Mechanistic Study of Antimicrobial Cyclic Peptide [R4W4] Antibacterial Effectiveness against Methicillin-resistant Staphylococcus aureus (MRSA)

<p>Antimicrobial peptides (AMPs) are being explored as a potential solution to combat antibiotic resistance, as they have shown promise in reducing susceptibility to antibiotics. This study explores if [R₄W₄] peptide is bacteriostatic or bactericidal using modified two-fold serial dilution and evaluates synergism of gentamicin and [R₄W₄] against <em>Escherichia coli</em> (<em>E. coli)</em> and Methicillin-resistant <em>Staphylococcus aureus</em> (MRSA) by checkered board assay. The MRSA resistant to [R₄W₄] and possibility with other antibiotics was evaluated with serial passage. Moreover, we investigated the mechanism of action of [R₄W₄] against MRSA by applying biophysical assays to evaluate zeta potential, cytoplasmic membrane depolarization, and Lipoteichoic acid (LTA) binding affinity. [R₄W₄] exhibits bactericidal activity against bacterial isolates (MBC/MIC £ 4), with a synergistic effect with gentamicin against <em>E. coli</em> (FICI=0.3), but not against MRSA (FICI=0.75). [R₄W₄] at 16 µg/ml concentration stabilizes the zeta potential of MRSA -33 ± 0.88 mV to -8.37 mV. Also, [R₄W₄] at 2 x MIC and 16 x MIC revealing a membrane perturbation process associated with concentration-dependent effects. Lastly, in the presence of BODIPY-Cadaverine fluorescence dyes, [R₄W₄] reveals binding affinity to LTA comparable with melittin, the positive control. In addition, a change in the antibacterial activity of [R₄W₄] against MRSA in the absence and presence of LTA did not change the MIC 8µg/ml. Therefore, the [R₄W₄] mechanism of action is bactericidal with the potential to interact with bacterial cell membranes, causing concentration-dependent cytoplasm membrane perturbation.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Pharmaceutical Sciences

Year dc:date.available

2024

Author dc:creator

• Akinwale, Ajayi

Contributors dc:contributor

• Jason Yamaki
• Rakesh Tiwari
• Ahmed Aftab
• Keykavous Parang

• Antimicrobial peptides
• Methicillin-resistant Staphylococcus aureus
• Mechanism of action
• Antimicrobial Cyclic Peptide [R4W4]
• Other Pharmacy and Pharmaceutical Sciences
• Pharmaceutics and Drug Design

Repository record dc:identifier

https://digitalcommons.chapman.edu/pharmaceutical_sciences_dissertations/36

OAI identifier oai:identifier

oai:digitalcommons.chapman.edu:pharmaceutical_sciences_dissertations-1037