059 Effects of Two Topical Antimicrobial Agents on Staphylococcus Aureus Biofilms in a Porcine Model

Abstract

Biofilms are a combination of microorganisms and extrapolysaccharide matrices. Our laboratory has previously demonstrated that biofilms are present in both acute and chronic wounds. Once biofilms are established, phagocytosis and diffusion of antibiotics are impaired thus contributing to antimicrobial resistance due to increased bacterial virulence. The purpose of this study was to determine the efficacy of two topical antimicrobial agents on partial thickness wounds containing Staphylococcus aureus biofilms. All wounds were inoculated with 106 CFU/ml and covered for 48 hrs under a polyurthene film to promote biofilm formation. Wounds were divided into three treatment groups; triple antibiotic ointment (Polymyxin B sulfate, bacitracin zinc, neomycin), mupirocin cream and untreated control. Wounds were treated twice daily. Wounds were cultured for bacterial quantitation at 24, 48, 72, 96, and 120 hrs. Significant reduction in CFU/ml was observed only after several days of treatments. This finding supports the antimicrobial resistance that occurs when bacteria live within biofilms. Our previous studies demonstrated that both of these agents were able to completely eliminate planktonic S. aureus(106) at the early time points. This study demonstrates that when bacterial biofilms are established in wounds there is a longer response time for topical antimicrobial activity suggesting bacterial resistance.