Date of Award
Spring 5-2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Pharmaceutical Sciences
First Advisor
Jason Yamaki
Second Advisor
Rakesh Tiwari
Third Advisor
Ahmed Aftab
Fourth Advisor
Keykavous Parang
Abstract
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 Escherichia coli (E. coli) and Methicillin-resistant Staphylococcus aureus (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 E. coli (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.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Recommended Citation
Akinwale, AD. Mechanistic Study of Antimicrobial Cyclic Peptide [R4W4] Antibacterial Effectiveness against Methicillin-resistant Staphylococcus aureus (MRSA). [dissertation]. Irvine, CA: Chapman University; 2024. https://doi.org/10.36837/chapman.000580
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Other Pharmacy and Pharmaceutical Sciences Commons, Pharmaceutics and Drug Design Commons