Impact of Gut Colonization by Antibiotic-Resistant Bacteria on the Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation: A Retrospective, Single-Center Study

The impact of colonization by multidrug resistant bacteria on graft survival, risk of infection, and mortality in recipients of solid organ transplant: systematic review and meta-analysis

BACKGROUND

The Global increase in colonization by multidrug-resistant (MDR) bacteria poses a significant concern. The precise impact of MDR colonization in solid organ transplant recipients (SOTR) remains not well established.

OBJECTIVES

To assess the impact of MDR colonization on SOTR's mortality, infection, or graft loss.

METHODS AND DATA SOURCES

Data from PROSPERO, OVID Medline, OVID EMBASE, Wiley Cochrane Library, ProQuest Dissertations, Theses Global, and SCOPUS were systematically reviewed, spanning from inception until 20 March 2023. The study protocol was registered with PROSPERO (CRD42022290011) and followed the PRISMA guidelines. STUDY ELIGIBILITY CRITERIA, PARTICIPANTS, INTERVENTIONS, AND ASSESSMENT OF RISK OF BIAS: Cohorts and case-control studies that reported on adult SOTR colonized by Methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), extended-spectrum β-lactamase (ESBL) or carbapenem-resistant Enterobacteriaceae. (CRE), or MDR-pseudomonas, and compared to noncolonized, were included. Two reviewers assessed eligibility, conducted a risk of bias evaluation using the Newcastle-Ottawa Scale, and rated certainty of evidence using the GRADE approach.

METHODS OF DATA SYNTHESIS

We employed RevMan for a meta-analysis, using random-effects models to compute pooled odds ratios (OR) and 95% confidence intervals (CI). Statistical heterogeneity was determined using the I2 statistic.

RESULTS

15,202 SOTR (33 cohort, six case-control studies) were included, where liver transplant and VRE colonization (25 and 14 studies) were predominant. MDR colonization significantly increased posttransplant 1-year mortality (OR, 2.35; 95% CI, 1.63-3.38) and mixed infections (OR, 10.74; 95% CI, 7.56-12.26) across transplant types (p < 0.001 and I2 = 58%), but no detected impact on graft loss (p 0.41, I2 = 0). Subgroup analysis indicated a higher association between CRE or ESBL colonization with outcomes (CRE: death OR, 3.94; mixed infections OR, 24.8; ESBL: mixed infections OR, 10.3; no mortality data) compared to MRSA (Death: OR, 2.25; mixed infection: OR, 7.75) or VRE colonization (Death: p 0.20, mixed infections: OR, 5.71).

CONCLUSIONS

MDR colonization in SOTR, particularly CRE, is associated with increased mortality. Despite the low certainty of the evidence, actions to prevent MDR colonization in transplant candidates are warranted.

Gut microbiome alterations at acute myeloid leukemia diagnosis are associated with muscle weakness and anorexia

The gut microbiota makes critical contributions to host homeostasis, and its role in the treatment of acute myeloid leukemia (AML) has attracted attention. We investigated whether the gut microbiome is affected by AML, and whether such changes are associated with hallmarks of cachexia. Biological samples and clinical data were collected from 30 antibiotic- free AML patients at diagnosis and matched volunteers (1:1) in a multicenter, cross-sectional, prospective study. The composition and functional potential of the fecal microbiota were analyzed using shotgun metagenomics. Fecal, blood, and urinary metabolomics analyses were performed. AML patients displayed muscle weakness, anorexia, signs of altered gut function, and glycemic disorders. The composition of the fecal microbiota differed between patients with AML and control subjects, with an increase in oral bacteria. Alterations in bacterial functions and fecal metabolome support an altered redox status in the gut microbiota, which may contribute to the altered redox status observed in patients with AML. Eubacterium eligens, reduced 3-fold in AML patients, was strongly correlated with muscle strength and citrulline, a marker of enterocyte mass and function. Blautia and Parabacteroides, increased in patients with AML, were correlated with anorexia. Several bacterial taxa and metabolites (e.g., Blautia, Prevotella, phenylacetate, and hippurate) previously associated with glycemic disorders were altered. Our work revealed important perturbations in the gut microbiome of AML patients at diagnosis, which are associated with muscle strength, altered redox status, and anorexia. These findings pave the way for future mechanistic work to explore the function and therapeutic potential of the bacteria identified in this study.

Prevalence and Molecular Epidemiology of Intestinal Colonization by Multidrug-Resistant Bacteria among Hematopoietic Stem-Cell Transplantation Recipients: A Bulgarian Single-Center Study

Background/Objectives: Intestinal colonization by multidrug-resistant (MDR) bacteria is considered one of the main risk factors for invasive infections in the hematopoietic stem-cell transplant (HSCT) setting, associated with hard-to-eradicate microorganisms. The aim of this study was to assess the rate of intestinal colonization by MDR bacteria and their microbial spectrum in a group of post-HSCT patients to study the genetic determinants of beta-lactam and glycopeptide resistance in the recovered isolates, as well as to determine the epidemiological relation between them. Methods: The intestinal colonization status of 74 patients admitted to the transplantation center of University Hospital "St. Marina"-Varna in the period January 2019 to December 2021 was investigated. Stool samples/rectal swabs were screened for third-generation cephalosporin and/or carbapenem-resistant Gram-negative bacteria, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Stenotrophomonas maltophilia. Identification and antimicrobial susceptibility testing were performed by Phoenix (BD, Sparks, MD, USA) and MALDI Biotyper sirius (Bruker, Bremen, Germany). Molecular genetic methods (PCR, DNA sequencing) were used to study the mechanisms of beta-lactam and glycopeptide resistance in the collected isolates, as well as the epidemiological relationship between them. Results: A total of 28 patients (37.8%) were detected with intestinal colonization by MDR bacteria. Forty-eight non-duplicate MDR bacteria were isolated from their stool samples. Amongst them, the Gram-negative bacteria prevailed (68.8%), dominated by ESBL-producing Escherichia coli (30.3%), and followed by carbapenem-resistant Pseudomonas sp. (24.2%). The Gram-positive bacteria were represented exclusively by Enterococcus faecium (31.2%). The main beta-lactam resistance mechanisms were associated with CTX-M and VIM production. VanA was detected in all vancomycin-resistant enterococci. A clonal relationship was observed among Enterobacter cloacae complex and among E. faecium isolates. Conclusions: To the best of our knowledge, this is the first Bulgarian study that presents detailed information about the prevalence, resistance genetic determinants, and molecular epidemiology of MDR gut-colonizing bacteria in HSCT patients.

Blood and guts: how the intestinal microbiome shapes hematopoiesis and treatment of hematologic disease

ABSTRACT

Over the past 10 years, there has been a marked increase in recognition of the interplay between the intestinal microbiome and the hematopoietic system. Despite their apparent distance in the body, a large literature now supports the relevance of the normal intestinal microbiota to steady-state blood production, affecting both hematopoietic stem and progenitor cells as well as differentiated immune cells. Microbial metabolites enter the circulation where they can trigger cytokine signaling that influences hematopoiesis. Furthermore, the state of the microbiome is now recognized to affect outcomes from hematopoietic stem cell transplant, immunotherapy, and cellular therapies for hematologic malignancies. Here we review the mechanisms by which microbiotas influence hematopoiesis in development and adulthood as well as the avenues by which microbiotas are thought to impact stem cell transplant engraftment, graft-versus-host disease, and efficacy of cell and immunotherapies. We highlight areas of future research that may lead to reduced adverse effects of antibiotic use and improved outcomes for patients with hematologic conditions.

Susceptible bacteria can survive antibiotic treatment in the mammalian gastrointestinal tract without evolving resistance

Antibiotic resistance and evasion are incompletely understood and complicated by the fact that murine interval dosing models do not fully recapitulate antibiotic pharmacokinetics in humans. To better understand how gastrointestinal bacteria respond to antibiotics, we colonized germ-free mice with a pan-susceptible genetically barcoded Escherichia coli clinical isolate and administered the antibiotic cefepime via programmable subcutaneous pumps, allowing closer emulation of human parenteral antibiotic dynamics. E. coli was only recovered from intestinal tissue, where cefepime concentrations were still inhibitory. Strikingly, "some" E. coli isolates were not cefepime resistant but acquired mutations in genes involved in polysaccharide capsular synthesis increasing their invasion and survival within human intestinal cells. Deleting wbaP involved in capsular polysaccharide synthesis mimicked this phenotype, allowing increased invasion of colonocytes where cefepime concentrations were reduced. Additionally, "some" mutant strains exhibited a persister phenotype upon further cefepime exposure. This work uncovers a mechanism allowing "select" gastrointestinal bacteria to evade antibiotic treatment.

