Vancomycin-resistant enterococcus infection in the hematopoietic stem cell transplant recipient: an overview of epidemiology, management, and prevention

Nutritional Strategies To Improve VRE Control

The rise of Vancomycin-resistant enterococci (VRE) strains among cellular therapy recipients raises concerns due to increased morbidity, mortality, and hospitalization costs, particularly impacting transplanted patients with diminished survival expectations. Recent research linking lactose to Enterococcus growth and graft-versus-host disease (GVHD) emphasizes the need for data on reducing lactose in the diets of VRE-carrying patients, especially in cellular therapy contexts like CAR-T or allogeneic hematopoietic stem cell transplantation. Responding to elevated VRE positivity rates in rectal swabs among patients in our BMT Unit, a unique nutritional strategy was implemented, introducing lactose-free milk and strictly enforcing lactose-free diets. This approach resulted in a significant reduction in VRE carriers, with a 16% positivity rate in the Lactose Group versus 3.6% in the Lactose-Free Group, as of June 2023. These results indicate the potential efficacy of this innovative nutritional strategy in high-risk departments, such as BMT Units and Intensive Care Units, with implications for reducing isolation strategies and inappropriate antibiotic use in cases of VRE colonization.

Incidence of infection with multidrug-resistant Gram-negative bacteria and vancomycin-resistant enterococci in carriers: a systematic review and meta-regression analysis

BACKGROUND

Carriers of multidrug-resistant bacteria are at risk of infections with these bacteria; the precise size of this risk is unclear. We aimed to quantify the effect of gut colonisation on subsequent risk of infection with multidrug-resistant bacteria.

METHODS

We performed a systematic review and meta-regression analysis. We searched PubMed, Embase, Web of Science Core Collection, and Google Scholar for follow-up studies published from Jan 1, 1995, to March 17, 2022, that measured the incidence of infections with multidrug-resistant Gram-negative bacteria (MDR-GNB) and from Jan 1, 1995, to March 15, 2022, that measured the incidence of infections with vancomycin-resistant enterococci (VRE). We included original cohort studies and case-control studies that used incidence-density sampling, included 50 or more patients with enteric colonisation or positive urinary samples as a surrogate marker of colonisation, or both, and analysed infections clearly preceded by colonisation. We did not use any language restrictions. We excluded studies not reporting length of follow-up. Summary data were extracted and independently cross-verified by two authors. Carriage was defined as MDR-GNB or VRE, detected in faecal or urinary cultures. Our primary outcomes were cumulative incidence and incidence density of infection in patients colonised by multidrug-resistant bacteria. To estimate pooled incidences, general linearised mixed-effects meta-regressions were used, adjusting for varying follow-up durations. This study is registered with PROSPERO, CRD42020222415.

FINDINGS

Of the 301 studies identified, 44 studies (26 on MDR-GNB, 14 on VRE, and four on both MDR-GNB and VRE) from 14 countries were retained for qualitative synthesis, 40 of which were analysed with meta-regression, comprising data for 14 049 patients colonised with multidrug-resistant bacteria. The pooled cumulative incidence of infection was 14% (95% CI 10-18; p<0·0001) at a median follow-up time of 30 days for MDR-GNB (845 cases of infection in 9034 patients colonised) and 8% (5-13; p<0·0001) at 30 days for VRE (229 cases of infection in 4747 patients colonised). Infection incidence density (4·26 infections per 1000 patient-days; 95% CI 1·69-6·82) and cumulative incidence of infection (19%, 95% CI 15-25; p<0·0001; 602 cases of infection in 4547 patients colonised) were highest for carbapenem-resistant Gram-negative bacteria at 30 days. Risk of bias was rated low to moderate.

INTERPRETATION

The risk of infection was substantial, with the highest risk for patients colonised with carbapenem-resistant Gram-negative bacteria and the lowest in patients with VRE. These data might help to guide prophylactic and treatment decisions and form a valuable resource for planning clinical trials on targeted prevention.

