# Comparative genomic, phenotypic, and clinical characterization of ST11-KL25 and ST11-KL64 hypervirulent carbapenem-resistant Klebsiella pneumoniae in a tertiary hospital, 2020–2023

## TL;DR

This study compares two subtypes of a dangerous antibiotic-resistant bacteria in a hospital, finding they differ in drug resistance and how they cause disease.

## Contribution

The study provides a detailed genomic and clinical comparison of ST11-KL25 and ST11-KL64 hv-CRKP subtypes in China.

## Key findings

- ST11-KL25 and ST11-KL64 show distinct resistance and virulence profiles.
- ST11-KL25 may have evolved from KL64 through capsular switching and has higher biofilm formation.
- ST11-KL64 shows broader drug resistance and higher in vivo virulence.

## Abstract

Hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) poses a significant challenge in healthcare settings due to its combination of high virulence and multidrug resistance. In China, ST11 is the predominant lineage, with KL64 and the recently identified KL25 as key capsular subtypes. The clinical and genomic characteristics of ST11-KL25 remain insufficiently characterized. A total of 239 hv-CRKP isolates collected from 2020 to 2023 were analyzed. Molecular typing, antimicrobial susceptibility testing, whole-genome sequencing, and phenotypic assays were used to compare the epidemiology, resistance mechanisms, and virulence traits of ST11-KL25 and ST11-KL64. Clinical data were reviewed to assess infection characteristics. ST11 accounted for 87.9% (210/239) of hv-CRKP isolates. Among ST11 isolates, KL64 (54.7%, 104/190) and KL25 (45.3%, 86/190) were the predominant capsular types. Phylogenetic analysis suggested that ST11-KL25 may have originated from KL64 through capsular switching, with increasing prevalence after 2021. Both sublineages exhibited extensive drug resistance; however, ST11-KL64 showed broader resistance, including higher rates of ceftazidime-avibactam and polymyxin resistance. Phenotypically, ST11-KL25 demonstrated greater competitive fitness and biofilm formation, while ST11-KL64 displayed higher in vivo virulence in the Galleria mellonella model. ST11-KL25 and ST11-KL64 exhibit distinct adaptation strategies within hv-CRKP. KL25 seems to be a stable, colonization-adapted subtype with consistent resistance and moderate virulence, while KL64 is more invasive, with broader resistance and higher virulence. Subtype-specific surveillance and intervention are essential to limit their spread and protect patient and public health.