Prevention of infection and graft-versus-host disease by suppression of intestinal microflora in children treated with allogeneic bone marrow transplantation

Gut microbiota variation and diversity and gut graft-versus-host disease (GVHD) in pediatrics: A systematic review

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) provides children with life-threatening conditions an opportunity for survival. Complications from graft-versus-host disease (GVHD) are a major source of morbidity and death, recently linked to gut dysbiosis in the hematopoietic stem cell transplantation (HSCT) population. But so far, no comprehensive study has been conducted to investigate this relationship in the children population. In this systematic study, we investigated the Gut microbiota variation and diversity and gut GVHD in pediatrics.

METHODS

A systematic review according to PRISMA standards was performed from inception till August 2024. Out of 568 originally chosen publications, 10 studies involving 490 pediatric subjects satisfied the eligibility criteria and were included.

RESULTS

The findings obtained from the study included in the present systematic study mostly indicated the use of combined treatments including Busulfan, Cyclophosphamide, and total body irradiation and in some studies the use of anti-thymocyte globulin and Melphalan as conditioning regimens. In addition, out of 10 reviewed studies, 9 reported a significant decrease in gut microbiota diversity following GVHD. However, in all studies, an increased variation was reported. So that most of the studies showed a decrease in the levels of beneficial bacteria and producers of short-chain fatty acid products in the intestine such as Ruminococcaceae and Enterococcus, which is also observed in the intestinal microbiota population of healthy people.

CONCLUSION

As a result, our findings indicated a decrease in diversity as well as a change in intestinal microbiota in children with GVHD under HSCT in most of the studies.

Levofloxacin Prophylaxis in Pediatric and Young Adult Allogeneic Hematopoietic Stem Cell Transplantation Recipients Does not Prevent Infective Complications and Infections-related Deaths

Background

The prophylactic use of quinolones in the setting of allogeneic hematopoietic stem cell transplantation (allo-HCT) is controversial and solid evidence is missing, particularly in children.

Methods

In this single-center retrospective study, we compared outcomes in patients receiving (n = 74) or not receiving (n = 70) levofloxacin (LVX) prophylaxis, assessing overall survival, event-free survival, acute graft-versus-host disease (aGvHD) and bloodstream infection incidence, and infection-related mortality. Gut microbiota composition was analyzed in a subgroup using 16S rRNA sequencing of stool samples collected pre-HCT and at engraftment.

Results

We analyzed 144 allo-HCT in 143 patients performed for any indication. No differences were found in the 2 groups regarding main HCT outcomes, namely, cumulative incidence of aGvHD (37.9% vs 43.5%; P = .733), grade III-IV aGvHD (12.2% vs 8.7%; P = .469), gut aGVHD (12.2% vs 17.5%; P = .451), bloodstream infections (25.6% vs 34.1%; P = .236) and death from bacterial infection (9.5% vs 4.3%; P = 0.179). In patients experiencing bacterial infections, those receiving prophylaxis showed higher incidence of quinolone-resistant strains (P = .001). On a subgroup of 50 patients, we analyzed the gut microbiota composition, showing a lower abundance of Blautia (P = .015), Enterococcus (P = .011), and Actinomyces (P = .07) at neutrophil engraftment in patients receiving LVX prophylaxis.

Conclusions

LVX prophylaxis in the setting of allo-HCT does not prevent infective complications and increases the prevalence of antibiotic-resistant strains.

Advancing therapeutic strategies for graft-versus-host disease by targeting gut microbiome dynamics in allogeneic hematopoietic stem cell transplantation: current evidence and future directions

Hematopoietic stem cell transplantation (HSCT) is a highly effective therapy for malignant blood illnesses that pose a high risk, as well as diseases that are at risk due to other variables, such as genetics. However, the prevalence of graft-versus-host disease (GVHD) has impeded its widespread use. Ensuring the stability of microbial varieties and associated metabolites is crucial for supporting metabolic processes, preventing pathogen intrusion, and modulating the immune system. Consequently, it significantly affects the overall well-being and susceptibility of the host to disease. Patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) may experience a disruption in the balance between the immune system and gut bacteria when treated with medicines and foreign cells. This can lead to secondary intestinal inflammation and GVHD. Thus, GM is both a reliable indicator of post-transplant mortality and a means of enhancing GVHD prevention and treatment after allo-HSCT. This can be achieved through various strategies, including nutritional support, probiotics, selective use of antibiotics, and fecal microbiota transplantation (FMT) to target gut microbes. This review examines research advancements and the practical use of intestinal bacteria in GVHD following allo-HSCT. These findings may offer novel insights into the prevention and treatment of GVHD after allo-HSCT.

Microbiome and Hemato-immune Aging

The microbiome is a highly complex and diverse symbiotic component that undergoes dynamic changes with the organismal aging. Microbial perturbations, termed dysbiosis, exert strong influence on dysregulating the bone marrow niche and subsequently promoting the aging of hematopoietic and immune system. Accumulating studies have revealed the substantial impact of intestinal microbiome on the initiation and progression of age-related hematologic alteration and diseases, such as clonal hematopoiesis and blood cancers. Current therapeutic approaches to restore the altered microbiome diversity target specific pathobionts and are demonstrated to improve clinical outcomes of antihematologic malignancy treatments. In this review, we discuss the interplay between the microbiome and the hemato-immune system during aging process. We also shed light on the emerging therapeutic strategies to tackle the dysbiosis for amelioration of aging and disease progression.

Open-Label Randomized Controlled Study of Ciprofloxacin vs Rifaximin as Neutropenia Prophylaxis in Allogeneic Hematopoietic Stem Cell Transplantation

Loss of microbiota diversity has been clearly associated with poor outcomes in the allogeneic hematopoietic stem cell transplantation setting. However, the choice of the optimal antibiotic prophylaxis during the pre-engraftment phase remains unclear. We designed a prospective randomized study to compare our standard-of-care neutropenia prophylaxis (ciprofloxacin) with rifaximin. We enrolled 38 consecutive adult patients who underwent allogeneic hematopoietic stem cell transplantation setting and were randomly assigned to receive ciprofloxacin (20 patients) or rifaximin (18 patients) at day -1. Pretransplant and transplant characteristics did not differ between groups. Cumulative incidence (CI) of acute graft-vs-host disease grade II to IV and moderate/severe chronic graft-vs-host disease was similar in both groups. With a median follow-up of 13.2 months (range, 6.8-30.2) in surviving patients, the 1-year CI of relapse was 20.8% in ciprofloxacin vs 17.8% in rifaximin (P = .616). Importantly, the 1-year CI of treatment-related mortality was significantly reduced in the ciprofloxacin group (10.2% vs 27.8%, P = .032), leading to higher 1-year overall survival (88.9% vs 74.6%, P = .038). In Cox-regression multivariate analysis, antibiotic prophylaxis remained the only predictor of overall survival, independently of donor type, disease risk index, and moderate/severe chronic graft-vs-host disease. Further studies are needed to assess the effects on microbiota diversity and confirm these outcomes.

