Fecal microbiota transfer for bowel disorders: efficacy or hype?

Dysbiosis has been related to the pathophysiology of disorders of - gut-brain interaction (DGBI) including irritable bowel syndrome (IBS) and functional constipation (FC). Accordingly, modulation of gut microbiota has been proposed as a potential treatment for these disorders. Gut microbiota modulation can be effected by probiotics, prebiotics, symbiotics, postbiotics, antibiotics and fecal transplantation (FMT) or bacteriotherapy. The latter is currently used for recurrent or severe Clostridium difficile colitis and has been the focus of recent research in IBS and FC.

Several case series reported promising results for FMT in patients with IBS and FC, which prompted the conduction of randomized controlled trials (RCT) in these DGBI.

Both case series and RCTs are herein discussed. To the best of our knowledge, as of yet, 5 RCTs have been published on IBS and one in FC with slow colonic transit. In IBS, the majority of studies have used the IBS severity scoring system (IBS-SSS) as an outcome measure; however, the selection criteria were different among the trials as well as the route and form of administration of the FMT. Therefore, the results are inconsistent and no conclusion can be drawn. Some studies suggest that the presence of post-infection (PI)-IBS and the baseline microbiota status in the donors could be predictor factors of successful FMT in IBS. In constipation with slow colonic transit, the FMT seems to be more effective, although the data is based on only one RCT. We believe that larger RCTs, controlled with true placebos and considering baseline intestinal microbiota of the study subjects as well as donors' microbiota are still needed before recommending FMT in IBS and/or FC. History of previous GI infection (e.g. PI-IBS) and IBS subtypes should also be taken into account.