New swine model of infected soft tissue blast injury.

Background: War injuries, especially blast injuries, have a high risk of infection. However, no animal models of infected war injuries have been built in large animals, which retards both the understanding and the treatment optimization of infected war injuries.

Methods: Soft tissue blast injuries were created by explosion of electric detonators in white domestic pigs. The ultra structure of the tissue around the wound was determined by transmission electron microscope. To develop infection of blast injury wounds, the pigs were housed in a standard animal house which was disinfected periodically, and the wounds were left untreated for 3 days. Wound specimens were collected daily to determine the bacterial load and bacterial components. To determine whether infection induces tissue necrosis in infected soft tissue blast injury wounds, uninfected blast injury wounds were created as controls of infected wounds by surgical debridement daily, and the wound area and wound depth of both wounds were measured.

Results: The wound area and the wound depth of the soft tissue blast injury created in this study fell in the range of human moderate soft tissue war injuries, and the ultra structure of the wounds was comparable with that of human blast injury wounds. The bacterial load of uninfected wounds was under 10 colony forming unit/g during the first 3 days of injury, while that of infected wounds was over 10 colony forming unit/g after 2 days of injury. The infected soft tissue blast injury wounds contained most of the bacteria frequently isolated in battlefield wounds. In addition, infection induced evident tissue necrosis in infected blast injury wounds.

Conclusion: The infected soft tissue blast injury wounds mimic those in human, and they can be used to address key points of treatment optimization.