Bacterial burden is one of the most consequential variables in a diabetic foot ulcer, and one of the hardest to see. Wounds carrying high bacterial loads heal more slowly and progress to clinical infection more often, yet the bacteria themselves are invisible under white light. Clinicians have long relied on classic signs and symptoms — erythema, warmth, purulence, odour, pain — to decide which wounds are heavily colonised. In people with diabetes, those signs are frequently blunted by neuropathy, ischaemia, and impaired inflammatory response. Point-of-care bacterial fluorescence imaging was developed to address that blind spot.
How Fluorescence Imaging Detects Bacteria at the Bedside
Handheld fluorescence imaging devices illuminate the wound bed with violet light at approximately 405 nm. Many clinically relevant bacterial species produce endogenous porphyrins, which emit a red fluorescence signal under that wavelength. The result is a real-time image showing where bacteria are concentrated — in the wound bed, at the margins, or in surrounding periwound skin — without contact, contrast agents, or waiting for culture results.
The first-in-human work was published by DaCosta and colleagues in PLoS One in 2015, studying 40 patients with chronic wounds, the majority of them diabetic foot ulcers. That Phase I trial established that autofluorescence imaging could be performed safely in seconds and used to direct where a swab or biopsy should be taken.
Diagnostic Accuracy: What the Trials Found
The question that followed was whether a red fluorescence signal genuinely corresponds to meaningful bacterial load. Rennie and colleagues addressed this in the Journal of Wound Care in 2017, imaging 60 chronic lower limb wounds and then sampling fluorescent regions under blinded conditions. Quantitative PCR and semi-quantitative culture of those regions yielded a positive predictive value of 100%, with bacterial loads at or above 104 CFU/g. Nine distinct pathogenic species were identified, with Staphylococcus aureus the most common.
The largest study to date is the Fluorescence Imaging Assessment and Guidance (FLAAG) trial, reported by Le and colleagues in Advances in Wound Care in 2020. Across 14 outpatient wound centres, 350 patients — including 138 with diabetic foot ulcers — underwent clinical assessment followed by fluorescence imaging, with biopsy confirmation of bacterial load. Eighty-two percent of wounds carried loads above 104 CFU/g, and clinical signs and symptoms alone missed 85% of them. Adding fluorescence imaging increased detection roughly fourfold without a meaningful loss of specificity.
A smaller pilot by Serena and colleagues in 2019 pointed the same direction, with sensitivity for identifying moderate-to-heavy bacterial loads rising from 22% with clinical assessment alone to 72% when fluorescence imaging was added.
Does It Change Management?
Detecting something only matters if it alters care. In the FLAAG trial, clinicians reported that fluorescence findings modified the treatment plan in 69% of wounds and influenced wound bed preparation in 85%. The changes most often described were targeted cleansing, image-guided debridement, and adjusted dressing selection.
Antimicrobial Stewardship
One of the more interesting signals concerns antibiotic use. Systemic antibiotics are heavily over-prescribed in chronic wound care, and Caputo and colleagues reviewed this problem in Diagnostics in 2022, noting that between 53% and 71% of patients receive at least one course per chronic wound. A retrospective pre/post analysis of 229 foot ulcers at a UK podiatry service, published by Price in 2020, found that introducing routine fluorescence imaging was associated with a 49% reduction in antimicrobial dressing prescriptions, a 33% reduction in antibiotic prescriptions, and an increase in 12-week healing rates from 39% to 48% — despite a 27% rise in the number of wounds treated.
Important Limitations
The evidence base has real constraints that deserve equal emphasis. Most supportive data come from diagnostic accuracy studies, observational cohorts, and before-and-after service evaluations rather than randomised trials with healing as the primary endpoint. The Price analysis, for instance, is retrospective and uncontrolled.
