This review identified a total of 2 randomised controlled trials and 28 case series evaluating FMT for the treatment of CDI in adults (mainly those with recurrent CDI). Only one of the RCTs compared FMT with standard antimicrobial therapy, highlighting the lack of good quality evidence for this promising therapy.
The authors note that despite this, a large positive effect was observed in all study types, with reported success rates larger than those typically seen with various other CDI treatments (although care needs to be taken when making such indirect comparisons). However the role of previous antimicrobial therapy (AMT) is unclear - FMT was administered after standard AMT, and in most cases seemed to be given with the intent to prevent recurrence after antimicrobial treatment had resolved all or the majority of symptoms. The authors therefore suggest that future FMT studies need to carefully consider their primary outcome (resolution of symptoms vs. revention of recurrence).
Studies are needed to determine the safety of FMT, although as harms appear to be rare, ongoing surveillance (e.g. publicly accessible registry) will be required. The technical aspects that have varied across studies (e.g. source of donor faeces) also require further study. There is currently insufficient evidence about the efficacy of FMT in patients with refractory CDI or for initial treatment of CDI.