Baicalin Weakens Staphylococcus aureus Pathogenicity by Targeting Sortase B

Area of Science:

• Microbiology
• Pharmacology
• Biochemistry

Background:

• Staphylococcus aureus (S. aureus) is a major cause of hospital-acquired pneumonia.
• Multidrug-resistant S. aureus infections pose significant treatment challenges.
• Novel anti-virulence strategies are needed to combat resistant bacterial infections.

Purpose of the Study:

• To investigate baicalin as a potential anti-virulence agent against S. aureus.
• To determine if baicalin targets the SrtB virulence factor.
• To evaluate baicalin's efficacy in reducing S. aureus-induced cellular damage and inflammation.

Main Methods:

• Minimum inhibitory concentration and growth curve assays to assess antibacterial activity.
• Cell-based assays (live/dead, LDH, adherence) to evaluate baicalin's effect on S. aureus-host cell interactions.
• Molecular dynamics simulations, site-directed mutagenesis, and fluorescence spectroscopy to elucidate baicalin-SrtB binding.

Main Results:

• Baicalin demonstrated no direct anti-S. aureus antibacterial activity.
• Baicalin significantly reduced S. aureus-induced injury to human alveolar epithelial cells.
• Baicalin decreased S. aureus adherence to host cells and attenuated macrophage inflammatory responses.
• Baicalin was confirmed to directly bind to the active site of SrtB, specifically interacting with residues Asn92 and Tyr128.

Conclusions:

• Baicalin functions as an anti-virulence agent by inhibiting S. aureus Sortase B.
• Baicalin reduces S. aureus pathogenicity by decreasing cell damage, adherence, and inflammation.
• Baicalin is a promising therapeutic candidate for treating drug-resistant S. aureus infections.