Results From a Randomized, Placebo-Controlled Clinical Trial of a RBX2660-A Microbiota-Based Drug for the Prevention of Recurrent Clostridium difficile Infection

Lipids from gut microbiota: pursuing a personalized treatment

The discovery of microbiome metabolites has enlivened the field of fecal transplantation for therapeutic purposes. However, the transfer of pathogenic living organisms was recently observed to limit its therapeutic potential by increasing the risk of infection. Lipids produced by gut microbiota enter the circulation and control many phenotypic changes associated with microbiota composition. Fecal lipids significantly impact the regulation of several cell signaling pathways, including inflammation. Focusing on these molecules, we review how bioactive gut microbiota-associated lipids affect cellular functioning and clinical outcome. Here, we interrogate whether the gut microbiota can be considered a cutting-edge biotechnological tool for rapid metabolic engineering of meaningful lipids to offer a novel personalized therapy.

Durable reduction of Clostridioides difficile infection recurrence and microbiome restoration after treatment with RBX2660: results from an open-label phase 2 clinical trial

BACKGROUND

Effective treatment options for recurrent Clostridioides difficile infection (rCDI) are limited, with high recurrence rates associated with the current standard of care. Herein we report results from an open-label Phase 2 trial to evaluate the safety, efficacy, and durability of RBX2660-a standardized microbiota-based investigational live biotherapeutic-and a closely-matched historical control cohort.

METHODS

This prospective, multicenter, open-label Phase 2 study enrolled patients who had experienced either ≥ 2 recurrences of CDI, treated by standard-of-care antibiotic therapy, after a primary CDI episode, or ≥ 2 episodes of severe CDI requiring hospitalization. Participants received up to 2 doses of RBX2660 rectally administered with doses 7 days apart. Treatment success was defined as the absence of CDI diarrhea without the need for retreatment for 8 weeks after completing study treatment. A historical control group with matched inclusion and exclusion criteria was identified from a retrospective chart review of participants treated with standard-of-care antibiotics for recurrent CDI who matched key criteria for the study. The primary objective was to compare treatment success of RBX2660 to the historical control group. A key secondary outcome was the safety profile of RBX2660, including adverse events and CDI occurrence through 24 months after treatment. In addition, fecal samples from RBX2660-treated participants were sequenced to evaluate microbiome composition and functional changes from before to after treatment.

RESULTS

In this Phase 2 open-label clinical trial, RBX2660 demonstrated a 78.9% (112/142) treatment success rate compared to a 30.7% (23/75) for the historical control group (p < 0.0001; Chi-square test). Post-hoc analysis indicated that 91% (88/97) of evaluable RBX2660 responders remained CDI occurrence-free to 24 months after treatment demonstrating durability. RBX2660 was well-tolerated with mostly mild to moderate adverse events. The composition and diversity of RBX2660 responders' fecal microbiome significantly changed from before to after treatment to become more similar to RBX2660, and these changes were durable to 24 months after treatment.

CONCLUSIONS

In this Phase 2 trial, RBX2660 was safe and effective for reducing rCDI recurrence as compared to a historical control group. Microbiome changes are consistent with restorative changes implicated in resisting C. difficile recurrence. Clinical Trials Registration NCT02589847 (10/28/2015).

Development and Validation of a Novel Microbiome-Based Biomarker of Post-antibiotic Dysbiosis and Subsequent Restoration

Background: The human gut microbiota are important to health and wellness, and disrupted microbiota homeostasis, or “dysbiosis,” can cause or contribute to many gastrointestinal disease states. Dysbiosis can be caused by many factors, most notably antibiotic treatment. To correct dysbiosis and restore healthier microbiota, several investigational microbiota-based live biotherapeutic products (LBPs) are in formal clinical development. To better guide and refine LBP development and to better understand and manage the risks of antibiotic administration, biomarkers that distinguish post-antibiotic dysbiosis from healthy microbiota are needed. Here we report the development of a prototype Microbiome Health Index for post-Antibiotic dysbiosis (MHI-A).

Methods: MHI-A was developed and validated using longitudinal gut microbiome data from participants in clinical trials of RBX2660 and RBX7455 – investigational LBPs in development for reducing recurrent Clostridioides difficile infections (rCDI). The MHI-A algorithm relates the relative abundances of microbiome taxonomic classes that changed the most after RBX2660 or RBX7455 treatment, that strongly correlated with clinical response, and that reflect biological mechanisms believed important to rCDI. The diagnostic utility of MHI-A was reinforced using publicly available microbiome data from healthy or antibiotic-treated populations.

Results: MHI-A has high accuracy to distinguish post-antibiotic dysbiosis from healthy microbiota. MHI-A values were consistent across multiple healthy populations and were significantly shifted by antibiotic treatments known to alter microbiota compositions, shifted less by microbiota-sparing antibiotics. Clinical response to RBX2660 and RBX7455 correlated with a shift of MHI-A from dysbiotic to healthy values.

Conclusion: MHI-A is a promising biomarker of post-antibiotic dysbiosis and subsequent restoration. MHI-A may be useful for rank-ordering the microbiota-disrupting effects of antibiotics and as a pharmacodynamic measure of microbiota restoration.