FUNDING

The Netherlands Organization for Health Research and Development.

Molecular Rapid Diagnostics Improve Time to Effective Therapy and Survival in Patients with Vancomycin-Resistant Enterococcus Bloodstream Infections

Delays in appropriate antibiotic therapy are a key determinant for deleterious outcomes among patients with vancomycin-resistant Enterococcus (VRE) bloodstream infections (BSIs). This was a multi-center pre/post-implementation study, assessing the impact of a molecular rapid diagnostic test (Verigene® GP-BC, Luminex Corporation, Northbrook, IL, USA) on outcomes of adult patients with VRE BSIs. The primary outcome was time to optimal therapy (TOT). Multivariable logistic and Cox proportional hazard regression models were used to determine the independent associations of post-implementation, TOT, early vs. delayed therapy, and mortality. A total of 104 patients with VRE BSIs were included: 50 and 54 in the pre- and post-implementation periods, respectively. The post- vs. pre-implementation group was associated with a 1.8-fold faster rate to optimized therapy (adjusted risk ratio, 1.841 [95% CI 1.234-2.746]), 6-fold higher likelihood to receive early effective therapy (<24 h, adjusted odds ratio, 6.031 [2.526-14.401]), and a 67% lower hazards for 30-day in-hospital mortality (adjusted hazard ratio, 0.322 [0.124-1.831]), after adjusting for age, sex, and severity scores. Inversely, delayed therapy was associated with a 10-fold higher risk of in-hospital mortality (aOR 10.488, [2.497-44.050]). Reduced TOT and in-hospital mortality were also observed in subgroups of immunosuppressed patients in post-implementation. These findings demonstrate that the addition of molecular rapid diagnostic tests (mRDT) to clinical microbiology and antimicrobial stewardship practices are associated with a clinically significant reduction in TOT, which is associated with lower mortality for patients with VRE BSIs, underscoring the importance of mRDTs in the management of VRE infections.

Phage Cocktails with Daptomycin and Ampicillin Eradicates Biofilm-Embedded Multidrug-Resistant Enterococcus faecium with Preserved Phage Susceptibility

Multidrug-resistant (MDR) Enterococcus faecium is a challenging nosocomial pathogen known to colonize medical device surfaces and form biofilms. Bacterio (phages) may constitute an emerging anti-infective option for refractory, biofilm-mediated infections. This study evaluates eight MDR E. faecium strains for biofilm production and phage susceptibility against nine phages. Two E. faecium strains isolated from patients with bacteremia and identified to be biofilm producers, R497 (daptomycin (DAP)-resistant) and HOU503 (DAP-susceptible dose-dependent (SDD), in addition to four phages with the broadest host ranges (ATCC 113, NV-497, NV-503-01, NV-503-02) were selected for further experiments. Preliminary phage-antibiotic screening was performed with modified checkerboard minimum biofilm inhibitory concentration (MBIC) assays to efficiently screen for bacterial killing and phage-antibiotic synergy (PAS). Data were compared by one-way ANOVA and Tukey (HSD) tests. Time kill analyses (TKA) were performed against R497 and HOU503 with DAP at 0.5× MBIC, ampicillin (AMP) at free peak = 72 µg/mL, and phage at a multiplicity of infection (MOI) of 0.01. In 24 h TKA against R497, phage-antibiotic combinations (PAC) with DAP, AMP, or DAP + AMP combined with 3- or 4-phage cocktails demonstrated significant killing compared to the most effective double combination (ANOVA range of mean differences 2.998 to 3.102 log10 colony forming units (CFU)/mL; p = 0.011, 2.548 to 2.868 log10 colony forming units (CFU)/mL; p = 0.023, and 2.006 to 2.329 log10 colony forming units (CFU)/mL; p = 0.039, respectively), with preserved phage susceptibility identified in regimens with 3-phage cocktails containing NV-497 and the 4-phage cocktail. Against HOU503, AMP combined with any 3- or 4-phage cocktail and DAP + AMP combined with the 3-phage cocktail ATCC 113 + NV-497 + NV-503-01 demonstrated significant PAS and bactericidal activity (ANOVA range of mean differences 2.251 to 2.466 log10 colony forming units (CFU)/mL; p = 0.044 and 2.119 to 2.350 log10 colony forming units (CFU)/mL; p = 0.028, respectively), however, only PAC with DAP + AMP maintained phage susceptibility at the end of 24 h TKA. R497 and HOU503 exposure to DAP, AMP, or DAP + AMP in the presence of single phage or phage cocktail resulted in antibiotic resistance stabilization (i.e., no antibiotic MBIC elevation compared to baseline) without identified antibiotic MBIC reversion (i.e., lowering of antibiotic MBIC compared to baseline in DAP-resistant and DAP-SDD isolates) at the end of 24 h TKA. In conclusion, against DAP-resistant R497 and DAP-SDD HOU503 E. faecium clinical blood isolates, the use of DAP + AMP combined with 3- and 4-phage cocktails effectively eradicated biofilm-embedded MDR E. faecium without altering antibiotic MBIC or phage susceptibility compared to baseline.

