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Published on: February 19, 2019
Phage-Encoded Virulence Factor, Gp05, Alters Membrane Phospholipids and Reduces Antimicrobial Susceptibility in
Yi Li1, Nagendra N Mishra1,2, Liang Chen3
1Lundquist Institute for Biomedical Innovation, Harbor-University of California, Los Angeles Medical Center, Torrance.
Background:
Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of endovascular infections. The prophage-encoded protein Gp05 has been identified as a critical virulence factor that contributes to MRSA persistence during vancomycin treatment in an experimental endocarditis model. However, the mechanisms underlying this persistence phenotype remain poorly understood.
Methods:
This study investigated the genetic factors contributing to Gp05-associated MRSA persistence utilizing RNA sequencing (RNA-seq) on an isogenic MRSA strain set, including a clinical persistent bacteremia isolate, its chromosomal gp05 deletion mutant, and gp05-complemented strains.
Results:
RNA-seq revealed significant downregulation of the GraSR two-component regulatory system and its downstream genes, mprF and dltABCD, in the gp05 deletion mutant compared to the wild-type and gp05-complemented strains. This downregulation led to a substantial shift in membrane phospholipid composition, with an increased phosphatidylglycerol and a corresponding decrease in lysyl-phosphatidylglycerol. These changes resulted in increased susceptibility of the gp05 deletion mutant to human cationic antimicrobial peptide (CAMP) LL-37, neutrophils, and vancomycin. These results were confirmed in an isogenic gp05 overexpression strain set in MRSA JE2 background.
Conclusions:
Gp05 modulates MRSA surface phospholipid components and charge, offering new insights into the molecular mechanisms underlying Gp05-mediated persistence in endovascular infections and potential therapeutic targets to combat these infections.
Insights
The prophage protein Gp05 helps methicillin-resistant Staphylococcus aureus (MRSA) survive vancomycin treatment by altering cell membranes. This makes MRSA more vulnerable to immune defenses and antibiotics.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Biology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) causes severe endovascular infections.
- The prophage protein Gp05 is a key virulence factor in MRSA persistence during vancomycin treatment.
- Mechanisms of Gp05-mediated MRSA persistence are not fully understood.
Purpose of the Study:
- To investigate the genetic factors behind Gp05-associated MRSA persistence.
- To elucidate the molecular mechanisms of MRSA persistence during vancomycin treatment.
Main Methods:
- Utilized RNA sequencing (RNA-seq) on isogenic MRSA strains.
- Compared a clinical persistent bacteremia isolate, its gp05 deletion mutant, and complemented strains.
- Analyzed gene expression and cell membrane composition.
Main Results:
- Gp05 deletion downregulated the graSR-vraFG system and mprF, dltABCD genes.
- This led to increased negatively charged phosphatidylglycerol (PG) and decreased lysyl-PG (LPG) in the cell membrane.
- Gp05 deletion mutant showed increased susceptibility to LL-37, PMN, and vancomycin.
Conclusions:
- Gp05 is crucial for MRSA persistence by modulating cell surface charge.
- Provides insights into Gp05-mediated persistence mechanisms in MRSA endovascular infections.
- Identifies potential therapeutic targets for persistent MRSA infections.
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