Microbiome-based therapeutics

Symbiotic microorganisms inhabiting the gastrointestinal tract promote health by decreasing susceptibility to infection and enhancing resistance to a range of diseases. In this Review, we discuss our increasing understanding of the impact of the microbiome on the mammalian host and recent efforts to culture and characterize intestinal symbiotic microorganisms that produce or modify metabolites that impact disease pathology. Manipulation of the intestinal microbiome has great potential to reduce the incidence and/or severity of a wide range of human conditions and diseases, and the biomedical research community now faces the challenge of translating our understanding of the microbiome into beneficial medical therapies. Our increasing understanding of symbiotic microbial species and the application of ecological principles and machine learning are providing exciting opportunities for microbiome-based therapeutics to progress from faecal microbiota transplantation to the administration of precisely defined and clinically validated symbiotic microbial consortia that optimize disease resistance.

The potential of microbiome replacement therapies for Clostridium difficile infection

PURPOSE OF REVIEW

There is a paradox when treating Clostridium difficile infection (CDI); treatment antibiotics reduce C. difficile colonization but cause further microbiota disruption and can lead to recurrent disease. The success of faecal microbiota transplants (FMT) in treating CDI has become a new research area in microbiome restorative therapies but are they a viable long-term treatment option?

RECENT FINDINGS

C. difficile displays metabolic flexibility to use different nutritional sources during CDI. Using microbiome therapies for the efficient restoration of bile homeostasis and to reduce the bioavailability of preferential nutrients will target the germination ability of C. difficile spores and the growth rate of vegetative cells. Several biotechnology companies have developed microbiome therapeutics for treating CDI, which are undergoing clinical trials.

SUMMARY

There is confidence in using restorative microbiome therapies for treating CDI after the demonstrated efficacy of FMT, where several biotechnology companies are aiming to supply what would be a 'first in class' treatment option. Efficient removal of C. difficile from the different intestinal biogeographies should be considered in future microbiome therapies. With the gut microbiota implicated in different diseases, more work is needed to assess the long-term consequences of microbiome therapies.

The development of live biotherapeutics against Clostridioides difficile infection towards reconstituting gut microbiota

Clostridioides difficile is the most prevalent pathogen of nosocomial diarrhea. In the United States, over 450,000 cases of C. difficile infection (CDI), responsible for more than 29,000 deaths, are reported annually in recent years. Because of the emergence of hypervirulent strains and strains less susceptible to vancomycin and fidaxomicin, new therapeutics other than antibiotics are urgently needed. The gut microbiome serves as one of the first-line defenses against C. difficile colonization. The use of antibiotics causes gut microbiota dysbiosis and shifts the status from colonization resistance to infection. Hence, novel CDI biotherapeutics capable of reconstituting normal gut microbiota have become a focus of drug development in this field.

Fecal microbiota transplantation for recurrent Clostridioides difficile, safety, and pitfalls

Clostridioides difficile infection (CDI) is one of the leading causes of hospital-acquired infection attributing to substantial morbidity, mortality, and healthcare cost. Recurrent CDI (rCDI) is common and occurs after effective treatment of first episode. Treatment of rCDI is based on accurate diagnoses, due to difficulty in distinguishing between colonization of C. difficile spores or CDI; coronavirus disease 2019 (COVID-19) added to the complexity of diagnoses as both entities can co-occur. It is difficult to eradicate rCDI, and there remains a critical gap regarding treatment of rCDI. The treatment goal of rCDI is to reestablish normal microbiota. Fecal microbiota transplantation (FMT) is suggested as a treatment for second episode of rCDI. Based on the collective evidence of all randomized controlled trials, FMT was reported more efficacious compared with vancomycin or fidaxomicin; however, these trials had limited number of patients and all patients were pre-treated with vancomycin prior to FMT. Furthermore, when comparing various routes of instillation and types of preparation of fecal microbiota, no difference was observed in cure rate. Despite the success rate of FMT, there remains a concern for transmission of infectious agents, such as Gram negative bacteremia or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), adverse events (diarrhea and abdominal pain), and reports of new diagnoses (inflammatory bowel disease, weight gain and irritable bowel syndrome). To lessen the risk of transmissible infections, donor screening should be performed, which includes screening for medical comorbidities and infectious pathogens in blood and feces. Scheduling complexities and reimbursement places an additional roadblock for using FMT. Microbiome-based therapies are being developed to eliminate the logistical challenges related to FMT. Large prospective and placebo-controlled studies are needed to evaluate the efficacy and long-term safety of FMT, so its use can be justified in clinical practice.

European Society of Clinical Microbiology and Infectious Diseases: 2021 update on the treatment guidance document for Clostridioides difficile infection in adults

SCOPE

In 2009, the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) published the first treatment guidance document for Clostridioides difficile infection (CDI). This document was updated in 2014. The growing literature on CDI antimicrobial treatment and novel treatment approaches, such as faecal microbiota transplantation (FMT) and toxin-binding monoclonal antibodies, prompted the ESCMID study group on C. difficile (ESGCD) to update the 2014 treatment guidance document for CDI in adults.

