Baseline Gut Microbiota Composition Is Associated with Major Infections Early after Hematopoietic Cell Transplantation

Gut Microbiome as a Potential Marker of Hematologic Recovery Following Induction Therapy in Acute Myeloid Leukemia Patients

BACKGROUND

The management of acute myeloid leukemia (AML) is hindered by treatment-related toxicities and complications, particularly cytopenia, which remains a leading cause of mortality. Given the pivotal role of the gut microbiota (GM) in hemopoiesis and immune regulation, we investigated its impact on hematologic recovery during AML induction therapy.

METHODS

We profiled the GM of 27 newly diagnosed adult AML patients using 16S rRNA amplicon sequencing and correlated it with key clinical parameters before and after induction therapy.

RESULTS

Our investigation revealed intriguing associations between the GM composition and crucial recovery indicators, including platelet, lymphocyte, and neutrophil counts, and identified early GM signatures predictive of improved hematologic recovery. Remarkably, patients demonstrating superior recovery had higher alpha diversity and enrichment in health-associated taxa belonging to the genera Faecalibacterium, Ruminococcus, Blautia, and Butyricimonas at diagnosis.

CONCLUSIONS

Despite certain study limitations, our findings suggest that evaluating GM features could serve as a potential marker for hematologic recovery. This preliminary work opens avenues for personalized risk assessment and interventions, possibly involving GM modulation tools, to optimize recovery in AML patients undergoing induction therapy and potentially enhancing overall outcomes in individuals with hematologic diseases.

Risk factors of bloodstream infection after allogeneic hematopoietic cell transplantation in children/adolescent and young adults

Allogeneic hematopoietic cell transplantation (HCT) is a crucial treatment for various diseases, including hematological malignancies, solid tumors, and genetic disorders. Despite its curative potential, HCT is associated with severe complications, notably infections, graft-versus-host disease, and organ damage. Infections, particularly bloodstream infections (BSIs), pose a significant threat in the initial weeks post-HCT, necessitating effective management strategies. This retrospective study aimed to clarify the incidence, pathogens, and risk factors associated with BSI within the first 30 days after allogeneic HCT in children/adolescents and young adults (AYAs). The study included 115 patients aged <31 years who underwent 121 allogeneic HCTs at the Department of Pediatrics, Nagoya University Hospital between January 1, 2018, and March 31, 2022. Data encompassed demographic characteristics, HCT details, and BSI information. Overall, 27 of 121 patients developed BSI with the cumulative incidence of 23.5% (95% confidence intervals [CI]: 17.0%-30.6%) at 30 days after HCT. The median onset time of BSI was 7 (range, 4-26 days) after HCT. Gram-positive bacteria accounted for 89% of pathogens isolated from blood cultures, with Streptococcus mitis/oralis being the most common. In multivariable analysis, tandem HCT (subdistribution hazard ratio [SHR]: 5.67, 95% CI: 2.74-11.7, p < 0.001) and peripherally inserted central catheters (SHR: 2.96, 95% CI: 1.34-6.55, p  =  0.007) were identified as independent risk factors for BSI. In patients receiving tandem HCT, the pathogens isolated from blood cultures were all gram-positive bacteria, with Streptococcus mitis/oralis accounting for up to 67% of the isolated pathogens. Tandem HCT and PICCs were identified as independent risk factors for BSI after allogeneic HCT in children/AYAs. The pathogens were commonly gram-positive, and Streptococcus mitis/oralis is important in patients who received tandem HCT. These data can provide valuable information for future studies to consider effective interventions to reduce the risk of BSI in high-risk patients.

Randomized Double-Blind Phase II Trial of Fecal Microbiota Transplantation Versus Placebo in Allogeneic Hematopoietic Cell Transplantation and AML

PURPOSE

Gut microbiota injury in allogeneic hematopoietic cell transplantation (HCT) recipients and patients with AML has been associated with adverse clinical outcomes. Previous studies in these patients have shown improvements in various microbiome indices after fecal microbiota transplantation (FMT). However, whether microbiome improvements translate into improved clinical outcomes remains unclear. We examined this question in a randomized, double-blind, placebo-controlled phase II trial.

METHODS

Two independent cohorts of allogeneic HCT recipients and patients with AML receiving induction chemotherapy were randomly assigned in a 2:1 ratio to receive standardized oral encapsulated FMT versus placebo upon neutrophil recovery. After each course of antibacterial antibiotics, patients received a study treatment. Up to three treatments were administered within 3 months. The primary end point was 4-month all-cause infection rate. Patients were followed for 9 months.

