PF748 ENTEROCOCCUS‐PREDOMINANT INTESTINAL MICROBIOTA INDICATES POOR PROGNOSIS AFTER HEMATOPOIETIC STEM CELL TRANSPLANTATION
Authors: Kusakabe S. , Fukushima K. , Yokota T. , Nakai R. , Hino A. , Nagate Y. , Doi Y. , Fujita J. , Motooka D. , Nakamura S. , Shibayama H. , Kanakura Y. 
Published: June 2019

Background:The human intestinal bacterial flora is composed of ≥ 100 trillion microorganisms. A number of reports has suggested the association of various diseases with intestinal microbiota, identified by metagenomic analysis targeting the 16S rRNA of intestinal bacterial flora. In addition, several studies have indicated that changes in gut flora are associated with poor prognosis after allogeneic hematopoietic stem cell transplantation (HSCT), incidence of graft versus host diseases, and the risk of bloodstream infection.Aims:Recently, we reported that both compositional change and loss of diversity in gut flora were strongly associated with patient survival (Kusakabe et al, ASH2018). Here, we extended our investigation to examine the significance of each bacterial component in the gut flora as a prognosis factor after allogeneic HSCT.Methods:Patients who received allogeneic HSCT at the Osaka University Hospital were enrolled after obtaining written informed consent. We analyzed 142 feces samples that were collected pre‐transplant, 1 month, 3 months, 6 months, and 12 months after transplantation from 35 patients between August 2016 and May 2018. As control, we collected and analyzed samples from 10 healthy donors (HC). All samples were collected in sterile centrifuge tubes and 16S rRNA deep sequencing was performed using MiSeq (Illumina).Results:UniFrac distance analyses, which evaluate beta diversity, revealed that the intestinal flora of patients undergoing allogeneic HSCT substantially differed from that of HC. Particularly, there was a significant reduction of Bifidobacterium (p = 0.005), Sutterella (p = 0.016), and butyrate producing genera such as Anaerostipes (p = 0.036), Butyricimonas (p = 0.041), Coprococcus (p < 0.001), Faecalibacterium (p = 0.014), and Lachnospiraceae (p < 0.01), while Enterococcus genus was significantly increased before transplantation (p = 0.032) in these patients, compared with HC. With the exception of Enterococcus, however, there was no significant association between bacteria and non‐relapse mortality or overall survival (OS). Moreover, we also analyzed other Firmicutes phyla at the order and genus levels, and there was no bacterial group that could be a significant indicator for prognosis. In contrast, the relative abundance of Enterococcus genus (> 1%) at 1‐month after HSCT correlated with a significant worse prognosis. The 2‐year OS of patients who had <1% of Enterococcus was 78.5 %, whereas it was 37.5% for patients who > 1% of Enterococcus (p = 0.031). However, no significant difference was observed in OS with conventional stool culture between 21 positive cases of Enterococcus and 9 negative cases (p = 0.605).Furthermore, Enterococcus genus did not decrease or disappear at 3, 6, 9, and 12 months after transplantation, although the beneficial bacteria reconstructed in some patients. These data indicated that Enterococcus might not be eliminated regardless of other bacteria after HSCT. Therefore, the prophylactic administration of probiotics or synbiotics, fecal microbiota transplantation should be considered to prevent Enterococcus infection in the future.Summary/Conclusion:Our study indicates that the relative abundance of Enterococcus might indicate destruction of the intestinal bacterial flora and could be a promising prognostic indicator in allogeneic HSCT. Additionally, we believe that it is critical to investigate dysbiosis and diversity in detail, beyond comprehensive evaluation of metagenomic analysis.