Salt-Tolerant, Protease-Stable and Non-Resistance Developing Cationic AMPs for Combatting Planktonic MRSA and its Biofilms.

The global antimicrobial resistance crisis has stimulated the development of innovative therapeutics. Methicillin-resistant Staphylococcus aureus (MRSA), a critical pathogen responsible for skin and soft tissue infections. MRSA biofilms exhibit greater resistance to antibiotics compared to planktonic cells. Antimicrobial peptides (AMPs) are potential alternatives but face challenges like high costs, salt sensitivity, toxicity, and protease degradability. This study developed highly potent, salt-tolerant, nontoxic, and proteolytically stable membranolytic AMPs: d-WRL (composed of all d-amino acids) and W-(Dab)-L (incorporating 2,4-diaminobutyric acid), which effectively prevented planktonic MRSA, inhibited biofilm formation, and eradicated ∼80% of mature biofilms, outperforming vancomycin with faster killing kinetics. The biofilm eradication ability was attributed to their protease stability. The developed AMPs prevented resistance development in MRSA over 96 generations, unlike ciprofloxacin, and thus are critical additions to the limited arsenal of potential MRSA-targeting therapeutics.