Fluorescence imaging also detects bacteria whether planktonic or within biofilm, but does not distinguish between the two — a clinically important gap. Wu and colleagues, publishing in Biomedicines in 2022, compared fluorescence imaging against a modified wound blotting technique in 53 patients and found that fluorescence showed only a weak association with wound culture and no significant association with 90-day healing outcomes, while wound blotting performed better on both counts. Conversely, Derwin and colleagues reported in 2023 that wounds in which bacterial fluorescence persisted showed poorer wound area reduction, suggesting the signal does carry prognostic information.
Consensus guidance published by Oropallo and colleagues in 2021, developed through a Delphi process with 32 wound experts, set out competencies and workflow recommendations for the technology. It is worth noting that the favourable outcome figures in that document reflect clinician-reported experience rather than measured trial endpoints. Meanwhile, the 2023 IWGDF/IDSA guidelines continue to define diabetes-related foot infection clinically, with adjunctive technologies positioned as supplementary to — not a replacement for — structured clinical assessment and appropriate microbiological sampling.
Clinical Summary
Fluorescence imaging reliably identifies areas of elevated bacterial load that clinical examination misses, with high positive predictive value and a consistent fourfold improvement in detection across wound types. Its clearest present value lies in guiding where to sample and where to debride, and in supporting more disciplined antimicrobial decision-making. What remains unproven is whether routine use translates into better healing and amputation outcomes in randomised trials, and how reliably the signal reflects biofilm. For now, the technology is best understood as an adjunct that sharpens clinical judgement about bacterial burden, rather than a diagnostic test for infection in its own right.
References
DaCosta RS, Kulbatski I, Lindvere-Teene L, et al. Point-of-care autofluorescence imaging for real-time sampling and treatment guidance of bioburden in chronic wounds: first-in-human results. PLoS One. 2015;10(3):e0116623. doi:10.1371/journal.pone.0116623
Rennie MY, Lindvere-Teene L, Tapang K, Linden R. Point-of-care fluorescence imaging predicts the presence of pathogenic bacteria in wounds: a clinical study. Journal of Wound Care. 2017;26(8):452–460. doi:10.12968/jowc.2017.26.8.452
Serena TE, Harrell K, Serena L, Yaakov RA. Real-time bacterial fluorescence imaging accurately identifies wounds with moderate-to-heavy bacterial burden. Journal of Wound Care. 2019;28(6):346–357. doi:10.12968/jowc.2019.28.6.346
Le L, Baer M, Briggs P, et al. 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. Advances in Wound Care. 2021;10(3):123–136. doi:10.1089/wound.2020.1272
Price N. Routine fluorescence imaging to detect wound bacteria reduces antibiotic use and antimicrobial dressing expenditure while improving healing rates: retrospective analysis of 229 foot ulcers. Diagnostics. 2020;10(11):927. doi:10.3390/diagnostics10110927
Oropallo AR, Andersen C, Abdo R, et al. Guidelines for point-of-care fluorescence imaging for detection of wound bacterial burden based on Delphi consensus. Diagnostics. 2021;11(7):1219. doi:10.3390/diagnostics11071219
Caputo WJ, Monterosa P, Beggs D. Antibiotic misuse in wound care: can bacterial localization through fluorescence imaging help? Diagnostics. 2022;12(12):3207. doi:10.3390/diagnostics12123207
Wu YF, Lin YC, Yang HW, Cheng NC, Cheng CM. Point-of-care wound blotting with Alcian blue grading versus fluorescence imaging for biofilm detection and predicting 90-day healing outcomes. Biomedicines. 2022;10(5):1200. doi:10.3390/biomedicines10051200
Derwin R, Patton D, Strapp H, Moore Z. Integrating point-of-care bacterial fluorescence imaging-guided care with continued wound measurement for enhanced wound area reduction monitoring. Diagnostics. 2024;14(1):2. doi:10.3390/diagnostics14010002
Senneville É, Albalawi Z, van Asten SA, et al. IWGDF/IDSA guidelines on the diagnosis and treatment of diabetes-related foot infections (IWGDF/IDSA 2023). Diabetes/Metabolism Research and Reviews. 2024;40(3):e3687. doi:10.1002/dmrr.3687
Comments
