*3.2. Fecal Microbiota Transplantation's E*ff*ectiveness in Non-Psychiatric Diseases*

If MD is actually associated with microbiota dysfunctions, replacing disturbed microbiota by a healthy one appears to be one of the most promising approach to improve MD [52]. FMT has been described as "the ultimate probiotic" as it provides an entire microbiome to the recipient. This therapy delivers a much greater number and diversity of bacteria than any current commercially available preparation. In the past decade, there has been a heightened interest in the use of this therapy [53], predominantly driven by increasing rates of recurrent *Clostridium di*ffi*cile* infection [54–56].

This procedure was proven associated with 87%–100% clinical resolution of recurrent or refractory *C. di*ffi*cile* infections [56–60]. This impressive success rate is presumably due to the ability of the transplanted bacteria to recolonize/occupy the missing components/niches of the normal intestinal microbiota thus removing the microbial niche that *C. di*ffi*cile* would otherwise exploit.

In addition to this main application, FMT has demonstrated promising results in other diseases as well such as ulcerative colitis [61,62] or inflammatory bowel diseases [63].
