By Michael Kahn

LONDON (Reuters) - A new technique using proteins to guide a drug targets superbugs such as MRSA much more accurately than previous methods, researchers said on Tuesday.

Laboratory experiments showed that the technique was 1,000 times more effective at killing methicillin-resistant Staphylococcus aureus (MRSA) bacteria than using the same drug without the proteins to home in on the infections, they said.

The drug, tin chlorin 6, is normally activated by light to produce toxic compounds that attack infections. The researchers added protein fragments called peptides that attach to the bacteria in topical infections such as burns and wounds.

"The results from laboratory studies are very encouraging and indicate that this technique might be effective at treating topical infections such as wound and burn infections," Linda Decker and colleagues from University College London said in a written report which will be presented on Wednesday.

"Due to the growing resistance of many organisms to antibiotics, this approach may be the only one available for use against microbes resistant to all known antibiotics."

MRSA infections can range from boils to more severe infections of the blood, lungs and the sites of surgery. Most cases are associated with hospitals, nursing homes or other health care facilities.

Such infections can often be treated only with expensive intravenous antibiotics.

Experts have been saying for years that poor hospital practices spread dangerous bacteria. Many studies have shown that health care workers, including doctors and nurses, often fail even to wash their hands as directed.

The findings, to be presented at a meeting of the Society for General Microbiology in Harrogate in Britain, highlighted the promise of attaching an antimicrobial drug to a peptide, which in turn attaches to bacteria.

The researchers attached a signaling peptide known as RNAII inhibiting peptide and this naturally targets a receptor molecule on the surface of the bacteria.

"You just put the peptide drug together with the bacteria and it sticks to the bacteria," Sean Nair, who worked on the study, said in a telephone interview. "This peptide is the natural binding partner for it."

In the study, the combination of the drug, the peptides and the light killed 99.97 percent of 10 million MRSA cells. This was a far more powerful rate than using the drug without added peptides.

The treatment also appears to have the potential to prevent bacteria from producing tissue-damaging toxins, and the way in which it targets cells makes it more difficult for bacteria to develop resistance to it, the researchers said.

It will need to be tested in animals before it can be considered for testing in people, they added.

(Reporting by Michael Kahn, editing by Jonathan Wright)

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