Secondary aims: Differences in pre- and post-FMT stool composition, and between early and late post-FMT samples, will be calculated with McNemar's test for significant differences in proportions of rRNA (ribosomal ribonucleic acid) sequences pertaining to the relevant bacterial phyla (Bacteroidetes, Firmicutes, and Proteobacteria), and paired t-tests and ANOVA's (or their non-parametric counterparts) for significant differences in Shannon diversity indices (a measure of bacterial diversity) and in concentrations of multiple bile acids. If these measures are different from pre- to post-FMT samples, then the relationship of percent differences in each stool parameter to clinical outcome will be evaluated using logistic regression with primary outcome of "primary cure" within two months of FMT, and a Cox proportional hazards model with the time variable as "days to primary cure" and the censor variable as "primary cure." Secondary analyses may be conducted with "any cure" as the outcome variable if repeat FMT is frequently needed. The investigators will also compare a sample of donor stool to the post-FMT samples with the same statistical tests, under the hypothesis that the closer that post-FMT stool resembles donor stool (and the more durable this resemblance), the better the clinical response. All statistical analyses will be performed at an alpha of 0.05.