Anti-biofilm effects and healing promotion by silver oxynitrate-based dressings

Abstract

Microbial growth within a wound often manifests as biofilms, which can prevent healing and is difficult to eradicate. Novel silver dressings claim to combat wound infection, but anti-biofilm efficacy and effects on healing independent of infection are often unclear. Using in vitro and in vivo S. aureus and P. aeruginosa biofilm models, we report the efficacy of a dressing which produces Ag1+ ions; an Ag1+ dressing containing ethylenediaminetetraacetic acid and benzethonium chloride (Ag1+/EDTA/BC), and a dressing containing silver oxynitrate (Ag Oxysalts) which produces Ag1+, Ag2+ and Ag3+ ions, against wound biofilms, and their effects on healing. Ag1+ dressings had minimal effect on in vitro and murine (C57BL/6j) wound biofilms. In contrast, Ag Oxysalts and Ag1+/EDTA/BC dressings significantly reduced viable bacteria within in vitro biofilms and demonstrated a visible reduction in bacteria and EPS components within murine wound biofilms. The dressings had different effects on the healing of biofilm-infected and uninfected wounds, with Ag Oxysalts dressings having a greater beneficial effect on re-epithelialisation, wound size and inflammation than the control treatment and the other silver dressings. The different physicochemical properties of the silver dressings result in varied effects on wound biofilms and healing which should be considered when selecting dressings to treat biofilm-infected wounds.

Assessment of Silver-Containing Gelling Fiber Dressings Against Antibiotic-Resistant Pathogens Using an in vitro Biofilm Model

“… 4 Our findings are inconsistent with a previous study which reported comparable antibiofilm activity between CSO and CISEB against non-antibiotic-resistant strains of P. aeruginosa and S. aureus using in vitro and ex vivo models. 5 Similarly, an in vitro evaluation of PSS demonstrated a reduction in MRSA biofilm of 4.6 log 10 after 24 hours and up to 4 log 10 after 7 days, which is far greater than the maximum reduction of 0.5 log 10 observed in the current study. 6 Dressing performance is more readily differentiated in biofilm models that are realistic and stringent, and the inconsistent findings with the previous studies are likely attributed to the different testing methods used.…”