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

Abstract

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 (10 4 -10 9 CFU/g). Quantitative tissue culture confirmed the total loads. Bacterial presence was confirmed in 131/138 ulcers. Of these, 93.9% had loads >10 4 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 10 4 -10 9 (P < .0001), peaking at 92.6% for >10 8 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.

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

“…Microbiology was not acquired to confirm accuracy of FL‐imaging and therefore this study focuses on treatment plan changes rather than reporting any measures of accuracy. For validation studies on diagnostic accuracy with use of gold standard tissue samples, the readers are referred to the following references 3, 5, 22, 36, 37. Data collection was limited to the planned treatments on a single day, such that some treatment plans and the full scope of management may be underrepresented (eg, NPWT and CTP placement).…”

“…Complicating matters, chronic wound patients usually have underlying conditions that frequently attenuate signs and symptoms of infection and stall the healing process. 1,2 Over 80% of chronic wounds with high bacterial loads (>10 4 CFU/g) fail to mount symptoms of infection, [3][4][5] and this can lead to clinical uncertainty, delayed or erroneous treatment decisions, and missed opportunities to reduce infection risk. In turn, this failure in diagnosis will increase both the risk of morbidity and mortality, and complication, resulting in delayed wound healing, longer hospital stays, and increased resource consumption (eg, costly ICU stays and disability).…”

“…Armstrong et al recently found that symptoms of infection are largely absent in diabetic foot ulcers, and do not correlate to, or increase proportionately with, bacterial loads up to 10 9 CFU/g. 5 Without objective, realtime diagnostics, standard of care (SoC) hygiene and debridement can focus on the wrong areas of interest or leave behind bacterial loads, [18][19][20][21] thereby risking the onset or exacerbation of an infection at the wound bed and potentially delaying/stalling wound healing.…”

Diabetic Foot Ulcer Imaging: An Overview and Future Directions

“…These multi-modal devices should be bedside, portable, and easy to use and provide objective physiological assessments to complement subjective clinician expertise. 84 Some of the more advanced parameters that provide an insight into wound-healing status are temperature, bacterial load, tissue oxygenation, and perfusion (as shown in Figure 1). 85,86 A multi-modal imaging device that measures several physiological parameters across an entire wound region should be our focus as we move forward to improve the quality of wound care management in DFUs.…”

“…These multi-modal devices should be bedside, portable, and easy to use and provide objective physiological assessments to complement subjective clinician expertise. 84…”