Assessment of the Antibiofilm Performance of Silver-Containing Wound Dressings: A Dual-Species Biofilm Model.

Background It is commonly accepted that microorganisms found within hard-to-heal wounds are present in biofilm form. Biofilms are often polymicrobial in nature, which increases their virulence and tolerance to antimicrobial agents. The aim of this study was to compare the antibiofilm activity of silver-containing antimicrobial wound dressings in a dual-species simulated wound biofilm model. Materials and methods Four silver-containing wound dressings were evaluated : Aquacel Ag+ Extra™ dressing, KerraContact Ag dressing, Durafiber* Ag dressing, and UrgoClean Ag dressing. Each dressing was applied to a simulated wound assembly containing biofilm-gauze inoculated with and methicillin-resistant (MRSA). Each biofilm-inoculated gauze was incubated at 35±3C for 6, 24, 48 and 72 hours. Enumeration of surviving biofilm bacteria at each time point was performed in triplicate for each test dressing and its equivalent control. Results Aquacel Ag+ Extra™ dressing was observed to reduce the biofilm population within 24 hours with a >4 log kill observed for and >6 log for MRSA from an initial biofilm challenge of 4.16×10 CFU/mL. This kill rate was sustained for the duration of the challenge period, with Aquacel Ag+ Extra™ dressing reducing the biofilm population to non-detectable levels (<30 Colony Forming Units (CFU) per test) by 72 hours for and by 48 hours for MRSA. KerraContact Ag dressing demonstrated an initial reduction at 6 hours of ~2 log in both and MRSA. Durafiber* Ag dressing exhibited a slight, gradual reduction in biofilm population over the course of the test period, reducing each challenge organism by ~2.5 log by 72 hours. UrgoClean Ag was shown to have little to no impact on the dual-species biofilm with levels remaining similar or greater than that recovered prior to dressing application. The no-dressing biofilm-colonised gauze control demonstrated that the biofilm bacteria remained viable throughout the test period and species population proportionality was maintained. Conclusion Using a dual-species simulated wound biofilm model comprising the pathogens and MRSA, Aquacel Ag+ Extra™ dressing demonstrated significantly greater antibiofilm activity than the other silver-containing dressings. The enhanced antibiofilm activity of Aquacel Ag+ Extra™ dressing in this study may be attributed to the additional antibiofilm agents, ethylenediaminetetraacetic acid and benzethonium chloride, contained within the dressing.