METHODS AND QUESTIONS

Key questions on CDI treatment were formulated by the guideline committee and included: What is the best treatment for initial, severe, severe-complicated, refractory, recurrent and multiple recurrent CDI? What is the best treatment when no oral therapy is possible? Can prognostic factors identify patients at risk for severe and recurrent CDI and is there a place for CDI prophylaxis? Outcome measures for treatment strategy were: clinical cure, recurrence and sustained cure. For studies on surgical interventions and severe-complicated CDI the outcome was mortality. Appraisal of available literature and drafting of recommendations was performed by the guideline drafting group. The total body of evidence for the recommendations on CDI treatment consists of the literature described in the previous guidelines, supplemented with a systematic literature search on randomized clinical trials and observational studies from 2012 and onwards. The Grades of Recommendation Assessment, Development and Evaluation (GRADE) system was used to grade the strength of our recommendations and the quality of the evidence. The guideline committee was invited to comment on the recommendations. The guideline draft was sent to external experts and a patients' representative for review. Full ESCMID endorsement was obtained after a public consultation procedure.

RECOMMENDATIONS

Important changes compared with previous guideline include but are not limited to: metronidazole is no longer recommended for treatment of CDI when fidaxomicin or vancomycin are available, fidaxomicin is the preferred agent for treatment of initial CDI and the first recurrence of CDI when available and feasible, FMT or bezlotoxumab in addition to standard of care antibiotics (SoC) are preferred for treatment of a second or further recurrence of CDI, bezlotoxumab in addition to SoC is recommended for the first recurrence of CDI when fidaxomicin was used to manage the initial CDI episode, and bezlotoxumab is considered as an ancillary treatment to vancomycin for a CDI episode with high risk of recurrence when fidaxomicin is not available. Contrary to the previous guideline, in the current guideline emphasis is placed on risk for recurrence as a factor that determines treatment strategy for the individual patient, rather than the disease severity.

Fecal Microbiota Transplantation and Microbial Therapeutics for the Treatment of Clostridioides difficile Infection in Pediatric Patients

Clostridioides difficile infection (CDI) is the most common cause of antibiotic-associated diarrhea and has high rates of recurrent disease. As a disease associated with intestinal dysbiosis, gastrointestinal microbiome manipulation and fecal microbiota transplantation (FMT) have evolved as effective, although relatively unregulated therapeutics and not without safety concerns. FMT for the treatment of CDI has been well studied in adults with increasing data reported in children. In this review, we discuss the current body of literature on the use of FMT in children including effectiveness, safety, risk factors for a failed FMT, and the role of FMT in children with comorbidities. We also review emerging microbial therapeutics for the treatment of rCDI.

RBX7455, a Non-frozen, Orally Administered Investigational Live Biotherapeutic, Is Safe, Effective, and Shifts Patients' Microbiomes in a Phase 1 Study for Recurrent Clostridioides difficile Infections

BACKGROUND

Recurrent Clostridioides difficile infections (rCDI) are a global public health threat. To reduce rCDI, microbiota-restoring therapies are needed, particularly standardized, easy-to-administer formulations.

METHODS

This phase I open-label trial assessed the safety, efficacy in preventing rCDI recurrence, and intestinal microbiome effects of RBX7455, a room temperature-stable, orally administered investigational live biotherapeutic. Adult participants with 1 or more prior episodes of rCDI received: 4 RBX7455 capsules twice daily for 4 days (group 1); 4 RBX7455 capsules twice daily for 2 days (group 2); or 2 RBX7455 capsules twice daily for 2 days (group 3). For all groups, the first dose was administered in clinic, with remaining doses self-administered at home. Adverse events were monitored during and for 6 months after treatment. Treatment success was defined as rCDI prevention through 8 weeks after treatment. Participants' microbiome composition was assessed prior to and for 6 months after treatment.

RESULTS

Nine of 10 group 1 patients (90%), 8 of 10 group 2 patients (80%), and 10 of 10 group 3 patients (100%) were recurrence-free at the 8-week endpoint with durability to 6 months. Seventy-five treatment-emergent adverse events were observed in 27 participants with no serious investigational product-related events. Prior to treatment, participants' microbiomes were dissimilar from the RBX7455 composition with decreased Bacteroidia- and Clostridia-class bacteria, whereas after treatment, responders' microbiomes showed increased Bacteroidia and Clostridia.

CONCLUSIONS

Three dosing regimens of RBX7455 were safe and effective at preventing rCDI. Responders' microbiomes converged toward the composition of RBX7455. These results support its continued clinical evaluation.

CLINICAL TRIALS REGISTRATION

NCT02981316.

Add-on interventions for the prevention of recurrent Clostridioides Difficile infection: A systematic review and network meta-analysis

OBJECTIVES

We aimed to assess the comparative efficacy and safety of adjunctive interventions for the prevention of Clostridioides difficile recurrence.

METHODS

We searched Medline, Embase, CENTRAL, and clinicaltrials.gov up to May 2021. We included randomized controlled trials comparing interventions added to antibiotic therapy for prevention of CDI recurrence, to placebo or each other. Efficacy outcomes were CDI and diarrhea recurrence. Safety outcomes included the incidence of any adverse event (AE), serious AEs, and discontinuation due to AEs. We performed random-effects network meta-analysis. We ranked interventions based on SUCRA (surface under the cumulative ranking curve) probabilities. We assessed confidence in estimates utilizing the CINeMA (Confidence in Network Meta-Analysis) framework.

