Antibacterial, Anti-Inflammatory, and Wound-Healing Effects of Micromeria fruticosa Essential Oil-Loaded Nanoemulsion in MRSA-Infected Diabetic Wounds: In Vitro and In Vivo Evaluation.

Abstract

Background/Objectives: Diabetic foot ulcers infected with methicillin-resistant Staphylococcus aureus (MRSA) heal poorly and respond inadequately to conventional antibiotic therapy. This study developed a Micromeria fruticosa essential oil-loaded nanoemulsion (Mf-NE) as a topical treatment for such wounds. Methods: The essential oil was obtained by hydrodistillation and analyzed by GC-MS. Nanoemulsions were developed from pseudoternary phase diagrams using oleic acid and a Cremophor^® EL/Tween 80-Transcutol^® system (2:1 surfactant/cosurfactant) and characterized physicochemically. Antibacterial activity against MRSA (ATCC 43300) was assessed by agar well diffusion and microdilution, antioxidant activity by DPPH and ABTS assays, and cytocompatibility by MTT assay on L929 fibroblasts. Efficacy was evaluated over 12 days in a streptozotocin-induced MRSA-infected diabetic wound model in rats. Results: Pulegone (42.81%) and piperitenone (29.73%) were the major constituents. Incorporation of 5% (w/w) essential oil raised the droplet size from 214.5 ± 14.4 to 292.9 ± 9.9 nm; both formulations had a dermatologically acceptable pH and Newtonian flow behavior. Mf-NE produced a 16.1 mm inhibition zone and a MIC of 1.25 mg/mL, whereas NE produced no inhibition zone and had a MIC of 5 mg/mL. Radical scavenging reached 61.5% by DPPH at 10 mg/mL and 71.5% by ABTS at 0.2 mg/mL, and cell viability remained above 87%. The NE and Mf-NE formulations also demonstrated good biocompatibility in L929 fibroblast cells. Topical Mf-NE reduced the remaining wound area to 4.8 ± 0.9% of the initial area by day 12, compared with 21.0 ± 1.9% for Fucidin, 26.1 ± 1.9% for NE and 57.2 ± 1.3% for the untreated group; bacterial colonization was almost completely suppressed, TNF-α and IL-1β expression was significantly decreased, and composite histopathological scores were lower than in the untreated group (p = 0.0007). Conclusions: Mf-NE is a promising topical candidate for MRSA-infected diabetic wounds. Formulation-specific dermal and systemic safety requires further evaluation.