Restrictive Versus Permissive Use of Broad-spectrum Antibiotics in Patients Receiving Allogeneic Stem Cell Transplantation and With Early Fever Due to Cytokine Release Syndrome: Evidence for Beneficial Microbiota Protection Without Increase in Infectious Complications

BACKGROUND

Intestinal microbiome contributes to the pathophysiology of acute gastrointestinal (GI) graft-versus-host disease (GvHD) and loss of microbiome diversity influences the outcome of patients after allogeneic stem cell transplantation (SCT). Systemic broad-spectrum antibiotics have been identified as a major cause of early intestinal dysbiosis.

METHODS

In 2017, our transplant unit at the university hospital in Regensburg changed the antibiotic strategy from a permissive way with initiation of antibiotics in all patients with neutropenic fever independent of the underlying cause and risk to a restrictive use in cases with high likelihood of cytokine release syndrome (eg, after anti-thymocyte globulin [ATG] therapy). We analyzed clinical data and microbiome parameters obtained 7 days after allogeneic SCT from 188 patients with ATG therapy transplanted in 2015/2016 (permissive cohort, n = 101) and 2918/2019 (restrictive cohort, n = 87).

RESULTS

Restrictive antibiotic treatment postponed the beginning of antibiotic administration from 1.4 ± 7.6 days prior to 1.7 ± 5.5 days after SCT (P = .01) and significantly reduced the duration of antibiotic administration by 5.8 days (P < .001) without increase in infectious complications. Furthermore, we observed beneficial effects of the restrictive strategy compared with the permissive way on microbiome diversity (urinary 3-indoxylsulfate, P = .01; Shannon and Simpson indices, P < .001) and species abundance 7 days post-transplant as well as a positive trend toward a reduced incidence of severe GI GvHD (P = .1).

CONCLUSIONS

Our data indicate that microbiota protection can be achieved by a more careful selection of neutropenic patients qualifying for antibiotic treatment during allogeneic SCT without increased risk of infectious complications.

Fecal Microbiota Transplantation for Acute Graft-versus-Host Disease After Allogeneic Hematopoietic Cell Transplantation: Expanding the Horizon into Pediatrics

The microbiome plays a vital role in maintaining homeostasis of the intestinal microenvironment and immune response in allogeneic hematopoietic cell transplantation (HCT) recipients. Disruption of the intestinal microbiome has been associated with the development of acute graft-versus-host disease (GVHD) of the lower GI tract and worse survival. Fecal microbiota transplantation (FMT) can achieve clinical responses in refractory GVHD, establishing the promise of microbiome-directed interventions in this population. While most data about microbial changes in HCT recipients have been generated from the adult population, children with refractory GVHD represent an important group that may benefit from FMT. In this review, we first highlight characteristics that distinguish the pediatric intestinal microbiome from adults. Subsequently, we explore multiple clinical factors that warrant careful consideration to optimize the application of FMT and other microbiome-directed therapeutics to children.

Longitudinal relationship between the gut microbiota variation and diversity and gut graft-versus-host disease (GVHD) following pediatric allogeneic hematopoietic cell transplantation (HCT) - Case series

Allogeneic Hematopoietic Cell Transplantation (HCT) offers children with life-threatening diseases a chance at survival. Complications from graft-versus-host disease (GVHD, Stages 0-4) represent a significant cause of morbidity and mortality which has been recently associated with gut dysbiosis the adult HCT population. Here, our objective was to conduct a prospective, longitudinal cohort study in nine pediatric allogeneic HCT participants by collecting longitudinally post-HCT stool specimens up to 1 year. Stool microbiota analyses showed that allogeneic HCT and antibiotic therapy lead to acute shifts in the diversity of the gut microbiota with those experiencing stages 3-4 gut GVHD having significantly greater microbiota variation over time when compared to control participants (p = 0.007). Pre-HCT microbiota diversity trended towards an inverse relationship with gut microbiota stability over time, however, this did not reach statistical significance (p = 0.05). Future large prospective studies are necessary to elucidate the mechanisms underlying these dynamic changes in the gut microbiota following pediatric allogeneic HCT.

The emerging role of nutritional support in the supportive care of pediatric patients undergoing hematopoietic stem cell transplantation

Allogeneic Hematopoietic Stem Cell Transplantation (allo-HSCT) represents a potentially curative strategy for many oncological, hematological, metabolic, and immunological diseases in children. The continuous effort in ameliorating supportive care represents one of the cornerstones in the improvement of outcome in these patients. Nowadays, more than ever nutritional support can be considered a key feature. Oral feeding in the early post-transplant period is severely impaired because of mucositis due to conditioning regimen, characterized by, mainly by vomiting, anorexia, and diarrhea. Gastrointestinal acute graft-versus-host-disease (GvHD), infections and associated treatments, and other medications, such as opioids and calcineurin inhibitors, have also been correlated with decreased oral intake. The consequent reduction in caloric intake combined with the catabolic effect of therapies and transplantation-related complications with consequent extended immobilization, results in a rapid deterioration of nutritional status, which is associated with decreased overall survival and higher complication rates during treatment. Thus, nutritional support during the early post-transplantation period becomes an essential and challenging issue for allo-HSCT recipients. In this context, the role of nutrition in the modulation of the intestinal flora is also emerging as a key player in the pathophysiology of the main complications of HSCT. The pediatric setting is characterized by less evidence, considering the challenge of addressing nutritional needs in this specific population, and many questions are still unanswered. Thus, we perform a narrative review regarding all aspects of nutritional support in pediatric allo-HSCT recipients, addressing the assessment of nutritional status, the relationship between nutritional status and clinical outcomes and the evaluation of the nutritional support, ranging from specific diets to artificial feeding.