RESULTS

Fifteen trials (3909 patients) assessed 9 interventions. Oligofructose (OR 0.17; 95% CI, 0.07 to 0.46), NTCD-M3 (OR 0.29; 95% CI, 0.12 to 0.68), rifaximin (OR 0.47; 95% CI, 0.24 to 0.93), RBX2660 (OR 0.47; 95% CI, 0.22 to 0.99), the combination bezlotoxumab/actoxumab (OR 0.47; 95% CI, 0.37 to 0.60), and bezlotoxumab (OR, 0.53; 95% CI, 0.42 to 0.68) were associated with lower incidence of CDI recurrence than placebo (moderate confidence). Oligofructose was ranked highest, however data for oligofructose were derived solely from one small trial. Probiotics, actoxumab and SER-109 were not superior to placebo (low confidence). Probiotics were not well tolerated (low confidence) and actoxumab showed high rates of serious AEs (moderate confidence).

CONCLUSION

Add-on treatment with oligofructose, NTCD-M3 spores, rifaximin, RBX2660, and bezlotoxumab likely reduces the risk of CDI. Evidence on probiotics and SER-109 are uncertain, thus adequately powered trials are warranted.

Microbiota restoration for recurrent Clostridioides difficile: Getting one step closer every day!

Clostridioides difficile infection (CDI) is an urgent health threat being the most common healthcare-associated infection, and its management is a clinical conundrum. Over 450 000 infections are seen in the United States with similar incidence seen in the rest of the developed world. The majority of infections seen are mild-moderate with fulminant disease and mortality being rare complications seen in the elderly and in those with comorbidities. The most common complication of CDI is recurrent infection with rates as high as 60% after three or more infections. A dilemma in the management of primary and recurrent CDI is testing due to the high sensitivity of the nucleic acid amplification tests such as the polymerase chain reaction, which leads to clinical false positives if patients are not chosen carefully (with symptoms) before testing. A newer testing regimen involving a 2-step strategy is emerging using glutamate dehydrogenase as a screening strategy followed by enzyme immunoassay for the C. difficile toxin. Microbiota restoration therapies are the cornerstone of management of recurrent CDI to prevent future recurrences. The most common modality of microbiota restoration is faecal microbiota transplantation, which has been tainted with heterogeneity and adverse events such as serious infectious transmission. The success rates for recurrence prevention from microbiota restoration therapies are over 90% compared with less than 50% of recurrence prevention with courses of antibiotics. This has led to development and emergence of standardized microbiota restoration therapies in capsule and enema forms. Capsule-based therapies include CP101 (positive phase II results), RBX7455 (positive phase I results), SER-109 (positive phase III results) and VE303 (ongoing phase II trial). Enema-based therapy includes RBX2660 (positive phase III data). This review summarizes the principles of management and diagnosis of CDI and focuses on emerging and existing data on faecal microbiota transplantation and standardized microbiota restoration therapies.

My Treatment Approach to Clostridioides difficile Infection

Clostridioides difficile infection is the most common cause of infectious diarrhea in hospitals with an increasing incidence in the community. Clinical presentation of C difficile infection ranges from diarrhea manageable in the outpatient setting to fulminant infection requiring intensive care admission. There have been significant advances in the management of primary and recurrent C difficile infection including diagnostics, newer antibiotics, antibody treatments, and microbiome restoration therapies. Because of the risk of clinical false-positive results with the polymerase chain reaction test, a two-step assay combining an enzyme immune assay for glutamate dehydrogenase and the C difficile toxin is being used. Cost permitting, I treat a first episode of C difficile infection preferably with fidaxomicin over vancomycin but not metronidazole. The most common complication after C difficile infection is recurrence. I manage a first recurrence with a vancomycin taper and pulse or fidaxomicin and recommend a single dose of intravenous bezlotoxumab (a monoclonal antibody against the toxin B) to reduce recurrence rates for those patients at high risk. Patients with multiply recurrent C difficile infection are managed with a course of antibiotics such as vancomycin or fidaxomicin followed by microbiota restoration. The success of fecal microbiota transplantation is greater than 85%, compared with the 40% to 50% success rate of antibiotics in this situation. Fecal microbiota transplantation is heterogeneous and has rare but serious risks such as transmission of infections. Standardized microbiota restoration therapies are in clinical development and have completed phase III clinical trials. This review answers common clinical questions in the management of C difficile infection.

The microbiome and host mucosal interactions in urinary tract diseases

The urinary tract consists of the bladder, ureters, and kidneys, and is an essential organ system for filtration and excretion of waste products and maintaining systemic homeostasis. In this capacity, the urinary tract is impacted by its interactions with other mucosal sites, including the genitourinary and gastrointestinal systems. Each of these sites harbors diverse ecosystems of microbes termed the microbiota, that regulates complex interactions with the local and systemic immune system. It remains unclear whether changes in the microbiota and associated metabolites may be a consequence or a driver of urinary tract diseases. Here, we review the current literature, investigating the impact of the microbiota on the urinary tract in homeostasis and disease including urinary stones, acute kidney injury, chronic kidney disease, and urinary tract infection. We propose new avenues for exploration of the urinary microbiome using emerging technology and discuss the potential of microbiome-based medicine for urinary tract conditions.

