Recipient factors in faecal microbiota transplantation: one stool does not fit all.

Faecal microbiota transplantation (FMT) is a promising therapy for chronic diseases associated with gut microbiota alterations. FMT cures 90% of recurrent Clostridioides difficile infections. However, in complex diseases, such as inflammatory bowel disease, irritable bowel syndrome and metabolic syndrome, its efficacy remains variable. It is accepted that donor selection and sample administration are key determinants of FMT success, yet little is known about the recipient factors that affect it. In this Perspective, we discuss the effects of recipient parameters, such as genetics, immunity, microbiota and lifestyle, on donor microbiota engraftment and clinical efficacy. Emerging evidence supports the possibility that controlling inflammation in the recipient intestine might facilitate engraftment by reducing host immune system pressure on the newly transferred microbiota. Deciphering FMT engraftment rules and developing novel therapeutic strategies are priorities to alleviate the burden of chronic diseases associated with an altered gut microbiota such as inflammatory bowel disease.