GUT MICROBIOTA DYSBIOSIS FOLLOWING AUTOLOGOUS BONE MARROW TRANSPLANTATION IN MULTIPLE MYELOMA PATIENTS: A PILOT METAGENOMIC STUDY

Background: Gut microbiota plays a crucial role in immune regulation, nutrient metabolism, and maintenance of intestinal homeostasis. Bone marrow transplantation (BMT) is associated with significant alterations in gut microbial communities due to conditioning chemotherapy, antimicrobial exposure, and immune suppression. However, data on microbiota changes following autologous transplantation in multiple myeloma patients remain limited.
Methods: This pilot longitudinal study evaluated gut microbiota alterations in two male patients with multiple myeloma undergoing autologous BMT. Both patients received four cycles of lenalidomide, bortezomib, and dexamethasone (RVD) followed by melphalan conditioning. Fecal samples were collected before transplantation and on Day +29/+30 post-transplantation. Microbial DNA was extracted and subjected to 16S rRNA gene sequencing using the Ion 16S Metagenomics Kit on the Ion Torrent platform. Taxonomic profiling and diversity analyses were performed using Ion Reporter software.
Results: Significant microbiota restructuring was observed after transplantation. Patient 1 exhibited marked depletion of Bacteroidetes with increased Firmicutes and Proteobacteria, accompanied by expansion of Enterococcaceae and Enterobacteriaceae and reduction of beneficial butyrate-producing taxa. In contrast, Patient 2 demonstrated increased abundance of Actinobacteria and Bacteroidetes, with dominance of Bifidobacteriaceae and enrichment of beneficial species including Bifidobacterium longum. Phylum-, family-, and species-level analyses revealed substantial inter-individual variability in microbial responses following transplantation.
Conclusion: Autologous BMT in multiple myeloma patients is associated with pronounced alterations in gut microbial composition. The observed dysbiosis and loss of beneficial commensal bacteria highlight the impact of transplantation-related interventions on intestinal microbial ecology. Larger longitudinal studies are required to clarify the clinical significance of these microbiome changes and their potential role in transplant outcomes.