Real-time bacterial fluorescence imaging accurately identifies wounds with moderate-to-heavy bacterial burden

Bacterial fluorescence imaging as a predictor of skin graft integration in burn wounds

BACKGROUND

Split-thickness skin graft (STSG)1 integration rates are susceptible to improvement. Infection and/or biofilm should be appropriately addressed prior to grafting to improve the likelihood of graft-take. Incorporating technological aids such as fluorescence (FL)2 imaging (MolecuLight®), which accurately locates areas of bacterial loads above 104 CFU/gr, for graft site assessment and preparation could yield better outcomes.

METHODS

This single-center, prospective observational study included adult burn patients with previously infected wounds that had been deemed clinically and microbiologically clean and were therefore candidates for grafting. Prior to grafting, a FL imaging assessment (blinded to the surgical team) localized areas positive for moderate-high bacterial loads (>104 CFU/gr). Intra-operatively, a standard swab sample from the recipient site was collected by the surgical team. Postoperatively, areas positive/negative for FL and areas of graft take and failure were overlapped and measured (cm2) over a 2D schematic. The performance and accuracy of FL imaging and swab sampling in relation to graft outcomes were assessed.

RESULTS

38 patients were enrolled in the study. The mean total body surface area (TBSA)3 involvement was 14.5 ± 12.4 % [range 0.8 - 40.2 %]. 25/38 of the subjects enrolled had complete graft take while 13 had partial graft losses. There were no total losses. FL-imaging was positive in 100 % of losses versus 31 % (4/13) of the swab microbiology. FL-imaging was found to have a sensitivity of 86 %, specificity of 98 %, PPV of 72 %, NPV of 99 %, and an accuracy of 94 % for predicting any type or range of graft loss in the entire cohort. Meanwhile, the sensitivity of microbiology from swab samples was 30 %, with a specificity of 76 %.

CONCLUSIONS

FL imaging is an accurate method for assessing recipient sites and predicting the outcome of a skin graft among burn patients. These findings suggest that FL imaging can inform better decision-making surrounding grafts that may lead to better outcomes.

LEVEL OF EVIDENCE

Level IIA, Therapeutic study.

Systematic review and meta-analysis of diagnostic test accuracy in chronic wound's microbiology

PURPOSE

This study aims to assess the diagnostic accuracy of non-culture-based methodologies for detecting microorganisms in chronic wounds.

METHODS

We systematically reviewed studies that evaluated the diagnostic accuracy of alternative tests in chronic wound samples, excluding studies focused on animal samples or unrelated conditions. The search encompassed PubMed, CINAHL, Scopus and Web of Science databases, employing the QUADAS-2 tool for risk of bias assessment. Our search included the PubMed, CINAHL, Scopus and Web of Science databases, and we assessed the risk of bias using the QUADAS-2 tool. A meta-analysis was conducted on polymerase chain reaction (PCR) and colorimetric methods to determine sensitivity, specificity, diagnostic odds ratio, and summary receiver-operating characteristic (sROC) curves using a random-effects model. For methods not suitable for quantitative synthesis, a narrative synthesis was performed.

RESULTS

Nineteen studies involving various types of chronic wounds were analysed, revealing diverse diagnostic methods including fluorescence, PCR, colorimetry, voltammetry, electronic nose, biosensors, enzymatic methods, staining and microscopy. Combining fluorescence with clinical signs and symptoms (CSS) versus culture showed significant accuracy. Colorimetry demonstrated low sensitivity but high specificity, with a diagnostic odds ratio of 6.3. PCR generally exhibited good accuracy, although significant heterogeneity was noted, even in subgroup analyses.

CONCLUSIONS

This study identified a broad spectrum of diagnostic approaches, highlighting the superior diagnostic accuracy achieved when microbiological analysis is combined with clinical assessments. However, the heterogeneity and methodological variations across studies present challenges in meta-analysis. Future research should aim for standardized and homogeneous study designs to enhance the assessment of diagnostic accuracy for alternative methods.

Improving Wound Healing and Infection Control in Long-term Care with Bacterial Fluorescence Imaging

BACKGROUND

High bacterial burden stalls wound healing and can quickly progress to infection and sepsis in complex, older-adult patients in long-term care (LTC) or skilled nursing facilities (SNFs).

OBJECTIVE

To investigate the outcomes of point-of-care fluorescence (FL) imaging (MolecuLight i:X) of bacterial loads, which are frequently asymptomatic, to inform customized wound treatment plans for patients in LTC/SNFs.

METHODS

In this retrospective pre/postinterventional cohort study, the authors compared the healing and infection-associated outcomes of 167 pressure injuries from 100 Medicare beneficiaries before and after implementation of FL imaging.

RESULTS

Most patient demographics and wound characteristics did not differ significantly between the standard-of-care (SOC; n = 71 wounds) and FL (n = 96 wounds) cohorts. Significantly more wounds (+71.0%) healed by 12 weeks in the FL cohort (38.5%) versus the SoC cohort (22.5%). Wounds in the FL cohort also healed 27.7% faster (-4.8 weeks), on average, and were 1.4 times more likely to heal per Kaplan-Meier survival analysis (hazard ratio = 1.40; 95% CI, 0.90-2.12). Infection-related complications decreased by 75.3% in the FL cohort, and a significant shift from largely systemic to topical antibiotic prescribing was evidenced.

CONCLUSIONS

Fluorescence-imaging-guided management of wounds significantly improved healing and infection outcomes in highly complex and multimorbid patients in LTC/SNFs. Proactive bacterial infection management via local treatments was enabled by earlier, objective detection. These reported outcome improvements are comparable to randomized controlled trials and cohort studies from less compromised, selectively controlled outpatient populations. Fluorescence imaging supports proactive monitoring and management of planktonic and biofilm-encased bacteria, improving patient care in a complex, real-world setting.

Assessing Pediatric Burn Wound Infection Using a Point-of-Care Fluorescence Imaging Device

Wound infection is the most common complication among pediatric burn patients. When not treated promptly, burn wound infection may lead to delayed healing, failure of skin grafts, or death. Standard burn wound assessment includes inspection for visual signs and symptoms of infection (VSSI) and microbial sampling. To aid in the assessment of burn wound infection, the MolecuLight, a point-of-care autofluorescence imaging device, was introduced at our pediatric burn program in 2020. The MolecuLight uses violet light to illuminate the wound bed, causing clinically relevant quantities of 29 different species of bacteria (>104 CFU/g) to fluoresce in real time. The objectives of this study were to evaluate the role of the MolecuLight in the management of pediatric burn wounds and determine if the findings from the MolecuLight corresponded to VSSI and/or microbial sampling. A retrospective review of patients 0-18 years who had burn wounds assessed with the MolecuLight between November 1, 2020 and June 8, 2023 was conducted. Data were extracted from the medical records of 178 eligible patients with 218 wounds imaged with the device. Fluorescence corresponded with VSSI in 81% of wounds and microbial findings in 82% of wounds. MolecuLight fluorescence, in combination with VSSI, improved sensitivity for detecting wound infections by 39% and decreased specificity by 19% compared to visual signs and symptoms in isolation. Incorporation of the MolecuLight in standard burn wound assessments can improve the detection of infections, which may promote improved wound healing outcomes and antimicrobial stewardship.

Determination of the Course of Cyan Fluorescence of Pseudomonas aeruginosa with a Handheld Bacterial Imaging Device

Chronic wound infections are of clinical concern as they often lead to high rates of mortality and morbidity. A point-of-care handheld bacterial fluorescence imaging has been designed to detect the auto-fluorescent characteristics of most clinically relevant species of bacteria. This device causes most species of bacteria to exhibit red fluorescence due to the production of exoproduct porphyrins. One of the most significant contributors to the pathogenicity of chronic wounds is the pathogen Pseudomonas aeruginosa, and interestingly, this organism exhibits an additional unique cyan fluorescence signature. There is an over 90% positive predictive value that, when a chronic wound exhibits cyan fluorescence with the bacterial fluorescence imaging device, the wound will harbor P. aeruginosa. This project seeks to understand what genetic factor(s) contribute to the cyan phenotype observed.

