One of the medical miracle stories of the past decade has been the astonishing efficacy of faecal microbiota transplantation (FMT) – colloquially known as poo transplants – for the treatment of hospital-acquired Clostridium difficile infections. Previously, patients usually endured several cycles of antibiotics to treat the condition – cycles that often turned vicious, as the antibiotics tended to reduce microbiome diversity, which in turn encouraged the return of C. difficile. But all this changed when a landmark study that found FMT – previously considered something of a quack form of medicine – had a success rate of over 90% in clearing the infection.
The discovery has focused attention on the importance of the intestinal microbiome in a number of diseases, particularly those with an autoimmune component, such as inflammatory bowel disease. There have been several trials of FMT for ulcerative colitis so far, with mixed but promising results. At the wilder end of the spectrum, researchers have talked up the possibility of FMT in diseases as disparate as rheumatoid arthritis, asthma, multiple sclerosis and autism.
What of irritable bowel syndrome, thought to affect over 10% of the population? It is notoriously difficult to treat, probably due to its multifactorial pathology. Many researchers in the field do think that targeting microbiota with FMT may prove effective, particularly given the strong evidence of the role of bacterial, viral and parasitic infections in triggering IBS, along with the transient relief of symptoms felt by many patients after antibiotics. But serious research is only at its initial stages. In fact, the first truly randomised, double-blind, placebo-controlled trial of FMT in moderate-to-severe IBS was only published earlier this year. That trial of 90 participants found a significant effect on IBS severity at three months, although not at 12 months, with no serious adverse effects reported.
A systematic review published this month has collated the results of 48 IBS patients across several conference abstracts and case reports, finding an improvement with FMT in 58% of cases. Two of the studies mapped the microbiome before and after FMT, finding greater diversity of bacterial species after treatment. The review authors say that although methodological differences between the studies make it hard to verify findings, they do lay the groundwork for further research in the area. Currently, eight randomised studies of FMT/IBS are registered on clinicaltralis.gov. Several of these include sequencing the microbiome before and after treatment, which should offer clues as to the real effects of FMT in this condition and where to go next.
One interesting mouse study involved colonising mouse guts with the faecal content of either healthy patients or those with diarrhoea-predominant IBS (IBS-D) with anxiety. The mice with IBS faecal content had faster gastrointestinal transit time and higher colonic paracellular permeability than the other mice, pointing to the importance of the microbiome in the disease. Oddly enough, the mice with material from patients with IBS-D with anxiety themselves showed more signs of anxiety-like behaviour in the laboratory environment.