The development of an accredited Ex Vivo Burn Wound Model for pre-clinical efficacy testing of antimicrobial agents.

Whilst survival rates have improved over the past few decades due to advances in modern medicine (Rafla and Tredget, 2011), infection is still the leading cause of morbidity and mortality for burn patients (Weber and Mcmanus, 2004). One of the organisms responsible for these infections is Pseudomonas aeruginosa (Coetzee et al., 2013); an opportunistic pathogen which is capable of infecting virtually all tissues and is often resistant to current therapeutic modalities. Another organism of particular concern for burn patients is Staphylococcus aureus due to its ability to excrete several protein exotoxins (Orenstein et al. 1997) which may lead to further complications.

On the burn surface, P. aeruginosa and S. aureus exist within a biofilm, which enhance their tolerance to antimicrobial agents significantly. To mimic an infected patient burn, an ex vivo burn wound model using porcine skin was developed, to enable the pre-clinical efficacy testing of antimicrobial agents such as antibiotics, topical creams and wound dressings. This method was selected for validation and accreditation as similar tests are not commercially available to ISO 17025 standards.

Method: P. aeruginosa and S. aureus biofilms were developed on individual burn wounds on the surface of porcine skin explants. The tissue was burnt using a burn wound array device and inoculated with P. aeruginosa or S. aureus and incubated at 37 ± 2 °C to form mature biofilms over a period of 72 ± 2 hours. The established biofilms were washed to remove planktonic organisms and treated for 24 hours. After the treatment period, samples were neutralised and remaining attached microorganisms were recovered and quantified.

Results/Discussion: An average of 8.05 ± 0.12 Log10CFUmL-1 and 6.14 ± 0.12 Log10CFUmL-1 was recovered from the negative controls for P. aeruginosa or S. aureus, respectively. An average of 4.95 ± 0.31 Log10CFUmL-1 and 5.36 ± 0.81 Log10CFUmL-1 was recovered from an active antibiotic for P. aeruginosa or S. aureus, respectively. No viable microorganisms were recovered from the positive control samples for either organism. Testing using a validated and real-world, challenging model can de-risk clinical trials and be used to predict performance clinically.