SER-109, an Investigational Microbiome Drug to Reduce Recurrence After Clostridioides difficile Infection: Lessons Learned From a Phase 2 Trial

BACKGROUND

Recurrent Clostridioides difficile infection (rCDI) is associated with loss of microbial diversity and microbe-derived secondary bile acids, which inhibit C. difficile germination and growth. SER-109, an investigational microbiome drug of donor-derived, purified spores, reduced recurrence in a dose-ranging, phase (P) 1 study in subjects with multiple rCDIs.

METHODS

In a P2 double-blind trial, subjects with clinical resolution on standard-of-care antibiotics were stratified by age (< or ≥65 years) and randomized 2:1 to single-dose SER-109 or placebo. Subjects were diagnosed at study entry by PCR or toxin testing. Safety, C. difficile-positive diarrhea through week 8, SER-109 engraftment, and bile acid changes were assessed.

RESULTS

89 subjects enrolled (67% female; 80.9% diagnosed by PCR). rCDI rates were lower in the SER-109 arm than placebo (44.1% vs 53.3%) but did not meet statistical significance. In a preplanned analysis, rates were reduced among subjects ≥65 years (45.2% vs 80%, respectively; RR, 1.77; 95% CI, 1.11-2.81), while the <65 group showed no benefit. Early engraftment of SER-109 was associated with nonrecurrence (P < .05) and increased secondary bile acid concentrations (P < .0001). Whole-metagenomic sequencing from this study and the P1 study revealed previously unappreciated dose-dependent engraftment kinetics and confirmed an association between early engraftment and nonrecurrence. Engraftment kinetics suggest that P2 dosing was suboptimal. Adverse events were generally mild to moderate in severity.

CONCLUSIONS

Early SER-109 engraftment was associated with reduced CDI recurrence and favorable safety was observed. A higher dose of SER-109 and requirements for toxin testing were implemented in the current P3 trial.

CLINICAL TRIALS REGISTRATION

NCT02437487, https://clinicaltrials.gov/ct2/show/NCT02437487?term=SER-109&draw= 2&rank=4.

Effectiveness of fecal microbiota transplant for the treatment of Clostridioides difficile diarrhea: a systematic review and meta-analysis

Clostridioides difficile is a major cause of health-care related infections and antibiotic-associated diarrhea. High recurrence rates following antibiotic treatment, along with the emergence of hypervirulent and multidrug resistant ribotypes makes essential the development of safe, effective, novel therapies for the treatment of C. difficile infections. The primary outcome evaluated in this meta-analysis was the effectiveness of fecal microbiota transplantation (FMT). Secondary outcomes were the proportion of patients suffering adverse effects along with the most effective administration route. The mean treatment effectiveness was 82% (95% CI: 75-89). Overall, patients receiving FMT via colonoscopy experienced more adverse effects than patients whom received enema, or oral capsules (71·6% vs 40·2%, and 35·3% respectively). Comparing administration of FMT by colonoscopy versus enema resulted in a Hedges' g of -0·74 (95% CI of -0·9 to -0·58), indicating a slight advantage in favor of colonoscopy. The comparison between colonoscopy and capsule returned a Hedges' g of 0·44 (95% CI of 0·20-0·69), indicating that delivery of the FMT by capsule was statistically significantly more effective. FMT provides an effective and safe treatment for C. difficile diarrhea. Further research into the efficacy of different preparation protocols is needed.

Microbiota-based Therapies Clostridioides difficile infection that is refractory to antibiotic therapy

Clostridioides difficile infection (CDI) has had a devastating impact worldwide with significant rates of mortality, especially among the elderly. Despite effective antibiotics, the incidence of recurrent CDI (rCDI) is increasing and more difficult to treat with antibiotics alone. Fecal Microbiota Transplantation (FMT) has emerged as a consistently effective treatment for rCDI. Mechanisms for FMT are not entirely understood, but remain an area of active investigation. There have been recent safety reports with the use of FMT regarding transmission of pathogens in a few patients that have led to serious illness. With appropriate screening, FMT can be safely administered and continue to have a significant impact on eradication of rCDI and improve the lives of patients suffering from this disease. In this review, we summarize current treatments for CDI with a focus on microbiota-based therapies used for antibiotic refractory disease.

A contemporary review of Clostridioides difficile infections in patients with haematologic diseases

Clostridioides (Clostridium) difficile (C. difficile) infection is one of the most common causes of increased morbidity and mortality. Approximately 500 000 C. difficile infections (CDIs) occur each year in the United States, and they result in more than 29 000 deaths. Patients with haematologic diseases are at a higher risk for this infection due to frequent hospitalization and exposure to treatment-associated risk factors. Whilst several currently available antimicrobial agents offer resolution, recurrence of infection remains a major concern. Recent advancement in deciphering C. difficile virulence mechanisms and identification of its allies in contributing to the infection has led to the development of alternative treatment strategies. Here, we will provide a contemporary discussion of how major risk factors in haematologic diseases, such as immunosuppression, chemoradiation, use of antibiotic, proton pump inhibitor and opioid, and deficiency in butyrate and antimicrobial peptides contribute to C. difficile infection. Next, we will highlight different approaches to control and mitigate this infection such as antibiotic stewardship and faecal microbiota transplantation. Finally, we will explore several emerging treatments such as use of pre- and probiotics, immunotherapy and microbiome-sparing agents.