How effective is simple mechanical wound debridement in reducing bacterial colonisation? Results of a prospective clinical study

BACKGROUND AND AIMS

Bacteria in wounds can lead to stagnation of wound healing as well as to local or even systemic wound infections up to potentially lethal sepsis. Consequently, the bacterial load should be reduced as part of wound treatment. Therefore, the efficacy of simple mechanical wound debridement should be investigated in terms of reducing bacterial colonisation.

PATIENTS AND METHODS

Patients with acute or chronic wounds were assessed for bacterial colonisation with a fluorescence camera before and after mechanical wound debridement with sterile cotton pads. If bacterial colonisation persisted, a second, targeted wound debridement was performed.

RESULTS

A total of 151 patients, 68 (45.0%) men and 83 (55.0%) women were included in this study. The male mean age was 71.0 years and the female 65.1 years. By establishing a new analysis method for the image files, we could document that the bacterial colonised areas were distributed 21.9% on the wound surfaces, 60.5% on the wound edges (up to 0.5 cm) and 17.6% on the wound surroundings (up to 1.5 cm). One mechanical debridement achieved a significant reduction of bacterial colonised areas by an average of 29.6% in the wounds, 18.9% in the wound edges and 11.8% in the wound surroundings and was increased by performing it a second time.

CONCLUSIONS

It has been shown that even a simple mechanical debridement with cotton pads can significantly reduce bacterial colonisation without relevant side effects. In particular, the wound edges were the areas that were often most contaminated with bacteria and should be included in the debridement with special attention. Since bacteria remain in wounds after mechanical debridement, it cannot replace antimicrobial therapy strategies, but offer a complementary strategy to improve wound care. Thus, it could be shown that simple mechanical debridement is effective in reducing bacterial load and should be integrated into a therapeutic approach to wounds whenever appropriate.

A Clinical Study to Evaluate Autofluorescence Imaging of Diabetic Foot Ulcers Using a Novel Artificial Intelligence Enabled Noninvasive Device

Diabetic foot ulcers, with worldwide prevalence ranging from 12%-25%, are an important cause of nontraumatic lower limb amputation. Evidence-based assessment of early infection can help the clinician provide the right first line treatment thus helping improve the wound closure rate. Illuminate®, a novel point of care device working on multispectral autofluorescence imaging, helps in the rapid identification and classification of bacteria. This study was aimed to evaluate the diagnostic accuracy of the device in detecting bacterial gram type against standard culture methods. A total of 178 patients from a tertiary care center for diabetes was recruited and 203 tissue samples were obtained from the wound base by the plastic surgeon. The device was handled by the trained investigator to take wound images. The tissue samples were taken from the color-coded infected region as indicated by the device's Artificial Intelligence algorithm and sent for microbial assessment. The results were compared against the Gram type inferred by the device and the device was found to have an accuracy of 89.54%, a positive predictive value of 86.27% for detecting Gram-positive bacteria, 80.77% for Gram-negative bacteria, and 91.67% for no infection. The negative predictive value corresponded to 87.25% for Gram-positive, 92% for Gram-negative, and 96.12% for no infection. The Results exhibited the accuracy of this novel autofluorescence device in identifying and classifying the gram type of bacteria and its potential in significantly aiding clinicians towards early infection assessment and treatment.

Identifying infection in chronic wounds in a community setting: A systematic review of diagnostic test accuracy studies

AIM

To determine the diagnostic accuracy of different methods currently available to identify infection in chronic wounds applicable to adult patients in a community setting.

DESIGN

Systematic review of diagnostic test accuracy studies.

REVIEW METHODS

Two authors independently completed screening, data extraction and quality and bias assessments (QUADAS2). Eligible studies compared a method (index test) for detecting infection (diagnosis of interest) with microscopy and culture of either deep tissue biopsy or wound swab (reference test) in adult patients with wounds of >4 weeks duration (participants). The results were synthesized narratively.

DATA SOURCES

We systematically searched CINAHL, Embase and Medline from 2011 to April 2022.

RESULTS

Four studies were included, all recruiting from secondary care wound clinics. Two studies assessed the diagnostic accuracy of Moleculight i:X, a bacterial fluorescence imaging device against deep tissue biopsy culture. One study assessed the diagnostic accuracy of the elevation of various enzymes detected in wound fluid against wound swab microscopy of culture. One study assessed the diagnostic accuracy of bacterial protease activity against wound swab microscopy and culture. Sensitivities of these methods ranged from 50 to 75% and specificities from 47 to 100%.

CONCLUSION

Only a small number of studies were included in this systematic review due to our strict inclusion criteria. We have not identified any methods for diagnosing infection in chronic wounds with either a sufficient quality of evidence to recommend their use in community settings at present. Further research is needed to develop and evaluate appropriate diagnostics for this purpose.

IMPACT

This study highlights the paucity of research into wound diagnostics in a community setting and should prompt further research in this area. Accurate diagnostic tests have the potential to improve community-based wound care by optimizing antibiotic use and potentially improving healing time.

REPORTING METHOD

PRISMA-DTA checklist.

PATIENT OR PUBLIC CONTRIBUTION

The PPI group for the NIHR Community Healthcare MIC were supportive of this topic of work.

Lights, fluorescence, action-Influencing wound treatment plans including debridement of bacteria and biofilms

High bacterial loads within chronic wounds increase the risk of infection and complication. Detection and localization of bacterial loads through point-of-care fluorescence (FL) imaging can objectively inform and support bacterial treatment decisions. This single time-point, retrospective analysis describes the treatment decisions made on 1000 chronic wounds (DFUs, VLUs, PIs, surgical wounds, burns, and others) at 211 wound-care facilities across 36 US states. Clinical assessment findings and treatment plans derived from them, as well as subsequent FL-imaging (MolecuLight®) findings and any associated treatment plan changes, were recorded for analysis. FL signals indicating elevated bacterial loads were observed in 701 wounds (70.8%), while only 293 (29.6%) showed signs/symptoms of infection. After FL-imaging, treatment plans changed in 528 wounds as follows: more extensive debridement (18.7%), more extensive hygiene (17.2%), FL-targeted debridement (17.2%), new topical therapies (10.1%), new systemic antibiotic prescriptions (9.0%), FL-guided sampling for microbiological analysis (6.2%), and changes in dressing selection (3.2%). These real-world findings of asymptomatic bacterial load/biofilm incidence, and of the frequent treatment plan changes post-imaging, are in accordance with clinical trial findings using this technology. These data, from a range of wound types, facilities, and clinician skill sets, suggest that point-of-care FL-imaging information improves bacterial infection management.

Is my wound infected? A study on the use of hyperspectral imaging to assess wound infection

Introduction

Clinical signs and symptoms (CSS) of infection are a standard part of wound care, yet they can have low specificity and sensitivity, which can further vary due to clinician knowledge, experience, and education. Wound photography is becoming more widely adopted to support wound care. Thermography has been studied in the medical literature to assess signs of perfusion and inflammation for decades. Bacterial fluorescence has recently emerged as a valuable tool to detect a high bacterial load within wounds. Combining these modalities offers a potential objective screening tool for wound infection.

Methods

A multi-center prospective study of 66 outpatient wound care patients used hyperspectral imaging to collect visible light, thermography, and bacterial fluorescence images. Wounds were assessed and screened using the International Wound Infection Institute (IWII) checklist for CSS of infection. Principal component analysis was performed on the images to identify wounds presenting as infected, inflamed, or non-infected.

Results

The model could accurately predict all three wound classes (infected, inflamed, and non-infected) with an accuracy of 74%. They performed best on infected wounds (100% sensitivity and 91% specificity) compared to non-inflamed (sensitivity 94%, specificity 70%) and inflamed wounds (85% sensitivity, 77% specificity).

