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Development of a preclinical model to study biofilm in full thickness cutaneous swine burn wound

Research Scholar

Kareem Hosny Mohammed, Center for Minimally Invasive Surgery (Egypt)
Chandra Sen, Faculty Mentor

Biography

Kareem Hosny Mohammed was born in Cairo, Egypt. He received his MD in medicine and surgery from Cairo University Medical School in 2009, and also holds a master's degree in orthopedic surgery.  He began working in the National Research center in Egypt as an orthopedic research specialist in 2009, and joined Chandan Sen's Lab in the Department of Surgery at the Wexner Medical Center at The Ohio State University in July 2012 as a postdoctoral researcher. He is currently focused on studying the involvement of biofilm infection in cutaneous wound healing.

What is the issue or problem addressed in your research?

A clinically relevant cutaneous wound biofilm model must meet the following criteria: based on clinically relevant animal species, bacteria attached to cutaneous wound-site surface, grow as micro-colonies in self-produced extracellular matrix, resistant to host immune response and antimicrobial therapies, and complicate healing outcomes. At present there is no in vivo biofilm model that meets all of the above-said criteria.

What methodology did you use in your research?

Anatomically as well as physiologically, the pig skin is widely recognized to closely resemble human skin. Burn wounds (2”x2”) were established on the dorsum of pigs using a specialized microprocessor controlled electrically heated device developed in our laboratory. The wounds were inoculated with Pseudomonas aeruginosa (PA) strain PAO1 by topical application of a suspension of 5X107 bacteria on day 3 post-burn. Biopsy samples (d7/14/28 post-inoculation) were analyzed for the presence of P. aeruginosa, biofilm formation and healing outcomes. Macroscopic inspection of wounds on day 7 post-inoculation, revealed yellowish green discoloration with discharge that worsened over time. Infection was local with no evidence of systemic involvement as tested by body temperature and blood culture. The bacterial load in homogenized tissue biopsies was 106 CFU/g tissues at days 7 and 14. Immunohistochemical staining demonstrated PA aggregates in the wound bed which was further characterized using scanning electron microscopy. PA aggregates were noted to be attached to the surface of the burn wounds and embedded in an extracellular polymeric substance (EPS). The silver dressing Acticoat 7, used as standard of care in burn clinics, killed PAO1 in vitro. However, PA population in the wound bed was resistant to Acticoat 7 wound dressing applied day 7-14 post-inoculation. Inoculated wounds displayed compromised re-epithelization at day 28 post-inoculation or day 31 post-burn compared to non-infected wounds. Measurement of Trans-epidermal Water loss (TEWL) showed water loss in infected wounds compared to non-infected wounds reflecting compromised barrier function of the skin.

What are the purpose/rationale and implications of your research?

This model successfully meets the criteria for cutaneous wound biofilm development. (Supported by DoD). We've studied how we can increase the healing process on burn wounds and decrease complications from it as biofilm is one of the most  difficult infection to be treated with high resistant to all antibiotics.