Evolution of ceftazidime-avibactam resistance driven by variation in bla _KPC-2 to bla _KPC-190 during treatment of ST11-K64 hypervirulent Klebsiella pneumoniae

Introduction: The emergence of Klebsiella pneumoniae carbapenemase (KPC) variants has significantly compromised the efficacy of ceftazidime-avibactam (CZA), a critical antibiotic for treating carbapenem-resistant K. pneumoniae (CRKP) infections. This study investigates the novel KPC-190 variant, identified in a hypervirulent ST11-K64 K. pneumoniae strain during CZA therapy, which confers resistance to CZA while partially restoring carbapenem susceptibility. Methods: The K. pneumoniae clinical isolate LX02 harboring bla_KPC-190 was characterized using antimicrobial susceptibility testing, whole-genome sequencing (Illumina and Nanopore), and plasmid analysis. Functional studies included plasmid transformation, cloning assays, and enzyme kinetics (spectrophotometric analysis of purified KPC-190 protein). Genetic context was mapped using bioinformatics tools (RAST, ResFinder, Proksee), and virulence determinants were identified. Results: KPC-190 exhibited a unique resistance profile: high-level CZA resistance (MIC >64 μg/mL) with reduced carbapenem MICs (imipenem MIC = 2 μg/mL). Enzyme kinetics revealed decreased Kcat/Km for carbapenems and ceftazidime, alongside a 9-fold higher IC50 for avibactam (0.13 μM vs. KPC-2’s 0.014 μM). Genomic analysis identified bla_KPC-190 within an IS26 flanked mobile element (IS26-ISKpn8-bla_KPC-ΔISKpn6-ΔtnpR-IS26) on an IncFII plasmid. The strain also carried hypervirulence markers (rmpA2, iucABCD-iutA, and type 1/3 fimbriae). Discussion: The KPC-190 variant underscores the adaptive evolution of bla_KPC under antibiotic pressure, combining CZA resistance via enhanced ceftazidime affinity and avibactam evasion with retained carbapenem hydrolysis. Its association with hypervirulence plasmids and IS26-mediated mobility poses a dual threat for dissemination. These findings highlight the urgent need for genomic surveillance and alternative therapies (e.g., meropenem-vaborbactam) to address KPC-190-mediated resistance.