gyrA and parC genes were first found in P. aeruginosa isolated from companion dogs in South Korea. These findings suggest that it is important to alert encourage the prudent use of fluoroquinolone antibiotics in canine pseudomona l s infection treatment.