Dr. Brian Kunimoto (biography and disclosures)
What I did before
I direct an outpatient clinic that treats patients with chronic leg ulcers. The majority of these wounds are venous in origin with some diabetic foot ulcers and pressure sores. The vast majority of patients do well with so-called ‘Best Clinical Practice’; however, it is not unusual for some ulcers to be very stubborn. In many cases, this failure to heal is characterized by the lack of development of healthy granulation tissue. The majority of these ulcers lacking granulation tissue have, instead, yellow/green, slimy, odourous material on the base. Despite this, we would try to facilitate proper moisture balance by applying modern wound dressings. Unfortunately, when this slimy material is prevalent, healing is impaired.
What changed my practice
I have always wondered just what that yellow slimy material was in the wound base. Yellow in the wound can signify different things. Fibrin presents as a gel usually on the base of venous leg ulcers. Yellow slough represents hydrated necrotic tissue and has the consistency of leather. We observed that when this yellow/green coloured slimy material persists, the wound does not heal and granulation tissue either does not develop or disappears.
One day, while flying to Toronto, I read an article in the Scientific American magazine I purchased at the airport. It was a review article by William Costerton, the man who coined the term, ‘Biofilm’, in 1979. He described the structure, formation, and the polymicrobial nature of biofilms in nature. In nature, biofilms often have the consistency of slime and it made sense that they could develop in a chronic wound. Furthermore, it seemed perfectly reasonable that this complex matrix of multiple species of bacteria could successfully compete with host immune defense and prevent healing. It also seemed logical that this material should be removed regularly in order to enhance healing. After all, if plaque, a prototypical biofilm of teeth, needs to be removed daily in order to avoid tooth decay and periodontal disease, wound biofilms would need to be regularly debrided to promote healing.
What I do now
The concept of biofilm in chronic wounds is in its infancy at the present time. It is just now being proposed that they play an important role in the pathogenesis of non-healing. It is also known that they are very resistant to treatment by systemic or topical antibiotics. Antimicrobial dressings, often consisting of sliver derivatives, are also unable to significantly impede biofilms. At the Wound Healing Clinic, we believe that almost every one of our poorly-healing leg ulcers possesses a healthy thriving biofilm. We now, routinely, debride biofilms using a disposable curette after providing topical local anesthesia (2% xylocaine gel applied under gauze for 10 minutes). I use the dull side of the curette to avoid cutting. Since the synonym for biofilm is ‘slime’, cutting and aggressive scraping are not required. Biofilms are extremely tenacious and so debridement must be relentless and repeated weekly at least. Although the biofilm usually returns quite quickly, eventually it ‘gives up’ and does not return. This is followed by rapid healing. Since we, at the Wound Healing Clinic, have instituted this form of debridement as part of wound bed preparation, better clinical outcomes have been realized.
References: (Note: Article requests might require a login ID with the BC College of Physicians website or UBC)
- Costerton, W. Battling Biofilms. Scientific American July 2001. (View article with CPSBC or UBC)
- James GA, et al. Biofilms in chronic wounds. Wound Rep Reg 16,37-44,2008. (View article with CPSBC or UBC)
- Bjarnsholt T, et al. Why chronic wounds will not heal: a novel hypothesis. Wound Rep Reg 16,2-10,2008. (View article with CPSBC or UBC)
- Cardinal M, et al. Serial surgical debridement: A retrospective study on clinical outcomes in chronic lower extremity wounds. Wound Rep Reg 17,306-311,2009. (View article with CPSBC or UBC)