Indole and 7-benzyloxyindole attenuate the virulence of Staphylococcus aureus

Area of Science:

• Microbiology
• Infectious Diseases
• Drug Discovery

Background:

• Antibiotic resistance is a growing threat, necessitating alternative treatments.
• Antivirulence compounds offer a promising strategy by targeting bacterial virulence factors without promoting resistance.
• Staphylococcus aureus is a significant pathogen causing nosocomial infections, employing virulence factors like staphyloxanthin for immune evasion.

Purpose of the Study:

• To investigate indole and its derivatives as potential antivirulence agents against Staphylococcus aureus.
• To assess the impact of indole derivatives on S. aureus virulence factors, including staphyloxanthin production and hemolytic activity.
• To evaluate the efficacy of these compounds in reducing bacterial resistance to host defenses and in vivo models.

Main Methods:

• Screening of indole and its derivatives for their effect on S. aureus virulence.
• Assessing staphyloxanthin production, hemolytic activity, and bacterial growth.
• Evaluating bacterial susceptibility to reactive oxygen species (ROS) and human whole blood.
• In vivo testing using a Caenorhabditis elegans infection model.
• Transcriptional analysis of virulence and regulatory genes.

Main Results:

• Indole and 7-benzyloxyindole (7BOI) treatment rendered S. aureus colorless, indicating reduced staphyloxanthin production.
• Hemolytic activity of S. aureus was inhibited by indole and 7BOI without affecting bacterial growth.
• Indole and 7BOI treatments increased S. aureus susceptibility to hydrogen peroxide (H₂O₂) and human whole blood.
• 7BOI demonstrated significant attenuation of S. aureus virulence in the C. elegans model.
• Transcriptional analysis revealed repression of key virulence genes (hla, seb, splA, sspA) and modulation of regulatory genes (agrA, sarA).

Conclusions:

• Indole derivatives, specifically 7BOI, are effective antivirulence compounds against Staphylococcus aureus.
• These compounds reduce bacterial virulence by inhibiting key factors and increasing susceptibility to host defenses.
• Indole derivatives represent a promising therapeutic strategy for combating persistent S. aureus infections and mitigating antibiotic resistance development.