Gut diversity and the resistome as biomarkers of febrile neutropenia outcome in paediatric oncology patients undergoing hematopoietic stem cell transplantation

The gut microbiota of paediatric oncology patients undergoing a conditioning regimen before hematopoietic stem cell transplantation is recently considered to play role in febrile neutropenia. Disruption of commensal microbiota and evolution of opportune pathogens community carrying a plethora of antibiotic-resistance genes play crucial role. However, the impact, predictive role and association of patient´s gut resistome in the course of the therapy is still to be elucidated. We analysed gut microbiota composition and resistome of 18 paediatric oncology patients undergoing hematopoietic stem cell transplantation, including 12 patients developing febrile neutropenia, hospitalized at The Bone Marrow Transplantation Unit of the National Institute of Children´s disease in Slovak Republic and healthy individuals (n = 14). Gut microbiome of stool samples obtained in 3 time points, before hematopoietic stem cell transplantation (n = 16), one week after hematopoietic stem cell transplantation (n = 16) and four weeks after hematopoietic stem cell transplantation (n = 14) was investigated using shotgun metagenome sequencing and bioinformatical analysis. We identified significant decrease in alpha-diversity and nine antibiotic-resistance genes msr(C), dfrG, erm(T), VanHAX, erm(B), aac(6)-aph(2), aph(3)-III, ant(6)-Ia and aac(6)-Ii, one week after hematopoietic stem cell transplantation associated with febrile neutropenia. Multidrug-resistant opportune pathogens of ESKAPE, Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli found in the gut carried the significant subset of patient's resistome. Over 50% of patients treated with trimethoprim/sulfamethoxazole, piperacillin/tazobactam and amikacin carried antibiotic-resistance genes to applied treatment. The alpha diversity and the resistome of gut microbiota one week after hematopoietic stem cell transplantation is relevant predictor of febrile neutropenia outcome after hematopoietic stem cell transplantation. Furthermore, the interindividual diversity of multi-drug resistant opportunistic pathogens with variable portfolios of antibiotic-resistance genes indicates necessity of preventive, personalized approach.

Epidemiology of bloodstream infections and the impact of antimicrobial resistance in pediatric hematopoietic cell transplant

Bloodstream infections (BSI) pose a substantial threat to the well-being and survival of patients undergoing hematopoietic stem cell transplantation (HSCT). Risk factors for these infections vary across the different post-HSCT phases. In the pre-engraftment period, patients are particularly susceptible to infection due to prolonged neutropenia, mucosal damage, and extensive use of central venous line (CVL). In the post-engraftment phase, the emergence of graft versus host diseases further compounds the risk. The epidemiology of these infections has undergone notable changes over the years due to multifactorial reasons, including the evolution of protocols that intensify immunosuppression. In this context, the emergence of multi-drug resistance (MDR) microorganisms can be a challenge due to the elevated risk of mortality in these vulnerable patients. Unfortunately, there is a lack of comprehensive data on this topic, particularly in pediatrics. This article aims to provide a summary of the epidemiology of BSI in the different post-transplant phases and the impact of MDR pathogens. Having knowledge about the local epidemiology of BSI can be instrumental in tailoring targeted therapies, leading to improved survival rates in HSCT recipients.

Long- and short-term effects of fecal microbiota transplantation on antibiotic resistance genes: results from a randomized placebo-controlled trial

In small series, third-party fecal microbiota transplantation (FMT) has been successful in decolonizing the gut from clinically relevant antibiotic resistance genes (ARGs). Less is known about the short- and long-term effects of FMT on larger panels of ARGs. We analyzed 226 pre- and post-treatment stool samples from a randomized placebo-controlled trial of FMT in 100 patients undergoing allogeneic hematopoietic cell transplantation or receiving anti-leukemia induction chemotherapy for 47 ARGs. These patients have heavy antibiotic exposure and a high incidence of colonization with multidrug-resistant organisms. Samples from each patient spanned a period of up to 9 months, allowing us to describe both short- and long-term effects of FMT on ARGs, while the randomized design allowed us to distinguish between spontaneous changes vs. FMT effect. We find an overall bimodal pattern. In the first phase (days to weeks after FMT), low-level transfer of ARGs largely associated with commensal healthy donor microbiota occurs. This phase is followed by long-term resistance to new ARGs as stable communities with colonization resistance are formed after FMT. The clinical implications of these findings are likely context-dependent and require further research. In the setting of cancer and intensive therapy, long-term ARG decolonization could translate into fewer downstream infections.

The association of intestinal microbiota diversity and outcomes of allogeneic hematopoietic cell transplantation: a systematic review and meta-analysis

Growing evidence suggests that highly intestinal microbiota diversity modulates host inflammation and promotes immune tolerance. Several studies have reported that patients undergoing allo-HSCT have experienced microbiota disruption that is characterized by expansion of potentially pathogenic bacteria and loss of microbiota diversity. Thus, the primary aim of this meta-analysis was to determine the association of intestinal microbiota diversity and outcomes after allo-HSCT, and the secondary aim was to analyze the associations of some specific microbiota abundances with the outcomes of allo-HSCT. Electronic databases of Pubmed, Embase, Web of Science, and Cochrane Library were searched from inception to August 2023, and 17 studies were found eligible. The pooled estimate suggested that higher intestinal microbiota diversity was significantly associated with overall survival (OS) benefit (HR = 0.66, 95% CI: 0.55-0.78), as well as decreased risk of transplant-related mortality (HR = 0.56, 95% CI: 0.41-0.76), and lower incidence of grade II-IV aGVHD (HR = 0.41, 95% CI: 0.27-0.63). Furthermore, higher abundance of Clostridiales was associated with a superior OS (HR = 0.40, 95% CI: 0.18-0.87), while higher abundance of Enterococcus (HR = 2.03, 95% CI: 1.55-2.65), γ-proteobacteria (HR = 2.82, 95% CI: 1.53-5.20), and Candida (HR = 3.80, 95% CI: 1.32-10.94) was an adverse prognostic factor for OS. Overall, this meta-analysis highlights the protective role of higher intestinal microbiota diversity on outcomes after allo-HSCT during both pre-transplant and post-transplant periods. Some specific microbiota can be useful in the identification of patients at risk of mortality, offering new tools for individualized pre-emptive or therapeutic strategies to improve allo-HSCT outcomes.

The Promise of Precision Nutrition for Modulation of the Gut Microbiota as a Novel Therapeutic Approach to Acute Graft-versus-host Disease

Acute graft-versus-host disease (aGVHD) is a severe side effect of allogeneic hematopoietic stem cell transplantation (aHSCT) that has complex phenotypes and often unpredictable outcomes. The current management is not always able to prevent aGVHD. A neglected actor in the management of aGVHD is the gut microbiota. Gut microbiota dysbiosis after aHSCT is caused by many factors and may contribute to the development of aGVHD. Diet and nutritional status modify the gut microbiota and a wide range of products are now available to manipulate the gut microbiota (pro-, pre-, and postbiotics). New investigations are testing the effect of probiotics and nutritional supplements in both animal models and human studies, with encouraging results. In this review, we summarize the most recent literature about the probiotics and nutritional factors able to modulate the gut microbiota and we discuss the future perspective in developing new integrative therapeutic approaches to reducing the risk of graft-versus-host disease in patients undergoing aHSCT.

Fecal microbiota transplantation promotes reduction of antimicrobial resistance by strain replacement

Multidrug-resistant organism (MDRO) colonization is a fundamental challenge in antimicrobial resistance. Limited studies have shown that fecal microbiota transplantation (FMT) can reduce MDRO colonization, but its mechanisms are poorly understood. We conducted a randomized, controlled trial of FMT for MDRO decolonization in renal transplant recipients called PREMIX (NCT02922816). Eleven participants were enrolled and randomized 1:1 to FMT or an observation period followed by delayed FMT if stool cultures were MDRO positive at day 36. Participants who were MDRO positive after one FMT were treated with a second FMT. At last visit, eight of nine patients who completed all treatments were MDRO culture negative. FMT-treated participants had longer time to recurrent MDRO infection versus PREMIX-eligible controls who were not treated with FMT. Key taxa (Akkermansia muciniphila, Alistipes putredinis, Phocaeicola dorei, Phascolarctobacterium faecium, Alistipes species, Mesosutterella massiliensis, Barnesiella intestinihominis, and Faecalibacterium prausnitzii) from the single feces donor used in the study that engrafted in recipients and metabolites such as short-chain fatty acids and bile acids in FMT-responding participants uncovered leads for rational microbiome therapeutic and diagnostic development. Metagenomic analyses revealed a previously unobserved mechanism of MDRO eradication by conspecific strain competition in an FMT-treated subset. Susceptible Enterobacterales strains that replaced baseline extended-spectrum β-lactamase-producing strains were not detectable in donor microbiota manufactured as FMT doses but in one case were detectable in the recipient before FMT. These data suggest that FMT may provide a path to exploit strain competition to reduce MDRO colonization.

