Efficacy of topical vancomycin and gentamicin loaded calcium sulfate beads or systemic antibiotics in eradicating polymicrobial biofilms isolated from diabetic foot infections within an in vitro wound model

Crowther, G S. Callaghan, N. Bayliss, M. Noel, A. Morley, R. Price, B. Antimicrob Agents Chemother. 2021 May 18;65(6):e02012-20. doi: 10.1128/AAC.02012-20. Print 2021 May 18.
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A frequent and serious complication of diabetes mellitus is the development of diabetic foot ulcers (DFUs), which effects an estimated 25% of those with diabetes within their lifetime. The ability of wound isolates to grow within biofilms is well documented, with polymicrobial biofilms present in up to 78% of Diabetic Foot Infections (DFIs). In order to investigate novel treatment approaches to DFI, in vitro modelling is required in the first instance, particularly in the case of biofilms. In this study the overall aim was to compare the anti-biofilm efficacy of a novel topical antibiotic combination and standard systemic antibiotics using an in-vitro model of biofilm infection. Blood and tissue samples were collected from patients with diabetic foot infections and measured for the concentration of antibiotics in the samples after systemic treatment. Additionally, the microbiota within the tissue before treatment and after seven days of systemic antibiotic therapy was also assessed. An in vitro model of polymicrobial biofilm infection inoculated with isolates from the tissues samples was used to simulate different methods of antibiotic administration by simulated systemic therapy or topical release from antibiotic loaded STIMULAN beads. These data show simulated systemic antimicrobial therapy did not significantly reduce biofilm bioburden in any of the wound models and substantial log reductions were elicited when biofilms in vitro were exposed to vancomycin and gentamicin loaded STIMULAN beads. These data support further studies of topical release of antibiotics from calcium sulfate beads in diabetic foot infections The abstract can be read, and the full paper can be obtained here.

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