Pig Infected Thermal Injury Healing

Duration of study - 1 to 4 days
Lead time - 30 days
Standard results - Burn Measurements, Clinical/Visual Evaluations, Microbiology, Photography, Histology

Model Utility:

This thermal injury infection model is used to screen thermal injury infection clearing products and medical devices for effectiveness and safety.

How the Model Works:

In this model, 2nd or 3rd degree burns are made on the dorsal thorax of the animal. Generally, protocols utilize twenty, 2.0 cm diameter wounds per animal, however the size and number of wounds created can vary based on the needs of the experiment. The wounds are then, typically, infected with Staphylococcus epidermidis and/or Pseudomonas aeruginosa. Other microbes can be used such as Candida albicans, Escherichia coli, and Klebsiella pneumoniae can be used as well.

Treatment can begin at any time. Typically, antibiofilm products will begin treatment 48 hours after infection. These treatments can be in the form of a liquid, gel, powder, or solid (typically cut to wound size). The wounds will be bandaged with an appropriate bandage for the type of material used. Treatments may be applied as often as once per day.

Wounds will be periodically sampled for bioburden with both non-selective and selective media.

At the end of the protocol, the animal is euthanized and the burned area can be collected for histological or other analysis.

Example Data:

In the example data set below wounds were infected with S. aureus and P. aeruginosa after burn creation. 24 hours later the infections were treated with a test material and then sampled at various time points to determine the bioburden of the infected burn. Statistical difference was determined by comparing all data to the non-treated, t=0 time point sample.

**Figure 1. A comparison of total bioburden of wounds treated 24 hours post-infection (t=0) of acute thermal injuries. Biopsies were taken at three timepoints to assess the bioburden of the wounds.**

Figure 2. A comparison of Staphylococcus bioburden of wounds treated 24 hours post-infection (t=0) of acute thermal injuries. Biopsies were taken at three timepoints to assess the bioburden of the wounds. — Figure 2. A comparison of *Staphylococcus* bioburden of wounds treated 24 hours post-infection (t=0) of acute thermal injuries. Biopsies were taken at three timepoints to assess the bioburden of the wounds.

Figure 3. A comparison of Pseudomonas bioburden of wounds treated 24 hours post-infection (t=0) of acute thermal injuries. Biopsies were taken at three timepoints to assess the bioburden of the wounds. — Figure 3. A comparison of *Pseudomonas* bioburden of wounds treated 24 hours post-infection (t=0) of acute thermal injuries. Biopsies were taken at three timepoints to assess the bioburden of the wounds.

Advantages:

This model is considered to very closely approximate human thermal injury healing. BRIDGE PTS has considerable experience and familiarity with this model. Due to the spacing of the wounds on the animal, multiple test materials can be tested on a single animal. This could allow for higher throughput screening.

Disadvantages:

If multiple test materials are placed on a single animal, it is difficult or impossible to assess systemic effects that the materials may have.

Although 2nd degree burns are included in this model, the severity of burn can be difficult to control.

Reference:

Telgenhoff D, Lam K, Ramsay S, Vasquez, V, Villareal K, Slusarewicz P, Attar P, Shroot B. Influence of papain urea copper chlorophylin on wound matrix remodeling. Wound Repair Regen. 2007 Sep-Oct;15(5):727-35.