Autofluorescence reveals bacteria in wounds for infection prevention

28 Aug 2024

USC survey points to reduction in chronic wound complications and improved patient outcomes.

Healing of chronic wounds requires sterile conditions and avoidance of infections. But methods for detecting the "bioburden," or quantity and types of bacteria present, are imperfect.

Semiquantitative analysis of swabs and biopsy samples, microbiological sampling, or molecular diagnostics can be used, but these tools are not always accessible or useful to clinics because of their high cost or insufficient speed.

A project at the University of Southern California's Keck Medical Center has now surveyed a possible alternative technique, based on autofluoresence (AF). Its report will be published in Advances in Wound Care.

"Over 6.5 million Americans experience chronic wounds; wounds that do not heal after a few months," commented the USC investigators, led by David Armstrong. "Almost all such wounds contain bacteria, which if not detected and removed can lead to severe infection and resulting complications, including amputation if a limb is involved."

One particular problem area is diabetic foot ulcers, where approximately 20 percent of those who develop such an ulcer will then require a lower-extremity amputation, according to the American Diabetes Association.

Earlier in 2024 the Israeli developer IR-MED described a spectroscopic device named PressureSafe aimed at the early detection of these diabetic foot ulcers. In PressureSafe, infra-red reflectance spectroscopy detects the differences in absorption and reflection of diseased tissues compared to healthy tissues, evaluating light intensity and patterns reflected from the different layers beneath the skin's surface.

The Keck Medical Center survey examined the use of a different principle, one exploiting the fact that 87 percent of bacteria that frequently appear in chronic wounds have fluorophores that fluoresce under violet light as red or cyan, depending on the type of fluorophore.

Use during surgical tissue removal

This variation in autofluorescence color could allow physicians to immediately determine how much and which types of bacteria are in the wound, according to the researchers.

Keck Medicine reviewed the literature of 25 studies examining the effectiveness of AF imaging in treating diabetic patients with foot ulcers, which showed that the technique can identify bacteria in wounds in approximately 9 out of 10 patients that traditional clinical assessments miss.

Those traditional assessments of bacteria involve physicians "debriding" wounds, removing tissue then sent for lab analysis to identify specific types of bacteria present and determine the best treatment protocol based on those findings. This process can take days, during which time an infection can set in, said Armstrong.

With AF imaging physicians are able to make medical decisions during the wound debridement, rather than waiting for lab results. Another benefit to the technology is that if bacteria is caught early, the patient may avoid being prescribed antibiotics, which in wound care can be prolonged, thus avoiding possible antibiotic resistance.

The study noted in particular the REVEAL device from developer Designs for Vision, an AF imaging instrument developed for dentistry and worn intraoperatively by the physician on top of a pair of glasses. The benefits of this arrangement include not requiring specific lighting conditions and not having to interpret the results using a handheld camera, allowing the device to be used during active surgical tissue removal.

"We're hopeful this new technology can help surgeons improve their accuracy when pinpointing and consequently removing bacteria from wounds and therefore improve patient outcomes, particularly for those with diabetic foot wounds," said David Armstrong. "The early detection and removal of bacteria from a wound is vital to preventing avoidable amputations."