Development of Antibacterial Peptides with Membrane Disruption and Folate Pathway Inhibitory Activities against...

Area of Science:

• Biochemistry
• Microbiology
• Drug Discovery

Background:

• Multidrug resistance in bacteria, particularly methicillin-resistant Staphylococcus aureus (MRSA), poses a significant global health threat.
• Antimicrobial peptides (AMPs) represent a promising avenue for developing new therapeutics against resistant pathogens.
• Existing treatments for MRSA infections are limited, necessitating the exploration of novel antimicrobial agents.

Purpose of the Study:

• To design and synthesize novel antimicrobial peptides (AMPs) with enhanced activity against MRSA.
• To investigate the mechanism of action of the designed peptides, focusing on their effects on bacterial membranes and essential metabolic pathways.
• To evaluate the efficacy and safety of the developed peptides in preclinical models.

Main Methods:

• Peptide design based on sea cucumber hemolytic lectin fragments.
• In vitro antibacterial activity testing against clinical MRSA isolates (MIC determination).
• Cytotoxicity assays to assess safety.
• In vivo efficacy studies in a mouse subeschar model.
• Mechanism of action studies, including membrane integrity assays and enzyme inhibition assays (formate-tetrahydrofolate ligase).

Main Results:

• Two novel peptides, CGS19 and CGS20, demonstrated potent activity against MRSA with minimum inhibitory concentrations (MICs) of 3-6 μM.
• No significant cytotoxicity was observed for CGS19 and CGS20 in vitro.
• Both peptides exhibited rapid bactericidal activity and significantly reduced MRSA bacterial counts in a mouse infection model.
• CGS19 and CGS20 were found to disrupt bacterial membrane integrity and inhibit formate-tetrahydrofolate ligase, a key enzyme in the MRSA folate metabolism pathway.

Conclusions:

• The designed peptides CGS19 and CGS20 show significant potential as lead candidates for the development of new drugs against MRSA infections.
• The dual mechanism of action, involving membrane disruption and enzyme inhibition, offers a robust strategy for combating drug-resistant bacteria.
• These findings highlight the potential of dual-acting peptides as an underappreciated approach for treating life-threatening bacterial pathogens.