In a randomized, controlled, double-blind clinical trial, fecal microbiota transplantation using donor stool seemed to be safe and was more efficacious than transplantation using the patient's own stool in curing multiply recurrent Clostridium difficile (C. diff) infection. However, results varied widely by study site, raising questions about the benefits and risk of the procedure. The findings are published in Annals of Internal Medicine.

C. diff is the most common health care-associated infection in U.S. hospitals. Antibiotics are frequently ineffective and recurrences are common. Fecal transplantation restores the normal composition of gut microbiota and is recommended when antibiotics fail to clear the infection after a third episode of infection. However, the evidence for fecal transplantation rests largely on case series and several open-label clinical trials.

Researchers assigned 46 patients with three or more recurrences of C. diff to receive fecal microbiota transplantation with donor stool or their own stool administered by colonoscopy at two academic medical centers - Montefiore Medical Center in the Bronx, New York, and The Miriam Hospital in Providence, Rhode Island. Overall, 91 percent of patients in the donor stool group achieved clinical cure compared with 63 percent receiving their own stool. However, cure rates in patients receiving their own stool were 90 percent in the New York medical center and about 43 percent at the Rhode Island medical center.

The author of an accompanying editorial suggests that these "striking" findings may be due to differences in patient characteristics including, locale, length of time between initial diagnosis and transplantation, and the type of antibiotic used, among other factors. More research is needed to answer some of the questions raised by this randomized trial.

Article: Are Microbial Politics Local?, Elizabeth L. Hohmann, Annals of Internal Medicine, doi:10.7326/M16-1784, published online 23 August 2016.