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The CpxR response regulator mediates the virulence of Klebsiella pneumoniae by regulating the expression of virulence associated genes

ABSTRACT: Klebsiella pneumoniae is a prominent human pathogen that has developed resistance to multiple antibiotics. While the roles of capsules and siderophores are well established, the identification of additional virulence determinants remains limited. In this study, we hypothesize that the two-component system response regulator CpxR is integral to the regulation of K. pneumoniae virulence via control of specific virulence-associated genes. Deletion of the cpxR gene resulted in reduced serum resistance and attenuated virulence in both Galleria mellonella larvae and murine infection models compared to the wild-type strain. To elucidate the repertoire of virulence-associated genes regulated by CpxR, a multidisciplinary workflow was employed, integrating RNA sequencing, Real-Time quantitative PCR, gene knockout strategies, serum resistance assays, and infection experiments utilizing Galleria mellonella. Among the genes identified with significantly diminished expression following cpxR deletion, KPHS_28080 emerged as a novel candidate virulence-associated gene. Deletion of KPHS_28080 impaired serum survival in both the carbapenem-resistant CRKp HS11286 and the hypervirulent hvKp ATCC43816 strains. Furthermore, deletion of KPHS_28080 in hvKp ATCC43816 led to significantly decreased colonization and impaired dissemination to multiple organs in murine models, corresponding with an overall reduction in virulence. The promoter region of KPHS_28080 harbors a conserved CpxR binding motif, which enhances promoter activity and gene transcription upon CpxR binding. Sequence alignment revealed that KPHS_28080 encodes a member of the short-chain dehydrogenase family, and this gene is highly conserved among K. pneumoniae strains. These results elucidate the pivotal role of CpxR in mediating virulence in K. pneumoniae and clarify its regulatory impact on virulence-associated gene expression.

ORGANISM(S): Klebsiella pneumoniae

PROVIDER: GSE300466 | GEO | 2025/07/10

REPOSITORIES: GEO

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Project description:The emergence of hypervirulent Klebsiella pneumoniae (hvKP) strains poses a significant threat to public health due to their high mortality rates and propensity to cause severe community-acquired infections in otherwise healthy individuals. The ability of hvKP to form biofilms and produce a protective capsule contributes to its enhanced virulence and is a significant challenge to effective antibiotic treatment. Therefore, understanding the molecular mechanisms underlying hvKP virulence and biofilm formation is crucial for developing new therapeutic strategies. Polyphosphate Kinase 1 (PPK1) is an enzyme responsible for inorganic polyphosphate synthesis and plays a vital role in regulating various physiological processes in bacteria. In this study, we investigated the impact of polyP metabolism on the biofilm and capsule formation and virulence traits in hvKP using Dictyostelium discoideum amoeba as a model host. We found that the PPK1 null-mutant was impaired in biofilm and capsule formation and showed attenuated virulence in D. discoideum compared to the wild-type strain. We performed a shotgun proteomic analysis of the PPK1 mutant and wild-type strain to gain further insight into the underlying molecular mechanism. The results revealed that the PPK1 mutant had a differential expression of proteins (DEP) involved in capsule synthesis (Wzi - Ugd), biofilm formation (MrkC-D-H), synthesis of the colibactin genotoxin precursor (ClbB), as well as proteins associated with the synthesis and modification of lipid A (ArnB -LpxC - PagP). These proteomic findings corroborate the phenotypic observations and indicate that the PPK1 mutation is associated with impaired biofilm and capsule formation and attenuated virulence in hypervirulent K. pneumoniae. Overall, our study highlights the importance of polyP synthesis in regulating extracellular biomolecules and virulence in K. pneumoniae and provides insights into potential therapeutic targets for treating K. pneumoniae infections.

Project description:Streptococcus anginosus is an important cause of brain and liver abscesses, meningitis, appendicitis, female genital tract infection, neonatal sepsis, and bacteremia. Recent studies show that S. anginosus is responsible for around 30% of streptococci associated purulent infections of internal organs. Genome sequencing of S. anginosus identified a phage-like chromosomal island (SanCI) integrated into the DNA mismatch repair operon. In S. pyogenes, related chromosomal islands (SpyCI) integrated into the same operon confer a mutator phenotype as well as alter global gene regulation, including the increased expression of many virulence factors. We hypothesized that SanCI will also alter global transcription patterns and virulence in S. anginosus. The SanCI from strain F0211 was introduced into a SanCI-free S. anginosus strain (J4211) by natural transformation. To provide a selectable marker for transformation, gene strA, encoding a predicted transcriptional regulator, was replaced in F0211 with the gene conferring erythromycin resistance (ermB), which after transfer created strain OKSan3. A functional copy of strA was then returned to this derivative of J4211, creating strain OKSan4. RNA sequencing (RNA-seq) of strains J4211, OKSan4 and OKSan3 confirmed that the addition of the SanCI altered S. anginosus global transcription patterns with increased expression of virulence, stress response and competence factors in a growth phase dependent manner. Virulence studies using Galleria mellonella as an acute infection model showed significantly increased inflammation and mortality in larvae challenged with strains OKSan4 and OKSan3 as compare to SanCI-free strain J4211. qRT-PCR analysis supported these results, revealing that antimicrobial factors of G. mellonella were more highly expressed after infection with OKSan4 compare to J4211 infection. Further, RNA-seq suggested that SanCI-encoded gene strA may encode one of the factors responsible for altered global transcriptional changes. The result of this study along with our previous studies in S. pyogenes demonstrate that streptococcal chromosomal islands are a unique class of virulence factors that improve the fitness of their host cell by altering global transcription patterns and increasing virulence.

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The CpxR response regulator mediates the virulence of Klebsiella pneumoniae by regulating the expression of virulence associated genes

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