Silver Dressings Augment the Ability of Negative Pressure Wound Therapy to Reduce Bacteria in a Contaminated Open Fracture Model

Abstract

Despite a lack of evidence supporting their use, silver dressings are often used with negative pressure wound therapy (NPWT). This study investigates the effectiveness of silver dressings to reduce bacteria in contaminated wounds when used with NPWT. Complex orthopedic wounds were created on the proximal left legs of anesthetized goats. The wounds were inoculated with either a strain of bioluminescent Pseudomonas aeruginosa or Staphylococcus aureus. These bacteria are genetically modified to emit photons, thereby allowing quantification of bacterial concentration with a photon-counting camera system. The wounds were debrided 6 hours after inoculation and were treated with silver impregnated gauze combined with NPWT. Repeat debridements were performed every 48 hours for 6 days. Imaging was performed pre- and postdebridement. These results were compared with standard NPWT controls that used dressings without silver. There were fewer bacteria in the silver groups than the standard NPWT groups at 6 days. In the groups that were inoculated with P. aeruginosa, wounds in the silver group contained 21% ± 5% of baseline bacterial load compared with 43% ± 14% in the standard NPWT group. The addition of the silver dressings has a more pronounced effect on Staphylococcus. Wounds in the silver group contained 25% ± 8% of baseline bacterial load compared with 115% ± 19% in the standard NPWT group. The use of silver dressings with NPWT is a fairly common practice with limited literature to support its use in contaminated wounds. This study demonstrates that the addition of a silver dressing to NPWT effectively reduces bacteria in contaminated wounds and is more beneficial on the gram-positive bacteria. These data support the use of silver dressings in contaminated wounds, particularly ones contaminated by S. aureus.