Genomic and Phenotypic Characterization of Two High-Risk Klebsiella pneumoniae Clones (ST258-blaKPC-2 and ST11-blaNDM-1) from a Greek Tertiary Hospital

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Background/Objectives: Klebsiella pneumoniae ST258 and ST11 are global high-risk antimicrobial-resistant clones known for their virulence and resistance gene dissemination. This study aims to identify these clones in a Greek tertiary hospital and understand their resistance profiles and transmission dynamics. Methods: In January 2025, we isolated two distinct carbapenem-resistant K. pneumoniae in a Greek tertiary hospital: INT18S from an ICU patient’s bronchioalveolar lavage and INT20U from a urine sample in the emergency unit. Antimicrobial susceptibility testing (via Microscan system) and Whole-Genome Sequencing (WGS) were conducted on both isolates and their genomes were submitted to the NCBI. Results: The INT18S isolate carried the blaKPC-2 gene and belonged to the ST258 clone. The INT20U isolate carried the blaNDM-1 gene and belonged to the ST11 clone lineage. Both isolates contained at least one of the extended spectra β-lactamase genes tested (TEM, SHV, OXA-1 and CTX-M group). Conclusions: The co-existence of the high-risk K. pneumoniae clones ST258 and ST11 in different hospital departments increases the risk of resistance gene transfer and suggests potential intra-hospital transmission pathways. Understanding their resistance profiles is critical for guiding treatment strategies and preventing the spread of multidrug-resistant pathogens.