Elevated wound fluid pH correlates with increased risk of wound infection

Introduction There is no definitive method to determine infection status in non-healing wounds. Measurement of wound pH might be a promising indicator of infection as it is relatively easy to perform, provides objective results within a few seconds, and is inexpensive. The aim of this investigation was to determine if wound pH could be a potential indicator of early or established infection in non-healing wounds. Methods We explored the relationship between wound pH and two indicators of wound infection: expert clinical judgement and elevated neutrophil-derived enzyme activity. Data was used from 120 wound samples previously collected at Medisch Spectrum Twente hospital. Results With increasing wound pH, there was also an increase in the proportion of infected wounds as determined by expert clinical judgement. In addition, increases in the activities of myeloperoxidase, elastase and lysozyme were also associated with elevated pH. Conclusions The strength of the relationship between wound pH and clinical judgement or enzyme activities observed in this study is not sufficient to promote the use of elevated pH alone as an indicator for wound infection. However, the use of pH in combination with other indicators for wound infection, such as elevated neutrophil enzyme activity, warrants further research

A Host-Directed Approach to the Detection of Infection in Hard-to-Heal Wounds

Wound infection is traditionally defined primarily by visual clinical signs, and secondarily by microbiological analysis of wound samples. However, these approaches have serious limitations in determining wound infection status, particularly in early phases or complex, chronic, hard-to-heal wounds. Early or predictive patient-derived biomarkers of wound infection would enable more timely and appropriate intervention. The observation that immune activation is one of the earliest responses to pathogen activity suggests that immune markers may indicate wound infection earlier and more reliably than by investigating potential pathogens themselves. One of the earliest immune responses is that of the innate immune cells (neutrophils) that are recruited to sites of infection by signals associated with cell damage. During acute infection, the neutrophils produce oxygen radicals and enzymes that either directly or indirectly destroy invading pathogens. These granular enzymes vary with cell type but include elastase, myeloperoxidase, lysozyme, and cathepsin G. Various clinical studies have demonstrated that collectively, these enzymes, are sensitive and reliable markers of both early-onset phases and established infections. The detection of innate immune cell enzymes in hard-to-heal wounds at point of care offers a new, simple, and effective approach to determining wound infection status and may offer significant advantages over uncertainties associated with clinical judgement, and the questionable value of wound microbiology. Additionally, by facilitating the detection of early wound infection, prompt, local wound hygiene interventions will likely enhance infection resolution and wound healing, reduce the requirement for systemic antibiotic therapy, and support antimicrobial stewardship initiatives in wound care

pH-responsive materials for optical monitoring of wound status

The monitoring of infection status of wounds is an emerging field and the pH of wound exudate is considered one potential indicator of infection. pH indicators intended for use in medical devices, such as swabs or dressings, need to be fixed in place, however, visual pH indicators are usually soluble molecules so are not inherently suitable for use in devices. To address this, we developed a rapid and simple immobilisation method for coupling pH-responsive dyes onto solid phases. The use of a silane based coupling agent for immobilisation of bromocresol purple led to a shift in the pH dependent spectral properties of the resulting material. The pH responsive material changes from yellow to green to blue with rising pH providing an ideal contrast to the reddish colour of most wound exudates. This is a key advantage over currently available alternatives when considering the suitability of this material for incorporation into various medical devices. In addition, we analysed clinical study samples to verify the association between wound infection and elevated pH-values. A device with an embedded indicator that changes to a contrast colour could represent a simple and easy-to-use system for detecting wounds at risk of infection