The mechanism of action of stool transplantation has not been
established. However, patients with recurrent C. difficile infection
have been found to have decreased diversity in their stool microbiome
[25,26]. Ordinarily, C. difficile growth is inhibited by a normal
stool microbiome, but a depleted microbiome is thought to provide
an opportunity for C. difficile overgrowth. By repopulating the
gastrointestinal tract with a healthy microbiome, stool transplantation
appears to reestablish resistance to C. difficile growth,
often called colonization resistance [16]. To confirm the association
between stool transplantation and microbiome diversity, future
studies should examine the microbiome of patients with RCDI
before and after transplantation. Interestingly, we as well as others
[22] noted that patients who experience a relapse of CDI following
FMT have a high likelihood of responding to a standard treatment
course of vancomycin, which may be explained by a partial reestablishment
of a healthy stool microbiome diversity afforded by the
prior stool transplantation.