Improved detection of clinically relevant wound bacteria using autofluorescence image‐guided sampling in diabetic foot ulcers

Abstract

Clinical wound assessment involves microbiological swabbing of wounds to identify and quantify bacterial species, and to determine microbial susceptibility to antibiotics. The Levine swabbing technique may be suboptimal because it samples only the wound bed, missing other diagnostically relevant areas of the wound, which may contain clinically significant bacteria. Thus, there is a clinical need to improve the reliability of microbiological wound sampling. To address this, a handheld portable autofluorescence (AF) imaging device that detects bacteria in real time, without contrast agents, was developed. Here, we report the results of a clinical study evaluating the use of real-time AF imaging to visualise bacteria in and around the wound bed and to guide swabbing during the clinical assessment of diabetic foot ulcers, compared with the Levine technique. We investigated 33 diabetic foot ulcers (n = 31 patients) and found that AF imaging more accurately identified the presence of moderate and/or heavy bacterial load compared with the Levine technique (accuracy 78% versus 52%, P = 0·048; adjusted diagnostic odds ratio 7·67, P < 0·00022 versus 3·07, P = 0·066) and maximised the effectiveness of bacterial load sampling, with no significant impact on clinical workflow. AF imaging may help clinicians better identify the wound areas with clinically significant bacteria, and maximise sampling of treatment-relevant pathogens.

Diagnosis of infection in the foot in diabetes: a systematic review

“…As infection differs from contamination in that it represents invasion of the host tissues, samples for culture of tissues are likely to provide more accurate data than superficial swabs. In the study by Ottolino‐Perry et al, real‐time autofluorescence was found to be useful for both assessing the “wound bioburden” and improving the sensitivity of swab cultures . In addition to the fact that current guidelines recommend against using swabs to collect wound specimens for microbiological assessments and the results of the recent Concordance in Diabetic Foot Ulcer Infection (CODIFI) study demonstrate the greater accuracy of tissue compared with swab specimens, the findings of the Ottolino‐Perry et al's study are mitigated by the fact that there is no widely accepted or validated definition of “wound bioburden.” The detection of pathogenic virulence genes is an interesting avenue of research that may help differentiate colonizers from pathogens, but studies to date have only included monomicrobial Staphylococcus aureus DFIs .…”

“…Ottolino-Perry et al, 64 real-time autofluorescence was found to be useful for both assessing the "wound bioburden" and improving the sensitivity of swab cultures. 64 In addition to the fact that current guidelines recommend against using swabs to collect wound specimens for microbiological assessments 8,9 The suspicion of osteomyelitis complicating an infected DFU is based on assessing clinical findings (eg, deep ulcer over a bony prominence, visible exposed bone, positive PTB test, and "sausage toe" appearance), laboratory tests (eg, serum biomarkers, tissue histology, and microbiology), and imaging studies (eg, cortical disruption, sequestrum, involucrum, marrow oedema, or tracer uptake) for bone abnormalities. 8,9 In one study, the combination of two relatively simple, widely available, and inexpensive tests-the PTB test and plain Xrays-was quite accurate with a reported sensitivity/specificity of 97%/93% in a population of high-risk patients and provided better results for diagnosing osteomyelitis than when the tests were considered separately.…”

Visualisierung von Bakterien auf Verbrennungswunden und Spalthauttransplantaten nach der MEEK/MESH-Technik – Eine Pilotstudie mit ersten Erfahrungen der klinischen Wundbeurteilung durch Autofluoreszenz

“…Durch die Methodik der Autofluoreszenz konnte vergleichsweise akkurater das Vorhandensein von bakterieller Besiedlung definiert werden [22]. Durch die AF-Darstellung könnte frühzeitig die Indikation zur operativen Therapie gestellt werden.…”

“…Ein gezieltes, frühes Débridement und eine gezielte Wundreinigung sind dadurch möglich [20]. [22]. Eine grüne Fluoreszenz wird bei Erregern wie Pseudomonas aeruginosa (PA), durch eine Emission von 405 nm hervorgerufen.…”

Appropriate use of dressings containing nanocrystalline silver to support antimicrobial stewardship in wounds

“…Technologies that supplement clinician judgement, particularly from a microbial load perspective, will aid more targeted approach to wound infection. New guidance devices such as Moleculight i:X ™, (Moleculight Inc., Toronto, Canada), which not only measure wound surface area but can also detect fluorescent bacteria above a threshold (>10 4 cfu/g), may aid more targeted sampling and support informed treatment decisions . Moreover, this is an important bridge to drive infection diagnostics, highlighted by the UK AMR strategy and the O'Neill report as one of the key focus areas to tackle AMR.…”