Discussion

Combining multiple imaging modalities enables the application of models to improve wound assessment. Infection detection by CSS is vulnerable to subjective interpretation and variability based on clinicians' education and skills. Enabling clinicians to use point-of-care hyperspectral imaging may allow earlier infection detection and intervention, possibly preventing delays in wound healing and minimizing adverse events.

The effect of inflammation management on pH, temperature, and bacterial burden

The aim of this feasibility study was to investigate the impact of inflammation management on wound pH, temperature, and bacterial burden, using the principles of TIME and Wound Bed Preparation. A quantitative non-comparative, prospective, descriptive observational design. Following ethical approval, 26 participants with 27 wounds of varying aetiologies were observed twice weekly for 2 weeks. Wounds were treated with cleansing, repeated sharp debridement, and topical cadexomer iodine. Wound pH (pH indicator strips), temperature (infrared camera), bacterial burden (fluorescence imaging) and size (ruler method) was monitored at each visit. The mean age of all participants was 47 years (SD: 20.3 years), and 79% (n = 19) were male, and most wounds were acute (70%; n = 19) and included surgical and trauma wounds, the remaining (30%; n = 8) were chronic and included vascular ulcers and non-healing surgical wounds. Mean wound duration was 53.88 days (SD: 64.49 days). Over the follow up period, pH values ranged from 6 to 8.7, temperature (centre spot) ranged from 28.4°C to 36.4°C and there was an average 39% reduction in wound size. Inflammation management had a positive effect on pH, temperature, bacterial burden, and wound size. This study demonstrated that it was feasible to practice inflammation management using a structured approach to enhance wound outcomes.

Point-of-care fluorescence imaging reveals extent of bacterial load in diabetic foot ulcers

Elevated levels of bacteria, including biofilm, increase the risk of chronic wound infection and inhibit healing. Addressing asymptomatic high bacterial loads is challenged by a lack of clinical terminology and diagnostic tools. This post-hoc multicenter clinical trial analysis of 138 diabetic foot ulcers investigates fluorescence (FL)-imaging role in detecting biofilm-encased and planktonic bacteria in wounds at high loads. The sensitivity and specificity of clinical assessment and FL-imaging were compared across bacterial loads of concern (104 -109  CFU/g). Quantitative tissue culture confirmed the total loads. Bacterial presence was confirmed in 131/138 ulcers. Of these, 93.9% had loads >104  CFU/g. In those wounds, symptoms of infection were largely absent and did not correlate with, or increase proportionately with, bacterial loads at any threshold. FL-imaging increased sensitivity for the detection of bacteria across loads 104 -109 (P < .0001), peaking at 92.6% for >108  CFU/g. Imaging further showed that 84.2% of ulcers contained high loads in the periwound region. New terminology, chronic inhibitory bacterial load (CIBL), describes frequently asymptomatic, high bacterial loads in diabetic ulcers and periwound tissues, which require clinical intervention to prevent sequelae of infection. We anticipate this will spark a paradigm shift in assessment and management, enabling earlier intervention along the bacterial-infection continuum and supporting improved wound outcomes.

Reliance on Clinical Signs and Symptoms Assessment Leads to Misuse of Antimicrobials: Post hoc Analysis of 350 Chronic Wounds

Objectives: Bacteria frequently impede wound healing and cause infection. Clinicians rely on clinical signs and symptoms (CSS) to assess for bacteria at the point of care, and inform prescription of antibiotics and other antimicrobials. Yet, robust evidence suggests that CSS has poor sensitivity for detection of problematic bacterial burden and infection, hindering antimicrobial stewardship efforts. This study evaluated CSS-based antimicrobial prescribing practices across 14 wound care centers. Approach: Data were analyzed from the fluorescence assessment and guidance (FLAAG) trial, a study of 350 chronic wounds across 20 clinicians. Clinicians reviewed patient history and assessed for CSS using the International Wound Infection Institute infection checklist. Wounds with >3 criteria or any overwhelming symptom were considered CSS+. Bacterial levels were confirmed with quantitative tissue culture of wound biopsies. Results: Antimicrobials (including dressings, topicals, and systemic antibiotics) were prescribed at a similar rate for wounds identified as CSS+ (75.0%) and CSS- (72.8%, p = 0.76). Antimicrobial dressings, the most frequently prescribed antimicrobial, were prescribed at a similar rate for CSS+ (83.3%) and CSS- (89.5%, p = 0.27) wounds. In 33.3% of patients prescribed systemic antibiotics, no CSS were present. Prescribing patterns did not correlate with bacterial load. Innovation: This study is the first to evaluate antimicrobial prescribing trends in a large, multisite cohort of chronic wound patients. Conclusions: Reliance on CSS to diagnose clinically significant bacterial burden in chronic wounds leads to the haphazard use of antimicrobials. Improved methods of identifying bacterial burden and infection are needed to enhance antimicrobial stewardship efforts in wound care. Clinicaltrials.gov ID. NCT03540004.

What COVID-19 taught us: New opportunities and pathways from telemedicine and novel antiseptics in wound healing

The COVID-19 pandemic deeply impacted the capacity of the health systems to maintain preventive and curative services, especially for the most vulnerable populations. During the pandemic, the wound healing centres in Italy assisted a significant reduction of the frequency of their hospital admission, since only urgencies, such as severe infections or wound haemorrhagic complications, were allowed to the hospital. The aim of this multidisciplinary work is to highlight the importance of a new pathway of wound care with patient-based therapeutic approach, tailored treatments based on the characteristics of the wound and fast tracks focused on the outpatient management, reserving hospital assessment only for patients with complicated or complex wounds. This analysis highlights the point that patients with chronic wounds need to be critically evaluated in order to find the best and most appropriate care pathway, which should vary according to the patient and, especially, to the characteristics of the wound. Moreover, the most adequate topic antiseptic should be started as soon as possible. An appropriate and correct management of the wound care will allow to link the knowledge based on years of clinical practice with the new challenges and the need to visit patients remotely, when possible.

The clinical progression and wound healing rate of dehisced perineal tears healing by secondary intention: A prospective observational study

OBJECTIVES

To establish the clinical progression of dehisced perineal wounds healing by secondary intention and to investigate the incidence and factors associated with delayed healing.

METHODS

Secondary analysis of women with perineal wound dehiscence recruited into the PERINEAL study between August 2020- August 2021 (NCT04480684). Three-dimensional wound measurements were taken with the Silhouette® camera. Significant bacterial colonisation was diagnosed using the MolecuLight i:X camera. As it is agreed that acute wounds should heal sufficiently within four weeks, diagnosis of delayed wound healing was made if a wound took longer than four weeks to heal. A wound was deemed to have healed if there was complete wound closure, with no evidence of granulation tissue or signs of infection on clinical examination.

RESULTS

55 women with perineal wound dehiscence participated. Wounds took an average of 3 weeks to heal (range 1-16) and 38 (69.1%) wounds healed in ≤ 4 weeks from the first clinical review. 17 (30.9%) wounds had significant bacterial colonisation, identified on bacterial fluorescence imaging. Women with a wound area of < 1.60 cm² or wound perimeter of < 5.57 cm had a 70% probability of wound healing in ≤ 4 weeks. 47.1% of wounds with significant bacteria colonisation healed within 4 weeks, in comparison to 78.9% of wounds not colonised (p = 0.03). 25.0 % (n = 2) of wounds with OASI healed within 4 weeks, in comparison to 76.5% (n = 36) of wounds with no OASI (p = 0.02). Bacterial fluorescence (OR 0.21 (0.05-0.87)) and OASIs (OR 0.09 (0.01-0.66)) were independent risk factors associated with delayed wound healing. The model including wound area, fluorescence and OASIs had the greatest AUC (0.81, 95% CI 0.67-0.94) indicating the best predictive model.

CONCLUSIONS

This is the first study to describe healing outcomes of dehisced perineal wounds and factors associated with delayed healing. The study findings will help clinicians counsel women effectively and tailor follow-up care at the first assessment, based on individual risk factors.