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.

Incidence of Vancomycin-Resistant Staphylococcus aureus Strains among Patients with Urinary Tract Infections

There has been a substantial rise in the number of vancomycin-resistant Staphylococcus aureus (VRSA) strains during the last several years. The proportion of vancomycin-resistant strains among isolated S. aureus has risen steadily in recent years, with the first spike occurring in critical care units and thereafter in general hospital wards. S. aureus isolates from urinary tract infection patients were studied for their prevalence and antibiotic resistance. From 292 urine samples, 103 bacterial strains (35.3%) were identified as S. aureus. Various antibiotics were used to test the isolates’ antibacterial resistance profiles. Antibiotic resistance to erythromycin was found in most bacterial isolates, whereas tobramycin antibiotic sensitivity was found in most of them. Vancomycin resistance was found in 23 of all S. aureus isolates in this study. Analysis for β-lactamase found that 71% of S. aureus isolates were positive in all isolates. There was a single plasmid with a molecular weight of 39.306 Kbp in five selected VRSA isolates that was subjected to plasmid analysis. There was evidence of vancomycin resistance among the S. aureus isolates collected from UTI patients in this investigation. This vancomycin resistance pretenses a challenge in the treatment of S. aureus infections and the need to precisely recognize persons who require last-resort medication such as tobramycin.

Antimicrobial therapy during cancer treatment: Beyond antibacterial effects

Cancer treatment options have evolved to include immunotherapy and targeted therapy, in addition to traditional chemoradiation. Chemoradiation places the patient at a higher risk of infection through a myelosuppressive effect. High clinical suspicion and early use of antimicrobials play a major role in decreasing any associated morbidity and mortality. This has led to a widespread use of antimicrobials in cancer patients. Antimicrobial use, however, does not come without its perils. Dysbiosis caused by antimicrobial use affects responses to chemotherapeutic agents and is prognostic in the development and severity of certain cancer treatment-related complications such as graft-versus-host disease and Clostridioides difficile infections. Studies have also demonstrated that an intact gut microbiota is essential in the anticancer immune response. Antimicrobial use can therefore modulate responses and outcomes with immunotherapy targeting immune checkpoints. In this review, we highlight the perils associated with antimicrobial use during cancer therapy and the importance of a more judicious approach. We discuss the nature of the pathologic changes in the gut microbiota resulting from antimicrobial use. We explore the effect these changes have on responses and outcomes to different cancer treatment modalities including chemotherapy and immunotherapy, as well as potential adverse clinical consequences in the setting of stem cell transplant.

