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Gentamicin-resistant menadione and hemin auxotrophic Staphylococcus aureus persist within cultured endothelial cells
J M Balwit1, P van Langevelde, J M Vann
1Department of Medical Microbiology, University of Wisconsin Medical School, Madison.
Abstract:
Staphylococcus aureus menadione and hemin auxotrophs, generated by in vitro gentamicin selection, demonstrated reduced hemolytic activity and enhanced intracellular survival within cultured bovine aortic endothelial cells relative to their hemolytic parent. Supplementation of the auxotrophs with exogenous menadione or hemin resulted in rapid growth, increased hemolytic activity, and reduced intracellular persistence to the level found for the hemolytic clinical parent. Aminoglycoside selection of staphylococcal menadione and hemin auxotrophs and subsequent persistence of these variants in the intracellular milieu may adapt S. aureus for evasion of host defenses and resistance to antimicrobial therapy.
Insights
Staphylococcus aureus auxotrophs showed reduced virulence but enhanced survival inside cells. Supplementation restored virulence, suggesting a mechanism for bacterial evasion of defenses and antimicrobial resistance.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Staphylococcus aureus is a significant human pathogen.
- Understanding bacterial adaptation and survival mechanisms is crucial for developing new treatments.
- Menadione and hemin are essential compounds for bacterial metabolism and virulence.
Purpose of the Study:
- To investigate the role of menadione and hemin auxotrophy in Staphylococcus aureus virulence.
- To determine the impact of menadione and hemin supplementation on bacterial growth, hemolytic activity, and intracellular survival.
- To explore the potential of aminoglycoside selection for generating S. aureus variants with altered virulence properties.
Main Methods:
- Generating menadione and hemin auxotrophs of Staphylococcus aureus using in vitro gentamicin selection.
- Assessing hemolytic activity of parent and auxotrophic strains.
- Evaluating intracellular survival of bacteria within cultured bovine aortic endothelial cells.
- Supplementing auxotrophs with exogenous menadione or hemin to observe effects on growth and virulence.
Main Results:
- Generated Staphylococcus aureus menadione and hemin auxotrophs exhibited reduced hemolytic activity.
- These auxotrophs demonstrated enhanced intracellular survival within endothelial cells compared to the hemolytic parent strain.
- Supplementation with menadione or hemin restored rapid growth, increased hemolytic activity, and reduced intracellular persistence.
- The restored virulence matched that of the original hemolytic clinical parent strain.
Conclusions:
- Aminoglycoside selection can generate Staphylococcus aureus auxotrophs with altered virulence.
- Menadione and hemin auxotrophy influences S. aureus hemolytic activity and intracellular survival.
- Persistence of these variants in the intracellular environment may contribute to immune evasion and antimicrobial resistance.
- Targeting menadione and hemin metabolism could be a strategy to combat S. aureus infections.