# Emergence and characterization of a novel ST627-KL8 carbapenem-resistant Klebsiella pneumoniae lineage associated with ICU transmission in a tertiary hospital, China

## TL;DR

A new carbapenem-resistant Klebsiella pneumoniae strain, ST627-KL8, was found in a hospital ICU and shown to spread easily with intermediate virulence.

## Contribution

Identification of a novel ST627-KL8 CRKP lineage with reduced capsule and intermediate virulence linked to ICU transmission.

## Key findings

- ST627-KL8 CRKP isolates showed clonal transmission within the ICU with ≤ 5 SNPs.
- The strain carries an IncFIIK34 plasmid encoding blaKPC–2 and has a thinner capsule compared to KL2.
- Intermediate virulence was observed in a Galleria mellonella model compared to hypervirulent and low-virulence strains.

## Abstract

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a serious threat to public health. We characterized a rarely reported ST627-KL8 CRKP lineage associated with intensive care unit (ICU) transmission.

Three isolates (ZJG29565, ZJG30140, and ZJG30146) were obtained from three patients in the ICU and subjected to antimicrobial susceptibility testing. Whole-genome sequencing (WGS) was performed to determine genomic characteristics, phylogenetic relationships, and plasmid content, followed by assessments of mucoviscosity, capsule quantification, serum resistance, and bacterial virulence using a Galleria mellonella (G. mellonella) infection model. Additionally, bacterial capsule morphology was observed via transmission electron microscopy (TEM).

SNP analysis (≤ 5 SNPs) confirmed clonal transmission within the ICU. Phylogenetic analysis placed ST627-KL8 as a distinct lineage closely related to ST14. All isolates carried an IncFIIK34 plasmid encoding blaKPC–2, consistent with their carbapenem-resistant phenotype. Phenotypic assays—including TEM, mucoviscosity testing, serum resistance, and uronic acid quantification—demonstrated a thinner capsule and reduced mucoviscosity compared with the KL2 reference strain. In the Galleria mellonella model, ST627-KL8 exhibited intermediate virulence (66.7%–76.7% survival), between the hypervirulent K. pneumoniae ATCC 43816 strain (30.0%) and the low-virulence K. pneumoniae ATCC 700603 strain (96.7%).

This study identified a novel ST627-KL8 CRKP clone with intermediate virulence, consistent with its reduced capsule phenotype and lack of classical hypervirulence genes. These features, together with the subtle clinical presentations, may contribute to reduced clinical vigilance and delayed optimization of antimicrobial therapy. Importantly, ST627-KL8 CRKP carried the IncFIIK34
blaKPC–2 plasmid, which has been reported to exhibit high conjugation frequency, posing a significant challenge in clinical settings.