The KW18 peptide acts as a dual antimicrobial and immunomodulatory therapeutic candidate in the context of antimicrobial resistance

Healthcare-associated infections and antimicrobial resistance present major challenges worldwide, especially for immunocompromised patients. This study aimed to evaluate the antimicrobial, antibiofilm, and immunomodulatory properties of KW18, a synthetic peptide (NH₂-KWIRRIIRRYVCFFRKFI-COOH) designed through bioinformatics to target multidrug-resistant bacteria and fungi, and to determine whether KW18 could serve as a dual-action therapy with potent microbicidal and anti-inflammatory effects. KW18 was tested against Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Pseudomonas aeruginosa) and fungi (Candida glabrata, C. tropicalis). MIC and MBC assays, time-kill curves, and checkerboard synergy tests were performed. Its antibiofilm activity was evaluated on mature biofilms. Membrane disruption was assessed using Sytox™ Green and ergosterol-binding assays. Immunomodulatory effects were analyzed in LPS-stimulated BV-2 microglial cells by measuring nitric oxide, IL-6, and IL-10 levels, and cytotoxicity was evaluated with cell viability assays. KW18 exhibited potent antimicrobial activity, with low MIC and MBC values across all strains, and retained antifungal effects even in the presence of ergosterol or sorbitol. Time-kill studies showed rapid, concentration-dependent microbicidal effects. The peptide worked synergistically with ciprofloxacin and amphotericin B, effectively inhibiting and eliminating mature biofilms and, in some cases, outperforming conventional treatments. Mechanistic tests confirmed membrane disruption. In BV-2 cells, KW18 reduced nitric oxide and IL-6 while increasing IL-10, all while maintaining over 85% cell viability, with a lower IC₅₀ for NO suppression than dexamethasone. KW18 demonstrates strong antimicrobial, antibiofilm, and immunomodulatory activities, supporting its potential as a promising dual-function therapeutic candidate for resistant infections.