Risk Factors for Carbapenem-Resistant Enterobacteriaceae Colonization and the Effect on Clinical Outcomes and Prognosis in Allogeneic Hematopoietic Stem Cell Transplanted Patients

Purpose

The current study assesses which are the main risk factors, clinical outcome and prognosis following the colonization of CRE in patients that underwent allo-HSCT.

Patients and Methods

A total of 343 patients subjected to allo-HSCT in the period comprised between June 2021 and June 2022 were enrolled in this retrospective study. The CRE colonization was diagnosed by clinical history and routine microbial culture of perirectal swab. In this regard, a clinical prediction model was designed based on independent risk factors underlying the pre-transplantation CRE colonization using a backward stepwise logistic regression, followed by the evaluation of its discrimination and calibration efficacies, along with clinical usefulness. Furthermore, univariate and multivariate Cox regression analyses were then conducted to assess the risk factors for post-transplantation clinical outcomes.

Results

Out of 343 patients enrolled in this study, 135 (39.3%) reported CRE colonization. The independent risk factor variables for CRE colonization were incorporated into the nomogram to build a prediction model, which showed an area under the curve of 0.767 (95% CI: 0.716-0.818), and well-fitted calibration curves (χ2 = 1.737, P = 0.9788). The patients with CRE colonization reported a significantly lower platelet engraftment rate with a higher risk of post-transplantation BSI when compared with the non-CRE colonization group (P = 0.02 and P < 0.001; respectively). The non-relapse mortality (NRM) value was higher in the CRE patients (P < 0.05), consistently with a survival probability that was thus significantly lower for the same timeframe (P < 0.05).

Conclusion

A reliable clinical prediction model for pre-transplantation CRE colonization was developed that demonstrated that the CRE colonization negatively affects platelet engraftment and survival outcomes following allo-HSCT.

Colonization by multidrug-resistant bacteria in hematological patients undergoing hematopoietic stem cell transplantation and clinical outcomes: A single-center retrospective cohort study

BACKGROUND

Bloodstream infections are a leading cause of death in patients who undergo hematopoietic stem cell transplantation (HSCT) and are more severe when caused by multidrug-resistant (MDR) bacteria. This study proposed to investigate if colonization by MDR bacteria negatively affects the clinical outcomes in hematological patients after HSCT, as well as to evaluate possible risk factors for death due to bacteremia by the same colonizing agent.

METHODS

A single-center retrospective cohort study was conducted with 405 hematological patients submitted to a single HSCT procedure between 2015 and 2021. Patients were classified as colonized (n = 132) or noncolonized (n = 273) based on the surveillance cultures from D-30 to D+30 of transplantation, and their relevant clinical and laboratory data were collected until D+100.

RESULTS

Colonization by MDR bacteria increased blood culture positivity by all micro-organisms and also specifically by MDR bacteria, with a more pronounced effect when caused by carbapenemase-producing Klebsiella pneumoniae. Patients colonized with carbapenem-resistant K. pneumoniae had increased overall mortality (HR = 4.07, 95% CI 1.85-8.91, P = .0005) and had prolonged hospital length of stay in the context of autologous transplantation. Risk factors for death due to bacteremia by the same colonizing agent were neutropenia, colonization by carbapenem-resistant K. pneumoniae and use of high-dose total body irradiation in conditioning.

CONCLUSION

Hematological patients colonized by MDR bacteria presented a higher incidence of bloodstream infections, and colonization by carbapenemase-producing K. pneumoniae was associated with reduced overall survival.

The Role of Fecal Microbiota Transplantation in the Allogeneic Stem Cell Transplant Setting

Microbiota changes during allogeneic hematopoietic stem cell transplantation has several known causes: conditioning chemotherapy and radiation, broad-spectrum antibiotic administration, modification in nutrition status and diet, and graft-versus-host disease. This article aims to review the current knowledge about the close link between microbiota and allogeneic stem cell transplantation setting. The PubMed search engine was used to perform this review. We analyzed data on microbiota dysbiosis related to the above-mentioned affecting factors. We also looked at treatments aimed at modifying gut dysbiosis and applications of fecal microbiota transplantation in the allogeneic stem cell transplant field, with particular interest in fecal microbiota transplantation for graft-versus-host disease (GvHD), multidrug-resistant and clostridium difficile infections, and microbiota restoration after chemotherapy and antibiotic therapy.

Susceptible bacteria survive antibiotic treatment in the mammalian gastrointestinal tract without evolving resistance

In vitro systems have provided great insight into the mechanisms of antibiotic resistance. Yet, in vitro approaches cannot reflect the full complexity of what transpires within a host. As the mammalian gut is host to trillions of resident bacteria and thus a potential breeding ground for antibiotic resistance, we sought to better understand how gut bacteria respond to antibiotic treatment in vivo . Here, we colonized germ-free mice with a genetically barcoded antibiotic pan-susceptible Escherichia coli clinical isolate and then administered the antibiotic cefepime via programmable subcutaneous pumps which allowed for closer emulation of human parenteral antibiotic pharmacokinetics/dynamics. After seven days of antibiotics, we were unable to culture E. coli from feces. We were, however, able to recover barcoded E. coli from harvested gastrointestinal (GI) tissue, despite high GI tract and plasma cefepime concentrations. Strikingly, these E. coli isolates were not resistant to cefepime but had acquired mutations â€" most notably in the wbaP gene, which encodes an enzyme required for the initiation of the synthesis of the polysaccharide capsule and lipopolysaccharide O antigen - that increased their ability to invade and survive within intestinal cells, including cultured human colonocytes. Further, these E. coli mutants exhibited a persister phenotype when exposed to cefepime, allowing for greater survival to pulses of cefepime treatment when compared to the wildtype strain. Our findings highlight a mechanism by which bacteria in the gastrointestinal tract can adapt to antibiotic treatment by increasing their ability to persist during antibiotic treatment and invade intestinal epithelial cells where antibiotic concentrations are substantially reduced.

Development and implementation of "handshake rounds": An antibiotic stewardship intervention for hospitalized adult patients with hematologic malignancies

Objective

To design and implement "handshake rounds" as an antibiotic stewardship intervention to reduce inpatient intravenous (IV) antibiotic use in patients with hematologic malignancies.

Design

Quasi-experimental analysis of antibiotic use (AU) and secondary outcomes before and and after handshake rounds were implemented.

Setting

Quaternary-care, academic medical center.

Patients

Hospitalized adults with hematologic malignancies receiving IV antibiotics.

Methods

We performed a retrospective review of a preintervention cohort prior to the intervention. A multidisciplinary team developed criteria for de-escalation of antibiotics, logistics of handshake rounds, and outcome metrics. Eligible patients were discussed during scheduled handshake rounds between a hematology-oncology pharmacist and transplant-infectious diseases (TID) physician. Prospective data were collected over 30 days in the postintervention cohort. Due to small sample size, 2:1 matching was used to compare pre- to and postintervention AU. Total AU in days of therapy per 1,000 patient days (DOT/1,000 PD) was reported. Mean AU per patient was analyzed using Wilcoxon rank-sum test. A descriptive analysis of secondary outcomes of pre- and postintervention cohorts was performed.

Results

Total AU was substantially lower after the intervention, with 517 DOT/1,000 PD compared to 865 DOT/1,000 PD before the intervention. There was no statistically significant difference in the mean AU per patient between the 2 cohorts. There was a lower rate of 30-day mortality in the postintervention cohort and rates of ICU admissions were similar.

Conclusions

Conducting handshake rounds is a safe and effective way to implement an antibiotic stewardship intervention among high-risk patient population such as those with hematologic malignancies.

Genomic and Functional Characterization of Vancomycin-Resistant Enterococci-Specific Bacteriophages in the Galleria mellonella Wax Moth Larvae Model

Phages are naturally occurring viruses that selectively kill bacterial species without disturbing the individual's normal flora, averting the collateral damage of antimicrobial usage. The safety and the effectiveness of phages have been mainly confirmed in the food industry as well as in animal models. In this study, we report on the successful isolation of phages specific to Vancomycin-resistant Enterococci, including Enterococcus faecium (VREfm) and Enterococcus faecalis from sewage samples, and demonstrate their efficacy and safety for VREfm infection in the greater wax moth Galleria mellonella model. No virulence-associated genes, antibiotic resistance genes or integrases were detected in the phages' genomes, rendering them safe to be used in an in vivo model. Phages may be considered as potential agents for therapy for bacterial infections secondary to multidrug-resistant organisms such as VREfm.