Melatonin and probiotics ameliorate nanoplastics-induced hematopoietic injury by modulating the gut microbiota-metabolism

Plastic pollution has become a non-negligible global pollution problem. Nanoplastics (NP) can reach the bone marrow with blood circulation and develop hematotoxicity, but potential mechanisms and prevention strategies are lacking. Here, we report the biological distribution of NP particles in the bone marrow of mice and hematopoietic toxicity after exposure to 60 μg of 80 nm NP for 42 days. NP exposure inhibited the capability of bone marrow hematopoietic stem cells to renew and differentiate. Notably, probiotics and melatonin supplementation significantly ameliorated NP-induced hematopoietic damage, and the former was superior to the latter. And interestingly, melatonin and probiotic interventions may involve different microbes and metabolites. After melatonin intervention, creatine showed a stronger correlation with NP-induced gut microbiota disorders. In contrast, probiotic intervention reversed the levels of more gut microbes and plasma metabolites. Of these, threonine, malonylcarnitine, and 3-hydroxybutyric acid might be potential performers in the regulation of hematopoietic toxicity by gut microbes, as they had a more significant relationship with the identified microbes. In conclusion, supplementation with melatonin or probiotics may be two candidates to prevent hematopoietic toxicity attributable to NP exposure. Also, the multi-omics results may lay the foundation for future investigations into in-depth mechanisms.

Recent Metabolic Advances for Preventing and Treating Acute and Chronic Graft Versus Host Disease

The therapeutic efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is limited by the development of graft-versus-host disease (GVHD). In GVHD, rigorous pre-conditioning regimen resets the immune landscape and inflammatory milieu causing immune dysregulation, characterized by an expansion of alloreactive cells and a reduction in immune regulatory cells. In acute GVHD (aGVHD), the release of damage- and pathogen- associated molecular patterns from damaged tissue caused by the conditioning regimen sets the stage for T cell priming, activation and expansion further exacerbating tissue injury and organ damage, particularly in the gastrointestinal tract. Studies have shown that donor T cells utilize multiple energetic and biosynthetic pathways to mediate GVHD that can be distinct from the pathways used by regulatory T cells for their suppressive function. In chronic GVHD (cGVHD), donor T cells may differentiate into IL-21 producing T follicular helper cells or tissue resident T helper cells that cooperate with germinal center B cells or memory B cells, respectively, to produce allo- and auto-reactive antibodies with subsequent tissue fibrosis. Alternatively, donor T cells can become IFN- γ/IL-17 cytokine expressing T cells that mediate sclerodermatous skin injury. Patients refractory to the first line standard regimens for GVHD treatment have a poor prognosis indicating an urgent need for new therapies to restore the balance between effector and regulatory immune cells while preserving the beneficial graft-versus-tumor effect. Emerging data points toward a role for metabolism in regulating these allo- and auto-immune responses. Here, we will discuss the preclinical and clinical data available on the distinct metabolic demands of acute and chronic GVHD and recent efforts in identifying therapeutic targets using metabolomics. Another dimension of this review will examine the changing microbiome after allo-HSCT and the role of microbial metabolites such as short chain fatty acids and long chain fatty acids on regulating immune responses. Lastly, we will examine the metabolic implications of coinhibitory pathway blockade and cellular therapies in allo-HSCT. In conclusion, greater understanding of metabolic pathways involved in immune cell dysregulation during allo-HSCT may pave the way to provide novel therapies to prevent and treat GVHD.

Impact of anti-anaerobic antibiotic activity on graft-versus-host disease in allogeneic hematopoietic stem cell transplant (HSCT) recipients at an institution that utilizes antibiotic cycling

BACKGROUND

At our institution, antibiotic cycling for febrile neutropenia is utilized to increase heterogeneity of antibiotic exposure in patients who have undergone an allogeneic hematopoietic stem cell transplantation (allo-HSCT). Development of acute graft-versus-host disease (aGVHD) has been associated with low diversity within stool microbiota. To date, discordant outcomes have been reported implicating anti-anaerobic antibiotic use with the development of aGVHD, and there is currently a lack of published data available in an antibiotic cycled environment. The objective of this study was to determine if there is a difference in the rate of aGVHD in patients who receive anti-anaerobic cycled antibiotics compared with other cycled antibiotics.

METHODS

This was a retrospective, observational study evaluating rates of aGVHD in patients who received antibiotics with anaerobic vs non-anaerobic coverage post-allo-HSCT from January 2008 to January 2018. Univariate and multivariable analyses were performed to assess associations with aGVHD. Secondary outcomes include rate of all stages of aGVHD, progression-free survival, overall survival, 100-day treatment-related mortality (TRM), and 1-year TRM.

RESULTS

A total of 273 patients were included in the study. Baseline characteristics were similar between groups, except patients who received anti-anaerobic antibiotics had more unrelated donors (P = .002), were more likely to get myeloablative preparatory regimens (P = .009), had less subtherapeutic calcineurin inhibitor serum concentrations (P = .001), and more often received T-cell depletion (P = .004). The incidence of grades II-IV aGVHD post-HSCT in patients who received anti-anaerobic antibiotics was 32.6% compared with 18.8% in patients who received other antibiotics (P = .015). Multivariable analysis showed that the occurrence of grades II-IV aGVHD was associated with cytomegalovirus reactivation (OR = 2.1, 95% CI = 1.0-4.5, P = .047), unrelated donors (OR = 6.1, 95% CI = 2.3-16.6, P < .001), and use of anti-anaerobic antibiotics (OR = 2.3, 95% CI = 1.1-4.8, P = .021). A 100-day TRM in patients who received anti-anaerobic antibiotics was 9.6% compared with 3.6% in patients who received other antibiotics (P = .046). One-year TRM in patients who received anti-anaerobic antibiotics was 25.2% compared with 13.8% in patients who received other antibiotics (P = .017). There was no statistically significant difference seen between groups in progression free survival or overall survival.

CONCLUSION

Variability in baseline characteristics limits ability to make strong conclusions, but patients who received antibiotics with anaerobic coverage during the first 30 days after an allogeneic HSCT appeared to be at an increased risk of developing aGVHD and TRM. Larger well-controlled trials are warranted to further clarify these relationships.

Gut Microbiota Influence in Hematological Malignancies: From Genesis to Cure

Hematological malignancies, including multiple myeloma, lymphoma, and leukemia, are a heterogeneous group of neoplasms that affect the blood, bone marrow, and lymph nodes. They originate from uncontrolled growth of hematopoietic and lymphoid cells from different stages in their maturation/differentiation and account for 6.5% of all cancers around the world. During the last decade, it has been proven that the gut microbiota, more specifically the gastrointestinal commensal bacteria, is implicated in the genesis and progression of many diseases. The immune-modulating effects of the human microbiota extend well beyond the gut, mostly through the small molecules they produce. This review aims to summarize the current knowledge of the role of the microbiota in modulating the immune system, its role in hematological malignancies, and its influence on different therapies for these diseases, including autologous and allogeneic stem cell transplantation, chemotherapy, and chimeric antigen receptor T cells.

