Preliminary Study on the Effect of Various Antimicrobial Formulations Containing Silver Oxynitrate on Reducing Pseudomonas Aeruginosa Using an in-vivo Porcine Burn Wound Model

Background: Silver has long been known for its antimicrobial effects and has been commonly applied topically to burn wounds for years. More recently, wound dressings compounded with silver ions, have been developed to prevent and treat wound infection in both burn and chronic wounds. 

Purpose: This preliminary study evaluates the effect of a proprietary silver oxynitrate creams on Pseudomonas aeruginosa (PA) biofilms using a well-established burn wound porcine model model. Swine were used due to their skins similarities to humans and response to wound treatments.  

Methods: Briefly, second degree burn wounds were created and inoculated with PA. Wounds were then covered for 24 hours with a polyurethane dressing to allow for biofilm formation. The polyurethane dressing was removed and wounds were randomly assigned to one of the following treatment groups: 1) silver oxynitrate cream 0%, 2) silver oxynitrate cream 4%, 3) silver oxynitrate cream 7%, 4) silver oxynitrate cream 10%, 5) silver oxynitrate powder, 6) silver sulfadiazine cream (SSD)~, or 7) untreated control.  All treatments groups were covered with a polyurethane dressing to prevent any cross contamination. On days 3 and 7 after wounding, wounds were cultured using an established scrub technique.

Results: Silver oxynitrate powder was the most effective treatment group at reducing PA counts. Silver oxynitrate 10% formulation had a high percentage of bacterial reduction. On day 7, compared to untreated control the silver oxynitrate 4, 7 and 10% treatments showed a 3.45, 4.05, and 4.30 log CFU/ml reduction, respectively.

Conclusion: These studies suggest that the silver oxynitrate formulations can reduce the bacterial bioburden in vivo against wounds that have PA biofilms. Additional animals are needed to substantiate these findings. Gram-negative bacteria such as PA pose a challenge for wound care practitioners and new effective therapies are needed.