• Andrea Y Moon, Emily J Bailey, Jonilee A Polanco, Wendy E Kurata, and Lisa M Pierce.
• Department of General Surgery, Tripler Army Medical Center, Tripler AMC, HI 96859, USA.
• Mil Med. 2023 Nov 8; 188 (Suppl 6): 526052-60.

IntroductionBecause antibiotic resistance is increasing worldwide and the leading cause of death in burn patients is an infection, an urgent need exists for nonantibiotic approaches to eliminate multidrug-resistant bacteria from burns to prevent their systemic dissemination and sepsis. We previously demonstrated the significant antibiofilm activity of a chitosan (CS) hydrogel containing the antimicrobial peptide epsilon-poly-l-lysine (EPL) against multidrug-resistant Pseudomonas aeruginosa using ex vivo porcine skin. In this study, we evaluated the in vivo antibacterial efficacy of a CS/EPL hydrogel against P. aeruginosa in a murine burn wound infection model.Materials And MethodsFull-thickness burns were created on the dorsum using a heated brass rod and were inoculated with bioluminescent, biofilm-forming P. aeruginosa (Xen41). Mice were treated with CS/EPL, CS, or no hydrogel applied topically 2 or 24 hours after inoculation to assess the ability to prevent or eradicate existing biofilms, respectively. Dressing changes occurred daily for 3 days, and in vivo bioluminescence imaging was performed to detect and quantitate bacterial growth. Blood samples were cultured to determine systemic infection. In vitro antibacterial activity and cytotoxicity against human primary dermal fibroblasts, keratinocytes, and mesenchymal stem cells were also assessed.ResultsCS/EPL treatment initiated at early or delayed time points showed a significant reduction in bioluminescence imaging signal compared to CS on days 2 and 3 of treatment. Mice administered CS/EPL had fewer bloodstream infections, lower weight loss, and greater activity than the untreated and CS groups. CS/EPL reduced bacterial burden by two orders of magnitude in vitro and exhibited low cytotoxicity against human cells.ConclusionA topical hydrogel delivering the antimicrobial peptide EPL demonstrates in vivo efficacy to reduce but not eradicate established P. aeruginosa biofilms in infected burn wounds. This biocompatible hydrogel shows promise as an antimicrobial barrier dressing for the sustained protection of burn wounds from external bacterial contamination.Published by Oxford University Press on behalf of the Association of Military Surgeons of the United States 2023. This work is written by (a) US Government employee(s) and is in the public domain in the US.

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