Designing bugs as drugs: exploiting the gut microbiome

The extensive investigation of the human microbiome and the accumulating evidence regarding its critical relationship to human health and disease has advanced recognition of its potential as the next frontier of drug development. The rapid development of technologies, directed at understanding the compositional and functional dynamics of the human microbiome, and the ability to mine for novel therapeutic targets and biomarkers are leading innovative efforts to develop microbe-derived drugs that can prevent and treat autoimmune, metabolic, and infectious diseases. Increasingly, academics, biotechs, investors, and large pharmaceutical companies are partnering to collectively advance various therapeutic modalities ranging from live bacteria to small molecules. We review the leading platforms in current development focusing on live microbial consortia, engineered microbes, and microbial-derived metabolites. We will also touch on how the field is addressing and challenging the traditional definitions of pharmacokinetics and pharmacodynamics, dosing, toxicity, and safety to advance the development of these novel and cutting-edge therapeutics into the clinic.

Microbiota restoration reduces antibiotic-resistant bacteria gut colonization in patients with recurrent Clostridioides difficile infection from the open-label PUNCH CD study

BACKGROUND

Once antibiotic-resistant bacteria become established within the gut microbiota, they can cause infections in the host and be transmitted to other people and the environment. Currently, there are no effective modalities for decreasing or preventing colonization by antibiotic-resistant bacteria. Intestinal microbiota restoration can prevent Clostridioides difficile infection (CDI) recurrences. Another potential application of microbiota restoration is suppression of non-C. difficile multidrug-resistant bacteria and overall decrease in the abundance of antibiotic resistance genes (the resistome) within the gut microbiota. This study characterizes the effects of RBX2660, a microbiota-based investigational therapeutic, on the composition and abundance of the gut microbiota and resistome, as well as multidrug-resistant organism carriage, after delivery to patients suffering from recurrent CDI.

METHODS

An open-label, multi-center clinical trial in 11 centers in the USA for the safety and efficacy of RBX2660 on recurrent CDI was conducted. Fecal specimens from 29 of these subjects with recurrent CDI who received either one (N = 16) or two doses of RBX2660 (N = 13) were analyzed secondarily. Stool samples were collected prior to and at intervals up to 6 months post-therapy and analyzed in three ways: (1) 16S rRNA gene sequencing for microbiota taxonomic composition, (2) whole metagenome shotgun sequencing for functional pathways and antibiotic resistome content, and (3) selective and differential bacterial culturing followed by isolate genome sequencing to longitudinally track multidrug-resistant organisms.

RESULTS

Successful prevention of CDI recurrence with RBX2660 correlated with taxonomic convergence of patient microbiota to the donor microbiota as measured by weighted UniFrac distance. RBX2660 dramatically reduced the abundance of antibiotic-resistant Enterobacteriaceae in the 2 months after administration. Fecal antibiotic resistance gene carriage decreased in direct relationship to the degree to which donor microbiota engrafted.

CONCLUSIONS

Microbiota-based therapeutics reduce resistance gene abundance and resistant organisms in the recipient gut microbiome. This approach could potentially reduce the risk of infections caused by resistant organisms within the patient and the transfer of resistance genes or pathogens to others.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01925417 ; registered on August 19, 2013.

Diagnostic and therapy of severe Clostridioides difficile infections in the ICU

PURPOSE OF REVIEW

The purpose of the review is to provide all the recent data focusing on the diagnostic and treatment of Clostridioides difficile infection in patients admitted in the ICU.

RECENT FINDINGS

In the ICU, diagnosis remains complicated with a large number of alternative diagnosis. The treatment classically relies on vancomycin but fidaxomicin and fecal microbiota transplantation are now potential solutions in selected indications.

SUMMARY

Data on ICU-related CDI remain limited and conflicting. To date, there is no unique and simple way to obtain a diagnosis for CDI, the combination of clinical signs and a two-step testing algorithm remains the recommended gold-standard. Two molecules can be proposed for first line treatment: vancomycin and fidaxomicin. Although metronidazole may still be discussed as a treatment option for mild CDI in low-risk patients, its use for ICU-patients does not seem reasonable. Several reports suggest that fecal microbiota transplantation could be discussed, as it is well tolerated and associated with a high rate of clinical cure. CDI is a dynamic and active area of research with new diagnostic techniques, molecules, and management concepts likely changing our approach to this old disease in the near future.

Cost-effectiveness analysis of a fecal microbiota transplant center for treating recurrent C.difficile infection

OBJECTIVE

We assessed the cost-effectiveness of establishing a fecal microbial transplant (FMT) unit in Canada for the treatment of recurrent CDI.

