Antimicrobial resistance profiles and molecular characterization of extended- spectrum β-lactamase/AmpC-harboring Klebsiella pneumoniae isolated from clinically ill dogs and cats in South Korea

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 2014–2023 in South Korea. Methods The obtained isolates (dogs, n = 130 and cats, n = 30) from urine, genital organs, diarrheal feces, skin/ear, and respiratory systems were assessed for antimicrobial sensitivity by broth microdilution, and the 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, tetracycline demonstrated the highest resistance rate, followed by cefazolin. In the sample levels, isolates from digestive samples showed overall higher antimicrobial resistance rates than non-digestive 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 bla _CTX−M−15 , bla _CTX−M−65 , and bla _CTX−M−55 being the predominant, while AmpC was detected in 20 isolates, with bla _DHA−1 and bla _CMY−2 was prevalent. Noticeably, co-occurrence of bla _CTX−M and bla _DHA 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, identical PFGE 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.