The emerging roles of the gut microbiome in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is used for the treatment of hematologic cancers and disorders. However, graft-versus-host disease (GVHD) in which the donor immune cells attack the genetically-disparate recipient is a significant cause of morbidity. Acute GVHD is an inflammatory condition and the gastrointestinal system is a major organ affected but is also tied to beneficial graft-versus-tumor (GVT) effects. There is increasing interest on the role of the microbiome on immune function as well as on cancer progression and immunotherapy outcomes. However, there are still significant unanswered questions on the role the microbiome plays in GVHD progression or how to exploit the microbiome in GVHD prevention or treatment. In this review, concepts of HSCT with the focus on GVHD pathogenesis as well as issues in preclinical models used to study GVHD will be discussed with an emphasis on the impact of the microbiome. Factors affecting the microbiome and GVHD outcome such as obesity are also examined. The bridging of preclinical models and clinical outcomes in relation to the role of the microbiome will also be discussed along with possibilities for therapeutic exploitation.

Applications of gut microbiota in patients with hematopoietic stem-cell transplantation

Studies of the gut microbiota (GM) have demonstrated the close link between human wellness and intestinal commensal bacteria, which mediate development of the host immune system. The dysbiosis, a disruption of the microbiome natural balance, can cause serious health problems. Patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) may cause significant changes in GM due to their underlying malignancies and exposure to extensive chemotherapy and systemic antibiotics, which may lead to different disorders. There are complex and multi-directional interactions among intestinal inflammation, GM and immune reactivity after HSCT. There is considerable effect of the human intestinal microbiome on clinical course following HSCT. Some bacteria in the intestinal ecosystem may be potential biomarkers or therapeutic targets for preventing relapse and improving survival rate after HSCT. Microbiota can be used as predictor of mortality in allo-HSCT. Two different strategies with targeted modulation of GM, preemptive and therapeutic, have been used for preventing or treating GM dysbiosis in patients with HSCT. Preemptive strategies include enteral nutrition (EN), prebiotic, probiotic, fecal microbiota transplantation (FMT) and antibiotic strategies, while therapeutic strategies include FMT, probiotic and lactoferrine usages. In this review, we summarize the advance of therapies targeting GM in patients with HSCT.

The gut microbiome in pediatric patients undergoing allogeneic hematopoietic stem cell transplantation

The gut microbiome (GM) has been associated with different clinical outcomes in the context of allogeneic hematopoietic stem cell transplantation (HSCT). Large multicenter cohort studies in adults have found significant correlations with overall survival, relapse, and incidence of complications. Moreover, GM is already a promising target for therapeutic interventions. However, few data are available in children, a population presenting unique features and challenges. During childhood, the GM evolves rapidly with large structural fluctuations, alongside with the maturation of the immune system. Furthermore, the HSCT procedure presents significant differences in children. These considerations underline the importance of a specific focus on the pediatric setting, and the role of GM and its age-dependent trajectory in influencing the immunity reconstitution and clinical outcomes. This review provides a comprehensive overview of the available evidence in the field of GM and pediatric HSCT, highlighting age-specific issues and discussing GM-based therapeutic approaches.

The Impact of Antibiotic-Mediated Modification of the Intestinal Microbiome on Outcomes of Allogeneic Hematopoietic Cell Transplantation: Systematic Review and Meta-Analysis

Accumulating evidence points toward a protective role of intestinal microbiota diversity in allogeneic hematopoietic cell transplantation (allo-HCT). The purpose of this systematic review and meta-analysis is to determine the effect of antibiotic-mediated disruption of microbiota on main allo-HCT outcomes (graft-versus-host disease [GVHD], treatment-related mortality [TRM], overall survival [OS]). Following literature search, 2 reviewers screened eligible studies and assessed risk of bias (RoB). Meta-analysis was performed using Review Manager Software. Among 443 screened references, 18 were eligible for meta-analysis. In studies with genomic markers, grade II to IV acute GVHD was significantly reduced in patients not receiving gut decontamination (GD) (odds ratio [OR], 1.56; 95% confidence interval [CI], 1.20 to 2.04). In subgroup analysis, prophylaxis with systemic antibiotics conferred an increased risk of acute GVHD (OR, 1.65; 95% CI, 1.08 to 2.53). When we incorporated RoB, we found a positive correlation of intestinal GVHD with GD (OR, 1.77; 95% CI, 1.29 to 2.44). Patients with higher microbiota diversity presented increased OS (risk ratio [RR], 1.58; 95% CI, 1.19 to 2.09) and lower TRM (RR, 0.45; 95% CI, 0.26 to 0.76). Our findings confirm that GD and prophylaxis with systemic antibiotics increase acute and intestinal GVHD. Importantly, our meta-analysis was the first to show a significant effect of microbiota diversity on TRM and OS.

Treating From the Inside Out: Relevance of Fecal Microbiota Transplantation to Counteract Gut Damage in GVHD and HIV Infection

The gastrointestinal (GI) tract is a complex and well-balanced milieu of anatomic and immunological barriers. The epithelial surface of the GI tract is colonized by trillions of microorganisms, known as the gut microbiota, which is considered an “organ” with distinctive endocrine and immunoregulatory functions. Dysregulation of the gut microbiota composition, termed dysbiosis, has been associated with epithelial damage and translocation of microbial products into the circulating blood. Dysbiosis, increased gut permeability and chronic inflammation play a major role on the clinical outcome of inflammatory bowel diseases, graft-vs.-host disease (GVHD) and HIV infection. In this review, we focus on GVHD and HIV infection, conditions sharing gut immune damage leading to dysbiosis. The degree of dysbiosis and level of epithelial gut damage predict poor clinical outcome in both conditions. Emerging interventions are therefore warranted to promote gut microbiota homeostasis and improve intestinal barrier function. Interventions such as anti-inflammatory medications, and probiotics have toxicity and/or limited transitory effects, justifying innovative approaches. Fecal microbiota transplantation (FMT) is one such approach where fecal microorganisms are transferred from healthy donors into the GI tract of the recipient to restore microbiota composition in patients with Clostridium difficile-induced colitis or inflammatory bowel diseases. Preliminary findings point toward a beneficial effect of FMT to improve GVHD and HIV-related outcomes through the engraftment of beneficial donor bacteria, notably those producing anti-inflammatory metabolites. Herein, we critically review the potential for FMT in alleviating dysbiosis and gut damage in patients with GVHD or HIV-infection. Understanding the underlying mechanism by which FMT restores gut function will pave the way toward novel scalable and targeted interventions.

