Phenotypic and Transcriptomic Characterization of Host-Associated Responses in a Carbapenem-Resistant Klebsiella...

Carbapenem-resistant Klebsiella pneumoniae (CRKP) sequence type 11 (ST11) is widely reported in Asia and represents an important clinical concern. Although antimicrobial resistance in ST11 isolates has been extensively investigated, less is known about the phenotypic characteristics and host-associated transcriptional responses of individual clinical isolates. In this study, we performed an in-depth characterization of a clinical ST11 CRKP isolate, NJGLYY4165. Phenotypic assays were used to evaluate bacterial growth, biofilm formation, serum resistance, inflammatory responses, and virulence in a Galleria mellonella infection model. Whole-genome sequencing and bacterial transcriptomic profiling were conducted to examine gene expression changes at 4 h during interaction with human intestinal epithelial cells and macrophages. NJGLYY4165 exhibited increased survival following exposure to normal human serum in vitro but displayed reduced lethality in the Galleria mellonella infection model compared with selected reference strains. Infection of host cells induced marked inflammatory responses. Transcriptomic analysis revealed extensive gene expression remodeling at the examined time point during host interaction, including upregulation of central metabolic pathways and iron acquisition systems, particularly under macrophage-associated conditions. This study provides a detailed phenotypic and single-time-point transcriptomic description of host-associated responses in a clinical ST11 CRKP isolate. The observed metabolic and iron acquisition responses may contribute to adaptation under host-associated conditions; however, because comparative analyses with non-ST11 or non-epidemic strains were not included, it remains unclear whether these features are isolate-specific, ST11-associated, or represent general adaptive responses of K. pneumoniae. Further comparative and time-course studies across diverse clinical isolates will be required to clarify temporal dynamics and broader epidemiological relevance.