A Novel Risk Predictive Scoring Model for Predicting Subsequent Infection After Carbapenem-Resistant Gram-Negative Bacteria Colonization in Hematological Malignancy Patients

Background

This study investigated the high-risk factors associated with the increased vulnerability for subsequent clinical CR-GNB infection in carbapenem-resistant Gram-negative bacteria (CR-GNB)-colonized hematological malignancy (HM) patients and built a statistical model to predict subsequent infection.

Method

All adult HM patients with positive rectoanal swabs culture for CR-GNB between January 2018 and June 2020 were prospectively followed to assess for any subsequent CR-GNB infections and to investigate the risk factors and clinical features of subsequent infection.

Results

A total of 392 HM patients were enrolled. Of them, 46.7% developed a subsequent clinical CR-GNB infection, with 42 (10.7%) cases of confirmed infection and 141 (36%) cases of clinically diagnosed infection. Klebsiella pneumoniae was the dominant species. The overall mortality rate of patients colonized and infected with CR-GNB was 8.6% and 43.7%. A multivariate analysis showed that remission induction chemotherapy and the duration of agranulocytosis, mucositis, and hypoalbuminemia were significant predictors of subsequent infection after CR-GNB colonization. According to our novel risk-predictive scoring model, the high-risk group were >3 times more likely to develop a subsequent infection in comparison with the low-risk group.

Conclusion

Our risk-predictive scoring model can early and accurately predict a subsequent CR-GNB infection in HM patients with CR-GNB colonization. The early administration of CR-GNB-targeted empirical therapy in the high-risk group is strongly recommended to decrease their mortality.

A Promising Insight: The Potential Influence and Therapeutic Value of the Gut Microbiota in GI GVHD

Allogeneic hematopoietic cell transplantation (allo-HSCT) is a reconstruction process of hematopoietic and immune functions that can be curative in patients with hematologic malignancies, but it carries risks of graft-versus-host disease (GVHD), thrombotic microangiopathy (TMA), Epstein–Barr virus (EBV) infection, cytomegalovirus infection, secondary hemophagocytic lymphohistiocytosis (sHLH), macrophage activation syndrome (MAS), bronchiolitis obliterans, and posterior reversible encephalopathy syndrome (PRES). Gastrointestinal graft-versus-host disease (GI GVHD), a common complication of allo-HSCT, is one of the leading causes of transplant-related death because of its high treatment difficulty, which is affected by preimplantation, antibiotic use, dietary changes, and intestinal inflammation. At present, human trials and animal studies have proven that a decrease in intestinal bacterial diversity is associated with the occurrence of GI GVHD. Metabolites produced by intestinal bacteria, such as lipopolysaccharides, short-chain fatty acids, and secondary bile acids, can affect the development of GVHD through direct or indirect interactions with immune cells. The targeted damage of GVHD on intestinal stem cells (ISCs) and Paneth cells results in intestinal dysbiosis or dysbacteriosis. Based on the effect of microbiota metabolites on the gastrointestinal tract, the clinical treatment of GI GVHD can be further optimized. In this review, we describe the mechanisms of GI GVHD and the damage it causes to intestinal cells and we summarize recent studies on the relationship between intestinal microbiota and GVHD in the gastrointestinal tract, highlighting the role of intestinal microbiota metabolites in GI GVHD. We hope to elucidate strategies for immunomodulatory combined microbiota targeting in the clinical treatment of GI GVHD.

The Role of Fecal Microbiota Transplantation in the Treatment of Acute Graft-versus-Host Disease

The number of allogeneic hematopoietic stem cell transplantations conducted worldwide is constantly rising. Together with that, the absolute number of complications after the procedure is increasing, with graft-versus-host disease (GvHD) being one of the most common. The standard treatment is steroid administration, but only 40–60% of patients will respond to the therapy and some others will be steroid-dependent. There is still no consensus regarding the best second-line option, but fecal microbiota transplantation (FMT) has shown encouraging preliminary and first clinically relevant results in recent years and seems to offer great hope for patients. The reason for treatment of steroid-resistant acute GvHD using this method derives from studies showing the significant immunomodulatory role played by the intestinal microbiota in the pathogenesis of GvHD. Depletion of commensal microbes is accountable for aggravation of the disease and is associated with decreased overall survival. In this review, we present the pathogenesis of GvHD, with special focus on the special role of the gut microbiota and its crosstalk with immune cells. Moreover, we show the results of studies and case reports to date regarding the use of FMT in the treatment of steroid-resistant acute GvHD.

Microbiota medicine: towards clinical revolution

The human gastrointestinal tract is inhabited by the largest microbial community within the human body consisting of trillions of microbes called gut microbiota. The normal flora is the site of many physiological functions such as enhancing the host immunity, participating in the nutrient absorption and protecting the body against pathogenic microorganisms. Numerous investigations showed a bidirectional interplay between gut microbiota and many organs within the human body such as the intestines, the lungs, the brain, and the skin. Large body of evidence demonstrated, more than a decade ago, that the gut microbial alteration is a key factor in the pathogenesis of many local and systemic disorders. In this regard, a deep understanding of the mechanisms involved in the gut microbial symbiosis/dysbiosis is crucial for the clinical and health field. We review the most recent studies on the involvement of gut microbiota in the pathogenesis of many diseases. We also elaborate the different strategies used to manipulate the gut microbiota in the prevention and treatment of disorders. The future of medicine is strongly related to the quality of our microbiota. Targeting microbiota dysbiosis will be a huge challenge.

Antibiotic Exposure, Not Alloreactivity, Is the Major Driver of Microbiome Changes in Hematopoietic Cell Transplantation

Both autologous hematopoietic cell transplantation (auto-HCT) and allogeneic hematopoietic cell transplantation (allo-HCT) are associated with significant alterations in the intestinal microbiome. The relative contributions of antibiotic use and alloreactivity to microbiome dynamics have not yet been elucidated, however. There is a lack of data on the kinetics of microbiome changes beyond 30 days post-transplantation and how they might differ between different transplantation modalities. A direct comparison of the differential effects of auto-HCT and allo-HCT on the microbiome may shed light on these dynamics. This study was conducted to compare intestinal microbial diversity between auto-HCT recipients and allo-HCT recipients from pre-transplantation to 100 days post-transplantation, and to examine the effect of antibiotics, transplant type (auto versus allo), and conditioning regimens on the dynamics of microbiome recovery. We conducted a longitudinal analysis of changes in the intestinal microbiome in 35 patients undergoing HCT (17 auto-HCT, 18 allo-HCT) at 4 time points: pre-conditioning and 14, 28, and 100 days post-transplantation. Granular data on antibiotic exposure from day -30 pre-transplantation to day +100 post-transplantation were collected. Pre-transplantation, allo-HCT recipients had lower α-diversity in the intestinal microbiome compared with auto-HCT recipients, which correlated with greater pre-transplantation antibiotic use in allo-HCT recipients. The microbiome diversity declined at days +14 and +28 post-transplantation in both cohorts but generally returned to baseline by day +100. Conditioning regimen intensity did not significantly affect post-transplantation α-diversity. Through differential abundance analysis, we show that commensal bacterial taxa involved with maintenance of gut epithelial integrity and production of short-chain fatty acids were depleted after both auto-HCT and allo-HCT. In our dataset, antibiotic exposure was the major driver of post-transplantation microbiome changes rather than alloreactivity, conditioning intensity, or immunosuppression. Our findings also suggest that interventions to limit microbiome injury, such as limiting the use of broad-spectrum antibiotics, should target the pre-transplantation period and not only the peri-transplantation period.

Faecal microbiota replacement to eradicate antimicrobial resistant bacteria in the intestinal tract - a systematic review

PURPOSE OF REVIEW

Antimicrobial resistance is a rising threat to global health and is associated with increased mortality. Intestinal colonisation with multidrug-resistant organisms (MDRO) can precede invasive infection and facilitates spread within communities and hospitals. Novel decolonisation strategies, such as faecal microbiota transplantation (FMT), are being explored. The purpose of this review is to provide an update on how the field of FMT for MDRO decolonisation has developed during the past year and to assess the efficacy of FMT for intestinal MDRO decolonisation.

RECENT FINDINGS

Since 2020, seven highly heterogenous, small, nonrandomised cohort studies and five case reports have been published. In line with previous literature, decolonisation rates ranged from 20 to 90% between studies and were slightly higher for carbapenem-resistant Enterobacteriaceae than vancomycin-resistant Enterococcus. Despite moderate decolonisation rates in two studies, a reduction in MDRO bloodstream and urinary tract infections was observed.

