Abstract
Background: The emergence of ESBL/AmpC-producing K. pneumoniae is a significant concern in humans and veterinary medicine. This study aims to ascertain the antimicrobial resistance profiles and molecular characteristics of ESBL/AmpC-producing K. pneumoniae isolated from diseased companion animals during 2018-2023 in South Korea. Methods: The obtained isolates (dogs, n = 130 and cats, n = 30) from urine, genital organs, diarrheal feces, skin/ear, and respiratory tract were assessed for antimicrobial susceptibility by broth microdilution. Molecular characteristics were determined by polymerase chain reaction (PCR), multi-locus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). Results: Among the tested antimicrobials, the highest resistance rates were demonstrated for tetracycline, followed by cefazolin. In the sample levels, isolates from non-digestive tract showed overall higher antimicrobial resistance rates than digestive tract samples for both dogs and cats. In general, 25% (40/160) of the K. pneumoniae isolates harbored ESBL and/or AmpC genes. Of them, ESBL was identified in 30 isolates, with blaCTX-M-15, blaCTX-M-65, and blaCTX-M-55 being the predominant, while AmpC was detected in 20 isolates, with blaDHA-1 and blaCMY-2. Noticeably, co-occurrence of blaCTX-M and blaDHA was found in 7 isolates. Virulence factors were identified in 40% of the isolates, mostly comprising terB (56.3%) and irp2 (43.8%). MLST analysis revealed that sequence types (ST)307 and ST15 were predominant among 18 STs. Furthermore, the identical PFGE pattern was detected in different hospitals, suggesting the clonal spread of K. pneumoniae. Conclusion: Taken together, the findings emphasize the role of dogs and cats as reservoirs of antimicrobial-resistant K. pneumoniae that could be transmitted to humans. Therefore, it is necessary to conduct continuous surveillance and ensure the judicious use of antimicrobials in companion animals.