Assessing the impact on intestinal microbiome and clinical outcomes of antibiotherapy optimisation strategies in haematopoietic stem cell transplant recipients: study protocol for the prospective multicentre OptimBioma study

INTRODUCTION

Haematopoietic stem cell transplantation (HSCT) is a life-saving treatment for a number of haematological diseases. Graft versus host disease (GVHD) is its main complication and hampers survival. There is strong evidence that intestinal microbiota diversity of the recipient may increase the risk of GVHD worsening survival. Antibiotic regimens used during the early phase of the transplant may influence clinical outcomes by reducing intestinal microbiota diversity. Present guidelines of European Conference on Infections in Leukaemia exhort to optimising antibiotic use in haematological patients including HSCT recipients. The present study aims to investigate if, in HSCT recipients, the optimisation of antibacterial use may preserve intestinal microbiota composition reducing the incidence and severity of acute GVHD and improving relevant clinical outcomes.

METHODS AND ANALYSIS

This is a prospective longitudinal observational study of two cohorts of HSCT recipients: (1) the intervention cohort includes patients treated in centres in which a predefined strategy of antibiotherapy optimisation is implemented, with the objective of optimising and reducing antibiotic administration according to clinical criteria and (2) the control cohort includes patients treated in centres in which a classic permissive strategy of antibiotic prophylaxis and treatment is used. Adult patient receiving a first HSCT as a treatment for any haematological condition are included. Clinical variables are prospectively recorded and up to five faecal samples are collected for microbiota characterisation at prestablished peritransplant time points. Patients are followed since the preconditioning phase throughout 1-year post-transplant and four follow-up visits are scheduled. Faecal microbiota composition and diversity will be compared between both cohorts along with acute GVHD incidence and severity, severe infections rate, mortality and overall and disease-free survival.

ETHICS AND DISSEMINATION

The study was approved between 2017 and 2018 by the Ethical Committees of participant centres. Study results will be disseminated through peer-reviewed journals and national and international scientific conferences.

TRIAL REGISTRATION NUMBER

NCT03727113.

The primacy of gastrointestinal tract antigen-presenting cells in lethal graft-versus-host disease

Allogeneic stem cell transplantation is a cornerstone of curative therapy for high-risk and/or advanced hematological malignancies but remains limited by graft-versus-host disease (GVHD). GVHD is initiated by the interaction between recipient antigen-presenting cells (APCs) and donor T cells, culminating in T-cell differentiation along pathogenic type-1 and type-17 paradigms at the expense of tolerogenic regulatory T-cell patterns. Type-1 and type-17 T cells secrete cytokines (eg, granulocyte-macrophage colony-stimulating factor and interferon-γ) critical to the cytokine storm that amplifies expansion of donor APCs and their alloantigen presentation. It has become increasingly clear that pathogenic donor T-cell differentiation is initiated by both professional recipient APCs (eg, dendritic cells [DCs]) and nonprofessional APCs (eg, epithelial and mesenchymal cells), particularly within the gastrointestinal (GI) tract. In the immediate peritransplantation period, these APCs are profoundly modified by pathogen-associated molecular pattern (PAMP)/damage-associated molecular pattern (DAMP) signals derived from conditioning and intestinal microbiota. Subsequently, donor DCs in the GI tract are activated by DAMP/PAMP signals in the colon that gain access to the lamina propria once the mucosal barrier mucosa is compromised by GVHD. This results in donor DC expansion and alloantigen presentation in the colon and subsequent migration into the mesenteric lymph nodes. Here, new donor T cells are primed, expanded, differentiated, and imprinted with gut-homing integrins permissive of migration into the damaged GI tract, resulting in the lethal feed-forward cascade of GVHD. These new insights into our understanding of the cellular and molecular factors initiating GVHD, both spatially and temporally, give rise to a number of logical therapeutic targets, focusing on the inhibition of APC function in the GI tract.

Brazilian Nutritional Consensus in Hematopoietic Stem Cell Transplantation: Graft- versus -host disease

The Brazilian Consensus on Nutrition in Hematopoietic Stem Cell Transplantation: Graft- versus -host disease was approved by Sociedade Brasileira de Transplante de Medula Óssea , with the participation of 26 Brazilian hematopoietic stem cell transplantation centers. It describes the main nutritional protocols in cases of Graft- versus -host disease, the main complication of hematopoietic stem cell transplantation.

Insights into the role of intestinal microbiota in hematopoietic stem-cell transplantation

The gut microbiota (GM) is able to modulate the human immune system. The development of novel investigation methods has provided better characterization of the GM, increasing our knowledge of the role of GM in the context of hematopoietic stem-cell transplantation (HSCT). In particular, the GM influences the development of the major complications seen after HSCT, having an impact on overall survival. In fact, this evidence highlights the possible therapeutic implications of modulation of the GM during HSCT. Insights into the complex mechanisms and functions of the GM are essential for the rational design of these therapeutics. To date, preemptive and curative approaches have been tested. The current state of understanding of the impact of the GM on HSCT, and therapies targeting the GM balance is reviewed herein.

MHC Class II Antigen Presentation by the Intestinal Epithelium Initiates Graft-versus-Host Disease and Is Influenced by the Microbiota

Graft-versus-host disease (GVHD) in the gastrointestinal (GI) tract is the principal determinant of lethality following allogeneic bone marrow transplantation (BMT). Here, we examined the mechanisms that initiate GVHD, including the relevant antigen-presenting cells. MHC class II was expressed on intestinal epithelial cells (IECs) within the ileum at steady state but was absent from the IECs of germ-free mice. IEC-specific deletion of MHC class II prevented the initiation of lethal GVHD in the GI tract. MHC class II expression on IECs was absent from mice deficient in the TLR adaptors MyD88 and TRIF and required IFNγ secretion by lamina propria lymphocytes. IFNγ responses are characteristically driven by IL-12 secretion from myeloid cells. Antibiotic-mediated depletion of the microbiota inhibited IL-12/23p40 production by ileal macrophages. IL-12/23p40 neutralization prevented MHC class II upregulation on IECs and initiation of lethal GVHD in the GI tract. Thus, MHC class II expression by IECs in the ileum initiates lethal GVHD, and blockade of IL-12/23p40 may represent a readily translatable therapeutic strategy.

