Extremity injury and complications such as wound infection remain a significant problem for the military. This study investigates the anti-microbial efficacy of four dressings used in militarily relevant complex extremity injury. Under general anaesthesia, the flexor carpi ulnaris of 24 New Zealand White rabbits was exposed to a high-energy impact and then inoculated with 106 colony forming units of Staphylococcus aureus. Dressings: gauze soaked in saline, Chlorhexidine, Betadine or Acticoat¯, were randomised and applied 3 hours post injury, to replicate casualty evacuation. Once recovered, animals were checked at least twice daily and body temperature recorded. Analgesia was administered once a day. At 48hrs animals were culled, the muscle harvested and analyzed by a blinded investigator. Group sizes of 6 were required to detect a statistically significant effect of a mean one log reduction in bacterial counts at 48 hours. No dressing gave a significant reduction in bacterial counts at 48 hours. A paired t-test of contamination versus recovered dose gave p values of 0.903, 0.648, 0.396 and 0.336 for saline, Acticoat¯, chlorhexidine and iodine respectively. Contamination dose between groups compared using ANOVA showed no significant difference (p=0.566). Recovered bacterial loads between groups revealed no significant difference (p=0.280). This study indicates that over a 48 hour period, dressings with reported anti-bacterial properties offer no advantage over saline soaked gauze in reducing the bacterial burden in a contaminated soft tissue injury. Future work will extend the study temporally and introduce multiple contaminants.
