Within-host co-evolution of KPC variants: plasmid-mediated dissemination of <i>bla</i> _Kpc-194 and <i>bla</i> _Kpc-33 in ST11-KL64 hypervirulent <i>Klebsiella pneumoniae</i> driving ceftazidime-avibactam resistance

This study elucidates the critical molecular mechanism and evolutionary pathway of a novel KPC variant, KPC-194, that confers resistance to the last-resort antibiotic combination ceftazidime-avibactam in a high-risk <i>Klebsiella pneumoniae</i> strain. We identified that two amino acid substitutions (D179Y/P183L) in KPC-194 are responsible for ceftazidime-avibactam resistance. Crucially, our work reveals a dual-threat dynamic: the resistance phenotype is not only caused by the KPC mutation but also profoundly exacerbated by horizontal gene transfer. <i>bla</i>_KPC-194 mobilized from a low-risk IncR plasmid to a highly transmissible IncFII plasmid via IS26-mediated replicative transposition. This event dramatically enhances the potential for widespread dissemination among clinical pathogens.