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Killing bacteria with lasers. Light copes with antibiotic-resistant pathogens

The world is facing a growing crisis Antibiotic resistance faced. The excessive use of Antibiotics in medicine, the food industry and in cosmetics leads to the occurrence of antibiotic-resistant bacteria. The penetration of antibiotics into the environment, with concentrations in some rivers exceeding safe levels by 300 times, forces the pathogens to continuously develop antibiotic resistance. Hundreds of bacterial antibiotic resistance genes have even been discovered in the intestines of children. Without new antibiotics or other solutions, the scenario of people dying again from common infections or currently harmless diseases becomes real.

A strategy outside of the chemical repertoire is use physical methods such as ultraviolet light, gamma radiation, or heat. While these methods are effective in inactivating pathogens, they cause severe tissue damage and therefore cannot be used in clinical practice.

It is for this reason that some scientists are interested in this visible light. At low intensity it is gentle on the tissue and at the same time has the ability to inactivate bacteria, viruses and other pathogens. Specialists studying this problem are especially interested in Femtosecond laserthat emit ultrashort light pulses, the duration of which is specified in femtoseconds (1 femtosecond is 1/1 000 000 000 000 000 second).

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Researchers at Washington University School of Medicine have shown that ultrashort pulses in the visible light range - with a wavelength of 415-425 nm - can be an effective weapon against antibiotic-resistant bacteria and their spores.

The scientists have that Laser tested on methicillin-resistant Staphylococcus aureus (MRSA) and E. coli. These bacteria are very resistant to numerous physical and chemical influences. the Laser was also tested on Bacillus cereus spores, which can cause food poisoning and are able to survive cooking. The tests have shown that the Laser 99,9% of the bacteria treated with it is inactivated.

The researchers explain that once their laser reaches a certain level, it begins to deactivate viruses. When the power is increased, it also affects the bacteria. However, its light remains safe for human tissue. Just an order of magnitude increase in output kills cells. So there is a specific therapeutic windowthat allows safe use.

Ultra-short laser pulses inactivate pathogens without damaging human proteins and cells. Imagine if the surgeon could disinfect a wound with a laser before closing it. I think this technology could soon be used to disinfect biological products in vitro, and in the near future it could also be used to disinfect the bloodstream. Patients could have dialysis and their blood could be passed through a laser device to disinfect it, says lead author of the study, Shew-Wei Tsen.

Together with Professor Samuel Achilefu, Tsen has been studying the ability for years ultra-short laser pulsesTo kill pathogens. They have already shown that they inactivate viruses and "normal" bacteria. Now, in collaboration with Shelley Haydel, a professor of microbiology at Arizona State University, they have expanded their research to include spores and antibiotic-resistant bacteria.

Viruses and bacteria contain densely packed Protein structures. The laser deactivates them by vibrating these structures so strongly that some of the bonds in the proteins break (denature). Such a broken end tries to connect to something as quickly as possible and usually connects to a different structure than the one it was connected to before. In this way, abnormal connections arise within and between the proteins within the pathogen, which lead to the proteins no longer working properly and thus the pathogen no longer working.

Everything that comes from humans or animals can be contaminated with pathogens. All blood products are tested for pathogens before they enter the patient's body. The problem, however, is that we need to know what we are looking for. If a new virus circulated in the blood, as was the case with HIV in the 1970s and 1980s, it could get into the bloodstream with such products. Ultrashort laser pulses are a method that can be used to ensure that blood products are free of pathogens.