Fecal microbiota diversity disruption and clinical outcomes after auto-HCT: a multicenter observational study

We have previously described clinically relevant reductions in fecal microbiota diversity of patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT). Recipients of high-dose chemotherapy and autologous hematopoietic cell transplantation (auto-HCT) incur similar antibiotic exposures and nutritional alterations. To characterize the fecal microbiota in the auto-HCT population, we analyzed 1,161 fecal samples collected from 534 adult recipients of auto-HCT for lymphoma, myeloma and amyloidosis in an observational study conducted at two transplant centers in the United States. Using 16S ribosomal gene sequencing, we assessed fecal microbiota diversity as measured by the inverse Simpson index, and composition. At both centers, early pre-transplant fecal microbiota diversity was lower than in healthy control subjects and decreased further during the course of transplantation. Loss of diversity and domination by specific bacterial taxa occurred during auto-HCT in patterns similar to allo-HCT. Above-median fecal intestinal diversity in the peri-engraftment period was associated with decreased risk of death or progression (PFS HR 0.46 [95% CI, 0.26-0.82], P=0.008), adjusting for disease and disease status. This suggests that further investigation into the health of the intestinal microbiota in auto-HCT patients and post-transplant outcomes should be undertaken.