Thursday, Dec 18, 2014
Health

Narrow UV light tackles bacteria, spares human cells


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Having three members of the Tampa Bay Buccaneers contract methicillin-resistant Staphylococcus aureus has shown a spotlight on the difficulty of controlling antibiotic-resistant bacteria.

According to researchers at the Columbia University Medical Center, light may hold the key to killing MRSA and other antibiotic-resistant pathogens without harming humans.

Writing in the journal PLoS One, the scientist in New York say narrow-spectrum ultraviolet light, at a wavelength of around 207 nanometers, can destroy the genetic material of MRSA and other bacteria but spares human cells from similar DNA damage.

Germicidal lamps that emit UV light have long been used to sterilize surgical equipment because of their ability to kill bacteria and other pathogens. These lamps, however, emit UV light in wavelengths between 200 and 400 nm.

"Unfortunately, this UV light is also harmful to human tissue and can lead to skin cancer and cataracts in the eye," said study leader David J. Brenner, the Higgins Professor of Radiation Biophysics, professor of environmental health sciences, and director of the Center for Radiological Research at CUMC. "UV light is almost never used in the operating room during surgery, as these health hazards necessitate the use of cumbersome protective equipment for both surgical staff and patients."

Because protein molecules are known to strongly absorb UV light of around 207 nm, Brenner and his colleagues decided to test it as a way of controlling bacteria without harming human tissue. They made the choice because they believed 207-nm UV light cannot reach the nuclei of much larger human cells, where DNA resides, and can't reach sensitive cells in the human skin and the lens of the eye.

"What this means is, if you shone 207-nm light on human skin or eyes, you would not expect to see any biological damage," Brenner said, "but it should kill any airborne bacteria that land on a surgical wound."

To put their hypothesis to the test, the researchers first bombarded cultured MRSA and human skin cells with 207-nm and standard wavelength UV light from a sturdy and long-lasting krypton-bromine excimer lamp. Both forms of UV light were equally effective when it came to killing the bacteria. Compared to the standard UV light, however, the 207-nm light caused 1,000 times less damage to the human skin cells.

In addition, they exposed human skin cells to standard UV and 207-nm light. The standard light caused extensive precancerous changes to the skin cells, while the 207-nm light didn't.

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