SUMMARY AND IMPLICATIONS

Although a number of smaller cohort studies show some effect of FMT for MDRO decolonisation, questions remain regarding the true efficacy of FMT (taking spontaneous decolonisation into account), the optimal route of administration, the role of antibiotics pre and post-FMT and the efficacy in different patient populations. The observed decrease in MDRO infections post-FMT warrants further research.

Early stool microbiome and metabolome signatures in pediatric patients undergoing allogeneic hematopoietic cell transplantation

BACKGROUND

The contribution of the gastrointestinal tract microbiome to outcomes after allogeneic hematopoietic cell transplantation (HCT) is increasingly recognized. Investigations of larger pediatric cohorts aimed at defining the microbiome state and associated metabolic patterns pretransplant are needed.

METHODS

We sought to describe the pretransplant stool microbiome in pediatric allogenic HCT patients at four centers. We performed shotgun metagenomic sequencing and untargeted metabolic profiling on pretransplant stool samples. Samples were compared with normal age-matched controls and by clinical characteristics. We then explored associations between stool microbiome measurements and metabolite concentrations.

RESULTS

We profiled stool samples from 88 pediatric allogeneic HCT patients, a median of 4 days before transplant. Pretransplant stool samples differed from healthy controls based on indices of alpha diversity and in the proportional abundance of specific taxa and bacterial genes. Relative to stool from healthy patients, samples from HCT patients had decreased proportion of Bacteroides, Ruminococcaeae, and genes involved in butyrate production, but were enriched for gammaproteobacterial species. No systematic differences in stool microbiome or metabolomic profiles by age, transplant indication, or hospital were noted. Stool metabolites demonstrated strong correlations with microbiome composition.

DISCUSSION

Stool samples from pediatric allogeneic HCT patients demonstrate substantial dysbiosis early in the transplant course. As microbiome disruptions associate with adverse transplant outcomes, pediatric-specific analyses examining longitudinal microbiome and metabolome changes are imperative to identify causal associations and to inform rational design of interventions.

Do weekly surveillance cultures contribute to antibiotic stewardship and correlate with outcome of HSCT in children - a multicentre real-world experience of 5 years from Indian subcontinent?

BACKGROUND

The utility of weekly rectal swab surveillance cultures (RSSC) as a resource to identify gut colonisation with Extended Spectrum Beta-Lactamase (ESBL)-producing E Coli or Klebsiella pneumoniae carbapenemase (KPC) producing organisms, to guide empirical antibiotic therapy in HSCT patients continues to be a subject of interest. There is urgency to assess and justify modifications to empirical antibiotics based upon regional epidemiology and patient groups.

OBJECTIVE

To study the utility of weekly rectal swab surveillance cultures (RSSC) to guide empirical antibiotics therapy and the impact of gut colonisation on transplant outcomes.

STUDY DESIGN

This is a retrospective analysis of 317 successive first transplants done in three pediatric bone marrow transplant centres in Indian sub-continent, mainly for hemoglobinopathies, between April 2016 and April 2021. Transplantation, infection control and febrile neutropenia management protocols are identical among the three centres. First line antibiotics were chosen based on RCCS reports i.e. meropenem and high dose meropenem with colistin for ESBL and carbapenemase resistant colonisation respectively for first half of the study and no adjustment was made in the second half. Clinical response to antibiotics, long term outcomes, antibiotic-resistant bacteraemia and acute GVHD were analysed. Log-rank test, Chi-squared test and Wilcoxon test were used to compare data using R Statistical software.

RESULTS

Of all 871 weekly RSSC done, 162 were positive for ESBL- or KPC-resistant organism. RCCS were ESBL-positive in 106 patients (33%) and KPC-positive in 10 patients (3%). Within 97 ESBL-positive patients for whom antimicrobial susceptibility testing (AST) report was available, only 22 (25%) demonstrated clinical resistance of Pip-Taz. Within the 10 KPC-positive patients' clinical resistance was observed only in 4 (40%) to Pip-Taz and 3 (30%) to meropenem. For ESBL-positive RSSC where 1st line empirical antibiotics were used, 66% of the patients responded clinically. Even within the 15 who were resistant to 1st line empirical antibiotics (Pip-Taz) on RSSC reports, 67% responded to Pip-Taz clinically. Within these patients 27 (56%) never needed any carbapenems. Using Pip-Taz empirically in ESBL-positive patients did not prolong meropenem use within 100 days of transplantation (p=0.18). For KPC-positive RSSC where 1st line empirical antibiotics were used, all patients clinically responded, including 4 who were resistant to Pip-Taz and 3 patients who were meropenem resistant on RCCS. Comparing patients who were ESBL-positive, KPC-positive and neither, no statistically significant difference was seen in overall survival (p=0.95), disease free survival (p=0.45), transplant related mortality (p=0.97), rejection (p=0.68) and rate of acute GVHD grade II-IV (p=0.78). Comparing the ESBL-positive patients who did and did not get higher-level empirical antibiotics, no statistical difference was seen in overall survival (p=0.32), disease free survival (p=0.64), transplant related mortality (p=0.65), rejection (p=0.46), acute GVHD grade II-IV (p=0.26) or antibiotic resistant bacteraemia (p=0.3).

CONCLUSIONS

In context of transplantation for non-malignant HSCTs, empiric antibiotic choice based on rectal swab surveillance cultures is not justified, even in regions with a high prevalence of antimicrobial resistance. Antimicrobial susceptibility testing (AST) reports in surveillance cultures did not correlate with in-vivo clinical response. Colonisation reported on weekly surveillance rectal swab cultures showed no correlation with clinical outcomes.

Effectiveness of surveillance cultures for high priority multidrug-resistant bacteria in hematopoietic stem cell transplant units

Surveillance strategies to detect colonization are an important tool to prevent and control the spread of microorganisms in hematopoietic stem cell transplant (HSCT) units. The aim of this study was to evaluate routine surveillance cultures for screening colonization and infection by carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Pseudomonas aeruginosa (CRPa), and vancomycin-resistant enterococci (VRE). Surveillance cultures were collected (1,323 samples) from 200 patients admitted to an HSCT unit over one year; swabs were taken on admission and then weekly. We compared the positivity of cultures for each site, agent, clinical and epidemiological data according to the colonization status. Infection due to multidrug-resistant organisms (MDROs) occurred in 52 (21.5%) patients, 45 (86.5%) due to blood stream infection; 12 (23%) patients had a positive surveillance culture before the infection. Cultures of 554 (41.8%) samples were performed for CRPa, 413 (31.2%) for VRE and 356 (27%) for CRE. Of these, 179 (13.5%) were positive. Colonization by any MDRO, CRE or CRPa was associated with increased risk of infection (P < 0.05), but not with death. Previous colonization by an MDRO was a significant risk for infection by these pathogens, specially by CRE. Overall, rectal swabs had the highest positivity rate compared with other sites, oropharynx swabs were an option for CRPa, and fecal cultures showed low positivity. Although the impact of the strategy on the mortality of patients undergoing HSCT is not clear, routine VRE surveillance should be questioned with regard to patients undergoing auto-HSCT due to the additional cost and little impact on survival rates.

The Role of the Gut Microbiome in Pathogenesis, Biology, and Treatment of Plasma Cell Dyscrasias

In response to emerging discoveries, questions are mounting as to what factors are responsible for the progression of plasma cell dyscrasias and what determines responsiveness to treatment in individual patients. Recent findings have shown close interaction between the gut microbiota and multiple myeloma cells. For instance, that malignant cells shape the composition of the gut microbiota. We discuss the role of the gut microbiota in (i) the development and progression of plasma cell dyscrasias, and (ii) the response to treatment of multiple myeloma and highlight faecal microbiota transplantation as a procedure that could modify the risk of progression or sensitize refractory malignancy to immunotherapy.

Gut Microbiome Modulation and Faecal Microbiota Transplantation Following Allogenic Hematopoietic Stem Cell Transplantation

Nowadays, allogenic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapy that is mainly recommended for hematologic malignancies. However, complications (such as graft-versus-host disease, mucositis, disease relapse, and infections) associated with the HSCT procedure contribute to the development of gut microbiota imbalance, gut-barrier disruption, and increased intestinal permeability. In the present narrative review, the crosstalk between gut microbiota products and intestinal homeostasis is discussed. Notably, gut-microbiota-related aspects have an impact on patients' clinical outcomes and overall survival. In accordance with the most recent published data, gut microbiota is crucial for the treatment effectiveness of many diseases, not only gastrointestinal cancers but also hematologic malignancies. Therefore, it is necessary to indicate a therapeutic method allowing to modulate gut microbiota in HSCT recipients. Currently, fecal microbiota transplantation (FMT) is the most innovative method used to alter/restore gut microbiota composition, as well as modulate its activity. Despite the fact that some previous data have shown promising results, the knowledge regarding FMT in HSCT is still strongly limited, except for the treatment of Clostridium difficile infection. Additionally, administration of prebiotics, probiotics, synbiotics, and postbiotics can also modify gut microbiota; however, this strategy should be considered carefully due to the high risk of fungemia/septicemia (especially in case of fungal probiotics).