DESIGN

We performed a cost-effectiveness analysis to determine the number of patients with recurrent CDI needed to treat (NNT) annually to make establishing a FMT unit cost-effective. We compared treating patients for their second recurrence of CDI with FMT in a jurisdiction with a FMT unit, compared to being treated with antibiotics; then sent to a medical center with FMT available for the third recurrence. We used a willingness to pay threshold of $50,000 per quality-adjusted-life-year gained.

RESULTS

The minimum annual NNT was 15 for FMT via colonoscopy, 17 for FMT via capsule, and 44 for FMT via enema compared with vancomycin, and 16, 18, and 47 compared with fidaxomicin, respectively. A medical center's minimum catchment area when establishing a FMT unit would have to be 56,849 if using FMT via colonoscopy, or 64,429 if using capsules.

CONCLUSION

We report the minimum number of patients requiring treatment annually with FMT to achieve cost-effectiveness, when including start-up and ongoing costs. FMT is cost-effective in Canada in populations with a sufficient number of eligible patients, ranging from 15 to 47 depending on the FMT modality used. This is crucial for medical jurisdictions making decisions about establishing a FMT unit for the treatment of recurrent CDI. The cost-effectiveness can be generalized in other countries.

Impact of investigational microbiota therapeutic RBX2660 on the gut microbiome and resistome revealed by a placebo-controlled clinical trial

BACKGROUND

Intestinal microbiota restoration can be achieved by complementing a subject's perturbed microbiota with that of a healthy donor. Recurrent Clostridioides difficile infection (rCDI) is one key application of such treatment. Another emerging application of interest is reducing antibiotic-resistant genes (ARGs) and organisms (AROs). In this study, we investigated fecal specimens from a multicenter, randomized, double-blind, placebo-controlled phase 2b study of microbiota-based investigational drug RBX2660. Patients were administered either placebo, 1 dose of RBX2660 and 1 placebo, or 2 doses of RBX2660 via enema and longitudinally tracked for changes in their microbiome and antibiotic resistome.

RESULTS

All patients exhibited significant recovery of gut microbiome diversity and a decrease of ARG relative abundance during the first 7 days post-treatment. However, the microbiome and resistome shifts toward average configurations from unperturbed individuals were more significant and longer-lasting in RBX2660 recipients compared to placebo. We quantified microbiome and resistome modification by RBX2660 using a novel "transplantation index" metric. We identified taxonomic and metabolic features distinguishing the baseline microbiome of non-transplanted patients and taxa specifically enriched during the process of transplantation. We elucidated the correlation between resistome and taxonomic transplantations and post-treatment dynamics of patient-specific and RBX2660-specific ARGs. Whole genome sequencing of AROs cultured from RBX2660 product and patient samples indicate ARO eradication in patients via RBX2660 administration, but also, to a lesser extent, introduction of RBX2660-derived AROs.

CONCLUSIONS

Through shotgun metagenomic sequencing, we elucidated the effects of RBX2660 in the microbiome and resistome. Antibiotic discontinuation alone resulted in significant recovery of gut microbial diversity and reduced ARG relative abundance, but RBX2660 administration more rapidly and completely changed the composition of patients' microbiome, resistome, and ARO colonization by transplanting RBX2660 microbiota into the recipients. Although ARGs and AROs were transmitted through RBX2660, the resistome post-RBX2660 more closely resembled that of the administered product-a proxy for the donor-than an antibiotic perturbed state.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02299570 . Registered 19 November 2014 Video Abstract.

Fecal Microbiota Transplantation for Recurrent Clostridium difficile Infection in Patients With Multiple Comorbidities: Long-Term Safety and Efficacy Results From a Tertiary Care Community Hospital

Background

Cure rates of Clostridium difficile infection (CDI) with fecal microbiota transplant (FMT) have been promising. However, there is debate regarding success of FMT in patients with comorbidities.

Methods

Electronic chart review was done to collect data on patients who underwent FMT from January 2015 to August 2017. Charts were analyzed in November 2018 with a median follow-up of 25.4 months (interquartile range 20 - 31 months).

Results

Twenty patients underwent FMT. The primary success rate at our institution was 90% and overall success rate was 100%. Six patients (43%) had FMT failure (two early and four late).

Conclusions

This case series is a description of our center’s initial experience with FMT for treatment of recurrent CDI. Our high success rate reiterates the efficacy and safety of FMT in this population including patients with comorbidities.

Prophage in Phage Manufacturing: Is the Risk Overrated Compared to Other Therapies or Food?

The rehabilitation of lytic bacteriophages, as living and replicative biological therapeutic agents, is only 2 decades old in western countries, compared to other therapeutic approaches using chemicals and inactivated or alive biologicals. This paper attempts to provide arguments to address prophage content issues in phage pharmaceutical preparations from a regulatory perspective. The author rebalances the risk associated with the presence of prophages in their pharmaceutical preparations in comparison (i) to lysogenic phages and prophages contained in various therapeutic anti-infective treatments, as well as in food or probiotics, (ii) to adventitious whole retroviruses or fragments contained in vaccines, and (iii) to the massive release of lysogenic phages and prophages induced by antibiotics usage.

