Story highlights US scientists modified the antibiotic of last resort, vancomycin, making it more powerful

Researchers say it could become a vital tool against deadly resistant infections

Testing is needed in animals and humans before it can be used to treat patients

(CNN) Scientists in the United States have developed a vital tool in the battle against superbugs by re-engineering a decades-old antibiotic.

A modified version of the antibiotic vancomycin is believed to be much more effective at fighting Enterococci bacteria, which is found in hospitals and can cause dangerous wound and blood infections. The drug, which has been used for 60 years, is described as an antibiotic of last resort, used only after treatment with other antibiotics has failed. But some infections have become resistant even to vancomycin in its current form.

The research team, from The Scripps Research Institute in San Diego, California, described the new drug as "magical" in its strength, the UK Press Association reported.

It could be years, however, before the completion of clinical trials needed to turn the lab discovery into a mass-produced medicine, Dr. Andrew Edwards, a lecturer in molecular microbiology at Imperial College, London, told CNN.

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