Oral Vancomycin Prophylaxis Is Highly Effective in Preventing Clostridium difficile Infection in Allogeneic Hematopoietic Cell Transplant Recipients

BACKGROUND

Clostridium difficile infection (CDI) is a leading cause of infectious complications in allogeneic hematopoietic cell transplant recipients (alloHCT). We sought to evaluate whether prophylactic oral vancomycin reduces the incidence of CDI in alloHCT recipients.

METHODS

We conducted a retrospective cohort study to examine the effectiveness of CDI prophylaxis with oral vancomycin, as compared to no prophylaxis, in 145 consecutive adult alloHCT recipients at the University of Pennsylvania between April 2015 and November 2016. Patients received oral vancomycin 125 mg twice daily, starting on admission and continuing until discharge. The primary outcome of interest was the association between oral vancomycin prophylaxis and CDI diagnosis. Secondary outcomes included graft-versus-host disease (GVHD) and relapse.

RESULTS

There were no cases of CDI in patients that received prophylaxis (0/90, 0%), whereas 11/55 (20%) patients who did not receive prophylaxis developed CDI (P < .001). Oral vancomycin prophylaxis was not associated with a higher risk of acute, grades 2-4 GVHD (subhazard ratio [sHR] 1.59; 95% confidence interval [CI] 0.88-2.89; P = .12), acute, grades 3-4 GVHD (sHR 0.65; 95% CI 0.25-1.66; P = .36), or acute, grades 2-4 gastrointestinal GVHD (sHR 1.95; 95% CI 0.93-4.07; P = .08) at day 180 post-transplant. No associations between oral vancomycin and relapse or survival were observed.

CONCLUSIONS

Prophylaxis with oral vancomycin is highly effective in preventing CDI in alloHCT recipients without increasing the risk of graft-versus-host disease or disease relapse. Further evaluation via a prospective study is warranted.

The gut microbiota and graft-versus-host disease

Graft-versus-host disease (GvHD) is a common complication of hematopoietic cell transplantation that negatively impacts quality of life in recipients and can be fatal. Animal experiments and human studies provide compelling evidence that the gut microbiota is associated with risk of GvHD, but the nature of this relationship remains unclear. If the gut microbiota is a driver of GvHD pathogenesis, then manipulation of the gut microbiota offers one promising avenue for preventing or treating this common condition, and antibiotic stewardship efforts in transplantation may help preserve the indigenous microbiota and modulate immune responses to benefit the host.

Positive stool culture could predict the clinical outcomes of haploidentical hematopoietic stem cell transplantation

We aimed to identify the effect of positive stool cultures (PSCs) on the clinical outcomes of patients undergoing haploidentical hematopoietic stem cell transplantation (haplo-HSCT) (n = 332). PSCs were observed in 61 patients (PSC group, 18.4%). Enterobacteriaceae in stool specimens was associated with a higher risk of bloodstream infection, and Candida in stool specimens was related to a higher risk of platelet engraftment failure. The cumulative incidence of infection-related mortality 1 year after haplo-HSCT in the PSC group was higher than that of the patients who showed persistently negative stool cultures (NSC group; 19.2% vs. 8.9%, P = 0.017). The probabilities of overall survival (71.4% vs. 83.8%, P = 0.031) and disease-free survival (69.6% vs. 81.0%, P = 0.048) 1 year after haplo-HSCT for the PSC group were significantly lower than those for the NSC group, particularly for patients who had Candida in their stool specimens. In multivariate analysis, Candida in stool specimens significantly increased the risk of mortality and was associated with poorer survival. Our results showed that PSC influenced the clinical outcomes after haplo-HSCT, particularly those who had Candida in their stool specimens.

[Prophylaxis of infections post-allogeneic transplantation: Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

Allogeneic hematopoietic stem cell transplantation is a curative treatment for many hematological diseases. However, this procedure causes the patient to be susceptible to infection. Prophylactic treatments are administered in clinical practice even thought the level of evidence of their effectiveness is not always high. In addition, changes in the transplantation procedures - use of reduced intensity conditioning, development of alternative graft sources - must lead to a rethinking of attitudes towards prophylaxis. Our working group based its recommendations on a review of referential articles and publications on the subject found in the literature. These recommendations concern the prophylaxis of infections caused by HSV1, HSV2, varicella zoster, and hepatitis B, as well as anti-bacterial and digestive decontamination prophylaxis, prevention of pneumocystis, toxoplasmosis, tuberculosis, as well as prophylaxis of fungal infections. Other infectious agents usually involved in infections post-allotransplant have been the subject of another set of recommendations from the French Society of Bone Marrow Transplantation and Cellular Therapy.

Stool Microbiota at Neutrophil Recovery Is Predictive for Severe Acute Graft vs Host Disease After Hematopoietic Cell Transplantation

Background

Graft-versus-host disease (GVHD) is common after allogeneic hematopoietic cell transplantation (HCT). Risk for death from GVHD has been associated with low bacterial diversity in the stool microbiota early after transplant; however, the specific species associated with GVHD risk remain poorly defined.

Methods

We prospectively collected serial weekly stool samples from 66 patients who underwent HCT, starting pre-transplantation and continuing weekly until 100 days post-transplant, a total of 694 observations in HCT recipients. We used 16S rRNA gene polymerase chain reaction with degenerate primers, followed by high-throughput sequencing to assess the relative abundance of sequence reads from bacterial taxa in stool samples over time.

Results

The gut microbiota was highly dynamic in HCT recipients, with loss and appearance of taxa common on short time scales. As in prior studies, GVHD was associated with lower alpha diversity of the stool microbiota. At neutrophil recovery post-HCT, the presence of oral Actinobacteria and oral Firmicutes in stool was positively correlated with subsequent GVHD; Lachnospiraceae were negatively correlated. A gradient of bacterial species (difference of the sum of the relative abundance of positive correlates minus the sum of the relative abundance of negative correlates) was most predictive (receiver operator characteristic area under the curve of 0.83) of subsequent severe acute GVHD.

Conclusions

The stool microbiota around the time of neutrophil recovery post-HCT is predictive of subsequent development of severe acute GVHD in this study.

