Therapies to modulate gut microbiota: Past, present and future.

The human gut microbiota comprises of a complex and diverse array of microorganisms, and over the years the interaction between human diseases and the gut microbiota has become a subject of growing interest. Disturbed microbial milieu in the gastrointestinal tract is central to the pathogenesis of several diseases including antibiotic-associated diarrhea and infection (CDI). Manipulation of this microbial milieu to restore balance by microbial replacement therapies has proven to be a safe and effective treatment for recurrent CDI. There is considerable heterogeneity in various aspects of stool processing and administration for fecal microbiota transplantation (FMT) across different centers globally, and standardized microbioal replacement therapies offer an attractive alternative. The adverse effects associated with FMT are usually mild. However, there is paucity of data on long term safety of FMT and there is a need for further studies in this regard. With our increasing understanding of the host-microbiome interaction, there is immense potential for microbial replacement therapies to emerge as a treatment option for several diseases. The role of microbioal replacement therapies in diseases other than CDI is being extensively studied in ongoing clinical trials and it may be a potential treatment option for inflammatory bowel disease, irritable bowel syndrome, obesity, multidrug resistant infections, and neuropsychiatric illnesses. Fecal microbiota transplantation for non-CDI disease states should currently be limited only to research settings.