Comparison of the efficacy of silver-based antimicrobial burn dressings in a porcine model of burn wounds.

Purpose: A variety of silver-based antimicrobial dressings are available on the market and are commonly used to prevent infection. Such prophylaxis is particularly important in treating burns, yet there is a paucity of evidence confirming the efficacy of commercially available dressingsin vivo. We describe here an in vivo porcine model of burns, which we use to test the antimicrobial efficacy of three common wound dressings and a control.

Procedures: Domestic Yorkshire-cross pigs were medicated for pain management before inflicting burns with a heated brass rod. The wounds were artificially challenged with a mixture of two pathogens commonly associated with burn wound infection:Staphylococcus aureus and Pseudomonas aeruginosa. The following dressing materials were sutured in place: gauze, nanocrystalline silver, silver-plated nylon, and polyethylene/polyester coated with high-oxidation silver salts. After 1 and 3 days, the wounds were assessed for erythema, swelling, and re-epithelialization, tissue was biopsied to determine the recovery of the challenge microorganisms, and histology was performed. We also examined the number of microorganisms present on the dressings themselves.

Results: Histology indicated that 30 s was sufficient to produce burns extending into the deep dermal layer. After 3 days, nanocrystalline silver and silver-plated nylon led to slightly reduced swelling relative to simple gauze, although none of the dressings significantly affected erythema or wound re-epithelialization. All the dressings led to decreased recovery of the challenge organisms from the burn tissue, relative to simple gauze. However, the magnitude of the reduction was greatest for nanocrystalline silver (log reduction = 4-5); additionally, only nanocrystalline silver gave a statistically significant decrease (P = 0.02). Notably, the antimicrobial effect for all dressings was reduced by Day 3 relative to Day 1. Similar trends were observed for microbial retention on the dressings themselves.

Conclusion: Nanocrystalline silver-based wound dressings generally outperformed silver-plated nylon and high-oxidation silver salts in thisin vivo model of burn wounds. Relative to prophylactic use, it may be advisable to change the dressings more frequently when treating an infected wound.