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Updated: Jul 26, 2025
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A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
Published on: February 19, 2019
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Complex Regulation of Gamma-Hemolysin Expression Impacts Staphylococcus aureus Virulence
Mariane Pivard1, Isabelle Caldelari2, Virginie Brun3,4
1CIRI, Centre International de Recherche en Infectiologie, Université de Lyon, Inserm U1111, Université Claude Bernard Lyon 1, CNRS UMR5308, ENS de Lyon, Lyon, France.
Microbiology Spectrum
|June 22, 2023
Summary
Staphylococcus aureus gamma-hemolysin CB (HlgCB) toxin levels vary significantly in pneumonia isolates due to genetic changes. A single 5' UTR SNP drastically impacts HlgC translation, affecting virulence.
Area of Science:
- Microbiology
- Molecular Biology
- Pathogenesis
Background:
- Staphylococcus aureus produces pore-forming toxins like gamma-hemolysin CB (HlgCB), targeting the C5a receptor.
- HlgCB is similar to Panton-Valentine leucocidin (PVL) and contributes to community-acquired pneumonia (CAP) severity.
- Variations in HlgCB expression exist among clinical isolates, impacting S. aureus virulence.
Purpose of the Study:
- To investigate the molecular basis for HlgCB expression and protein production variations in S. aureus clinical strains.
- To determine the impact of genetic variations on HlgCB levels and HlgC/HlgB ratios.
- To correlate HlgCB levels with S. aureus virulence in a pneumonia model.
Main Methods:
- Absolute quantification of HlgCB using mass spectrometry in 39 CAP isolates.
- Analysis of hlgCB expression at promoter, mRNA processing, and translation levels.
- Identification of single nucleotide polymorphisms (SNPs) in regulatory regions of hlgCB.
- Assessment of HlgCB virulence in a rabbit pneumonia model.
Main Results:
- Significant variations in HlgC and HlgB yields were observed between isolates, with dissociated levels in 10% of strains.
- HlgCB level and HlgC/HlgB ratio depend on hlgC promoter activity, mRNA processing, and translation.
- A single SNP in the 5' UTR of hlgCB mRNA strongly impaired HlgC translation in the USA300 strain.
- High HlgCB levels correlated with mortality in a rabbit pneumonia model.
Conclusions:
- Subtle genomic variations, particularly SNPs in noncoding regions, can significantly impact S. aureus HlgCB expression and virulence.
- HlgCB plays a crucial role in S. aureus virulence in PVL-negative pneumonia strains.
- Understanding these regulatory mechanisms is key to deciphering bacterial pathogenesis and developing targeted therapies.
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