Canadian hospitals fighting diarrhea in patients infected with C. difficile may soon have a new weapon in their arsenal.
In Wednesday's online issue of the New England Journal of Medicine, Montreal researchers and their Canadian and U.S. co-authors reported fidaxomicin nearly halved relapses of C. difficile.
The study showed it worked as well as the leading existing antibiotic treatment for resolving symptoms after 10 days.
Fidaxomicin is not approved by the U.S. Food and Drug Administration or Health Canada.
Since 2005, C. diff has caused an increasing number of cases of severe diarrhea in Canadian hospitals that persist for months despite repeated treatments.
Outbreaks have also occured in nursing homes, where residents are more vulnerable, particularly when they've been taking antibiotics, which reduces levels of beneficial microbes in the gut.
When C. diff grows, some strains produce a toxin that damages cells lining the intestine, scientists say.
"In the last 30 to 40 years, there's been nothing new for C. difficile treatment," said the paper's second author, Dr. Mark Miller, head of infectious diseases and chief of microbiology at Jewish General Hospital in Montreal.
"This is really the first drug to come along to address C. difficile in terms of, 'Can we get a better treatment?"'
Infectious disease experts are particularly encouraged by the relapse findings on 596 patients. An earlier study suggested that after successful initial treatment with the antibiotics metronidazole or vancomycin, 20 to 30 per cent of patients have a second outbreak, usually within the first two weeks.
"When you've dealt with people that have had the disease and you see them relapse and you see them having their colons removed because you can't cure them with antibiotics and things, it's really quite shocking," said Dr. Michael Gardam, medical director of infection prevention and control at Toronto's University Health Network, commenting on the research.
"Having another drug in the pipeline to be able to potentially treat them, especially if further studies show it works well for severe disease, is wonderful."
In the study, the recurrence rate among those taking the current gold-standard antibiotic, vancomycin, was 25 per cent (67 out of 265), compared with 15.4 per cent (39 of 253) for the new antibiotic.
But the clinical trial did not include the most severely ill C. diff patients.
No help for worrisome strain
The study did include participants with the potentially lethal NAP1 strain that first caused an epidemic at hospitals in Montreal in 2005, and is now found at hospitals across Canada. These patients didn't gain benefits from fidaxomicin.
"Anywhere from 30 to 50 per cent of the disease in Canadian hospitals today is caused by the NAP1, and there was apparently no benefit in reducing the recurrence rate," said Dr. Andrew Simor, chief of microbiology and infectious diseases at Sunnybrook Health Sciences Centre in Toronto, who was not involved in the study.
Vancomycin is expensive, Gardam noted, and the cost of oral fidaxomicin is not yet known.
In the study, side-effects of fidaxomicin and vancomycin were similar.
If fidaxomicin is approved by regulators, doctors still need to figure out the best drug for each case.
Fidaxomicin seems to works against bacteria in the colon and is minimally absorbed in the blood stream. It may help kill C. diff without harming beneficial microbes in the gut, a journal editorial accompanying the study suggested.
Fidaxomicin was developed by Optimer Pharmaceuticals of San Diego.
Several authors reported financial ties to Optimer and other drug companies.