Silver dressings improve diabetic wound healing without reducing bioburden

Introduction. Silver dressings are widely used in the treatment of chronic wounds to reduce bacterial bioburden. However, little is known about the mechanism of silver ions on the healing process. In this study, a mouse model of wound healing was used to examine the effect of silver dressings in normal and diabetic wounds.

Two 5-mm full-thickness wounds were created on the dorsal skin of diabetic BKS.Cg- m+/+Leprdb/J mice (experimental group) and wild type C57BL/6 mice (control group), and treated with either a silver or gauze dressing. Measurement of wound areas by digital planimetry demonstrated faster healing in the silver-treated wounds of both diabetic and control mice.

Quantitative bacterial cultures showed a reduction of bioburden in silver-treated wounds in wild type mice. Unexpectedly, there was no decrease in bioburden in the silver-treated diabetic wounds compared to the control diabetic wounds, despite improved healing in the silver-treated diabetic wounds. Staphylococcus xylosus, a known biofilm producer, was the only bacteria identified in all the wounds. In vitro studies showed S. xylosus produced biofilms faster in higher glucose environments; this may explain the increased bioburden in the wounds in diabetic mice compared to wild type mice.

The results demonstrate improved healing and reduced bioburden in normal wounds with silver dressings. In contrast, silver dressings improved healing in diabetic wounds despite no effect on bioburden, suggesting silver may have beneficial effects in addition to its antimicrobial properties.