Fecal Microbiota Transplant Mitigates Adverse Outcomes Seen in Patients Colonized With Multidrug-Resistant Organisms Undergoing Allogeneic Hematopoietic Cell Transplantation

The gut microbiome can be adversely affected by chemotherapy and antibiotics prior to hematopoietic cell transplantation (HCT). This affects graft success and increases susceptibility to multidrug-resistant organism (MDRO) colonization and infection. We performed an initial retrospective analysis of our use of fecal microbiota transplantation (FMT) from healthy donors as therapy for MDRO-colonized patients with hematological malignancy. FMT was performed on eight MDRO-colonized patients pre-HCT (FMT-MDRO group), and outcomes compared with 11 MDRO colonized HCT patients from the same period. At 12 months, survival was significantly higher in the FMT-MDRO group (70% versus 36% p = 0.044). Post-HCT, fewer FMT-MDRO patients required intensive care (0% versus 46%, P = 0.045) or experienced fever (0.29 versus 0.11 days, P = 0.027). Intestinal MDRO decolonization occurred in 25% of FMT-MDRO patients versus 11% non-FMT MDRO patients. Despite the significant differences and statistically comparable patient/transplant characteristics, as the sample size was small, a matched-pair analysis between both groups to non-MDRO colonized control cohorts (2:1 matching) was performed. At 12 months, the MDRO group who did not have an FMT had significantly lower survival (36.4% versus 61.9% respectively, p=0.012), and higher non relapse mortality (NRM; 60.2% versus 16.7% respectively, p=0.009) than their paired non-MDRO-colonized cohort. Conversely, there was no difference in survival (70% versus 43.4%, p=0.14) or NRM (12.5% versus 31.2% respectively, p=0.24) between the FMT-MDRO group and their paired non-MDRO cohort. Collectively, these data suggest that negative clinical outcomes, including mortality associated with MDRO colonization, may be ameliorated by pre-HCT FMT, even in the absence of intestinal MDRO decolonization. Further work is needed to explore this observed benefit.

Impact of broad-spectrum antibiotic exposures and multidrug-resistant gram-negative bacteremia on hematopoietic cell transplantation outcomes

INTRODUCTION

There is a close association between the use of broad-spectrum antibiotics, gut microbiome alteration, multidrug resistant (MDR) gram-negative bacilli (GNB) bacteremia, graft versus host disease (GVHD), and mortality post-allogeneic hematopoietic cell transplantation (allo-HCT). This study reports the impact of the high use of carbapenems and colistin and MDR bacteremia pre- and post-HCT on HCT outcomes.

METHODS

This was a single-center, partial retrospective, and prospective study from 2016 to 2020. Both pre- and post-HCT antibiotic exposures and blood culture/sensitivity were recorded. MDR GNB was defined as either non-susceptibility to third-generation cephalosporin or carbapenems. In the absence of positive cultures, the treating physician escalated antibiotics from third-generation cephalosporins to carbapenem and/or colistin as per clinical discretion. De-escalation policy was not strictly enforced.

RESULTS

MDR GNB bacteremia was seen in 29 of 76 (38%) of patients peri-HCT. The utilization rates for carbapenems and colistin was significantly higher in the cohort with MDR GNB bacteremia pre-HCT (70% vs. 32%, p = 0.002 and 31% vs. 6.4%, p = 0.007, respectively) and post-HCT (100% vs. 74.5%, p = 0.002, and 55.2% vs. 8.5%, p < 0.0001, respectively). The cohort with MDR GNB bacteremia had significantly more severe acute GVHD at day+100 (45% vs. 17.5%, p = 0.009). The median survival was 204 days compared to not reached in the cohort without any MDR GNB bacteremia (p = 0.005).

CONCLUSION

This study shows pre- and post-HCT MDR GNB bacteremia is associated with an increased risk of severe acute GVHD and mortality. Patients with MDR GNB bacteremia had higher exposure to pre- and post-HCT carbapenems and colistin.

Impact of decontamination therapy on gastrointestinal acute graft-versus-host disease after allogeneic hematopoietic cell transplantation in children: Decontamination therapy in allo-HCT

INTRODUCTION

Gut colonization with antibiotic-resistant bacteria (ARB) is associated with a significantly decreased overall survival in adult patients undergoing allo-HCT because of an increased treatment-related mortality.

OBJECTIVE

The objective of this multicenter study was the analysis of impact of gut colonization status and the use of antibiotics on development of gastro-intestinal (GI) graft-versus-host disease (GVHD) of allo-HCT in children.

METHODS

All consecutive patients who underwent allo-HCT over a period of three years in all pediatric HCT centers in Poland were analyzed for the impact of gut colonization on GI GVHD, with respect to standard of care including prophylaxis of infections and supportive therapy.

RESULTS

At the time of allo-HCT, 44.2% of pediatric patients were colonized by ARB. Decontamination therapy with antibiotics was applied in 78% of children. Gut decontamination prophylactic therapy with antibiotics decreased the risk of acute GI GVHD. The use of gentamicin contributed to decreased rate of GVHD, while the use of ciprofloxacin and colistin contributed to increased incidence of GVHD after allo-HCT in children. Sepsis with ARB and non-MFD transplant contributed significantly to worse survival, while neither colonization nor gut decontamination had an impact on overall survival.

CONCLUSIONS

Gut decontamination therapy contributed to lower incidence of acute GI GVHD in children undergoing allo-HCT, and the use of specific antibiotics might be responsible for this effect.

Gut microbiota diversity after autologous fecal microbiota transfer in acute myeloid leukemia patients

Acute myeloid leukemia (AML) intensive chemotherapy combined with broad-spectrum antibiotics, leads to gut microbiota dysbiosis promoting pathological conditions and an increased incidence of complications. Here we report findings from a phase II single-arm, multicenter study evaluating autologous fecal microbiota transfer (AFMT) in 25 AML patients treated with intensive chemotherapy and antibiotics (ClinicalTrials.gov number: NCT02928523). The co-primary outcomes of the study are to evaluate the efficacy of AFMT in dysbiosis correction and multidrug-resistant bacteria eradication. The main secondary outcomes are to define a dysbiosis biosignature, to evaluate the effect of dysbiosis correction on patient clinical status, to assess the short and mid-term safety of AFMT in this immunocompromised population, and to evaluate the feasibility of the AFMT procedure and acceptability by the patient. Intensive induction chemotherapy induces a dramatic decrease of α-diversity indices, and a microbial dysbiosis with a significant shift of the microbial communities and domination of pro-inflammatory families. After AFMT treatment, α-diversity indices return to their initial mean levels and the similarity index shows the restoration of microbial communities. The trial meets pre-specified endpoints. AFMT appears to be safe and may be effective for gut microbiota restoration in AML patients receiving intensive chemotherapy and antibiotics, with an excellent gut microbiota reconstruction based on both richness and diversity indices at the species level.

The combination of chemotherapy and broad-spectrum antibiotics induces gut microbiota (GM) dysbiosis in acute myeloid leukaemia (AML) leading to additional complications. Here, the authors report the efficacy in GM restoration and safety of autologous faecal microbiota transfer in treated AML patients in a phase II clinical trial.

Tandem fecal microbiota transplantation cycles in an allogeneic hematopoietic stem cell transplant recipient targeting carbapenem-resistant Enterobacteriaceae colonization: a case report and literature review

BACKGROUND

Due to limited antibiotic options, carbapenem-resistant Enterobacteriaceae (CRE) infections are associated with high non-relapse mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Also, intestinal CRE colonization is a risk factor for subsequent CRE infection. Several clinical studies have reported successful fecal microbiota transplantation (FMT) for the gut decontamination of a variety of multidrug-resistant bacteria (MDRB), even in immunosuppressed patients. Similarly, other studies have also indicated that multiple FMTs may increase or lead to successful therapeutic outcomes.

CASE PRESENTATION

We report CRE colonization in an allo-HSCT patient with recurrent CRE infections, and its successful eradication using tandem FMT cycles at 488 days after allo-HSCT. We also performed a comprehensive microbiota analysis. No acute or delayed adverse events (AEs) were observed. The patient remained clinically stable with CRE-negative stool culture at 26-month follow-up. Our analyses also showed some gut microbiota reconstruction. We also reviewed the current literature on decolonization strategies for CRE.