Is it time to reconsider prophylactic antimicrobial use for hematopoietic stem cell transplantation? a narrative review of antimicrobials in stem cell transplantation

INTRODUCTION

Hematopoietic Stem Cell Transplantation (HSCT) is a life-saving procedure for multiple types of hematological cancer, autoimmune diseases, and genetic-linked metabolic diseases in humans. Recipients of HSCT transplant are at high risk of microbial infections that significantly correlate with the presence of graft-versus-host disease (GVHD) and the degree of immunosuppression. Infection in HSCT patients is a leading cause of life-threatening complications and mortality.

AREAS COVERED

This review covers issues pertinent to infection in the HSCT patient, including bacterial and viral infection; strategies to reduce GVHD; infection patterns; resistance and treatment options; adverse drug reactions to antimicrobials, problems of antimicrobial resistance; perturbation of the microbiome; the role of prebiotics, probiotics, and antimicrobial peptides. We highlight potential strategies to minimize the use of antimicrobials.

EXPERT OPINION

Measures to control infection and its transmission remain significant HSCT management policy and planning issues. Transplant centers need to consider carefully prophylactic use of antimicrobials for neutropenic patients. The judicious use of appropriate antimicrobials remains a crucial part of the treatment protocol. However, antimicrobials' adverse effects cause microbiome diversity and dysbiosis and have been shown to increase morbidity and mortality.

Emergence and Transmission of Daptomycin and Vancomycin-Resistant Enterococci Between Patients and Hospital Rooms

BACKGROUND

Vancomycin-resistant enterococci (VRE) are a major cause of morbidity and mortality in immunocompromised patients. Tracking the dissemination of VRE strains is crucial to understand the dynamics of emergence and spread of VRE in the hospital setting.

METHODS

Whole genome sequencing (WGS) and phylogenetic analyses were performed to identify dominant VRE strains and potential transmission networks between 35 patients with VRE-positive rectal swabs and their rooms (main rooms and bathrooms) on the leukemia (LKM) and the hematopoietic cell transplant (HCT) floors. Sequence types (STs), drug resistance genes, and patients' outcomes were also determined.

RESULTS

A total of 89 VRE strains grouped into 10 different STs, of which newly described STs were isolated from both floors (ST736, ST494, ST772, and ST1516). We observed highly genetically related strains transmitted between rooms, floors, and time periods in an average period of 39 days (ranging from 3 to 90 days). Of 5 VRE bacteremia events, 3 strains were lacking the pili operon fms14-17-13 (ST203) and the remaining 2 were resistant to daptomycin (DAP; ST736, ST664). Of 10 patients harboring DAP-resistant strains, only 2 were exposed to DAP within 4 months before strain recovery.

CONCLUSION

Our comparisons of VRE strains derived from the environment and immunocompromised patients confirmed horizontal transfer of highly related genetic lineages of multidrug-resistant (particularly to DAP) VRE strains between HCT and LKM patients and their room environment. Implementing WGS can be useful in distinguishing VRE reservoirs where interventions can be targeted to prevent and control the spread of highly resistant organisms.

A Review of Infections After Hematopoietic Cell Transplantation Requiring PICU Care: Transplant Timeline Is Key

Despite major advances in antimicrobial prophylaxis and therapy, opportunistic infections remain a major cause of morbidity and mortality after pediatric hematopoietic cell transplant (HCT). Risk factors associated with the development of opportunistic infections include the patient's underlying disease, previous infection history, co-morbidities, source of the donor graft, preparative therapy prior to the graft infusion, immunosuppressive agents, early and late toxicities after transplant, and graft-vs.-host disease (GVHD). Additionally, the risk for and type of infection changes throughout the HCT course and is greatly influenced by the degree and duration of immunosuppression of the HCT recipient. Hematopoietic cell transplant recipients are at high risk for rapid clinical decompensation from infections. The pediatric intensivist must remain abreast of the status of the timeline from HCT to understand the risk for different infections. This review will serve to highlight the infection risks over the year-long course of the HCT process and to provide key clinical considerations for the pediatric intensivist by presenting a series of hypothetical HCT cases.

