Introduction to Bacteria and Pressure Ulcers: The Role of Silver versus Traditional antimicrobials

T his supplement is based on the satellite symposium proceedings of the European Pressure Ulcer Advisory Panel Meeting, held in Budapest on September 19, 2002. Gary Sibbald, MD, (Canada) and Marco Romanelli, MD, PhD, (Italy) chaired the meeting. Diagnosing infection in chronic wounds often is a difficult challenge for wound care practitioners. Lindholm reminds us that high morbidity and mortality are associated with infections in pressure ulcers, but if antimicrobials are overused, multiresistant bacteria may emerge. Many clinicians recognize the classical signs and symptoms of infection, but other less dramatic signs and symptoms are also important. Increased damage from bacteria prevents healing before overt infection is diagnosed. All chronic wounds are contaminated with bacteria on the surface. When the bacteria proliferate and attach to tissue, colonization is established. Chronic wounds can still progress towards healing with established colonization. If bacterial byproducts such as metalloproteases overwhelm host resistance, critical colonization or a state of increased bacterial burden exists and a chronic wound may stop healing. At this point, increased exudate may be evident before it is frankly purulent, and the granulation tissue on the surface becomes bright red, friable, and often exuberant above the surface, retarding reepithelialization. Dow reminds, "Wounds should be cultured only when infection is suspected so patients rather than culture results are treated." Evidence is increasing that a properly obtained bacterial swab will approximate the results of a quantitative tissue biopsy. Clinicians and microbiological colleagues must coordinate their efforts to obtain useful information from bacteriological studies. In the paper by Sibbald, the clinician is challenged to assess the role of bacteria in a chronic wound. If no clinical or subclinical signs and symptoms of infection are present, no specific antimicrobial therapy is required. If surface changes are noted, an initial trial of topical antimicrobials may be indicated. The presence of deep symptoms or signs of infection requires systemic treatment. In the past several years, interest has been a renewed in topical silver formulations for the local application to chronic wounds. Burrell discusses the history of the use of silver as an antimicrobial agent, noting several advantages and few disadvantages. Newer nanocrystalline silver particles are less than 20 nm - an advantage for the antibacterial properties of silver. Combining silver with absorptive modern moist wound dressings provides clinicians with new topical antimicrobial and absorptive dressings. Falanga notes that a chronic wound is different from an acute wound. Chronic wound fluid may be detrimental to healing, containing several inhibitors to the proliferative and reepithelialization stages of a wound. Despite the development of growth factors and living skin equivalents, these new agents, promising in vitro have not often translated to the expected clinical trial results in vivo. Even when improved healing has resulted from the idealized conditions of the clinical trial, these results may not be advantageous in the less stringent conditions of clinical practice. The concept of wound bed preparation has been developed to optimize endogenous healing and facilitate the effectiveness of various therapeutic agents. In the "preparing the wound bed" model, several factors need to be corrected for healing to progress at the expected rate. Infection, necrotic debris, exudate, and persistence of inflammatory cells are all known potential healing inhibitors. Factors such as cytokines, growth factors, and metalloproteases and their inhibitors need to be studied further and therapeutic interventions designed to promote healing at an optimal rate. This supplement offers readers the opportunity to examine with a fresh perspective the problem of bacterial burden and infection in chronic wounds. Subclinical subtle signs and symptoms need to be considered along with selective microbiological testing to optimize topical or systemic approaches to controlling bacterial burden that may delay or prevent wound healing.