CONCLUSIONS

CRE colonization led to a high no-relapse mortality after allo-HSCT; however, well-established decolonization strategies are currently lacking. The successful decolonization of this patient suggests that multiple FMT cycles may be potential options for CRE decolonization.

The clinical role of the gut microbiome and fecal microbiota transplantation in allogeneic stem cell transplantation

Outcomes of allogeneic hematopoietic stem cell transplantation (allo- HSCT) have improved in the recent decade; however, infections and graft-versus-host disease remain two leading complications significantly contributing to early transplant-related mortality. In past years, the human intestinal microbial composition (microbiota) has been found to be associated with various disease states, including cancer, response to cancer immunotherapy and to modulate the gut innate and adaptive immune response. In the setting of allo-HSCT, the intestinal microbiota diversity and composition appear to have an impact on infection risk, mortality and overall survival. Microbial metabolites have been shown to contribute to the health and integrity of intestinal epithelial cells during inflammation, thus mitigating graft-versus-host disease in animal models. While the cause-andeffect relationship between the intestinal microbiota and transplant-associated complications has not yet been fully elucidated, the above findings have already resulted in the implementation of various interventions aiming to restore the intestinal microbiota diversity and composition. Among others, these interventions include the administration of fecal microbiota transplantation. The present review, based on published data, is intended to define the role of the latter approach in the setting of allo-HSCT.

Prevention and management of carbapenem-resistant Enterobacteriaceae in haematopoietic cell transplantation

Carbapenem-resistant Enterobacteriaceae (CRE) infections are associated with high morbidity and mortality rates in haematopoietic cell transplantation (HCT) recipients. Factors like mucositis, neutropenia, prolonged hospital stay, and frequent use of prophylactic antimicrobials make HCT recipients especially susceptible to CRE infections. Low culture positivity rates, delay in microbiological diagnosis, and resistance to empirical antimicrobial therapy for febrile neutropenia are responsible for high mortality rates in HCT recipients infected with CRE. In this review we discuss the epidemiology, diagnosis, and management of CRE infections with particular emphasis on patients undergoing HCT. We emphasise the need for preventive strategies like multidisciplinary antimicrobial stewardship, and pre-emptive screening for CRE colonisation in prospective HCT patients as measures to mitigate the adverse impact of CRE on HCT outcomes. Newer diagnostic tests like polymerase chain reaction and matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF) assay that enable earlier and better identification of CRE isolates are discussed. Antimicrobial agents available against CRE, including newer agents like ceftazidime-avibactam and meropenem-vaborbactam, have been reviewed. We also discuss the data on promising experimental treatments against CRE: phage therapy and healthy donor faecal microbiota transplant. Finally, this review puts forth recommendations as per existing literature on diagnosis and management of CRE infections in blood and marrow transplant (BMT) unit.

Current Prophylaxis and Treatment Approaches for Acute Graft-Versus-Host Disease in Haematopoietic Stem Cell Transplantation for Children With Acute Lymphoblastic Leukaemia

Acute graft-versus-host disease (aGvHD) continues to be a leading cause of morbidity and mortality following allogeneic haematopoietic stem cell transplantation (HSCT). However, higher event-free survival (EFS) was observed in patients with acute lymphoblastic leukaemia (ALL) and grade II aGvHD vs. patients with no or grade I GvHD in the randomised, controlled, open-label, international, multicentre Phase III For Omitting Radiation Under Majority age (FORUM) trial. This finding suggests that moderate-severity aGvHD is associated with a graft-versus-leukaemia effect which protects against leukaemia recurrence. In order to optimise the benefits of HSCT for leukaemia patients, reduction of non-relapse mortality-which is predominantly caused by severe GvHD-is of utmost importance. Herein, we review contemporary prophylaxis and treatment options for aGvHD in children with ALL and the key challenges of aGvHD management, focusing on maintaining the graft-versus-leukaemia effect without increasing the severity of GvHD.

Clinical effects and applications of the gut microbiome in hematologic malignancies

The gut microbiome and its effects on host immunity have exciting implications for cancer prognosis and therapy. Examples in allogeneic hematopoietic stem cell transplantation (allo-SCT) demonstrate the role of the gut microbiome as a biomarker for clinical outcomes, and animal models demonstrate how microbiota manipulation may augment therapeutic responses. There are multiple mechanisms that gut microbiota may have in affecting distant tumor environments, including control of cytokine release, dendritic cell activation, and T-cell lymphocyte stimulation. Recently, there has been a marked interest in understanding interactions between host and microbiome in hematologic malignancies. This review summarizes the current understanding of the gut microbiome and its impact on leukemia, lymphoma, multiple myeloma, and allo-SCT and highlights several broad methods for targeting the gut microbiome in therapeutic trials.

Targeting the gut microbiome: An emerging trend in hematopoietic stem cell transplantation

Mounting evidence has demonstrated the critical role of the gut microbiome in different cancer treatment modalities showing intensive crosstalk between microbiota and the host immune system. In cancer patients receiving hematopoietic stem cell transplantation (HSCT), conditioning regimens including chemotherapy, radiotherapy, and immunosuppressive therapy, as well as antimicrobial prophylaxis, result in intestinal barrier disruption and massive changes in microbiota composition. According to clinical studies, a drastic loss of microbial diversity during HSCT is associated with enhanced pro-inflammatory immune response and an increased risk of transplant-related complications such as graft-versus-host disease (GvHD) and mortality. In this review, we outline the current understanding of the role of microbiota diversity in the patient response to cancer therapies and highlight the impact of changes in the gut microbiome on clinical outcomes in post-HSCT patients. Moreover, the therapeutic implications of microbiota modulation by probiotics, prebiotics, and fecal microbiota transplantation (FMT) in hematologic cancer patients receiving HSCT are discussed.

Broad-Spectrum Antibiotics and Risk of Graft-versus-Host Disease in Pediatric Patients Undergoing Transplantation for Acute Leukemia: Association of Carbapenem Use with the Risk of Acute Graft-versus-Host Disease

Variation in the gastrointestinal (GI) microbiota after hematopoietic cell transplantation (HCT) has been associated with acute graft-versus-host disease (aGVHD). Because antibiotics induce dysbiosis, we examined the association of broad-spectrum antibiotics with subsequent aGVHD risk in pediatric patients undergoing HCT for acute leukemia. We performed a retrospective analysis in a dataset merged from 2 sources: (1) the Center for International Blood and Marrow Transplant Research, an observational transplantation registry, and (2) the Pediatric Health Information Services, an administrative database from freestanding children's hospitals. We captured exposure to 3 classes of antibiotics used for empiric treatment of febrile neutropenia: (1) broad-spectrum cephalosporins, (2) antipseudomonal penicillins, and (3) carbapenems. The primary outcome was grade II-IV aGVHD; secondary outcomes were grade III-IV aGVHD and lower GI GVHD. The adjusted logistic regression model (full cohort) and time-to-event analysis (subcohort) included transplantation characteristics, GVHD risk factors, and adjunctive antibiotic exposures as covariates. The full cohort included 2550 patients at 36 centers; the subcohort included 1174 patients. In adjusted models, carbapenems were associated with an increased risk of grade II-IV aGVHD in the full cohort (adjusted odds ratio [aOR], 1.24; 95% confidence interval [CI], 1.02 to 1.51) and subcohort (sub hazard ratio [HR], 1.31; 95% CI, 0.99 to 1.72), as well as with an increased risk of grade III-IV aGVHD (subHR, 1.77; 95% CI, 1.25 to 2.52). Early carbapenem exposure (before day 0) especially impacted aGVHD risk. For antipseudomonal penicillins, the associations with aGVHD were in the direction of increased risk but were not statistically significant. There was no identified association between broad-spectrum cephalosporins and aGVHD. Carbapenems, more than other broad-spectrum antibiotics, should be used judiciously in pediatric HCT recipients to minimize aGVHD risk. Further research is needed to clarify the mechanism underlying this association.

