The early detection of wound infection in situ can dramatically improve patient care pathways and clinical outcomes. There is increasing evidence that within an infected wound the main bacterial mode of living is a biofilm: a confluent community of adherent bacteria encased in an extracellular polymeric matrix. Here we have reported the development of a prototype wound dressing, which switches on a fluorescent color when in contact with pathogenic wound biofilms. The dressing is made of a hydrated agarose film in which the fluorescent dye containing vesicles were mixed with agarose and dispersed within the hydrogel matrix. The static and dynamic models of wound biofilms, from clinical strains of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis, were established on nanoporous polycarbonate membrane for 24, 48, and 72 h, and the dressing response to the biofilms on the prototype dressing evaluated. The dressing indicated a clear fluorescent/color response within 4 h, only observed when in contact with biofilms produced by a pathogenic strain. The sensitivity of the dressing to biofilms was dependent on the species and strain types of the bacterial pathogens involved, but a relatively higher response was observed in strains considered good biofilm formers. There was a clear difference in the levels of dressing response, when dressings were tested on bacteria grown in biofilm or in planktonic cultures, suggesting that the level of expression of virulence factors is different depending of the growth mode. Colorimetric detection on wound biofilms of prevalent pathogens (S. aureus, P. aeruginosa, and E. faecalis) is also demonstrated using an ex vivo porcine skin model of burn wound infection.

The aim of this study was to measure the pH on the wound surface of 30 burn patients and test the hypothesis that wound surface pH is correlated to healing time and burn depth. Inclusion criteria were any adult outpatient with burn injury. Patient age was 17 to 75 years (mean, 44), burn depth ranged from superficial to full thickness with a TBSA of 0.4 to 4%. Cause of burn included scalds, flame burn, and contact burns. On admission, and at each dressing change, the pH on the wound surface was measured. The pH in both healing and nonhealing wounds was found to decrease with each dressing change. At the second dressing change, wounds that went on to heal were found to have a significantly lower pH of 7.32 in comparison with pH 7.73 in wounds that failed to heal and therefore required subsequent grafting (P = .004). Wound pH was also correlated to depth at the second dressing change (superficial = pH 6.05, full thickness = pH 8.0). The correlation between pH and wound outcome could be used as an additional diagnostic tool to predict poor healing in wounds. Early identification of a nonhealing wound may allow a more aggressive treatment regimen, including skin grafting, to bring about rapid wound healing.

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