Advanced Wound Diagnostics: Toward Transforming Wound Care into Precision Medicine

Significance: Nonhealing wounds are an ever-growing global pandemic, with mortality rates and management costs exceeding many common cancers. Although our understanding of the molecular and cellular factors driving wound healing continues to grow, standards for diagnosing and evaluating wounds remain largely subjective and experiential, whereas therapeutic strategies fail to consistently achieve closure and clinicians are challenged to deliver individualized care protocols. There is a need to apply precision medicine practices to wound care by developing evidence-based approaches, which are predictive, prescriptive, and personalized. Recent Advances: Recent developments in "advanced" wound diagnostics, namely biomarkers (proteases, acute phase reactants, volatile emissions, and more) and imaging systems (ultrasound, autofluorescence, spectral imaging, and optical coherence tomography), have begun to revolutionize our understanding of the molecular wound landscape and usher in a modern age of therapeutic strategies. Herein, biomarkers and imaging systems with the greatest evidence to support their potential clinical utility are reviewed. Critical Issues: Although many potential biomarkers have been identified and several imaging systems have been or are being developed, more high-quality randomized controlled trials are necessary to elucidate the currently questionable role that these tools are playing in altering healing dynamics or predicting wound closure within the clinical setting. Future Directions: The literature supports the need for the development of effective point-of-care wound assessment tools, such as a platform diagnostic array that is capable of measuring multiple biomarkers at once. These, along with advances in telemedicine, synthetic biology, and "smart" wearables, will pave the way for the transformation of wound care into a precision medicine. Clinical Trial Registration number: NCT03148977.

Challenges in the diagnosis and management of wound infection

Human epithelia are constantly exposed to microorganisms present in the environment or residing as part of commensal flora. Despite this exposure, infections involving the skin and subcutaneous tissue in healthy individuals are, fortunately, quite rare. Many of the wounds that afflict the human body occur in individuals of ill health and/or where the mechanism of wounding is impeded by host immunological, physiological or regenerative dysfunction. The interplay between microorganisms and host immunity is complex and remains ill defined; however, the interpretation of downstream manifestations of the host response to invading microorganisms is still based largely on the clinical signs and symptoms of an active infectious process. In this review article we will provide a brief overview of the current challenges clinicians face in diagnosing wound infections, how chronic infections caused by biofilms are a major challenge, and how there have been minimal advancements in developing new diagnostics or therapeutics in the identification and management of wound infections.

The efficacy of sodium hypochlorite antiseptic: a double-blind, randomised controlled pilot study

OBJECTIVE

According to a recent clinical trial, 82% of hard-to-heal wounds harbour levels of bacteria that impede healing. A follow-up analysis of trial data revealed that the use of antiseptic cleansers did not correlate with bacterial burden. At a minimum, these findings suggest the need for clinical research into the efficacy of antiseptics in reducing bacterial burden. Evidence supporting the bacterial killing ability of antiseptics is largely derived from preclinical and laboratory studies. Few clinical trials have examined bacterial levels and healing rates in hard-to-heal wounds. Fortunately, the advent of fluorescence imaging to detect bacterial burden has simplified the conduct of clinical research examining the effectiveness of antiseptics in the clinic setting. The aim of this study was to evaluate the efficacy of a modified sodium hypochlorite (NaOCl) solution in reducing wound size and bacterial load in hard-to-heal wounds.

METHOD

In this randomised, double-blind pilot study, patients were randomised to one of two groups: daily wound cleansing with either normal saline solution (NSS) or NaOCl. Patients and investigators were blinded to the allocation. All wound types were included.

RESULTS

A total of 16 patients consented to participate. At the initial visit, the target ulcer was measured and a fluorescence image to evaluate bacterial load obtained. The wound was then cleansed with either NSS or NaOCl and fluorescence imaging repeated. Patients cleansed the wound daily in accordance with the randomisation schedule. They returned to the clinic weekly for four weeks, and on each visit the wound was measured and a fluorescence image captured. Patients receiving NaOCl had a greater percent reduction in wound area versus NSS; although the first phase of the study was not powered for statistical significance, there was a strong trend favouring NaOCl. In addition, there was greater bacterial reduction in the NaOCl group.

CONCLUSION

Based on the results of this pilot study, enrolment has continued in order to increase the study's power. This pilot study suggests that sodium hypochlorite is efficacious in reducing bacterial burden and promoting healing.

Uncovering the high prevalence of bacterial burden in surgical site wounds with point-of-care fluorescence imaging

Detection of bacterial burden within or near surgical wounds is critical to reducing the occurrence of surgical site infection (SSI). A distinct lack of reliable methods to identify postoperative bioburden has forced reliance on clinical signs and symptoms of infection (CSS). As a result, infection management has been reactive, rather than proactive. Fluorescence imaging of bacterial burden (FL) is positioned to potentially flip that paradigm. This post hoc analysis evaluated 58 imaged and biopsied surgical site wounds from the multi‐centre fluorescence imaging assessment and guidance clinical trial. Diagnostic accuracy measures of CSS and FL were evaluated. A reader study investigated the impact of advanced image interpretation experience on imaging sensitivity. Forty‐four of fifty‐eight surgical site wounds (75.8%) had bacterial loads >10⁴ CFU/g (median = 3.11 × 10⁵ CFU/g); however, only 3 of 44 were CSS positive (sensitivity of 6.8%). FL improved sensitivity of bacterial detection by 5.7‐fold compared with CSS alone (P = .0005). Sensitivity improved by 11.3‐fold over CSS among clinicians highly experienced with FL interpretation (P < .0001). Surgical sites that reach the stage of referral to a wound specialist frequently harbour asymptomatic high bacterial loads that delay healing and increase infection risk. Advanced imaging of pathological bacterial burden improves surgical site monitoring and may reduce the rate of SSIs.

Wound infection: A review of qualitative and quantitative assessment modalities

Surgical site infections (SSI) and chronic wounds represent a burden to patients and the health care system. One in 24 surgical patients will develop an SSI, making SSI the most common nosocomial infection in the USA. Early detection and monitoring of wound infection are critical for timely healing and return to normal function. However, the mainstay of wound infection diagnostic entails subjective clinical examination and semi-quantitative, invasive microbiological tests. In this review, we present current wound infection assessment modalities in the clinical and translational fields. There is a need for a point-of-care assessment tool that provides fast, accurate, and quantitative information on wound status, with minimal to no contact with the patient. In the next ten years, the evolution of wound diagnostic tools reported here may allow medical providers to optimize patient care while minimizing patient discomfort.

Efficacy and safety of biofilm dispersal by glycoside hydrolases in wounds

Novel anti-biofilm and dispersal agents are currently being investigated in an attempt to combat biofilm-associated wound infections. Glycoside hydrolases (GHs) are enzymes that hydrolyze the glycosidic bonds between sugars, such as those found within the exopolysaccharides of the biofilm matrix. Previous studies have shown that GHs can weaken the matrix, inducing bacterial dispersal, and improving antibiotic clearance. Yet, the number of GH enzymes that have been examined for potential therapeutic effects is limited. In this study, we screened sixteen GHs for their ability to disperse mono-microbial and polymicrobial biofilms grown in different environments. Six GHs, α-amylase (source: A. oryzae), alginate lyase (source: various algae), pectinase (source: Rhizopus sp.), amyloglucosidase (source: A. niger), inulinase (source: A. niger), and xylanase (source: A. oryzae), exhibited the highest dispersal efficacy in vitro. Two GHs, α-amylase (source: Bacillus sp.) and cellulase (source: A. niger), used in conjunction with meropenem demonstrated infection clearing ability in a mouse wound model. GHs were also effective in improving antibiotic clearance in diabetic mice. To examine their safety, we screened the GHs for toxicity in cell culture. Overall, there was an inverse relationship between enzyme exposure time and cellular toxicity, with twelve out of sixteen GHs demonstrating some level of toxicity in cell culture. However, only one GH exhibited harmful effects in mice. These results further support the ability of GHs to improve antibiotic clearance of biofilm-associated infections and help lay a foundation for establishing GHs as therapeutic agents for chronic wound infections.

