Microbiology of Wounds

Abstract

Chronic wounds are a serious public health issue. The incidence and prevalence of the different types of chronic wounds are largely unknown worldwide, but 13 years ago George1 estimated the worldwide burden of wounds to be: Surgical wounds, 40 to 50 millio• n • Leg ulcers, 8 to 10 million • Pressure ulcers, 7 to 8 million • Burns, 7 to 10 million In the United States alone, the estimated number of chronic wounds includes 1 to 2 million diabetic foot ulcers, 1 to 2 million venous leg ulcers, 3 to 5 million pressure ulcers, and 1% surgical site infections. One of the underlying pathologies known to increase the prevalence of chronic wounds is diabetes mellitus. Diabetes mellitus in the Western world is growing continuously at a double-digit rate. However, this figure is not truly representative of the extent of the problem. Figures from the Centers for Disease Control and Prevention (CDC) state that there are approximately 24 million patients with diabetes mellitus (24 million diabetics). Cutaneous wounds in the United States alone cost society over $25 billion annually. The management of infected wounds remains an area of confusion and hence great debate. No definition or authoritative clinical guidelines of what constitutes an infected wound exists. Terminology in wound care such as colonization, critical colonization, biofilm, and other descriptions of bacterial behavior on the surface of the wound are not clearly defined. Even the term infection requires redefining in light of recently generated insight into the prevalence and behavior of the biofilm phenotype. In addition, many of the concepts concerning wound infections are not backed up with meaningful scientific support. Consequently many terms used in wound care have led to confusion and unnecessary or inappropriate management of chronic wounds. It is well established that wound healing is dynamic, infinitely complex, nonlinear, and prodigiously individualized to the context of the patient. Understanding the intricacies of chronic wounds becomes even more complex when one considers the myriad of host variables that contribute to the disease state. The plausible common barrier that may impair many of these wounds from healing is chronic infection as a result of biofilm infection. Chronic biofilm-based infections constitute 80% of all human infection. Accordingly, acute infections remain as the minority census of all infectious disease. The definition of acute infection is based on clinical characteristics of rapid onset and aggressive bacterial behavior, which responds rapidly and completely to antibiotics or the host immune response. Chronic infections are persistent and recalcitrant. It is interesting to note that acute and chronic infections have not been clearly differentiated on a molecular level and may be explained by bacteria pursuing widely divergent survival strategies only now becoming elucidated through research.