Molecular epidemiology and genomic plasticity of ESBL-producing and carbapenem-non-susceptible Klebsiella pneumoniae in a tertiary care hospital in northern Thailand.

Multidrug-resistant Klebsiella pneumoniae is spreading rapidly worldwide. The emergence of high-risk clones reinforces the vital need for genomic surveillance to monitor emerging antimicrobial resistance. In this study, we characterized 19 non-duplicate ESBL-producing and carbapenem-non-susceptible K. pneumoniae clinical isolates from a tertiary hospital in northern Thailand. The bacterial isolates were sequenced using Oxford Nanopore, and in silico characterization further explored genomic profiles of resistance, virulence, and plasmid content. Our bacterial collection was highly diverse, encompassing 17 sequence types. The most common ESBL gene was blaCTX-M-15 (73.7%), detected on both chromosomes and plasmids. IncF plasmids were frequently associated with the insertion elements ISEcp1 and IS26. Five isolates exhibited carbapenem non-susceptibility, including three carbapenemase producers (blaNDM-1 in KP03 and blaOXA-181 in KP02 and KP05, the latter located on IncX3 plasmids co-harboring qnrS1 within an IS26-mediated composite transposon) and two isolates lacking carbapenemase genes. Virulence profiling identified limited hypervirulence determinants; one ST25/K2 isolate (KP06) carried a KpVP-1-like virulence plasmid, suggesting potential convergence of antimicrobial resistance and virulence. Overall, our findings indicate extensive ESBL dissemination across diverse lineages and show that carbapenem non-susceptibility can arise via both carbapenemase and non-carbapenemase mechanisms, highlighting the importance of ongoing genomic surveillance.