A drug that is being investigated for the treatment of arthritis and cancer, may also be able to treat a stubborn bacterial infection, a study suggests.

A stubborn bacterial infection often acquired in hospitals and which can be deadly may have a new treatment on the horizon, US researchers say.

Antibiotics only work about 25 per cent of the time in wiping out Clostridium difficile, or C. diff, a pathogen that infects the digestive tract and kills about 15,000 people and hospitalises 250,000 each year in the United States.

But the antioxidant drug ebselen was shown to kill C. diff by targeting its toxins, not by killing the bacteria and wiping out beneficial gut microbes at the same time, researchers from the Stanford University School of Medicine said.

The study in the journal Science Translation Medicine was done on mice, but researchers say human trials could be expedited because the drug is already being investigated for the treatment of cardiovascular diseases, arthritis, stroke, atherosclerosis and cancer.

"Unlike antibiotics - which are both the frontline treatment for C. difficile infection and, paradoxically, possibly its chief cause - the drug didn't kill the bacteria," said senior author Matthew Bogyo, professor of pathology and of microbiology and immunology.

Rather, it disabled a toxin produced by the pathogen and prevented intestinal damage and inflammation.

C. diff costs the United States more than $US4 billion ($A5 billion) in healthcare expenses and it often recurs in patients, requiring further hospitalisation, researchers said.

The infection is particularly perilous for those with weakened immune systems.

About seven per cent of people who are infected die within a month of diagnosis.