The medical literature describes numerous in vitro and in vivo wound-healing models. The selection of an animal model depends on a number of factors including availability, cost, ease of handling, investigator familiarity, and anatomical/functional similarity to humans. Small mammals are frequently used for wound healing studies, however, these mammals differ from humans in a number of anatomical and physiological ways. Anatomically and physiologically, pig skin is more similar to human skin. The many similarities between man and pig would lead one to believe that the pig should make an excellent animal model for human wound healing. The purpose of this paper is to review the existing literature for evidence of this supposition and determine how well the various models correlate to human wound healing. Studies of wound dressings, topical antimicrobials, and growth factors are examined. Over 180 articles were utilized for this comparative review. Our conclusion is that the porcine model is an excellent tool for the evaluation of therapeutic agents destined for use in human wounds.

A biofilm is a collection of microbial cells that are attached to a surface and embedded in a self-produced extrapolymeric substance. The understanding of the biofilm phenotype is important in the understanding of bacteria in vitro but it has been difficult to translate biofilm science to the clinical setting. More recently, preliminary criteria for defining biofilm associated diseases have been proposed and the purpose of this study was to create a biofilm-associated wound model based on these criteria. Using a porcine model, partial thickness wounds were inoculated with a wound isolate Staphylococcus aureus strain. Wounds were then treated with either one of two topical antimicrobial agents (mupriocin cream or triple antibiotic ointment) within 15 minutes to represent planktonic bacteria or 48 hours after initial inoculation to represent biofilm-associated wound infection. Using light microscopy, scanning electron microscopy and epifluorescence microscopy, we were able to observe biofilm-like structures in wounds after 48 hours of inoculation and occlusion. The in vivo antimicrobial assay was used to demonstrate that both mupirocin cream and the triple antibiotic ointment were effective in reducing planktonic S. aureus but had reduced efficacy against biofilm-embedded S. aureus. Our results demonstrated that S. aureus form firmly attached microcolonies and colonies of bacteria encased in an extracellular matrix on the surface of the wounds. These biofilm-like communities also demonstrated increased antimicrobial resistance when compared with their planktonic phenotype in vivo. The structural and physiological results support the hypothesis that bacterial biofilms play a role in wound colonization and infection.

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We studied the effects of direct electric current supplied by an energized silver-coated electrode on dermal and epidermal wound healing. Keratome-induced wounds (0.3 mm deep) on the skin of young domestic pigs were treated with either an energized (50-300 microA) electrode (DC), an unenergized electrode (placebo), or left untreated. Wounds were excised on days 1-7 after wounding and the epidermis was separated from the dermis. The epidermal sheet was evaluated for reepithelialization and the dermis was assayed for collagen biosynthetic capacity. Dermal collagen production among treatments did not differ markedly on days 1-4 after wounding. However, a highly significant increase (p less than 0.001) in the collagen synthetic capacity was observed on days 5, 6, and 7 in wound treated with DC. There was no significant difference in collagen synthesis among treatments when collagen production was corrected for DNA content. The rate of wound epithelialization was also significantly accelerated (p less than 0.05) in DC-treated wounds. These results suggest that the proliferative and/or migratory capacity of epithelial and connective tissue cells involved in repair and regeneration can be affected by an electrical field.

Epidermal healing of superficial, excised wounds in domestic white pigs was evaluated visually and histologically after separation of the epidermis and dermis. The visual determination of epidermal healing correlated well with the histologic studies of surface re-epithelialization. Wounds healed 40% faster when occluded with polyethelene film. Topical triamcinolone acetonide treatment delayed healing (62% slower than control).

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The rapidity of biofilm growth suggests that bacteria in wounds possess the capacity of producing this shield against antibiotics and immune effector cells early in the infection process. Therefore, efforts to prevent or slow the proliferation of bacteria and biofilms should occur soon after a wound is created. Additionally, this staining technique can be used to demonstrate the ability of agents to slow biofilm growth or to interrupt formed biofilm and may be useful in future studies of chronically infected wounds.

The effect of four commonly used topical antimicrobial agents on the rate of reepithelialization of clean wounds was evaluated in white domestic pigs. Neosporin Ointment was found to significantly increase the rate of reepithelialization by 25%, while Furacin significantly retarded the healing rate by 24%. Pharmadine, a preparation containing povidone-iodine, did not affect the rate of healing. Both Silvadene and its vehicle significantly increased the rate of reepithelialization by 28% and 21%, respectively. The effects of these agents cannot be explained on the basis of their antimicrobial activity.