Unraveling the Intestinal Microbiota Conundrum in Allogeneic Hematopoietic Stem Cell Transplantation: Fingerprints, Clinical Implications and Future Directions

Intestinal microbiota dysbiosis represents a critical determinant of clinical outcomes in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT), with distinct microbiota patterns serving as potential prognostic biomarkers and therapeutic targets. However, the exponential growth in microbiota research and analytical complexity have created significant interpretive challenges for clinicians. This review provides a synthesis of current literature examining microbiota fingerprints and their clinical implications. We analyzed key studies evaluating the clinical implications of intestinal microbiota fingerprints in allo-HSCT. Additionally, we examined current therapeutic strategies for microbiota modulation and approaches for translating research findings into clinical practice. We identified three major microbiota fingerprints: 1) decreased intestinal diversity, 2) reduced abundance of short-chain fatty acid-producing bacteria, and 3) Enterococcus domination. These fingerprints are associated with critical clinical outcomes including overall survival, graft-versus-host disease, transplant-related mortality, and infectious complications. While fecal microbiota transplantation and dietary interventions appear promising, current studies suffer from limited sample sizes and lack standardized protocols. Despite advances in microbiota research, biological, methodological, and logistical challenges continue to impede clinical translation. Understanding microbiota fingerprints represents a promising avenue for improving allo-HSCT outcomes. However, successful clinical implementation requires standardized methodologies, mechanistic studies, and multi-center collaborations to translate research into actionable clinical tools.