Development of a contaminated ischemic porcine wound model and the evaluation of bromelain based enzymatic debridement

Objectives: There are no well accepted animal models of chronic wounds, limiting advances in understanding and treatment of chronic ulcers. We developed a porcine wound model which combines multiple factors involved in chronic wounds to create a contaminated necrotic eschar and evaluated the debriding efficacy of a novel bromelain based enzymatic debriding agent (EscharEx). Methods: Contaminated ischemic wounds were created on the flanks of domestic pigs by ‘sandwiching’ the skin between 2 ‘O’ rings (1 placed on the surface of the skin and the other underneath the skin) for 24 h prior to dermatomal excision of the necrotic eschar and its contamination with Staphylococcus aureus and Candida albicans. After confirming the development of infected eschars, additional animals were used to compare the effects of daily application of topical EscharEx or its hydrating vehicle on eschar debridement as a control. Results: In all cases, application of the ‘O’ rings resulted in full thickness necrotic ecshars with invasive infections, which did not reepithelialize and sloughed off spontaneously within 14–21 days. All wounds reepithelialized within 28–42 days forming contracted scars. All EscharEx treated eschars were completely debrided within 7–9 days, while no debridement was evident in eschars treated with the control gel. Conclusions: Our model simulates the initial phase of chronic wounds characterized by a contaminated necrotic eschar allowing evaluation of wound debriding agents, and that a bromelain-based debriding agent completely debrides the contaminated necrotic eschars within one week in this model.