RESULTS

In the HCT cohort (74 patients), 4-month infection density was 0.74 and 0.91 events per 100 patient-days in FMT and placebo arms, respectively (infection rate ratio, 0.83; 95% CI, 0.48 to 1.42; P = .49). In the AML cohort (26 patients), 4-month infection density was 0.93 in the FMT arm and 1.25 in the placebo arm, with an infection rate ratio of 0.74 (95% CI, 0.32 to 1.71; P = .48). Unique donor bacterial sequences comprised 25%-30% of the fecal microbiota after FMT. FMT improved postantibiotic recovery of microbiota diversity, restored several depleted obligate anaerobic commensals, and reduced the abundance of expanded genera Enterococcus, Streptococcus, Veillonella, and Dialister.

CONCLUSION

In allogeneic HCT recipients and patients with AML, third-party FMT was safe and ameliorated intestinal dysbiosis, but did not decrease infections. Novel findings from this trial will inform future development of FMT trials.

Adverse effects of antibiotics in children with cancer: are short-course antibiotics for febrile neutropenia part of the solution?

INTRODUCTION

Febrile neutropenia is a common complication experienced by children with cancer or those undergoing hematopoietic stem cell transplantation. Repeated episodes of febrile neutropenia result in cumulative exposure to broad-spectrum antibiotics with potential for a range of serious adverse effects. Short-course antibiotics, even in patients with high-risk febrile neutropenia, may offer a solution.

AREAS COVERED

This review addresses the known broad effects of antibiotics, highlights developments in understanding the relationship between cancer, antibiotics, and the gut microbiome, and discusses emerging evidence regarding long-term adverse antibiotic effects. The authors consider available evidence to guide the duration of empiric antibiotics in pediatric febrile neutropenia and directions for future research.

EXPERT OPINION

Broad-spectrum antibiotics are associated with antimicrobial resistance, Clostridioides difficile infection, invasive candidiasis, significant disturbance of the gut microbiome and may seriously impact outcomes in children with cancer or undergoing allogenic hematopoietic stem cell transplant. Short-course empiric antibiotics are likely safe in most children with febrile neutropenia and present a valuable opportunity to reduce the risks of antibiotic exposure.

Febrile Neutropenia Duration Is Associated with the Severity of Gut Microbiota Dysbiosis in Pediatric Allogeneic Hematopoietic Stem Cell Transplantation Recipients

Simple Summary

Febrile neutropenia is a common complication in pediatric patients undergoing allogeneic hematopoietic stem cell transplantation. Its genesis is often attributed to infections; however, a specific cause frequently cannot be defined. We hypothesize that the composition of the intestinal flora may contribute to the genesis of the neutropenic fever. We analyzed the microbial composition of stool samples from pediatric patients from three European centers and assessed the relationship with the duration of the fever during neutropenia. We found that a more stable composition of the microbiota during the transplantation course is associated with a shorter duration of fever. Moreover, patients with a higher duration of fever presented higher levels of Collinsella, Megasphaera, Prevotella, Roseburia, Eggerthella and Akkermansia in the stool.

Abstract

Febrile neutropenia (FN) is a common complication in pediatric patients receiving allogeneic hematopoietic stem cell transplantation (HSCT). Frequently, a precise cause cannot be identified, and many factors can contribute to its genesis. Gut microbiota (GM) has been recently linked to many transplant-related complications, and may also play a role in the pathogenesis of FN. Here, we conducted a longitudinal study in pediatric patients receiving HSCT from three centers in Europe profiling their GM during the transplant course, particularly at FN onset. We found that a more stable GM configuration over time is associated with a shorter duration of fever. Moreover, patients with longer lasting fever exhibited higher pre-HSCT levels of Collinsella, Megasphaera, Prevotella and Roseburia and increased proportions of Eggerthella and Akkermansia at the engraftment. These results suggest a possible association of the GM with the genesis and course of FN. Data seem consistent with previous reports on the relationship of a so-called “healthy” GM and the reduction of transplant complications. To our knowledge, this is the first report in the pediatric HSCT setting. Future studies are warranted to define the underling biological mechanisms and possible clinical implications.

