Carbapenem-Resistant Hypervirulent Klebsiella pneumoniae ST23 in China
Imagine a pathogen that can infect perfectly healthy people, cause devastating infections throughout the body, and withstand nearly all our strongest antibiotics.
This isn't science fiction—it's the alarming reality of carbapenem-resistant hypervirulent Klebsiella pneumoniae ST23, a "superbug" that has emerged in China and poses a serious threat to global public health. In early 2024, the World Health Organization issued warnings after 12 out of 43 countries reported detections of this dangerous pathogen 2 .
What makes this microbe so concerning is its deadly combination of hypervirulence, meaning it can cause severe disease in healthy individuals, and carbapenem resistance, which makes it untreatable with most last-resort antibiotics 2 4 . This article explores the emergence and molecular evolution of this superbug in China, where dedicated scientists are racing to understand and contain this growing threat before it spirals out of control.
CR-hvKP strains identified in China
Of carbapenem-resistant isolates
ST23 CR-hvKP clinical isolates
To understand why CR-hvKP ST23 is so dangerous, we must first understand its two distinct evolutionary lineages that have tragically converged.
An opportunistic pathogen that typically causes infections in hospitalized or immunocompromised patients. Over time, some of these strains acquired resistance genes to multiple antibiotics, eventually becoming carbapenem-resistant K. pneumoniae (CRKP), which can withstand our most powerful antibiotics 1 5 .
First identified in Taiwan in 1986 when it caused severe liver abscesses in healthy individuals, hvKP possesses special weapons that make it exceptionally invasive 2 5 . Unlike classic strains, hvKP can infect young, healthy people and cause devastating infections throughout the body 5 .
The convergence of these two paths has created a nightmare scenario: CR-hvKP, combining hypervirulence with extensive drug resistance 5 . Researchers have identified three primary ways this convergence occurs:
Among the various strains of K. pneumoniae, sequence type 23 (ST23) stands out as particularly concerning. ST23 hvKP has long been recognized as a major cause of severe community-acquired infections across China and Taiwan 2 .
hvKP first identified in Taiwan
First ST23 CR-hvKP case in Zhejiang, China
WHO warnings issued after detections in 12 countries
Historically, ST23 hvKP was primarily community-acquired and remained largely antibiotic-sensitive. However, recent years have witnessed an alarming shift as these hypervirulent strains began acquiring carbapenem resistance genes, transforming them into the superbug we face today 2 .
The earliest known case of ST23 CR-hvKP in China dates back to 2013 in Zhejiang province, where a strain carried the blaKPC-2 carbapenemase gene alongside全套毒力基因 2 . Since then, these converged strains have been detected with increasing frequency across China.
Mapping the Superbug's Footprint
A comprehensive analysis of 5,036 K. pneumoniae genomes from China (2005-2023) identified 1,538 CR-hvKP strains, accounting for 44.6% of carbapenem-resistant isolates and 69.5% of hypervirulent isolates 1 . Among these, ST23 represents a significant portion, with studies identifying approximately 120 ST23 CR-hvKP clinical isolates from China 2 .
| Province | Percentage of Isolates | Predominant Carbapenemase |
|---|---|---|
| Hebei | 25.2% | blaNDM |
| Jiangxi | 22.7% | blaKPC |
| Zhejiang | Early case (2013) | blaKPC-2 |
Source: 2
| Carbapenemase Type | Ambler Class | Geographic Preference |
|---|---|---|
| blaKPC | A | Southern China |
| blaNDM | B | Northern China |
| blaOXA-48-like | D | Less common |
Source: 2
The carbapenemase distribution reveals a notable north-south divide within China. Northern provinces like Hebei show predominance of blaNDM enzymes, while southern regions including Jiangxi more commonly harbor blaKPC variants 2 . This geographical distribution reflects the complex interplay between regional antibiotic usage practices and the dissemination of specific mobile genetic elements.
ST23 CR-hvKP possesses an impressive arsenal of virulence factors that explain its ability to cause severe disease:
Considered one of the most important siderophores for hvKP 2
Another efficient siderophore that helps scavenge iron 2
Enhance capsule production, contributing to the hypermucoviscous phenotype 2
Additional siderophore system often located on integrative conjugative elements 1
These virulence factors are typically carried on a large virulence plasmid, often similar to pK2044 (approximately 224 kb), originally identified in the classic ST23 strain NTUH-K2044 from Taiwan 2 . The loss of this plasmid dramatically reduces virulence, confirming its essential role in hypervirulence.
On the resistance side, ST23 CR-hvKP primarily acquires carbapenem resistance through the acquisition of carbapenemase genes located on mobile genetic elements, especially plasmids.
What makes the situation particularly dangerous is the location of these resistance genes on plasmids that can readily transfer between different bacterial strains. A study analyzing the genetic background of CR-hvKP in China found high-risk endemic STs such as ST11, ST15, and ST23 were predominant, with the core genome analysis revealing that 89.0% of CR-hvKP isolates clustered into 131 clonal groups, indicating widespread dissemination 1 .
Tracking a Superbug in Detail
In 2024, researchers at The Affiliated Li Huili Hospital in Ningbo conducted an in-depth investigation of a CR-hvKP strain isolated from a patient in their region. Their comprehensive approach provides an excellent example of how scientists are working to understand and characterize these superbugs 9 .
The researchers began by collecting 96 carbapenem-resistant K. pneumoniae strains from January 2021 to December 2022. They then subjected these strains to a series of sophisticated analyses:
Through this screening process, they identified one CR-hvKP strain (designated CR-hvKP57), representing an isolation frequency of 1.04% among carbapenem-resistant strains in their collection 9 .
Identified as ST23 with K1 capsule, harboring three distinct plasmids
Caused high mortality in mice with increased pro-inflammatory cytokines
Resistance plasmid could be transferred to E. coli recipients
Resistant to multiple antibiotic classes, susceptible to few last-line agents
pLVPK-like virulence plasmid
Carrying rmpA, rmpA2, iroB, iucA, terB
Transposable elements
Containing IS15 and IS26 sequences
Resistance plasmid
Harboring the blaKPC-3 carbapenem resistance gene
The presence of both a complete virulence plasmid and a carbapenem resistance plasmid in a single ST23 strain exemplifies the convergence that creates these superbugs 9 .
The emergence and spread of ST23 CR-hvKP in China represents a critical public health threat that demands urgent action. Several strategies are essential to combat this superbug:
Comprehensive monitoring of CR-hvKP strains is crucial to track their emergence and spread 1 .
Strict implementation of infection prevention protocols in healthcare settings .
Judicious use of antibiotics to reduce selective pressure favoring resistant strains 9 .
Investigation of phage therapy, vaccines, and novel antimicrobial strategies .
The emergence of carbapenem-resistant hypervirulent ST23 Klebsiella pneumoniae in China represents a disturbing evolution in the superbug threat. By combining hypervirulence with extensive antibiotic resistance, these strains challenge our current treatment paradigms and threaten to reverse decades of progress in controlling infectious diseases.
Ongoing research continues to uncover the complex molecular mechanisms driving the evolution and spread of these pathogens. As one study noted, analysis of 584 global ST23 genomes suggests independent plasmid-mediated acquisition of carbapenemase genes, with evidence of clonal transmission both among humans and between humans and environmental niches 2 . This highlights the complex epidemiology of these strains and the challenges in controlling their spread.
The situation demands a coordinated global response, enhanced surveillance, and continued research to develop new countermeasures. As scientists work to unravel the complexities of these superbugs, their findings provide hope that we can stay one step ahead in this ongoing evolutionary arms race between human ingenuity and bacterial adaptation.
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