Uncovering the role of microbiota and fecal microbiota transplantation in Crohn's disease: Current advances and future hurdles.

Crohn's disease (CD) is an idiopathic, chronic, and recurrent inflammatory condition of the gastrointestinal tract. Recent studies suggest a potential role of gut microbiota in CD, particularly dysbiosis-an imbalance in gut bacteria. While dysbiosis is consistently observed in CD, it remains uncertain whether it is a cause or a consequence of the disease. Given its association with CD, the therapeutic potential of fecal microbiota transplantation (FMT) has been explored. This review examines the role of gut microbiota in CD, evaluates the therapeutic potential of probiotics and FMT, and highlights current research findings and limitations. Key studies on the relationship between gut dysbiosis, probiotics, and FMT in CD were analyzed, with a focus on randomized trials, meta-analyses, and clinical observations. Dysbiosis is a consistent feature of CD, but its causative role remains unclear. Probiotics, prebiotics, and synbiotics have shown no efficacy in inducing or maintaining remission in CD. FMT shows potential as a therapeutic option for CD, but its efficacy remains inconsistent and inconclusive. The variability in outcomes, including diminished effects over time despite repeated FMT, underscores the need for larger, well-controlled trials. Only one randomized controlled trial (RCT) has compared FMT with sham transplantation, but the sample size was very small. Other studies are limited by factors such as small sample sizes, lack of control groups, short follow-up periods, and inconsistent methodologies, making it challenging to draw definitive conclusions. While gut dysbiosis likely plays a role in CD pathogenesis, its causative role remains uncertain. Current evidence does not support FMT as a reliable treatment for inducing or maintaining remission in CD, though it appears generally safe. Larger, standardized, RCTs are necessary to clarify the therapeutic role of FMT in CD management.