Point-of-care fluorescence imaging reveals extent of bacterial load in diabetic foot ulcers #ActAgainstAmputation #Diagnostics #Theragnostics #DiabeticFoot

This study from my colleagues Tom Serena and Mike Edmonds and me.

Long ago, CLI was adopted for “Critical Limb Ischemia”– as if there was some sort of critical point over which someone descended into ischemia. We know that this is not how it works for our patients with diabetes. This is chronic. These patients don’t show up with an acute cold limb. This developed into what we now call chronic limb threatening ischemia- or CLTI.

We think that the same thing might be true for what was once called “critical colonization”. It now might be called “chronic inhibitory bacterial load” or CIBL.

Bottom line: just as we have chronic limb threatening ischemia (CLTI), we likely have chronic inhibitory bacterial load (CIBL). If it is inhibiting healing and inflammation on one end or pushing over the edge toward a frank and obvious infection on the other, it is very likely important but presently not visible. 

The good thing now is that this can be detected, and we can likely knock it back with consistent debridement and maybe ultimately effective antimicrobials.

Key findings of the study include:

  • Less than 12% of diabetic ulcers exhibited clinical symptoms of bacteria and infection, despite the presence of loads >10^4 CFU/g in over 90% (average bacterial load of 108 CFU/g). Even as bacterial loads increased up to >10^8 CFU/g, detection of clinical signs and symptoms of infection did not increase.
  • Bacterial loads >10^4 CFU/g can preclude wounds from healing through various biological mechanisms and are contraindicated for many advanced therapies. This study showed that the occurrence of delayed healing increased alongside bacterial load.
  • Fluorescence imaging using MolecuLight increased sensitivity for the detection of CIBL across loads 10^4–10^9 (p 10^8 CFU/g. This was 8.3 times superior to standard clinical assessment alone. 
  • Fluorescence imaging further showed that 84.2% of ulcers contained high loads in the periwound region, an area that is frequently overlooked.


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.

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