New antibiotic reduces recurrence of deadly C. difficile infections, researchers say

An experimental antibiotic called fidaxomicin is more effective than the gold standard drug vancomycin at reducing recurrences of the often-lethal bacterial infection Clostridium difficile, Canadian and American researchers reported Wednesday. The drug’s manufacturer, Optimer Pharmaceuticals Inc. of San Diego has applied to the Food and Drug Administration for accelerated approval of the antibiotic, and the agency is expected to reach a decision by the middle of this year. If the drug is approved, it would represent the first new drug to treat C. difficile in at least a decade and “an important advance” in treating the infections, according to Dr. Herbert L. DuPont of the University of Texas School of Public Health in Houston.

By some estimates, C. difficile is responsible for as many as 3 million infections in the United States each year, making it the most common cause of bacterial diarrhea. It is commonly treated with metronidazole or vancomycin, but 20% to 30% of patients suffer a recurrence, apparently because the bacterium forms spores that survive in the gut after treatment ends. Moreover, the normal antibiotics destroy healthy bacteria in the gut, creating a niche for C. difficile to recur.

Fidaxomicin is a macrolide antibiotic that resides largely in the gut and that seems to have only a modest effect on other bacteria there. In the new study, Dr. Mark A. Miller of Jewish General Hospital in Montreal and his colleagues studied 629 patients with C. difficile infections. Half received 200 mg. of fidaxomicin twice daily for 10 days, and half received 125 mg. of vancomycin four times daily for the same period. The researchers reported in the New England Journal of Medicine that 88.2% of those treated with fidaxomicin and 85.8% of those treated with vancomycin were cured. Significantly fewer patients in the fidaxomicin group had a recurrence of infection, 15.4%, compared with 25.3%.

DuPont, who wrote an editorial accompanying the study, suggested that the results might have been even better if the patients had been treated for longer periods, perhaps for a month or six weeks. He noted that such long periods of treatment are more effective for other spore-forming bacteria, and suggested that the results might be the same for C. difficile.