Colonization with multidrug-resistant bacteria increases the risk of complications and a fatal outcome after allogeneic hematopoietic cell transplantation

Composition of the gut microbiota seems to influence early complications of allogeneic hematopoietic cell transplantation (HCT) such as bacterial infections and acute graft-versus-host disease (GVHD). In this study, we assessed the impact of colonization with multidrug-resistant bacteria (MDRB) prior to HCT and the use of antibiotics against anaerobic bacteria on the outcomes of HCT. We retrospectively analyzed the data of 120 patients who underwent HCT for hematologic disorders between 2012 and 2014. Fifty-one (42.5%) patients were colonized with MDRB and 39 (32.5%) had infections caused by MDRB. Prior colonization was significantly correlated with MDRB infections (P < 0.001), especially bacteremia (P = 0.038). A higher incidence of MDRB infections was observed in patients with acute (P = 0.014) or chronic (P = 0.002) GVHD and in patients aged > 40 years (P = 0.002). Colonization had a negative impact on overall survival (OS) after HCT (64 vs. 47% at 24 months; P = 0.034) and infection-associated mortality (P < 0.001). Use of metronidazole was correlated with an increased incidence of acute GVHD (P < 0.001) and lower OS (P = 0.002). Patients colonized with MDRB are more susceptible to life-threatening infections. Colonization with virulent flora is the most probable source of neutropenic infection; therefore, information about prior positive colonization should be crucial for the selection of empiric antibiotic therapy. The use of metronidazole, affecting the biodiversity of the intestinal microbiome, seems to have a significant impact on OS and acute GVHD.

Role of the intestinal mucosa in acute gastrointestinal GVHD

Intestinal graft-versus-host disease (GVHD) remains a significant obstacle to the success of allogeneic hematopoietic cell transplantation. The intestinal mucosa comprises the inner lining of the intestinal tract and maintains close proximity with commensal microbes that reside within the intestinal lumen. Recent advances have significantly improved our understanding of the interactions between the intestinal mucosa and the enteric microbiota. Changes in host mucosal tissue and commensals posttransplant have been actively investigated, and provocative insights into mucosal immunity and the enteric microbiota are now being translated into clinical trials of novel approaches for preventing and treating acute GVHD. In this review, we summarize recent findings related to aspects of the intestinal mucosa during acute GVHD.

Gut microbiota and acute graft-versus-host disease

Although allogeneic stem cell transplantation (allo-SCT) is a potentially curative treatment for various hematological diseases, acute graft-versus-host disease (GVHD) is a major cause of morbidity and mortality, and its management is clinically important. Advances in biological techniques have led to great progress in understanding the complex interactions between the host and the gut microbiota. The gut microbiota clearly modulates the immune response and is associated with the pathogenesis of various disorders. Also in allo-SCT, both preclinical and clinical results indicate that the gut microbiota is closely associated with the development of acute GVHD and transplant outcomes. These results led to the idea that improvement in quantitative and/or qualitative abnormalities of microbiota (dysbiosis) may be a new treatment strategy for acute GVHD. Evaluations of therapies targeting the gut microbiota such as probiotics or fecal microbiota transplantation have just begun. Furthermore, intervention in the gut microbiota with a nutritional approach including prebiotics, postbiotics, and antibiotics selection may also be another promising treatment option for acute GVHD.

The intestinal microbiota in allogeneic hematopoietic cell transplant and graft-versus-host disease

Hematopoietic cell transplantation (HCT) is a critical treatment of patients with high-risk hematopoietic malignancies, hematological deficiencies, and other immune diseases. In allogeneic HCT (allo-HCT), donor-derived T cells recognize host tissues as foreign, causing graft-versus-host disease (GVHD) which is a main contributor to morbidity and mortality. The intestine is one of the organs most severely affected by GVHD and research has recently highlighted the importance of bacteria, particularly the gut microbiota, in HCT outcome and in GVHD development. Loss of intestinal bacterial diversity is common during the course of HCT and is associated with GVHD development and treatment with broad-spectrum antibiotics. Loss of intestinal diversity and outgrowth of opportunistic pathogens belonging to the phylum Proteobacteria and Enterococcus genus have also been linked to increased treatment-related mortality including GVHD, infections, and organ failure after allo-HCT. Experimental studies in allo-HCT animal models have shown some promising results for prebiotic and probiotic strategies as prophylaxis or treatment of GVHD. Continuous research will be important to define the relation of cause and effect for these associations between microbiota features and HCT outcomes. Importantly, studies focused on geographic and cultural differences in intestinal microbiota are necessary to define applicability of new strategies targeting the intestinal microbiota.

The gastrointestinal tract: properties and role in allogeneic hematopoietic stem cell transplantation

INTRODUCTION

The GI-tract is a major target for both the intensive chemo and/or radiotherapy conditioning as well as for GVHD and therefore is closely associated with transplant outcome. Apart from being a target, the GI-tract is also a mediator and therefore is also a key player of the pathogenetic process following allogeneic transplantation. Areas covered: The intestinal homeostasis is regulated through complicated interactions between the key players of this process which are the intestinal epithelium, the intestinal immune system, and the intestinal microbiota. A brief description of these elements, based on published english-language articles in PubMed, as well as their role during the process of allo-HSCT is discussed in this review. Expert commentary: Data on GI-tract properties suggest a central role for the intestine in regulation of immunity, both in healthy - steady state conditions and in pathological states such as during allo-HSCT. Given the fact that in the allogeneic transplant setting severe complications such as infections and GVHD are limiting this treatment modality, understanding the mechanisms that mediate intestinal homeostasis could lead to new preventive methods and improved outcomes.

Toward revision of antimicrobial therapies in hematopoietic stem cell transplantation: target the pathogens, but protect the indigenous microbiota

Host microbiota plays important roles in providing colonization resistance to pathogens and instructing development and function of the immune system. Antibiotic treatments intended to target pathogens further weaken the host defenses and may paradoxically increase the risk of systemic infections. This consequence is especially problematic in patients undergoing hematopoietic stem cell transplantation, where the mucosal defenses are already weakened by the conditioning regimens. This review discusses the roles that indigenous microbiota plays in protecting the host and maintaining immune homeostasis. In addition, we highlight possible strategies that are being developed to allow targeted antimicrobial therapy against pathogens, while minimizing the harm to indigenous microbiota.

Sensing danger: toll-like receptors and outcome in allogeneic hematopoietic stem cell transplantation

Pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) play key roles in initiating innate and adaptive immune responses. Based mainly on animal studies there is growing evidence to suggest that TLRs are involved in the development of chemotherapy-induced mucositis and in the propagation of graft versus host reactions as well as graft versus tumor effects in allogeneic hematopoietic stem cell transplantation (HSCT). In this review we discuss these findings along with the emerging, although still preliminary, clinical evidence, that points to a role of PRRs in determining the outcome of HSCT and new therapeutic perspectives that may be related to this development.