The 2020 BMT CTN Myeloma Intergroup Workshop on Immune Profiling and Minimal Residual Disease Testing in Multiple Myeloma

The fifth annual Blood and Marrow Transplant Clinical Trials Network Myeloma Intergroup Workshop on Immune Profiling and Minimal Residual Disease Testing in Multiple Myeloma was conducted as one of the American Society of Hematology Annual Meeting Scientific Workshops on Thursday December 3, 2020. This workshop focused on four main topics: (1) integrating minimal residual disease into clinical trial design and practice; (2) the molecular and immunobiology of disease evolution and progression in myeloma; (3) adaptation of next-generation sequencing, next-generation flow cytometry, and cytometry by time of flight techniques; and (4) chimeric antigen receptor T-cell and other cellular therapies for myeloma. In this report, we provide a summary of the workshop presentations and discuss future directions in the field.

Gut Microbiota Dysbiosis Associated with Persistent Fatigue in Hematopoietic Cell Transplantation Survivors

Fatigue is one of the most prevalent and distressing complications among hematopoietic stem cell transplantation (HCT) survivors, negatively affecting physical, social, and emotional domains of quality of life. Chronic systemic inflammation has been linked to alterations in nervous system activity and initiation of distressing symptoms, such as fatigue. Damage to gut mucosa due to alteration in gut microbiota (GM) composition and microbial translocation has been shown to increase systemic proinflammatory cytokines. The aim of this study was to evaluate the relationship between fatigue and GM by measuring the differences in GM composition in HCT survivors with and without persistent fatigue. This cross-sectional study included 30 adults who underwent HCT for a hematologic disease and were at least 1 year post-HCT. Patients with chronic graft-versus-host disease were excluded. Fatigue severity was assessed by the Brief Fatigue Inventory (BFI). Based on the BFI score, patients were grouped into 2 categories: 0 to 3 (without fatigue) and ≥4 (with fatigue). The V1 to V3 region of the 16S rRNA gene from fecal specimens was sequenced using the Illumina MiSeq. Sequencing reads were processed, denoised, and replicated, chimeras were filtered, amplicon sequence variants (ASVs) were generated, and taxonomy was assigned using DADA2. Beta diversity analysis through principal coordinate analysis was generated using the Bray-Curtis dissimilarity matrix, and the difference was tested using linear model with generalized least squares in R. An alpha diversity analysis was performed using Chao1. Linear discriminant analysis effect size (LEfSe) was used to find markers that differ between the 2 groups. Based on the BFI results, patients were categorized into 2 cohorts: with fatigue (n = 14) and without fatigue (n = 16). The 2 cohorts were similar in terms of demographics, disease, and transplant characteristics. Based on the GM analysis, there was a significant difference in GM composition (beta diversity) between the 2 cohorts (P = .001). Alpha diversity (richness) was also significantly lower in survivors with fatigue (P =.002). LEfSe analysis identified 46 discriminative features (P < .05; linear discriminant analysis score >2) whose relative abundance varied significantly among individuals with fatigue and those without fatigue. Ten ASVs were associated with the patients with fatigue, and 36 ASVs were associated with those without fatigue. Several ASVs enriched in survivors with fatigue included organisms such as Klebsiella and Enterococcus, which have been implicated in inflammatory bowel diseases. The ASVs enriched in the cohort without fatigue were members of the Ruminococcaceae family (Oscillospira spp) and the Lachnospiraceae family (Fusicatenibacter and Coprococcus spp), which are known to have the ability to ferment complex plant carbohydrates. These findings show an association between GM composition and fatigue and suggest a microbial contribution to clinically significant fatigue post-HCT, which may guide the development of new approaches to treating fatigue based on manipulation of the GM.

Introduction to host microbiome symbiosis in health and disease

Humans share a core intestinal microbiome and yet human microbiome differs by genes, species, enterotypes (ecology), and gene count (microbial diversity). Achievement of microbiota metagenomic analysis has revealed that the microbiome gene count is a key stratifier of health in several immune disorders and clinical conditions. We review here the progress of the metagenomic pipeline analysis, and how this has allowed us to define the host-microbe symbiosis associated with a healthy status. The link between host-microbe symbiosis disruption, the so-called dysbiosis and chronic diseases or iatrogenic conditions is highlighted. Finally, opportunities to use microbiota modulation, with specific nutrients and/or live microbes, as a target for personalized nutrition and therapy for the maintenance, preservation, or restoration of host-microbe symbiosis are discussed.