Patterns of infection and infectious-related mortality in patients receiving post-transplant high dose cyclophosphamide as graft-versus-host-disease prophylaxis: impact of HLA donor matching

Post-transplant cyclophosphamide (PTCy) has become a promising option after allo-SCT, but infections may be more common than in traditional protocols. We herein report 117 consecutive adults who received PTCy-based alloSCT in our hospital: HaploSCT (34%), MRD (19%), and VUD (47%), respectively. The 18-month incidence of severe bacterial, viral, and IFI was 56%, 69%, and 8.7%, without differences between donor type, except for CMV infection and viral hemorrhagic cystitis, which had a higher incidence in the haploSCT cohort (58% vs. 43% and 30% vs. 8% on day +90, p < 0.05). Late infections by conventional respiratory viruses were common in all groups [33/87 (38%)]. The 2-year survival was 72% and did not differ by donor type. IRM at day 30, day 100, and 18 months was 1.7%, 4.4%, and 12%, without differences by donor type (p = 0.7). The primary cause of IRM was bacterial infection (42%). Grade 2–4 acute GvHD was the only independent predictor of IRM. Donor type had no impact on IRM or on survival. In our study, severe infections were common in all donor types using PTCy, with higher rates of early post-engraftment CMV-I and viral HC in haploSCT recipients, although lethal infections were uncommon and similar in all donor types.

Effectiveness of Bath Wipes After Hematopoietic Cell Transplantation: A Randomized Trial

Objective: Bacteremia is a leading cause of morbidity and mortality in children undergoing hematopoietic cell transplantation (HCT). Infections of vancomycin-resistant enterococci (VRE) and multidrug resistant (MDR) gram-negative rods (GNRs) are common in this population. Our objective was to assess whether experimental bath wipes containing silver were more effective than standard bath wipes containing soap at reducing skin colonization by VRE and MDR GNRs, and nonmucosal barrier injury bacteremia. Study Design: Patients undergoing autologous or allogeneic HCT in a tertiary referral center were randomized to receive experimental or standard bath wipes for 60 days post-HCT. Skin swabs were collected at baseline, discharge, and day +60 post-HCT. The rate of VRE colonization was chosen as the marker for efficacy. Results: Experimental bath wipes were well tolerated. Before the study, the rate of colonization with VRE in HCT recipients was 25%. In an interim analysis of 127 children, one (2%) patient in the experimental arm and two (3%) in the standard arm were colonized with VRE. Two (3%) patients had nonmucosal barrier injury bacteremia in the standard arm, with none in the experimental arm. MDR GNRs were not isolated. The trial was halted because the interim analyses indicated equivalent efficacy of the two methods. Conclusions: Skin cleansing with silver-containing or standard bath wipes resulted in very low and equivalent rates of bacteremia and colonization with VRE and MDR GNRs in children post-HCT. Future studies in other high-risk populations are needed to confirm these results.

Microbiota as Predictor of Mortality in Allogeneic Hematopoietic-Cell Transplantation

BACKGROUND

Relationships between microbiota composition and clinical outcomes after allogeneic hematopoietic-cell transplantation have been described in single-center studies. Geographic variations in the composition of human microbial communities and differences in clinical practices across institutions raise the question of whether these associations are generalizable.

METHODS

The microbiota composition of fecal samples obtained from patients who were undergoing allogeneic hematopoietic-cell transplantation at four centers was profiled by means of 16S ribosomal RNA gene sequencing. In an observational study, we examined associations between microbiota diversity and mortality using Cox proportional-hazards analysis. For stratification of the cohorts into higher- and lower-diversity groups, the median diversity value that was observed at the study center in New York was used. In the analysis of independent cohorts, the New York center was cohort 1, and three centers in Germany, Japan, and North Carolina composed cohort 2. Cohort 1 and subgroups within it were analyzed for additional outcomes, including transplantation-related death.

RESULTS

We profiled 8767 fecal samples obtained from 1362 patients undergoing allogeneic hematopoietic-cell transplantation at the four centers. We observed patterns of microbiota disruption characterized by loss of diversity and domination by single taxa. Higher diversity of intestinal microbiota was associated with a lower risk of death in independent cohorts (cohort 1: 104 deaths among 354 patients in the higher-diversity group vs. 136 deaths among 350 patients in the lower-diversity group; adjusted hazard ratio, 0.71; 95% confidence interval [CI], 0.55 to 0.92; cohort 2: 18 deaths among 87 patients in the higher-diversity group vs. 35 deaths among 92 patients in the lower-diversity group; adjusted hazard ratio, 0.49; 95% CI, 0.27 to 0.90). Subgroup analyses identified an association between lower intestinal diversity and higher risks of transplantation-related death and death attributable to graft-versus-host disease. Baseline samples obtained before transplantation already showed evidence of microbiome disruption, and lower diversity before transplantation was associated with poor survival.

CONCLUSIONS

Patterns of microbiota disruption during allogeneic hematopoietic-cell transplantation were similar across transplantation centers and geographic locations; patterns were characterized by loss of diversity and domination by single taxa. Higher diversity of intestinal microbiota at the time of neutrophil engraftment was associated with lower mortality. (Funded by the National Cancer Institute and others.).

[Multidrug-resistant bacteria detection in patients undergoing allogeneic hematopoietic cell transplantation: Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

The Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC) organizes annual workshops in the attempt to harmonize clinical practices among different francophone transplantation centers. Here we report our recommendations regarding detection of the multidrug-resistant bacteria in hematology.

Vancomycin-resistance gene cluster, vanC, in the gut microbiome of acute leukemia patients undergoing intensive chemotherapy

Two recent reports suggested that the less common, less virulent enterococcal species, Enterococcus gallinarum and E. casseliflavus, with low-level vancomycin resistance due to chromosomally encoded vanC1 and vanC2/3, may influence host immunity. We reported that peri-transplant gut colonization with E. gallinarum and E. casseliflavus is associated with lower mortality after allogeneic hematopoietic cell transplantation (HCT). Because most acute leukemia patients undergoing HCT have received intensive chemotherapy (usually requiring prolonged hospitalization) for their underlying disease before HCT, we hypothesized that some may have acquired vanC-positive enterococci during chemotherapy. Therefore, we evaluated the presence of the vanC gene cluster using vanC1 and vanC2/3 qPCR in thrice-weekly collected stool samples from 20 acute leukemia patients undergoing intensive chemotherapy. We found that an unexpectedly large proportion of patients have detectable vanC1 and vanC2/3 (15% and 35%, respectively) in at least one stool sample. Comparing qPCR results with 16S rRNA gene sequencing results suggested that E. gallinarum may reach high abundances, potentially persisting into HCT and influencing transplant outcomes.

Fecal microbiota transplantation before or after allogeneic hematopoietic transplantation in patients with hematologic malignancies carrying multidrug-resistance bacteria

Fecal microbiota transplantation is an effective treatment in recurrent Clostridium difficile infection. Promising results to eradicate multidrug-resistant bacteria have also been reported with this procedure, but there are safety concerns in immunocompromised patients. We report results in ten adult patients colonized with multidrug-resistant bacteria, undergoing fecal microbiota transplantation before (n=4) or after (n=6) allogeneic hematopoietic stem cell transplantation for hematologic malignancies. were obtained from healthy related or unrelated donors. Fecal material was delivered either by enema or via nasogastric tube. Patients were colonized or had infections from either carbapenemase-producing bacteria (n=8) or vancomycin-resistant enterococci (n=2). Median age at fecal microbiota transplantation was 48 (range, 16-64) years. Three patients needed a second transplant from the same donor due to initial failure of the procedure. With a median follow up of 13 (range, 4-40) months, decolonization was achieved in seven of ten patients. In all patients, fecal micro-biota transplantation was safe: one patient presented with constipation during the first five days after FMT and two patients had grade I diarrhea. One case of gut grade III acute graft-versus-host disease occurred after fecal microbiota transplantation. In patients carrying or infected by multidrug-resistant bacteria, fecal microbiota transplantation is an effective and safe decolonization strategy, even in those with hematologic malignancies undergoing hematopoietic stem cell transplantation.

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.

Gut resistome plasticity in pediatric patients undergoing hematopoietic stem cell transplantation

The gut microbiome of pediatric patients undergoing allo-hematopoietic stem cell transplantation (HSCT) has recently been considered as a potential reservoir of antimicrobial resistance, with important implications in terms of patient mortality rate. By means of shotgun metagenomics, here we explored the dynamics of the gut resistome - i.e. the pattern of antibiotic resistance genes provided by the gut microbiome - in eight pediatric patients undergoing HSCT, half of whom developed acute Graft-versus-Host Disease (aGvHD). According to our findings, the patients developing aGvHD are characterized by post-HSCT expansion of their gut resistome, involving the acquisition of new resistances, as well as the consolidation of those already present before HSCT. Interestingly, the aGvHD-associated bloom in resistome diversity is not limited to genes coding for resistance to the antibiotics administered along the therapeutic course, but rather involves a broad pattern of different resistance classes, including multidrug resistance, as well as resistance to macrolides, aminoglycosides, tetracyclines and beta-lactams. Our data stress the relevance of mapping the gut resistome in HSCT pediatric patients to define the most appropriate anti-infective treatment post HSCT.