Fecal microbiota transplantation from psychiatric patients to mice - systematic review of methodologies and a call for standardization

Background: Fecal microbiota transplantation (FMT) has emerged as a key tool to explore the role of the microbiome-gut-brain axis in psychiatric disorders. However, the field is hindered by significant methodological inconsistencies. Methods: A comprehensive literature search identified 31 studies performing FMT from human patients with psychiatric conditions into rodent models. Results: None of the 31 studies followed an identical FMT protocol. Significant heterogeneity was observed across studies in rodent model selection, including germ-free, antibiotic-pretreated, or specific pathogen-free approaches, in antibiotic regimens, timing and microbiota depletion verification, as well as in FMT donor strategy, dosage, frequency, engraftment assessment, and behavioral testing schedules. Conclusions: This review highlights the necessity for standardized methodologies in microbiome research. Evidence-based recommendations are provided to promote reproducibility in future work. Investigators are encouraged to publish transparent and rigorous protocols, to enhance the translational potential of microbiome-gut-brain axis research.