"Fecal bacterial communities of recurrent [C. diff]  patients shift towards [healthy] fecal bacterial communities after FMT. Pre-FMT patient samples (red circle); post-FMT patient samples (green circles); trajectory of patient fe… — "Fecal bacterial communities of recurrent [*C. diff*] patients shift towards [healthy] fecal bacterial communities after FMT. Pre-FMT patient samples (red circle); post-FMT patient samples (green circles); trajectory of patient fecal communities after FMT (blue line)."
Image and caption from the *C. diff* paper: Weingarden *et al.* *Microbiome* 2015 3:10 doi:10.1186/s40168-015-0070-0

Two important papers regarding fecal microbiota transplants (FMTs) were published last week. The first was an examination of a patient’s microbiome over time after he or she undergoes an FMT to treat C. difficile. The second showed the results of clinical trials that used FMTs in an attempt to treat ulcerative colitis. The FMT papers, which are described below, improve our understanding of this procedure, which holds promise to treat various microbiome-based diseases.

The C. diff paper, published in the journal Microbiome, attempted to answer the question: Do the microbiome changes that occur after FMT remain long after the procedure? We know that FMTs are highly effective in treating C. diff because they install a healthy microbiome that can crowd out the infection. However, it is unknown if these new bugs that take hold are transient, or if they become permanent members of the gut. The researchers sampled the microbiomes of FMT donors and recipient patients before and up to 84 days after an FMT procedure to treat C. diff. They discovered that the recipients’ dysbiotic microbiomes stabilized quickly, and after just one day they closely resembled the donors’ microbiomes. Continued measurements showed that the microbiomes deviated over the next few weeks, but that they remained healthy.

The colitis clinical trial, published in the journal Gastroenterology, attempted to discover if FMTs could treat ulcerative colitis. Ulcerative colitis is widely considered to somehow be related to a dysbiosis in the microbiome, so can FMTs from healthy donors treat this disease? The study was a double blind randomized clinical in which 48 people suffering from ulcerative colitis either received stool from healthy donors (treatment) or just an FMT of their own stool (control). 7/23 patients who received stool from a healthy donor were in remission after 12 weeks, while 5/25 patients who received their own stool were in remission at that time. Unfortunately, this is not a clinically significant result based on the number of patients involved. The researchers measured the bacterial abundance in all of the patients microbiomes before and after treatment. Before treatment the microbiomes all had some baseline similarity. After treatment, though, the patients who responded to treatment from a healthy donor all had an increase in certain Clostridia, and the patients who responded to treatment from their own stool all had in increase in certain Bacilli, Proteobacteria and Bacteriodetes. The researchers feel that this information warrants further study.

FMTs are an exciting new therapy that may be important in treating some really nasty diseases. We do want to remind people, though, that it is still an unproven technique that should only be performed under the guidance of a doctor. As we have written about before, the promise of the microbiome is what makes FMTs both attractive, but potentially dangerous at the same time.