Fecal microbiota transplantation: Screening and selection to choose the optimal donor

In the past decade, fecal microbiota transplantation (FMT) has rapidly spread worldwide in clinical practice as a highly effective treatment option against recurrent Clostridioides difficile infection. Moreover, new evidence also supports a role for FMT in other conditions, such as inflammatory bowel disease, functional gastrointestinal disorders, or metabolic disorders. Recently, some studies have identified specific microbial characteristics associated with clinical improvement after FMT, in different disorders, paving the way for a microbiota-based precision medicine approach. Moreover, donor screening has become increasingly more complex over years, along with standardization of FMT and the increasing number of stool banks. In this narrative review, we discuss most recent evidence on the screening and selection of the stool donor, with reference to recent studies that have identified specific microbiological features for clinical conditions such as Clostridioides difficile infection, irritable bowel syndrome, inflammatory bowel disease, and metabolic disorders.