Treatment of Pseudomonas aeruginosa biofilm-infected wounds with clinical wound care strategies: a quantitative study using an in vivo rabbit ear model.

BACKGROUND: Bacterial biofilm is recognized as a major detriment to wound healing. The efficacy of traditional wound care against biofilm has never been studied. The authors evaluated the effect of clinical strategies against biofilm-infected wounds in a quantitative, in vivo model.
METHODS: Using a rabbit ear biofilm model, wounds were inoculated with Pseudomonas aeruginosa or left as uninfected controls. Inoculated wounds acted as untreated controls or underwent treatment: every-other-day sharp débridement (I), lavage (II), Silvadene (III), or lavage and Silvadene (IV), or initial débridement with daily lavage and Silvadene (V). Wounds were harvested on days 12 and 18. Histological wound healing parameters and viable bacterial counts were measured. Biofilm structure was studied with scanning electron microscopy.
RESULTS: Uninfected controls healed better than P. aeruginosa biofilm-infected wounds across all parameters (p = 0.01). Groups IV and V demonstrated improved healing (p = 0.05) and decreased bacterial count (p = 0.05) compared with untreated P. aeruginosa biofilm, whereas groups I through III showed no differences in either. Scanning electron microscopy following a group V treatment showed temporary disruption of biofilm structure, which reformed in 24 hours.
CONCLUSIONS: Pseudomonal biofilm markedly impairs wound healing, shown quantitatively using our in vivo model. Despite common practice, wound care strategies cannot restore biofilm wounds to a healing phenotype when used alone or infrequently. The durability of biofilm extends nonhealing wound chronicity, thus requiring aggressive, multimodal therapy aimed at reducing bacterial burden. The authors' novel, rigorous study validates critical principles applicable to all clinical wound care.