BACTERIAL PROTEASES: A MARKER FOR A ‘STATE OF PATHOGENESIS’ IN CHRONIC WOUNDS
Chronic wounds are open to the environment and are susceptible to contamination by bacteria, potentially leading to infection. Some of the consequences of a chronic wound infection are tissue breakdown, pain, additional impedance of the healing ability of the wound, amputation (e.g. in a diabetic foot ulcer) and systemic infection, which can be life-threatening. Identifying infection in chronic wounds is challenging because current clinical practice employs using clinical signs and symptoms (‘NERDS’) which are not necessarily distinct from other conditions, such as chronic inflammation. Bacteria and their proteases can stimulate a pro-inflammatory host response and, eventually, clinical signs due to this inflammatory response and tissue damage may be seen. The host response often includes elevated inflammatory markers, e.g. cytokines including tumour necrosis factor alpha (TNFα) and interleukin-1 beta (IL1-β). Unfortunately, clinical signs may not be apparent if the inflammatory response is impaired or defective (e.g. when other co-morbidities are present, such as diabetes or immunosuppressive conditions), thereby increasing the risk of infection. Bacteria are in a pathogenic state when they are either in the process of, or they are capable of, causing disease, i.e. infection. One indication of pathogenicity is the production of enzymatic virulence factors or bacterial proteases. The detection of bacterial protease activity (BPA) in a chronic wound would be indicative of the presence of bacterial pathogenesis which is a precursor to clinical signs and symptoms of infection. Bacterial pathogenesis is undesirable since, at this stage, the wound is in a part of the wound infection continuum that typically requires intervention.
Testing wound fluid for BPA using a rapid point of care test may be a useful method for detecting the presence of pathogenic bacteria, at a clinically significant stage in the infection continuum, even before the signs of infection are apparent. Integrating a point of care test for BPA as part of routine wound assessment could be a valuable tool in treatment pathways to inform clinicians that the wound is in a ‘state of pathogenesis’ which could lead to overt infection and be a possible contributor to wound chronicity and have a negative effect on morbidity and mortality of the patient.