Mechanistic Study of Antimicrobial Effectiveness of Cyclic Amphipathic Peptide [R₄W₄] against Methicillin-Resistant <i>Staphylococcus aureus</i> Clinical Isolates

• Main Authors: Ajayi David Akinwale (Author), Keykavous Parang (Author), Rakesh Kumar Tiwari (Author), Jason Yamaki (Author)
• Format: Book
• Published: MDPI AG, 2024-06-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

Antimicrobial peptides (AMPs) are being explored as a potential strategy to combat antibiotic resistance due to their ability to reduce susceptibility to antibiotics. This study explored whether the [R₄W₄] peptide mode of action is bacteriostatic or bactericidal using modified two-fold serial dilution and evaluating the synergism between gentamicin and [R₄W₄] against <i>Escherichia coli</i> (<i>E. coli</i>) and methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) by a checkered board assay. [R₄W₄] exhibited bactericidal activity against bacterial isolates (MBC/MIC ≤ 4), with a synergistic effect with gentamicin against <i>E. coli</i> (FICI = 0.3) but not against MRSA (FICI = 0.75). 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] at a 16 mg/mL concentration stabilized the zeta potential of MRSA −31 ± 0.88 mV to −8.37 mV. Also, [R₄W₄] at 2 × MIC and 16 × MIC revealed a membrane perturbation process associated with concentration-dependent effects. Lastly, in the presence of BODIPY-TR-cadaverine (BC) fluorescence dyes, [R₄W₄] exhibited binding affinity to LTA comparable with melittin, the positive control. In addition, the antibacterial activity of [R₄W₄] against MRSA remained unchanged in the absence and presence of LTA, with an MIC of 8 µg/mL. Therefore, the [R₄W₄] mechanism of action is deemed bactericidal, involving interaction with bacterial cell membranes, causing concentration-dependent membrane perturbation. Additionally, after 30 serial passages, there was a modest increment of MRSA strains resistant to [R₄W₄] and a change in antibacterial effectiveness MIC [R₄W₄] and vancomycin by 8 and 4 folds with a slight change in Levofloxacin MIC 1 to 2 µg/mL. These data suggest that [R₄W₄] warrants further consideration as a potential AMP.

Item Description

10.3390/antibiotics13060555
2079-6382