Olefinic side chain modification of fusidic acid enhances anti-MRSA activity and mitigates resistance development

Area of Science:

• Medicinal Chemistry
• Microbiology
• Drug Discovery

Background:

• Antibiotic resistance is a growing global health threat, necessitating new antimicrobial agents.
• Fusidic acid (FA) is used against methicillin-resistant Staphylococcus aureus (MRSA) but faces resistance challenges.
• Previous modifications of FA's side chain had limited efficacy against Gram-positive bacteria.

Purpose of the Study:

• To engineer novel fusidic acid derivatives with improved anti-MRSA activity and reduced resistance.
• To evaluate the efficacy of these derivatives against Gram-positive bacteria and their biofilm formation.
• To assess the therapeutic potential of lead compounds in a preclinical infection model.

Main Methods:

• Systematic engineering of the fusidic acid olefinic side chain using Wittig and olefin metathesis reactions.
• Synthesis and characterization of 26 novel fusidic acid derivatives.
• Evaluation of antimicrobial activity (MIC), biofilm disruption, and gene expression analysis in vitro.
• Assessment of efficacy in a murine skin infection model.

Main Results:

• Compound 10a demonstrated superior activity against MRSA compared to fusidic acid, with a lower minimum inhibitory concentration (MIC) and reduced resistance development.
• Compound 10a significantly inhibited MRSA biofilm formation (61.4% reduction) and downregulated key biofilm regulators.
• In vivo studies showed compound 10a effectively inhibited bacterial growth and promoted wound healing in a murine model.

Conclusions:

• Compound 10a is a highly promising candidate molecule for treating multidrug-resistant Gram-positive bacterial infections.
• The engineered fusidic acid derivative exhibits potent antibacterial, anti-biofilm, and in vivo therapeutic properties.
• This study highlights the potential of targeted side chain modification to overcome limitations of existing antibiotics.