High alert: Blue light means the end of many infections. Image: Thinkstock
Reading It seems almost too simple to be true: US researchers have discovered that simple blue light can completely kill bacteria in infected burns - without damaging the injured skin. Even otherwise, the scientists could not observe a side effect of the treatment in mice. If the method proves to work well in humans, there would finally be a new, gentle way to treat skin infections - even if they are caused by antibiotic-resistant bacteria. Lighting up bacteria is not a completely new idea. There have already been tests with UV radiation of different wavelengths and different intensities, which should kill the microbes. Although this works, the high-energy radiation often causes severe damage to the treated areas of the skin. A potential alternative would be the so-called photodynamic therapy. She has been working in the clinic for a long time, for example against certain types of skin cancer or against vascular proliferations in the eye. In this case, the tissue to be treated is prepared before irradiation with a substance which decomposes through the light and thereby forms the actual active ingredient. He then kills the unwanted cells.

No additional active ingredient needed

However, to treat infections, the photosensitive material would have to be modified so that it penetrates exclusively into the microbial cells - and that is precisely what has not been achieved. In the case of burns, which are particularly frequent bacteria, it is also the fact that the skin itself is already extremely badly damaged and should not come into contact with chemicals. At this point, the blue light method comes into play: Although it uses the same principle as the photo-dynamics, but requires no additional photosensitive agent. Because the blue light disintegrates certain molecules that naturally occur in the interior of bacterial cells, but not in cells of mammals or humans. The principle has already been proven in studies of gingivitis and (?) In certain forms of acne.

The team led by dermatologist Michael Hamblin of Harvard Medical School now tested whether blue light can also do something about the - generally much more serious - infections in burn victims. To do so, they first tested in the laboratory what effects irradiation with blue light had on cultivated skin cells and on bacteria of the Pseudomonas aeruginosa type. These microorganisms, which often cause skin infections, are particularly feared because they are often resistant to all common antibiotics. Result of the test: The bacteria lost their activity relatively quickly, whereas the skin cells did not show damage until much later. Optimal conditions for a blue light therapy against P. aeruginosa. display

Resounding success

Subsequently, the scientists tested their method in mice in which they had infected burns in the chest area with the bacteria. They irradiated the burned skin several times with a blue light-emitting diode and then observed how many bacteria were still alive and active. The results were extremely impressive, the team reports: While nine out of eleven died from untreated animals after less than three days of sepsis, not only do all the mice that were irradiated survive, their infections were virtually completely healed after this time. The treated skin also did not cause any damage, only a slight swelling had occurred shortly after the treatment, the team reports.

Despite the lack of data, the scientists assume that the method will prove to be just as effective in clinical trials as it is now in its trial. It is only necessary to check whether human skin survives the treatment as unscathed as the mouse skin, and whether over time can not resist resistance to radiation. The researchers themselves consider this unlikely, but can not completely rule it out. However, they see great potential in the method and suspect that it can also be used with other types of bacteria and infection types.

Tianhong Dai (Massachusetts General Hospital, Boston) et al .: Antimicrobial Agents and Chemotherapy, doi: 10.1128 / AAC.01652-12 © science.de - Ilka Lehnen-Beyel

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