A retrospective metagenomic analysis of fecal microbiota transplantation donors from five countries: Safety considerations for donor screening and core microbiome profiles of qualified donors

Fecal microbiota transplantation (FMT) has been successfully applied on clinical aspects, but its clinical outcomes remain unpredictable due to inconsistent donor screening protocols across hospitals, institutions, and countries. Hence, a retrospective analysis of metagenomic data from published studies on FMT donors via a unified bioinformatics workflow might contribute to the understanding of the safety considerations for donor screening and the fecal microbial profiles of qualified donors. In this study, we reanalyzed metagenomic data of 475 screened donor fecal samples from 24 studies spanning China, the USA, Canada, New Zealand, and the Netherlands. The genomic safety risks were evaluated by profiling antibiotic resistance genes (ARGs) and virulence factors (VFs), the results of which showed that no major toxin-associated virulence genes, such as Shiga toxin, Shiga-like toxin, or botulinum neurotoxin (BoNTs) genes harbored in the detected Escherichia coli, Clostridium butyricum, and Streptococcus pneumoniae, but several high-risk ARGs remained insufficiently addressed. The distribution of ARG-harboring bacteria in eligible FMT donors was country-specific. The alpha-diversity and microbial community structure were comparable between donor fecal samples from China and the USA. Interestingly, the core microbiome in fecal samples from Canada, the Netherlands, and New Zealand formed a single guild, while that from China and the USA formed two guilds, with predominantly positive intra-guild and negative inter-guild correlations, indicating that the co-abundance patterns of the core microbiome were conserved among certain countries. Furthermore, an exploratory retrospective classifier was developed based on core microbiome profiles to distinguish eligible FMT donors from general healthy individuals. These results provide evidence for integrating metagenomic sequencing into future FMT donor screening strategies.