Reducing infectious complications after allogeneic stem cell transplant

INTRODUCTION

Infections remain a significant problem, in patients undergoing an allogeneic hematopoietic stem-cell transplant (HSCT) and efforts have been made over the years, to reduce the incidence, morbidity and mortality of infectious complications.

AREAS COVERED

This manuscript is focused on the epidemiology, risk factors and prevention of infections after allogeneic HSCT. A systematic literature review was performed using the PubMed database, between November 2019 and January 2020, with the following MeSH terms: stem-cell transplantation, infection, fungal, bacterial, viral, prophylaxis, vaccines, prevention. The authors reviewed all the publications, and following a common revision, a summary report was made and results were divided in three sections: bacterial, fungal and viral infections.

EXPERT OPINION

Different infections occur in the early, intermediate and late post-transplant period, due to distinct risk factors. Improved diagnostic techniques, pre-emtive therapy and better prophylaxis of immunologic complications, have reduced the morbidity and mortality of infections. The role of the gut microbiota is under careful scrutiny and may further help us to identify high-risk patients.

Bloodstream Infection Due to Vancomycin-resistant Enterococcus Is Associated With Increased Mortality After Hematopoietic Cell Transplantation for Acute Leukemia and Myelodysplastic Syndrome: A Multicenter, Retrospective Cohort Study

BACKGROUND

We examined the impact of vancomycin-resistant Enterococcus (VRE) bloodstream infection (BSI) on outcomes of allogeneic hematopoietic cell transplantation (HCT) utilizing the Center for International Blood and Marrow Transplant Research database.

METHODS

Adult and pediatric patients (N = 7128) who underwent first HCT for acute leukemia or myelodysplastic syndrome from 2008 through 2012 were analyzed as 3 groups-VRE BSI, non-VRE BSI, without BSI-according to BSI status at 100 days (D100) after allogeneic HCT. Multivariable models examined the effect of VRE BSI for overall survival (OS) and nonrelapse mortality (NRM) at 1 year.

RESULTS

Of 7128 patients, 258 (3.2%) had VRE BSI, 2398 (33.6%) had non-VRE BSI, and 4472 (63%) had no BSI. The median time to VRE BSI and non-VRE BSI were D11 and D15, respectively. Compared with non-VRE BSI patients, VRE BSI patients were older, had advanced-stage acute leukemia, and received umbilical cord blood (UCB) allografts. In multivariable models, VRE BSI was associated with lower OS (relative risk [RR], 2.9;(99% confidence interval [CI], 2.2-3.7) and increased NRM (RR, 4.7; 99% CI, 3.6-6.2) (P < .0001) for both. Other predictors for worse OS and increased NRM were non-VRE BSI, older age, advanced disease stage, UCB allograft, - mismatch, comorbidity index ≥3, and cytomegalovirus seropositivity (P < .001 for all variables).

CONCLUSIONS

VRE BSI is associated with lowest OS and highest NRM compared with patients without BSI or non-VRE BSI. Novel interventions that address the pathophysiology of VRE BSI have the potential of improving survival after HCT.

Molecular mechanisms of enterococcal-bacteriophage interactions and implications for human health

Once overlooked as passive bystanders of the human intestinal microbiota, new evidence is shedding light on the importance of enterococci and their bacteriophages (phages) in shaping human health. Natural predators of enterococci, phages represent a narrow spectrum, precision targeting modality for the eradication of problematic enterococci within the microbiota or infected tissue. The identification of enterococcal phage receptors, absorption factors, and transcriptional responses following phage infection reveals a complex predator-prey relationship that modulates enterococcal cell surface architecture, susceptibility to antibiotics, and adaptation to host associated environments. Considering the dry up of contemporary antibiotic discovery pipelines in the pharmaceutical industry and a continued emergence of multidrug-resistant enterococci, enterococcal phages may serve as bonafide therapeutics. We highlight current advances in enterococcal phage biology with emphasis on recent breakthroughs in potential therapeutic applications that place enterococcal phages at the forefront of next-generation biologics.

