Fig. 1

Strain sharing among donors and recipients in a fecal microbiota transplant cohort. A Transmission network in the FMT study. Stool samples from five healthy donors and eight recipients enrolled in a clinical study were collected for metagenomic sequencing and analysis [39]. B Visualization of criteria used to define a putative transmission event. Each box shows examples of strain sharing events that would be considered transmission (included) or not considered transmission (excluded) based on increasingly stringent criteria concerning the prevalence of the strain in the population. All criteria were cumulative; e.g., the list of strain sharing events absent in pre-FMT recipients was used as the starting point to further select strain sharing events that were unique to a single donor. Inferred transmission events under each successive set of criteria are shown using solid lines to connect samples; x’s mark the presence of shared strains. C Species sharing across increasingly stringent definitions of transmission. The number of shared microbial species among matched donor-recipient dyads (blue) and all other donor-recipient comparisons (mismatched: red) is shown following serially more stringent filtering criteria. D Strain sharing across varying definitions of transmission. The percentage of strain sharing events among matched donor-recipient dyads (blue) and all other comparisons (red) is shown following serially more stringent filtering criteria. Boxplots are bounded by the lower and upper quartiles, with the middle line showing the median value and whiskers extending to 1.5 times the interquartile range. Asterisks represent significant differences between matched and mismatched cohorts based on a t-test followed by Benjamini-Hochberg correction: ***p < 0.001, **0.001 ≤ p < 0.01, *0.01 ≤ p < 0.05. E Subsets of strain sharing events detected under varying criteria for transmission. The log-scaled proportion of total strain sharing events that were classified as transmission under varying criteria. Strain sharing between matched pairs is represented in blue, and strain sharing between mismatched pairs is represented in red