Page 15 - Introduction to FMT

FMT Introduction

Though FMT is relatively easy to perform, there is wide inter-institutional variability in methodology. For
example, in preparation for FMT, some institutions give their patients multiple doses of doxycycline or
vancomycin in an effort to reduce the native, dysbiotic population [29]. In many institutions, immediately
prior to FMT, patients are typically given a polyethylene glycol colon preparation to increase the
opportunity for the transplanted microbiome to successfully colonize the gut regardless of whether the
FMT is introduced in the upper GI tract or through a colonoscopy. However, there is no published
evidence suggesting that this preparation improves FMT clinical outcomes [22].

The processing of fecal matter for transplant is not standardized and needs to be experimentally
validated for optimal efficacy. The general principal, however, is more or less universal. As outlined in
Figure 1, the donated stool is first mixed with saline solution to homogenize it into a liquid sample, and is
then filtered to remove any solid feces that may interfere with the transplant. In order to standardize the
processing of fecal matter, studies have compared the efficacy of frozen versus fresh stool samples prior
to processing and transplantation. These studies have thus far shown no significant difference in primary
outcomes [30,31]. While studies have performed 16s rRNA sequencing before and after processing to
evaluate sample loss, fecal matter contains 99 percent anaerobic species which may not survive vigorous
aerobic blending [32,33]. Furthermore, 16s rRNA sequencing does not discriminate viable from dead cells.
Nevertheless, the overwhelming number of positive results obtained from FMT in treating CDI patients
suggests that either the viability of the cells is relatively unimportant, or that a small proportion of
survived cells is sufficient to induce a change in the recipient’s microbiome and a therapeutic effect.

Figure 1

Fecal Microbiota Transplantation schematic. A) Donor fecal matter is blended with saline solution and
pushed through a metal sieve to achieve a homogenous liquid solution. B) Processed fecal microbiota is
either delivered via a duodenal tube or colonoscopy. C) Representative data showing metagenomic
diversity increases following FMT from lean donor to obese recipient.

FMT Introduction