Harnessing Multifaceted Next-Generation Technologies for Improved Skin Wound Healing

Dysregulation of sequential and synchronized events of skin regeneration often results in the impairment of chronic wounds. Conventional wound dressings fail to trigger the normal healing mechanism owing to the pathophysiological conditions. Tissue engineering approaches that deal with the fabrication of dressings using various biomaterials, growth factors, and stem cells have shown accelerated healing outcomes. However, most of these technologies are associated with difficulties in scalability and cost-effectiveness of the products. In this review, we survey the latest developments in wound healing strategies that have recently emerged through the multidisciplinary approaches of bioengineering, nanotechnology, 3D bioprinting, and similar cutting-edge technologies to overcome the limitations of conventional therapies. We also focus on the potential of wearable technology that supports complete monitoring of the changes occurring in the wound microenvironment. In addition, we review the role of advanced devices that can precisely enable the delivery of nanotherapeutics, oligonucleotides, and external stimuli in a controlled manner. These technological advancements offer the opportunity to actively influence the regeneration process to benefit the treatment regime further. Finally, the clinical relevance, trajectory, and prospects of this field have been discussed in brief that highlights their potential in providing a beneficial wound care solution at an affordable cost.

Diagnosis and treatment of the invasive extension of bacteria (cellulitis) from chronic wounds utilising point-of-care fluorescence imaging

Early diagnosis of wound‐related cellulitis is challenging as many classical signs and symptoms of infection (erythema, pain, tenderness, or fever) may be absent. In addition, other conditions (ie, chronic stasis dermatitis) may present with similar clinical findings. Point‐of‐care fluorescence imaging detects elevated bacterial burden in and around wounds with high sensitivity. This prospective observational study examined the impact of incorporating fluorescence imaging into standard care for diagnosis and management of wound‐related cellulitis. Two hundred thirty‐six patients visiting an outpatient wound care centre between January 2020 and April 2021 were included in this study. Patients underwent routine fluorescence scans for bacteria (range: 1‐48 scans/patient). Wound‐related cellulitis was diagnosed in 6.4% (15/236) of patients. In these patients, fluorescence scans showed an irregular pattern of red (bacterial) fluorescence extending beyond the wound bed and periwound that could not be removed through cleansing or debridement, indicating the invasive extension of bacteria (wound‐related cellulitis). Point‐of‐care identification facilitated rapid initiation of treatments (source control and antibiotics, when warranted) that resolved the fluorescence. No patients had worsening of cellulitis requiring intravenous antibiotics and/or hospitalisation. These findings demonstrate the utility of point‐of‐care fluorescence imaging for efficient detection and proactive, targeted management of wound‐related cellulitis.

Detection of bacterial fluorescence from in vivo wound biofilms using a point-of-care fluorescence imaging device

Wound biofilms must be identified to target disruption and bacterial eradication but are challenging to detect with standard clinical assessment. This study tested whether bacterial fluorescence imaging could detect porphyrin-producing bacteria within a biofilm using well-established in vivo models. Mouse wounds were inoculated on Day 0 with planktonic bacteria (n = 39, porphyrin-producing and non-porphyrin-producing species, 107  colony forming units (CFU)/wound) or with polymicrobial biofilms (n = 16, 3 biofilms per mouse, each with 1:1:1 parts Staphylococcus aureus/Escherichia coli/Enterobacter cloacae, 107  CFU/biofilm) that were grown in vitro. Mouse wounds inoculated with biofilm underwent fluorescence imaging up to Day 4 or 5. Wounds were then excised and sent for microbiological analysis. Bacteria-matrix interaction was assessed with scanning electron microscopy (SEM) and histopathology. A total of 48 hours after inoculation with planktonic bacteria or biofilm, red fluorescence was readily detected in wounds; red fluorescence intensified up to Day 4. Red fluorescence from biofilms persisted in excised wound tissue post-wash. SEM and histopathology confirmed bacteria-matrix interaction. This pre-clinical study is the first to demonstrate the fluorescence detection of bacterial biofilm in vivo using a point-of-care wound imaging device. These findings have implications for clinicians targeting biofilm and may facilitate improved visualisation and removal of biofilms.

Utility of MolecuLight i:X for Managing Bacterial Burden in Pediatric Burns

Pediatric burn injuries are vulnerable to severe complications, most often infection, making prompt and precise diagnosis of bacterial bioburden vital to preventing detrimental consequences and optimizing patients' outcomes. Currently, burn wounds are assessed for infection via examining the clinical signs and symptoms of infection, which can be confirmed by swab culture analysis. While the former approach is subjective and experience-dependant, the latter technique is susceptible to missing subsurface, biofilm-associated colonization, and any peripheral bacterial burden, and also delays confirmation by up to 5 days. The MolecuLight i:X is a handheld, noncontact fluorescence imaging device, which can reveal real-time information about clinically significant levels of bacteria and their biodistribution in surface and subsurface burn wound tissues. We conducted a single-center observational study to assess the device efficacy in identifying critical bacterial levels in pediatric burn wounds and to test the children's compliance and the overall feasibility of the device integration into the current diagnostic practice. Ten patients with 16 wounds were recruited and assessed for the presence or absence of clinical signs and symptoms of infection and the presence or absence of bacterial fluorescence on images, with swabs taken to confirm findings. Results demonstrate the device's ability to visualize clinically significant bacterial burden and to localize distribution of pathogens. All clinicians agreed on the high compliance with the device and high feasibility of incorporating the device into routine wound assessments. The results of this study may pave the way toward including bacterial fluorescence imaging into the standard diagnostic algorithm for pediatric burn population.

Are Semi-Quantitative Clinical Cultures Inadequate? Comparison to Quantitative Analysis of 1053 Bacterial Isolates from 350 Wounds

Early awareness and management of bacterial burden and biofilm is essential to wound healing. Semi-quantitative analysis of swab or biopsy samples is a relatively simple method for measuring wound microbial load. The accuracy of semi-quantitative culture analysis was compared to 'gold standard' quantitative culture analysis using 428 tissue biopsies from 350 chronic wounds. Semi-quantitative results, obtained by serial dilution of biopsy homogenates streaked onto culture plates divided into 4 quadrants representing occasional, light, moderate, and heavy growth, were compared to total bacterial load quantified as colony-forming units per gram (CFU/g). Light growth, typically considered an insignificant finding, averaged a clinically significant 2.5 × 105 CFU/g (SE = 6.3 × 104 CFU/g). Occasional growth (range: 102-106 CFU/g) and light growth (103-107 CFU/g) corresponded to quantitative values that spanned a 5-log range; moderate and heavy growth corresponded to a range of 4-log and 6-log, respectively, with a high degree of overlap in range of CFU/g per category. Since tissue biopsy and quantitative culture cannot be widely practiced and semi-quantitative analysis is unreliable, other clinically relevant approaches are required to determine wound bioburden and guide best management practices. Fluorescence imaging is a point-of-care technology that offers great potential in this field.

Guidelines for Point-of-Care Fluorescence Imaging for Detection of Wound Bacterial Burden Based on Delphi Consensus

Excessive levels of bacteria impede wound healing and can lead to infectious complications. Unfortunately, clinical signs and symptoms of elevated bacterial burden are often unreliable. As a result, point--of--care fluorescence imaging, used to detect critical bacterial burden in wounds, is becoming widely recognized and adopted by clinicians across the globe as an accepted and added component of wound assessment protocol. A Delphi method was employed to establish consensus guidelines describing fluorescence imaging use. A multidisciplinary panel of 32 wound experts (56% MD, 22% podiatrist, 12.5% nurses/nurse practitioners) representing multiple sites of service (e.g., hospital outpatient, inpatient, private office, long-term care) completed two rounds of online questionnaires. The Delphi included key topics, including competencies required to perform imaging, clinical indications for imaging (e.g., signs/symptoms present, procedures warranting imaging), frequency of imaging, and a clinical workflow algorithm. Describing their clinical experiences of imaging impact, >80% reported changes in treatment plans, 96% reported that imaging-informed treatment plans led to improved wound healing, 78% reported reduced rates of amputations, and 83% reported reduced rates of microbiological sampling. The guidelines provided here will help to standardize use of fluorescence imaging among wound care providers and enhance the quality of patient care.

