CLINICAL APPLICATIONS, SAFETY ASPECTS, AND EMERGING APPROACHES OF FECAL MICROBIOTA TRANSPLANTATION

Although FMT is currently approved primarily for the treatment of recurrent Clostridioides difficile infection, growing evidence suggests that the gut microbiota plays a critical role in the pathogenesis of numerous neurological, psychiatric, gastrointestinal, autoimmune, metabolic, cardiovascular, renal, hepatic, and oncological diseases. Consequently, FMT is being actively investigated as a potential therapeutic strategy across a wide range of clinical conditions. The chapter highlights the importance of the gut–brain axis, emphasizing how dysbiosis contributes to neuroinflammation, altered neurotransmitter metabolism, and impaired blood–brain barrier integrity. Experimental and limited clinical evidence suggests that FMT may modulate disease processes in conditions such as Parkinson’s disease, Alzheimer’s disease, multiple sclerosis, epilepsy, autism spectrum disorder, depression, and anxiety. However, most data remain preclinical or derived from small, uncontrolled studies, and FMT in neurological and psychiatric disorders is therefore considered experimental. FMT has shown the most promising results in gastrointestinal diseases, particularly ulcerative colitis, where clinical trials have demonstrated improved remission rates, increased microbial diversity, and reduced intestinal inflammation. In contrast, outcomes in Crohn’s disease and irritable bowel syndrome are more variable, reflecting disease heterogeneity and challenges in microbial engraftment. Beyond intestinal disorders, FMT has been explored in autoimmune and allergic diseases, metabolic syndrome and diabetes, cardiovascular disease, chronic kidney disease, liver disease, and psoriasis, with preliminary findings suggesting potential benefits through immune modulation, restoration of barrier function, and metabolic regulation. The chapter also addresses the role of FMT in cancer therapy, particularly its ability to enhance responses to chemotherapy and immunotherapy by reshaping the gut microbiota and strengthening antitumor immune responses. Additionally, FMT has emerged as a promising strategy for decolonization of multidrug-resistant organisms, offering a novel tool in the fight against antimicrobial resistance. Safety considerations are discussed in detail, including short-term adverse effects, rare but serious complications, donor-derived pathogen transmission, and uncertainties regarding long-term metabolic and immunological consequences. Ethical and regulatory challenges, donor selection, informed consent, and long-term patient monitoring are emphasized as essential components of safe clinical implementation. Finally, the chapter introduces emerging alternatives to conventional FMT, such as synthetic microbiota transplantation, bacteriotherapy, and omics-based approaches. These strategies aim to improve safety, reproducibility, and personalization by using defined microbial consortia and advanced multi-omics technologies to better understand host–microbiome interactions.