How Biofilm Affects Healing In Diabetic Foot Wounds

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Rhonda Cornell, DPM

   Chronic lower extremity wounds are a significant complication of diabetes. Approximately 15 to 20 percent of people with diabetes will develop a diabetic foot ulcer in their lifetime.1 As the number of people diagnosed with diabetes continues to rise, so will the number of diabetic foot ulcers. It is estimated that the number of people diagnosed with diabetes will double to an estimated 48 million people in the United States by the year 2050.1

   Chronic diabetic foot ulcers that do not heal in a timely manner are more likely to be complicated by infection, hospitalization and amputation. Delayed wound healing is often complicated by the development of infection. Infection accounts for nearly 20 percent of all diabetes-related hospital admissions and also serves as a major risk factor for the development of non-traumatic amputation.1

   It is vital that we attempt to develop treatment modalities and paradigms that promote effective wound healing, reduce the spread of infection and limit progression from wound development into lower extremity amputation.

   Sheehan and colleagues studied the probability of complete wound closure in difficult to heal diabetic foot ulcerations.2 They found that monitoring the area of a wound over a four-week period is a strong predictor of healing rates at 12 weeks. The authors found this to be independent of the treatment modality utilized.

   This landmark study helped set a standard to evaluate the rate of wound healing. The researchers concluded that ulcers that fail to decrease in size by approximately 50 percent over the first four weeks of treatment are unlikely to achieve wound healing in a reasonable amount of time.2

   Panuncialman and Falanga have recently reviewed the science of wound bed preparation.3,4 They underscore the importance of debridement as a critical step in the transition of a chronic wound into an acute wound to expedite the healing process.

   The role of bacteria in the healing or lack thereof in chronic wounds can be a controversial topic. Although one cannot achieve complete sterility of the chronic wound bed, control of bacterial burden, in terms of bacterial density and pathogenicity, is a goal in wound bed preparation along with the reduction of biofilm formation in these chronic wounds.

A Closer Look At The Science Of Biofilm

   So what exactly is a biofilm and how does it have an impact on diabetic foot wounds? A biofilm is a polymicrobial sessile community of microorganisms that develop on the surface of chronic wounds. As the bacteria attach to each other and the wound surface, they produce an extra-polymeric substance that contributes to the structure of the biofilm. The depth of the biofilm can vary from a single cell layer to a thick community of cells surrounded by the extrapolymeric matrix. The biofilm forms a barrier around itself, making it very difficult for antimicrobial agents to penetrate it.

   The science of biofilm and biofilm engineering have been active fields of study since the first description of sessile communities in 1978.5 Bacterial biofilms have gained increasing attention in recent years as their role in chronic wounds is becoming more apparent. Microbial biofilms have been implicated in up to 80 percent of human infections such as nephrolithiasis, endocarditis, cystic fibrosis, oral infections, chronic otitis media and infections associated with indwelling devices to name a few.6-8

   Not everything is understood about the role of biofilms or the most effective way to get rid of them. What is understood is that biofilms play a significant role in chronic wounds.

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