Efficacy and safety of a porcine peritoneum-derived matrix in diabetic foot ulcer treatment: a pilot study

OBJECTIVE

A third of people with diabetes will develop a foot ulcer during their lifetime. The absence of pain secondary to neuropathy often leads to a delay in diagnosis and treatment. Diabetic foot ulcer (DFU) complications, such as infection and amputation, increase mortality and strain the financial resources of health systems across the world. Cellular and/or tissue products (CTPs) have played an important role in the closure of DFUs. Investigators continue to search for new CTPs that facilitate healing. The aim of this study was to assess the efficacy and safety of a porcine peritoneum-derived matrix in DFU treatment.

METHOD

Patients with longstanding DFUs participated in this institutional review board-approved, multicentre, prospective pilot study evaluating the time to healing over 12 weeks. In addition to weekly assessments for wound size, investigators analysed bacterial burden using the MolecuLight procedure (MLiX) and bacterial protease (BPA) testing. Participants received a weekly application of Meso Wound Matrix Scaffold (MWM), a lyophilised porcine peritoneum-derived matrix (DSM Biomedical Inc., Exton, PA, US) for up to eight weeks. Descriptive statistics were chosen for this analysis.

RESULTS

A total of 12 male patients and three female patients with an average age of 57 years were enrolled over a two-month period. The average wound duration was 30 weeks. Due to unrelated health issues, four participants were withdrawn. For the study endpoint of complete wound closure at 12 weeks, six (55%) of the remaining 11 patients achieved complete closure, and four (36%) patients healed during the 8-week treatment period. The average number of CTP applications was six. Patients who healed all had negative BPA by nine weeks and no fluorescence on MLiX, indicating low bacterial load.

CONCLUSION

This small pilot study indicates that patients with longstanding DFUs may respond to a porcine peritoneal-derived CTP. In this study, the CTP appears to have inhibited bacterial growth in the wound; however, further research is needed.

Evaluation of the combination of a biofilm-disrupting agent and negative pressure wound therapy: a case series

OBJECTIVE

Approximately three million people in the US have hard-to-heal pressure ulcers (PUs), including 10% of hospitalised patients. Healing depends on ulcer stage and patient comorbidities. Despite advances in nutrition and wound care, PUs can take months or years to reach complete closure. To date, clinical studies have focused on single modality therapy. However, there is no one therapy that can address all of the deficits in these complex, hard-to-heal wounds. A commonly used treatment for PUs, negative pressure wound therapy (NPWT), has demonstrated improved healing in Stage 3 and 4 PUs. NPWT entails applying suction to a porous sponge fitted into the wound cavity and sealed with an occlusive dressing. Negative pressure facilitates wound healing by removing wound fluid containing harmful proteases, stimulating the formation of granulation tissue and promoting wound contracture. However, it does not affect biofilm formation. We hypothesised that adding an antibiofilm agent might increase the effectiveness of NPWT in recalcitrant PUs.

METHOD

A prospective case series was conducted in outpatient wound care centres and a skilled nursing facility to examine the combination of a biofilm-disrupting antimicrobial agent (Blast-X, Next Science, US) in combination with NPWT (VAC, 3M, US) in healing and reducing bacterial burden in treatment-resistant pressure ulcers. Patients consented to application of the antibiofilm agent and NPWT three times per week for four weeks. The wounds were measured, imaged for bacteria and tested for host and bacterial protease activity weekly.

RESULTS

Of the 10 patients, four dropped out of the study before the end of the four weeks. Of the remaining six, four patients experienced a reduction in wound surface area and volume, reduced protease activity and lower bacterial levels.

CONCLUSION

The results of this study showed that multimodal therapy, including NPWT and biofilm disruption, may restart the healing of stagnant treatment-resistant PUs.

Diagnostics for Wound Infections

Significance: Infections can significantly delay the healing process in chronic wounds, placing an enormous economic burden on health care resources. Identification of infection biomarkers and imaging modalities to observe and quantify them has seen progress over the years. Recent Advances: Traditionally, clinicians determine the presence of infection through visual observation of wounds and confirm their diagnosis through wound culture. Many laboratory markers, including C-reactive protein, procalcitonin, presepsin, and bacterial protease activity, have been quantified to assist diagnosis of infection. Moreover, imaging modalities like plain radiography, computed tomography, magnetic resonance imaging, ultrasound imaging, spatial frequency domain imaging, thermography, autofluorescence imaging, and biosensors have emerged for real-time wound infection diagnosis and showed their unique advantages in deeper wound infection diagnosis. Critical Issues: While traditional diagnostic approaches provide valuable information, they are time-consuming and depend on clinicians' experiences. There is a need for noninvasive wound infection diagnostics that are highly specific, rapid, and accurate, and do not require extensive training. Future Directions: While innovative diagnostics utilizing various imaging instrumentation are being developed, new biomarkers have been investigated as potential indicators for wound infection. Products may be developed to either qualitatively or quantitatively measure these biomarkers. This review summarizes and compares all available diagnostics for wound infection, including those currently used in clinics and still under development. This review could serve as a valuable resource for clinicians treating wound infections as well as patients and wound care providers who would like to be informed of the recent developments.

Bacterial protease activity as a biomarker to assess the risk of non-healing in chronic wounds: Results from a multicentre randomised controlled clinical trial

Millions worldwide suffer from chronic wounds challenging clinicians and burdening healthcare systems. Bacteria impede wound healing; however, the diagnosis of excessive bacterial burden or infection is elusive. Clinical signs and symptoms of infection are inaccurate and unreliable. This trial evaluated a novel, point-of-care, lateral flow diagnostic designed to detect virulence factors released by the most common bacteria found in chronic wounds. A multicentre prospective cohort clinical trial examined the efficacy of a diagnostic test in detecting bacterial proteases taken from swab samples of chronic venous, arterial, pressure and mixed aetiology chronic wounds. Two hundred and sixty six wounds were included in the analysis of the study. The wounds were tested at the start of the study after which investigators were permitted to use whatever dressings they desired for the next 12 weeks. Healing status at 12 weeks was assessed. The presence of elevated bacterial protease activity decreased the probability of wound healing at 12 weeks. In contrast, a greater proportion of wounds were healed at 12 weeks if they had little or no bacterial protease activity at study start. In addition, the presence of elevated bacterial protease activity increased the time it takes for a wound to heal and increased the risk that a wound would not heal, when compared to the absence of bacterial protease activity. The results of this clinical trial indicate that bacterial protease activity, as detected by this novel diagnostic test, is a valid clinical marker for chronicity in wounds. The diagnostic test offers a tool for clinicians to detect clinically significant bacteria in real time and manage bacteria load before the clinical signs and symptoms of infection are evident.

Functional Imaging in Wounds: Imaging Modalities of Today and Tomorrow

Wound care is a multidisciplinary field with significant economic burden to our healthcare system. Not only does wound care cost the US healthcare system $20 billion annually, but wounds also remarkably impact the quality of life of patients; wounds pose significant risk of mortality, as the five-year mortality rate for diabetic foot ulcers (DFUs) and ischemic ulcers is notably higher compared to commonly encountered cancers such as breast and prostate. Although it is important to measure how wounds may or may not be improving over time, the only relative "marker" for this is wound area measurement-area measurements can help providers determine if a wound is on a healing or non-healing trajectory. Because wound area measurements are currently the only readily available "gold standard" for predicting healing outcomes, there is a pressing need to understand how other relative biomarkers may play a role in wound healing. Currently, wound care centers across the nation employ various techniques to obtain wound area measurements; length and width of a wound can be measured with a ruler, but this carries a high amount of inter- and intrapersonal error as well as uncertainty. Acetate tracings could be used to limit the amount of error but do not account for depth, thereby making them inaccurate. Here, we discuss current imaging modalities and how they can serve to accurately measure wound size and serve as useful adjuncts in wound assessment. Moreover, new imaging modalities are also discussed and how up-and-coming technologies can provide important information on "biomarkers" for wound healing.

