Testing wound dressings using an in vitro wound model

Objective: To determine whether or not there are any significant differences in the effects of wound dressings on bacterial bioburden. Method: A selection of non-occlusive, non-adhesive dressings was tested for their effect on bacterial bioburden. The dressings selected included two dressings with antimicrobial properties (one containing silver and one containing PHMB), a cotton-based dressing enclosed in a perforated sleeve of poly(ethylene terephthalate), a carboxymethyl cellulose-based dressing, a fibre-free alginate dressing, and a 12-ply 100% cotton gauze. Using the colony-drip flow reactor (DFR) model, a meticillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa biofilm was grown underneath a dressing sample. Biofilm growth was examined via plate counts, fluorescent microscopy and scanning electron microscopy. Results: The dressings containing antimicrobial agents had the greatest effect on bacterial load. In the MRSA experiments, both antimicrobial dressings produced lower bacteria counts than the other dressings (p <= 0.001), while in the P. aeruginosa experiments, only the silver-containing sample had fewer bacteria (p <= 0.0001). However, neither antimicrobial dressing was able to completely eradicate the bacteria when testing with either microorganism. Conclusion: The results presented herein illustrate that bacteria can grow unchallenged within the dressing environment and that an antimicrobial dressing can limit this bacterial growth.