Objective: Chronic infections are often related to the formation of single or polymicrobial biofilms, which lead to hard-to-treat infections, difficult wound management, and recurrent infections. In this study, we evaluated in vitro antibiofilm properties of a silver and zinc bioelectric dressing (Procellera).
Method: We customised and established a poloxamer biofilm model using glass coverslips for the efficacy evaluation of the bioelectric dressing. For antimicrobial susceptibility testing, each bacterial pathogen was diluted to 10(5)CFUs/ml, mixed with 30% poloxamer hydrogels and dropped onto round glass coverslips (25mm diameter) as an abiotic support. Additionally, we mixed four bacterial strains and developed multi-species biofilms in the poloxamer model to examine anti-biofilm efficacy testing against polymicrobial biofilms.
Results: After 24 hours incubation, we observed significant inhibition of bacterial growth in nine pathogens (∼2- or 3-fold log10 reduction) compared to controls (no treatment, gauze, and blank polyester with no silver and zinc). The smallest effect was seen with Enterococcus faecalis strain where there was approximately a 1-fold log10 reduction of microbial growth. The antibiofilm efficacy against multi-species (four pathogens) biofilms, evaluated on chromogenic agar plates, was 1- or 2-fold log10 reduction compared to controls.
Conclusion: This poloxamer biofilm model was easy to set up, simple to apply, and demonstrated appropriate biofilm formation. The data showed the formation of biofilms inoculated with either single or polymicrobial bacteria under no shear condition, and the bioelectric dressing tested in this study showed effective antibiofilm activity against both the mono- and multi-species biofilms.
Declaration of interest: None. The opinions or assertions contained here are the private views of the authors, based on scientific investigation, and are not to be construed as official or as reflecting the views of the US Department of the Army, the Department of Defense, the Department of Veterans Affairs, or the Henry M. Jackson Foundation for the Advancement of Military Medicine.
Keywords: anti-biofilm property; bioelectric dressing; clinical wound pathogen; poloxamer biofilm model.