Bacterial Autofluorescence Digital Imaging Guides Treatment in Stage 4 Pelvic Pressure Injuries: A Preliminary Case Series

Pelvic pressure injuries in long-term care facilities are at high risk for undetected infection and complications from bacterial contamination and stalling of wound healing. Contemporary wound healing methods must address this problem with mechanical debridement, wound irrigation, and balanced dressings that reduce bacterial burden to enable the normal healing process. This study evaluated the impact of bacterial autofluorescence imaging to indicate wound bacterial contamination and guide treatment for severe stage 4 pelvic pressure injuries. A handheld digital imaging system was used to perform bacterial autofluorescence imaging in darkness on five elderly, high-risk, long-term care patients with advanced stage 4 pelvic pressure injuries who were being treated for significant bacterial contamination. The prescient findings of bacterial autofluorescence imaging instigated treatment strategies and enabled close monitoring of the treatment efficacy to ameliorate the bacterial contamination. Wound sepsis recurrence, adequate wound cleansing, and diagnosis of underlying periprosthetic total joint infection were confirmed with autofluorescence imaging showing regions of high bacterial load. By providing objective information at the point of care, imaging improved understanding of the bacterial infections and guided treatment strategies.

Use of a bacterial fluorescence imaging system to target wound debridement and accelerate healing: a pilot study

OBJECTIVE

Optimal wound-bed preparation consists of regular debridement to remove devitalised tissues, reduce bacterial load, and to establish an environment that promotes healing. However, lack of diagnostic information at point-of-care limits effectiveness of debridement.

METHOD

This observational case series investigated use of point-of-care fluorescence imaging to detect bacteria (loads >10⁴CFU/g) and guide wound bed preparation. Lower extremity hard-to-heal wounds were imaged over a 12-week period for bacterial fluorescence and wound area.

RESULTS

A total of 11 wounds were included in the study. Bacterial fluorescence was present in 10 wounds and persisted, on average, for 3.7 weeks over the course of the study. The presence of red or cyan fluorescent signatures from bacteria correlated with an average increase in wound area of 6.5% per week, indicating stalled or delayed wound healing. Fluorescence imaging information assisted in determining the location and extent of wound debridement, and the selection of dressings and/or antimicrobials. Elimination of bacterial fluorescence signature with targeted debridement and other treatments correlated with an average reduction in wound area of 27.7% per week (p<0.05), indicative of a healing trajectory.

CONCLUSION

These results demonstrate that use of fluorescence imaging as part of routine wound care enhances assessment and treatment selection, thus facilitating improved wound healing.

Diagnostic Accuracy of Point-of-Care Fluorescence Imaging for the Detection of Bacterial Burden in Wounds: Results from the 350-Patient Fluorescence Imaging Assessment and Guidance Trial

Objective: High bacterial load contributes to chronicity of wounds and is diagnosed based on assessment of clinical signs and symptoms (CSS) of infection, but these characteristics are poor predictors of bacterial burden. Point-of-care fluorescence imaging (FL) MolecuLight i:X can improve identification of wounds with high bacterial burden (>10⁴ colony-forming unit [CFU]/g). FL detects bacteria, whether planktonic or in biofilm, but does not distinguish between the two. In this study, diagnostic accuracy of FL was compared to CSS during routine wound assessment. Postassessment, clinicians were surveyed to assess impact of FL on treatment plan. Approach: A prospective multicenter controlled study was conducted by 20 study clinicians from 14 outpatient advanced wound care centers across the United States. Wounds underwent assessment for CSS followed by FL. Biopsies were collected to confirm total bacterial load. Three hundred fifty patients completed the study (138 diabetic foot ulcers, 106 venous leg ulcers, 60 surgical sites, 22 pressure ulcers, and 24 others). Results: Around 287/350 wounds (82%) had bacterial loads >10⁴ CFU/g, and CSS missed detection of 85% of these wounds. FL significantly increased detection of bacteria (>10⁴ CFU/g) by fourfold, and this was consistent across wound types (p < 0.001). Specificity of CSS+FL remained comparably high to CSS (p = 1.0). FL information modified treatment plans (69% of wounds), influenced wound bed preparation (85%), and improved overall patient care (90%) as reported by study clinicians. Innovation: This novel noncontact, handheld FL device provides immediate, objective information on presence, location, and load of bacteria at point of care. Conclusion: Use of FL facilitates adherence to clinical guidelines recommending prompt detection and removal of bacterial burden to reduce wound infection and facilitate healing.

Rapid Diagnosis of Pseudomonas aeruginosa in Wounds with Point-Of-Care Fluorescence Imaing

Pseudomonas aeruginosa (PA) is a common bacterial pathogen in chronic wounds known for its propensity to form biofilms and evade conventional treatment methods. Early detection of PA in wounds is critical to the mitigation of more severe wound outcomes. Point-of-care bacterial fluorescence imaging illuminates wounds with safe, violet light, triggering the production of cyan fluorescence from PA. A prospective single blind clinical study was conducted to determine the positive predictive value (PPV) of cyan fluorescence for the detection of PA in wounds. Bacterial fluorescence using the MolecuLight i:X imaging device revealed cyan fluorescence signal in 28 chronic wounds, including venous leg ulcers, surgical wounds, diabetic foot ulcers and other wound types. To correlate the cyan signal to the presence of PA, wound regions positive for cyan fluorescence were sampled via curettage. A semi-quantitative culture analysis of curettage samples confirmed the presence of PA in 26/28 wounds, resulting in a PPV of 92.9%. The bacterial load of PA from cyan-positive regions ranged from light to heavy. Less than 20% of wounds that were positive for PA exhibited the classic symptoms of PA infection. These findings suggest that cyan detected on fluorescence images can be used to reliably predict bacteria, specifically PA at the point-of-care.

Diagnosing Burn Wounds Infection: The Practice Gap & Advances with MolecuLight Bacterial Imaging

Burn injuries constitute a critical economic burden on healthcare infrastructures worldwide. They are often associated with high mortality rates due to severe complications. Infection is the most common complication, highlighting the importance of prompt and precise diagnosis in order to prevent detrimental consequences and to optimize patient outcomes. Here we examine the current standard of care for diagnosing infection in both burn and chronic wounds followed by an investigation into the research surrounding a relatively new technique for bacterial detection, fluorescence imaging. With five years of published research on bacterial fluorescence imaging (MolecuLight i:X device), we have summarized and analysed the validity of the procedure and compared it to the current standard of care; clinical assessment and microbiological analysis. We highlight the benefits that could be obtained through the use of this technology as well as the limitations and the feasibility of incorporating this novel procedure into the standard of care.