A suspected septic transfusion reaction associated with posttransfusion contamination of a platelet pool by vancomycin-resistant Enterococcus faecium

BACKGROUND

Vancomycin-resistant enterococci (VRE) are antibiotic-resistant organisms associated with both colonization and serious life-threatening infection in health care settings. Contamination of platelet concentrates (PCs) with Enterococcus can result in transfusion-transmitted infection.

CASE PRESENTATION

This report describes the investigation of a septic transfusion case involving a 27-year-old male patient with relapsed acute leukemia who was transfused with a 5-day-old buffy coat PC pool and developed fever and rigors.

DISCUSSION

Microbiology testing and pulse-field gel electrophoresis (PFGE) was done on patient blood cultures obtained from peripheral and central lines. Microbiology and molecular testing were also performed on the remaining posttransfusion PC pool, which was refrigerated for 24 hours before microbiology testing. Red blood cell (RBC) and plasma units associated with the implicated PCs were screened for microbial contamination. Patient blood cultures obtained from peripheral and central lines yielded vancomycin-resistant Enterococcus faecium. Gram stain of a sample from the platelet pool was negative but coagulase-negative Staphylococcus (CNST) and VRE were isolated on culture. Antibiotic sensitivity and PFGE profiles of several VRE isolates from the patient before and after transfusion, and the PC pool, revealed that all were closely related. Associated RBC and plasma components tested negative for microbial contamination.

CONCLUSIONS

Microbiological and molecular investigations showed a relationship between VRE isolated from the patient before and after transfusion, and therefore it is postulated that a patient-to-PC retrograde contamination (from either blood or skin) occurred. As the CNST isolated from the PC pool was not isolated from patient samples, its implication in the transfusion event is unknown.

Aztreonam and Vancomycin for Initial Treatment of Febrile Neutropenia in Penicillin-Allergic Patients During Hematopoietic Stem Cell Transplantation

Most patients who undergo hematopoietic stem cell transplantation develop neutropenic fever and are at high risk for developing potentially life-threatening infections. β-lactam antibiotics remain the cornerstone for initial empiric treatment of neutropenic fever. In cancer patients with allergy or intolerance to β-lactams, guidelines recommend using aztreonam with vancomycin (AV) for neutropenic fever treatment. To date, the efficacy of AV for the treatment of neutropenic fever during stem cell transplantation is unknown. A retrospective study was conducted to identify hematopoietic stem cell transplantation recipients who were initially treated with concomitant AV for neutropenic fever between 2007 and 2013. Febrile neutropenia was classified as neutropenia with unexplained fever, neutropenic fever with a local source of infection, or neutropenic fever with a microbiologically documented infection. Seventy-six patients were identified who received AV as initial treatment for neutropenic fever over the study period. Responses to AV for neutropenia with unexplained fever (n = 41), febrile neutropenia with local site of infection (n = 11 [pneumonia = 9, other = 2]), and neutropenic fever with microbiologically documented infection (n = 34) were 75%, 55% (45% pneumonia), and 46% respectively. Infection-related mortality was 5%. Aztreonam with vancomycin was effective in treating neutropenia with unexplained fever. For patients with neutropenic fever and local source or microbiologically documented infection, alternative antibiotic treatments should be considered.

Comparative Efficacies of Linezolid vs. Tedizolid in an Experimental Murine Model of Vancomycin-Resistant Enterococcal (VRE) Bacteremia

Tedizolid (TZD) is an oxazolidinone derivative which demonstrates bacteriostatic activity through inhibition of protein synthesis. We compared the efficacies of TZD and an earlier-generation oxazolidinone, linezolid (LZD), in an experimental murine model of bacteremia caused by two VRE strains (one each E. faecium and E. faecalis). LZD exhibited significantly better efficacy in terms of reduced VRE blood and target tissue densities than TZD in this model.