Optimization of ultrasound contrast agent and treatment duration for drug delivery to methicillin-resistant Staphylococcus aureus diabetic wound biofilms in mice

Abstract

Chronic wounds are frequently infected with bacterial biofilms which pose a barrier to drug diffusion, drug uptake, and facilitate drug tolerance, thereby prolonging the healing process in chronic wounds and increasing the likelihood of relapse. A major contributor to relapse is persister cells, a subset resilient to high antibiotic doses. Previous work by our group showcased significantly improved gentamicin efficacy in a diabetic murine wound model using ultrasound, nanodroplets, and an anti-persister drug. Here, we aim to optimize nanodroplet formulation for persister cell targeting and treatment duration for clinical translation. In a methicillin-resistant Staphylococcus aureus (MRSA) diabetic wound model in SKH-1 hairless mice (n = 5), wounds were treated twice daily with gentamicin, ultrasound, and nanodroplets containing oxygen or palmitoleic acid (PA). These components aim to increase oxygenation and enhance persister uptake, respectively. Additionally, treatments with gentamicin, PA nanodroplets, and ultrasound for 2, 5, and 10 minutes were investigated (n = 3). Preliminary findings indicate PA most effectively potentiates antibiotic activity, 10- minute treatments improve efficacy by 1-log compared to 5-minutes, and 2-minute treatments achieve comparable efficacy to 5-minutes. These initial findings suggest a promising strategy for enhancing antibiotic efficacy and targeting persister cells in biofilms, with consideration for resource-efficient treatment times for clinical application.