Role of the intestinal mucosa in acute gastrointestinal GVHD

Intestinal graft-versus-host disease (GVHD) remains a significant obstacle to the success of allogeneic hematopoietic cell transplantation. The intestinal mucosa comprises the inner lining of the intestinal tract and maintains close proximity with commensal microbes that reside within the intestinal lumen. Recent advances have significantly improved our understanding of the interactions between the intestinal mucosa and the enteric microbiota. Changes in host mucosal tissue and commensals posttransplant have been actively investigated, and provocative insights into mucosal immunity and the enteric microbiota are now being translated into clinical trials of novel approaches for preventing and treating acute GVHD. In this review, we summarize recent findings related to aspects of the intestinal mucosa during acute GVHD.

Intestinal microbiome changes and stem cell transplantation: Lessons learned

Studies of the microbiome in the setting of haematopoietic stem cell transplantation (SCT) have shown evidence that intestinal microbes appear to play a particularly important role in determining the outcome of treatment, impacting complications such as infection or graft-versus-host disease. Past studies may vary in terms of the level at which the microbiome is examined, leading to different but overlapping systems of taxonomy or nomenclature, which may be difficult for non-specialists to understand. This article will review the current body of work examining the clinical impact of the microbiome on SCT, and will provide a basic framework for the bacterial phylogenetic structure upon which the results of these studies rest. With this framework it can be shown that recurring patterns do emerge in prior studies identifying the microbes that confer benefit in this population.

Bacteremia during neutropenic episodes in children undergoing hematopoietic stem cell transplantation with ciprofloxacin and penicillin prophylaxis

Bacteremia during neutropenic episodes is a cause of morbidity and mortality in patients undergoing hematopoietic stem cell transplantation (HSCT). We have used oral ciprofloxacin and penicillin V, from the start of the conditioning regimen until engraftment, for the prophylaxis of bacterial infection. The objective of this study was to retrospectively analyze the prevalence of and risk factors for breakthrough bacteremia during neutropenic episodes in autologous and allogeneic HSCT patients. There were 215 patients enrolled, with a median age of 8.32 years (range 0.51-21.64 years) between 2002 and 2014. The common underlying diseases were thalassemia and acute leukemia. Bacteremia was documented in 33 patients (15.3 %), with 39 microorganisms isolated. Escherichia coli (28.2 %) and Streptococcus viridans (12.8 %) were the most commonly isolated Gram-negative and Gram-positive bacteria, respectively. Multidrug resistant strains were found in 32 and 14.3 % of Gram-negative and Gram-positive bacteria, respectively. Risk factors for bacteremia were receiving anti-thymocyte globulin (ATG) [odds ratio (OR) 2.44, 95 % confidence interval (CI) 1.06-5.65, P = 0.037] and umbilical cord blood as a stem cell graft (OR 6.60, 95 % CI 1.04-41.83, P = 0.045). In conclusion, the prevalence of bacteremia was 15.3 % and the use of ATG and cord blood were risk factors for bacteremia during neutropenic episodes.

Modulation of Immunoregulatory Properties of Mesenchymal Stromal Cells by Toll-Like Receptors: Potential Applications on GVHD

In the last decade, the immunomodulatory properties of mesenchymal stromal cells (MSCs) have attracted a lot of attention, due to their potential applicability in the treatment of graft-versus-host disease (GVHD), a condition frequently associated with opportunistic infections. The present review addresses how Pathogen-Associated Molecular Patterns (PAMPS) modulate the immunosuppressive phenotype of human MSCs by signaling through Toll-like receptors (TLRs). Overall, we observed that regardless of the source tissue, human MSCs express TLR2, TLR3, TLR4, and TLR9. Stimulation of distinct TLRs on MSCs elicits distinct inflammatory signaling pathways, differentially influencing the expression of inflammatory factors and the ability of MSCs to suppress the proliferation of immune system cells. The capacity to enhance the immunosuppressive phenotype of MSCs through TLRs stimulation might be properly elucidated in order to improve the MSC-based immunotherapy against GVHD.

Antibiotic-mediated modification of the intestinal microbiome in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is curative for many patients with severe benign and malignant hematologic disorders. The success of allogeneic HSCT is limited by the development of transplant-related complications such as acute graft-versus-host disease (GvHD). Early pre-clinical studies suggested that intestinal microflora contribute to the pathogenesis of acute GvHD, and that growth suppression or eradication of intestinal bacteria prevented the development of acute GvHD even in MHC-mismatched transplants. These observations led to the practice of gut decontamination (GD) with oral non-absorbable antibiotics in patients undergoing allogeneic HSCT as a method of acute GvHD prophylaxis. Microbiome studies in the modern sequencing era are beginning to challenge the benefit of this practice. In this review, we provide a historical perspective on the practice of GD and highlight findings from the limited number of clinical trials evaluating the use of GD for acute GvHD prevention in allogeneic HSCT patients. In addition, we examine the role of the gut microbiota in allogeneic HSCT in the context of recent studies linking the microflora to regulation of intestinal immune homeostasis. We discuss the implications of these findings for future strategies to reduce acute GvHD risk by selective manipulation of the microbiota.

Fecal microbiota transplantation for the intestinal decolonization of extensively antimicrobial-resistant opportunistic pathogens: a review

Treatment options for multidrug-resistant (MDR) bacterial infections are limited and often less effective. Non-pharmacologic approaches to preventing or treating MDR infections are currently restricted to improved antimicrobial stewardship and infection control practices. Fecal microbiota transplantation (FMT), a highly effective treatment for recurrent Clostridium difficile infection, has emerged as a promising therapy for intestinal MDR bacterial decolonization. A total of eight case reports have been published showing FMT resulted in intestinal decolonization of extended spectrum β-lactamase (ESBL)-producing and carbapenemase-producing Enterobacteriaceae, vancomycin-resistant Enterococci, or methicillin-resistant Staphylococcus aureus. The procedure has been shown to work even in immunocompromised patients and those experiencing medical crises without any adverse events. Five trials are currently underway to further investigate the use of FMT for MDR bacterial decolonization. FMT is a completely novel way to eradicate drug-resistant bacteria from the intestinal reservoir and should be further investigated to address the global problem of difficult-to-treat, MDR bacterial infections.