Diagnostic markers of infection, in chronic wounds.

A complication associated with wound healing is wound infection. The diagnosis of infection in chronic wounds can be a difficult clinical decision. Signs and symptoms used to diagnose infection can often be masked by factors relating to the host, chronic inflammation and the tissue damage, associated with chronic wounds. This Study aimed to determine whether there is a measurable biochemical host response that could serve as potential biomarkers of chronic wound infection, providing an alternative diagnostic tool to aid the Clinician. An in vitro model further investigated the expression of markers from neutrophils, in response to bacterial supernatant from Pseudomonas aeruginosa and Staphylococcus aureus commonly associated with chronic wounds and their infections. Chronic venous leg ulcer and diabetic foot ulcer wound fluids were collected, wound microflora assessed, and a variety of host factors, including serine proteases, matrix metalloproteinase, their inhibitors and cytokines/growth factors, IL-ip, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, 11-12 p40, IL-12p70 and IL-13, angiogenin, IFN-y, TGF-pi, VEGF, TNF-a, TNF-r2, ICAM-1 and IP-10, analysed. No significant differences (p>0.1) in the activities/levels of host factors were observed between non-infected and infected wounds, based on clinical diagnosis. Significant differences (p<0.05) in a variety of these host factors were observed in these ulcer types, upon defining infection by wound microbial bioburden, the number of genera or bacterial species. Of these factors, cytokines were found to distinguish on two of the three defining parameters. Specifically, a number of cytokines were found to be significantly elevated in venous leg ulcer wounds, IL-lp, TNF-a, TNFr2 and ICAM-1, with an additional set of cytokines, IL-2, IL-5, IL-12p40, IL-12p70, IFN-y and TGF-P,, significantly decreased within diabetic foot ulcer wounds. in vitro, neutrophils were treated with Pseudomonas aeruginosa or Staphylococcus aureus 'acellular' supernatants, at mid-log or stationary growth phases, for 4 and 24h. Significant increases (p<0.05) in the levels of proteases and cytokines were observed from neutrophils, treated with both mid-log and stationary phase supernatants, from both species. These increases were both neutrophil donor- and growth phase-dependent. A larger cytokine response was induced from neutrophils stimulated with stationary phase, compared with mid-log phase supernatants. Combined with the increased expression of virulence factors, including bacterial enzymes, this Study suggests that bacterial growth is an important feature of chronic wound infection