Incorporating Point-of-Care Bacterial Fluorescence into a Wound Clinic Antimicrobial Stewardship Program

Background: In 2014 the World Health Organization (WHO) warned of an emerging world-wide crisis of antibiotic-resistant microorganisms. In response, government and professional organizations recommended that health care systems adopt antimicrobial stewardship programs (ASPs). In the United States, the Centers for Medicare Services (CMS) mandated antimicrobial stewardship in the hospital inpatient setting. Effective 1 January 2020, the Joint Commission required ambulatory centers that prescribe antibiotics, such as wound centers, to institute an ASP. Chronic wounds often remain open for months, during which time patients may receive multiple courses of antibiotics and numerous antimicrobial topical treatments. The wound clinician plays an integral role in reducing antimicrobial resistance in the outpatient setting: antibiotics prescribed for skin and soft tissue infections are among the most common in an outpatient setting. One of the most challenging aspects of antimicrobial stewardship in treating chronic wounds is the inaccuracy of bacterial and infection diagnosis. Methods: Joint Commission lists five elements of performance (EP): (1) identifying an antimicrobial stewardship leader; (2) establishing an annual antimicrobial stewardship goal; (3) implementing evidence-based practice guidelines related to the antimicrobial stewardship goal; (4) providing clinical staff with educational resources related to the antimicrobial stewardship goal; and (5) collecting, analyzing, and reporting data related to the antimicrobial stewardship goal. This article focuses on choosing and implementing an evidence-based ASP goal for 2020. Discussion: Clinical trials have demonstrated the ability of fluorescence imaging (MLiX) to detect clinically significant levels of bacteria in chronic wounds. Combined with clinical examination of signs and symptoms of infection, the MLiX procedure improves the clinician’s ability to diagnose infection and can guide antimicrobial use. In order to satisfy the elements of performance, the MLiX procedure was incorporated into the annual ASP goal for several wound care centers. Clinicians were educated on the fluorescence imaging device and guidelines were instituted. Collection of antimicrobial utilization data is underway.

Routine Fluorescence Imaging to Detect Wound Bacteria Reduces Antibiotic Use and Antimicrobial Dressing Expenditure While Improving Healing Rates: Retrospective Analysis of 229 Foot Ulcers

Foot ulcers and their bacterial burden produce a significant strain on the National Healthcare System (NHS). Subjectivity of wound infection assessment makes appropriate dressing selection challenging. To aid point-of-care detection of bacterial burden, a fluorescence imaging device (MolecuLight i:X) was introduced to the Whipps Cross Hospital Podiatry clinic. This retrospective pre/post-analysis evaluated how implementation of fluorescence imaging impacted (1) antimicrobial dressings and antibiotics use and (2) wound healing rates. Over a 2-year period 229 lower extremity wounds were treated. Wound-related outcomes and antimicrobial dressing costs were quantified over 1-year before (2018/2019) and after (2019/2020) incorporating fluorescence imaging into routine practice. The period of fluorescence imaging saw a 27% increase in the number of wounds seen, yet annual antimicrobial dressing expenditure decreased by 33%. Implementation of fluorescence imaging was also associated with a 49% decrease in prescription of antimicrobial dressings, a 33% decrease in antibiotic prescriptions, and a 23% increase in wound healing rates within 12-weeks (48% vs. 39%), likely due to earlier bacterial detection and improved wound hygiene. This increased healing rate is projected to decrease annual wound costs by 10% (£762 per patient). Routine bacterial imaging appears to diminish clinical and economic burden to patients and the NHS.

Prospective clinical study on the efficacy of bacterial removal with mechanical debridement in and around chronic leg ulcers assessed with fluorescence imaging

Bacterial colonisation in wounds delays healing, mandating regular bacterial removal through cleaning and debridement. Real-time monitoring of the efficacy of mechanical debridement has recently become possible through fluorescence imaging. Red fluorescence, endogenously produced during bacterial metabolism, indicates regions contaminated with live bacteria (>104 CFU/g). In this prospective study, conventional and fluorescence photos were taken of 25 venous leg ulcers before and after mechanical debridement, without use of antiseptics. Images were digitally segmented into wound bed and the periwound regions (up to 1.5 cm outside bed) and pixel intensity of red fluorescence evaluated to compute bacterial area. Pre-debridement, bacterial fluorescence comprised 10.4% of wound beds and larger percentages of the periwound area (~25%). Average bacterial reduction observed in the wound bed after a single mechanical debridement was 99.4% (p<0.001), yet periwound bacterial reduction was only 64.3%. On average, across bed and periwound, a single mechanical debridement left behind 29% of bacterial fluorescence positive tissue regions. Our results show the substantial effect that safe, inexpensive, mechanical debridement can have on bacterial load of venous ulcers without antiseptic use. Fluorescence imaging can localise bacterial colonised areas and showed persistent periwound bacteria post-debridement. Fluorescence-targeted debridement can be used quickly and easily in daily practice.

A shell-less hen's egg test as infection model to determine the biocompatibility and antimicrobial efficacy of drugs and drug formulations against Pseudomonas aeruginosa

A shell-less hen's egg based infection test with Pseudomonas aeruginosa was established to investigate the antimicrobial efficacy of drugs and drug formulations close to the in vivo situation. The test system using preincubated fertilized chicken eggs transferred in petri dishes was optimized with respect to the controlled local application of liquid materials and bacteria as well as the bacterial cultivation conditions. The applicability of the ex ovo infection model was confirmed with antimicrobial susceptibility tests using tobramycin, ciprofloxacin and meropenem. The validity of the ex ovo data was demonstrated by correlation with in vitro data of the CellTiter®-Blue and the microplate laser nephelometry assay. Real-time imaging of the progress of infection and the efficacy of the treatment could be realized by the MolecuLight i:X™ technique. Furthermore, in a proof-of-concept efficacy, biocompatibility and even the presence of irritants were determined side-by-side using commercial ophthalmics. In conclusion, this egg based infection model could bridge the gap between in vitro and in vivo models for the evaluation of antimicrobial susceptibility to reduce animal tests according to the 3R concept.

Use of a bacterial fluorescence imaging device: wound measurement, bacterial detection and targeted debridement

OBJECTIVE

Diagnostics which provide objective information to facilitate evidence-based treatment decisions could improve the chance of wound healing. Accurate wound measurements, objective bacterial assessment, and the regular, consistent tracking of these parameters are important aspects of wound care. This study aimed to assess the accuracy, clinical incorporation and documentation capabilities of a handheld bacterial fluorescence imaging device (MolecuLight i:X).

METHOD

Benchtop wound models with known dimensions and clinical wound images were repeatedly measured by trained clinicians to quantify accuracy and intra/inter-user coefficients of variation (COV) of the imaging device measurement software. In a clinical trial of 50 wounds, wound dimensions were digitally measured and fluorescence images were acquired to assess for the presence of bacteria at moderate-to-heavy loads. Finally, fluorescence imaging was implemented into the routine assessment of 22 routine diabetic foot ulcers (DFU) to determine appropriate debridement level and location based on bacterial fluorescence signals.

RESULTS

Wound measurement accuracy was >95% (COV <3%). In the clinical trial of 50 wounds, 72% of study wounds demonstrated positive bacterial fluorescence signals. Levine sampling of wounds was found to under-report bacterial loads relative to fluorescence-guided curettage samples. Furthermore, fluorescence documentation of bacterial presence and location(s) resulted in more aggressive, fluorescence-targeted debridement in 17/20 DFUs after standard of care debridement failed to eliminate bacterial fluorescence in 100% of DFU debridements.

CONCLUSION

The bacterial fluorescence imaging device can be readily implemented for objective, evidenced-based wound assessment and documentation at the bedside. Bedside localisation of regions with moderate-to-heavy bacterial loads facilitated improved sampling, debridement targeting and improved wound bed preparation.

In vitro detection of porphyrin-producing wound bacteria with real-time fluorescence imaging

Aim: Fluorescence imaging can visualize polymicrobial populations in chronic and acute wounds based on porphyrin fluorescence. We investigated the fluorescent properties of specific wound pathogens and the fluorescence detected from bacteria in biofilm. Methods: Utilizing Remel Porphyrin Test Agar, 32 bacterial and four yeast species were examined for red fluorescence under 405 nm violet light illumination. Polymicrobial biofilms, supplemented with δ-aminolevulinic acid, were investigated similarly. Results: A total of 28/32 bacteria, 1/4 yeast species and polymicrobial biofilms produced red fluorescence, in agreement with their known porphyrin production abilities. Conclusion: These results identify common wound pathogens capable of producing porphyrin-specific fluorescence and support clinical observations using fluorescence imaging to detect pathogenic bacteria in chronic wounds.