Effective management of microbial contamination in cultured skin substitutes after grafting to athymic mice

Cultured skin substitutes have become therapeutic alternatives for treatment of acute and chronic skin wounds, but all models of these substitutes are avascular and susceptible to microbial destruction during vascularization. To develop a practical management protocol for increased survival of skin substitutes, experimental wounds were contaminated with Pseudomonas aeruginosa and treated with a formulation of noncytotoxic antimicrobial agents (polymyxin B, neomycin, ciprofloxacin, mupirocin, amphotericin B) in a nutrient medium (vehicle). Cultured skin substitutes consisting of human keratinocytes and fibroblasts attached to collagen‐glycosaminoglycan sponges were grafted to 2 × 2 cm full‐thickness wounds on athymic mice that were contaminated with the strain SBI‐N of P. aeruginosa at 1 × 104, 1 × 105, and 1 × 106 organisms/wound. Experimental wounds were irrigated with 1 ml/day topical antimicrobial solution for 10 days, and controls received vehicle only. Two, three, and four weeks after grafting, wounds were traced and swabbed for microbial culture and areas were measured with planimetry. At 4 weeks, biopsy samples were scored histochemically for immunoreactivity to HLA antigens. Data analysis by chi‐square, analysis of variance, and Tukey's test shows that treatment of contaminated wounds with noncytotoxic topical antimicrobials is associated with an increased area of healed wounds, positive detection of HLA antigens, and negative cultures for P. aeruginosa. These results show that microbial contamination of cultured skin substitutes on full‐thickness wounds may be managed effectively during graft vascularization. However, this formulation of antimicrobial agents is not currently approved for human use and is investigational only. Effective management of microbial contamination suggests that clinical efficacy of avascular tissue analogs may be increased by local application of noncytotoxic antimicrobial agents.