Background and aims: Large wounds such as major burns are susceptible to microbial infection and resulting biofilm. Consequences of infected wounds include mortality and also significant morbidity from complications such as delayed wound healing, contracture and skin graft loss. Antimicrobial dressings such as those containing silver are widely used. These release ionised silver ions which have a wide mechanism of action. Such dressings are, however, expensive and, because of the concern for oxidisation of the silver within once opened, these products are currently for single use only, which is less cost effective. This study aimed to investigate the effectiveness of commonly used antimicrobial silver dressings if opened and used in piecemeal fashion over 3 months.
Method: Commercially available silver based dressings were tested in vitro against staphylococcus aureus, pseudomonas aeruginosa and escherichia coli. The standard Kirby-Brauer diffusion disc lab assay was used, which measures the Zone of Inhibition surrounding antimicrobial agent on lawned agar plates. Fresh dressings were tested for then divided and stored at three temperature points in a sealed container. Dressings were sampled and re tested at 1, 3, 6 and 12 weeks to detect any reduction in effectiveness.
Results: Aquacel Ag, Acticoat and Acticoat 7 were all effective against the pathogens with no loss of antimicrobial activity at any storage temperature over the 3 month period. Mepilex Ag yielded no zone of inhibition against any pathogen, however this is consistent with previous studies.
Conclusion: Except for Mepilex Ag, there seems to be no reduction in in vitro effectiveness of antimicrobial silver dressings for 3 months once packaging is opened, regardless of storage temperature. This suggests that any oxidation of silver is not clinically significant and that economically minded use of silver dressings in piecemeal, opened packaging fashion may be safe.