When Is a Chronic Wound Infected?

Abstract

Humans are not germ free. In fact, the number of bacterial cells in our body exceeds the number of all our other cells. We live in relative harmonywith our bacterial flora. Therefore, the presence of bacteria alone is not an indication of infection. Intact skin is one of the major barriers to development of infection. A break in the skin; that is, a wound, opens the possibility of bacterial penetration and infection. The consequences of wound infection are formidable: delayed wound healing, extension of infection into muscle (necrosis) or bone (osteomyelitis) or bloodstream (sepsis), and increased mortality.1 Thus, determining when infection is present is critical to effective wound management. Onewould suppose that criteria fordiagnosingawound infection would be widely recognized, given the frequency of wound infections in the population. However, a reviewof the literature indicates that this is not the case. Considerable research over the years has simply elaborated how complicated this really is.2 What is clear is that acute wounds, such as surgical wounds or full-thickness burn injuries, differ considerably from chronic wounds, such as pressure ulcers, diabetic ulcers, venous stasis ulcer, or arterial ulcers.3 Moreover, it is increasingly clear that the symptoms/signs of infection differ among these chronic wounds themselves. How do we determine that a wound is infected? The diagnosis of awound infection requires two essential criteria: The presence of bacteria in the wound AND evidence that the bacteria is producing tissue damage (usually in the form of an inflammatory response). In the past 5 decades, a large amount of research has focused on the concept of “bacterial burden.” For example, a quantitative relationship between bacteria and urinary tract infection is widely accepted. A concentration of greater than 100,000 organisms per milliliter of urine is necessary to establish the diagnosis of pyelonephritis. If fewer than 100,000 organisms per milliliter are present, asymptomatic bacteriuria is present.4 The consequence of bacterial burden in acute wounds and in wounds healing by secondary intention is well established. Data