• colorectal motility

We agree with the comments1 2 on the recently reported randomised double-blind, placebo-controlled trial from our group on the efficacy of faecal microbiota transplantation (FMT) in patients with IBS3 that caution is required when using FMT to treat this condition. However, we have some further comments concerning the efficacy and safety of FMT in IBS.

The patients with IBS included in our randomised controlled trial (RCT)3 were only those with moderate symptom severity (IBS Symptom Severity Score (IBS-SSS) score between 175 and 300)2 and severe symptom severity (IBS-SSS score of ≥300).4 One way to evaluate the efficacy of FMT when using the IBS-SSS, as pointed out by Camilleri, is to look at the proportions of patients with moderate symptom severity and severe symptom severity at different time intervals after FMT.2 The raw results for our RCT from the IBS-SSS questionnaire categorised in this manner are summarised in table 1. As Camilleri mentioned in his comments, about 20% of the patients treated with FMT experienced adverse events in the form of abdominal pain, cramping, tenderness, diarrhoea or constipation, compared with 2% of those in the placebo group. It is noteworthy that these adverse events were mild, self-limiting and occurred during the first 2 days after FMT.3 In addition, two patients with known diverticulosis developed diverticulitis, compared with none in the placebo group. Both these patients had experienced several diverticulitis attacks before FMT, and so it is difficult to establish whether these new attacks were connected to FMT. However, it should be kept in mind that the adverse events seen in the previously mentioned RCT study3 were observed in a cohort of patients in whom the presence of systemic disease, immune deficiency and treatment with immune-modulating medication were exclusion criteria. Thus, none of the patients included in the trial suffered from systemic disease and they had a normal immune defence system.

Serious adverse events or infection transmission have not been reported for several placebo-controlled trials of FMT.5 However, two recently reported patients developed bacteraemia with an antibiotic-resistant Escherichia coli strain following FMT with capsules derived from the same donor.5 6 This adverse event resulted in one fatality.5 6 These two patients were 69 and 73 years old and had advanced liver cirrhosis and myelodysplastic syndrome, while both were also immunosuppressed and had risk factors for bacteraemia.5

We believe that improving the screening of FMT donors—including testing the donor stool for beta-lactase extended-spectrum beta-lactamase (ESBL) E. coli and severe acute respiratory syndrome coronavirus 2—would reduce the risks of infection by known agents.7 8 Moreover, restricting the selection of patients with IBS for FMT to those without systemic disease, immune deficiency, treatment with immune-modulating medication and severe illness would reduce further the risks.

IBS is a benign condition, but affected patients can be unable to start or continue education, obtain or keep a job, or build or retain a family, which results in social isolation. While patients with IBS do not die of the disorder, they do not have a worthy life. There is still no effective treatment for IBS, with the treatments offered in the clinic instead focusing on symptom relief. FMT seems to be a simple and effective treatment for IBS. However, like for all treatments, the trade-off between the risks and benefits of FMT should be evaluated.