A common but dangerous infection that often hits hospitals, caused by Clostridium difficile, might be beaten down using a "friendly" version of the same bacteria, researchers say.

C. difficile infections, which can result in abdominal cramps, diarrhea and sometimes severe inflammation of the colon, often hit during or following a stay in hospital, especially if a person has had a long course of antibiotic treatments or has a compromised immune system.

A prolonged use of antibiotics can be a problem because it often kills off "good" bacteria in the human gut that would normally fight off toxin-producing versions of C. difficile, researchers say.

"The antibiotics don't completely get rid of the C. diff bacteria, and if the patient hasn't developed an immune response against the toxin the bacteria produces, they'll get sick again," says Dr. Dale Gerding, a professor of medicine at Loyola University Chicago Stritch School of Medicine.

C. difficile infections have reached an all-time high in U.S. hospitals and are linked to around 29,000 deaths each year, he notes.

Around 30 percent of patients with infections who are treated with antibiotics fall ill again, Gerding says, so he and his research team decided to try a new strategy against C. difficile.

After patients had been successfully treated with antibiotics, they were give a non-toxic "friendly" strain of C. difficile, with the hope that it would occupy areas in the gut the toxic version normally inhabits and prevent it from coming back.

"What we're doing is establishing competition with the original, toxic strain," Gerding explained.

In the trial, patients in whom the friendlier version took hold in their gut had only a one in 50 recurrence of infection, whereas in patients where the friendly bacteria failed to colonize the gut there was a one in three chance of another infection, the researchers report in the Journal of the American Medical Association.

Following the treatment, the friendly bacteria "don't stay around forever," Gerding says, and such therapies could prepare a patient's normal gut bacteria populations to be re-established.

Eventually, the researchers suggest, people preparing to go on a long course of antibiotics could be given the friendly version of C. difficile in advance to prevent the toxic infection from ever gaining a foothold in their system.

Other experts said they welcomed the new research.

"This is a very important study because of the high recurrence rate of C. difficile infections, and because [recurrent] infections become progressively harder to treat," says Dr. Lawrence Brandt, emeritus chief of gastroenterology at Montefiore Medical Center in New York City.