Fecal microbiota transplantation for treatment of patients with recurrent Clostridioides difficile infection

INTRODUCTION

Recurrent Clostridiodes difficile infection (rCDI) is a growing public health burden, and is associated with poor patient outcomes. Fecal microbiota transplantation (FMT) is a novel therapy with an aim to restore the disrupted microbiota with demonstrated success in the management of rCDI and a favorable safety profile.

AREAS COVERED

This review includes a comprehensive overview of a search of the literature including epidemiology of rCDI, basics of the gut microbiome, antibiotic therapy for rCDI along with rationale for safety and efficacy of FMT for rCDI.

EXPERT OPINION

Patients exposed to risk factors, such as antimicrobial agents, are at risk for disruption of the gut microbiome resulting in the reduction of microbial diversity and dysbiosis. Dysbiotic microbiota predispose to primary and rCDI. Strategies to improve the current and future management of rCDI are under clinical investigation, including narrow-spectrum antibiotics, monoclonal antibodies and FMT, which has shown a high success rate for rCDI. Further investigation is needed to determine optimal standardization of the methodological components of FMT including donor screening, stool preparation, storage and instillation and patient follow-up. Newer methods of microbiota replacement therapies including enema- and capsule-based therapies are under investigation.

Fecal transplant clinical trials for Clostridioides difficile: an interview with Sahil Khanna

This interview was conducted by Atiya Henry, Commissioning Editor of Future Microbiology. Sahil Khanna is an Associate Professor of Medicine in the Division of Gastroenterology and Hepatology at Mayo Clinic, Rochester (MN, USA). He currently directs the Comprehensive Gastroenterology Interest group, Clostridioides difficile clinic, Fecal Microbiota Transplantation program and C. difficile related clinical trials at Mayo Clinic. He completed Medical School at the All India Institute of Medical Sciences, New Delhi; followed by Post Doctoral Research at University of California, San Diego (CA, USA); residency in Internal Medicine and Fellowship in Gastroenterology and Hepatology at Mayo Clinic, before joining the Faculty. He also completed Masters in Clinical and Translational Sciences during his fellowship. His research and clinical interests include epidemiology, outcomes and emerging therapeutics for C. difficile infection, an arena in which he has had numerous publications and presentations. He has over 100 peer-reviewed publications, serves as reviewer, is on the editorial board of several journals and has won numerous awards.

Patients Eligible for Trials of Microbe-Based Therapeutics Do Not Represent the Population With Recurrent Clostridioides difficile Infection

BACKGROUND & AIMS

Although there are many industry-funded trials of microbe-based therapeutics for Clostridioides (formerly Clostridium) difficile infection (CDI), not all patients are eligible for these trials, due to their strict enrollment criteria. Furthermore, given the widespread availability of fecal microbiota transplantation (FMT) and overwhelming evidence to support its efficacy, patients might refuse enrollment in trials with a placebo group. We analyzed willingness and eligibility of patients with recurrent CDI to participate in randomized controlled trials of microbe-based therapeutic agents.

METHODS

We performed a retrospective study of 199 patients referred to 4 tertiary referral centers for treatment of CDI from August 1, 2018 through January 31, 2019. We collected data on eligibility for FMT and enrollment in randomized controlled trials.

RESULTS

Of 130 patients deemed appropriate for FMT, 98 patients (75%) were ineligible for participation in a randomized controlled trial and 16 patients (17%) were eligible but refused to enroll. Immune compromise and inflammatory bowel diseases were the most common reasons for exclusion from trials.

CONCLUSIONS

Most patients with CDI who meet the guideline criteria for FMT are ineligible or unwilling to participate in randomized controlled trials of microbe-based therapeutics. Trial populations therefore do not represent the population of patients with CDI.

The Efficacy and Safety of Fecal Microbiota Transplant for Recurrent Clostridium difficile Infection: Current Understanding and Gap Analysis

The leading risk factor for Clostridioides (Clostridium) difficile infection (CDI) is broad-spectrum antibiotics, which lead to low microbial diversity, or dysbiosis. Current therapeutic strategies for CDI are insufficient, as they do not address the key role of the microbiome in preventing C. difficile spore germination into toxin-producing vegetative bacteria, which leads to symptomatic disease. Fecal microbiota transplant (FMT) appears to reduce the risk of recurrent CDI through microbiome restoration. However, a wide range of efficacy rates have been reported, and few placebo-controlled trials have been conducted, limiting our understanding of FMT efficacy and safety. We discuss the current knowledge gaps driven by questions around the quality and consistency of clinical trial results, patient selection, diagnostic methodologies, use of suppressive antibiotic therapy, and methods for adverse event reporting. We provide specific recommendations for future trial designs of FMT to provide improved quality of the clinical evidence to better inform treatment guidelines.

The Route to Palatable Fecal Microbiota Transplantation

The community of symbiotic microorganisms that reside in our gastrointestinal tract is integral to human health. Fecal microbiota transplantation (FMT) has been shown to be highly effective in treating recurrent Clostridioides difficile infection (rCDI) and is now recommended by medical societies for patients suffering from rCDI who have failed to respond to conventional therapy. The main challenges with FMT are its accessibility, acceptability, lack of standardization, and regulatory complexity, which will be discussed in this review. Access to FMT is being addressed through the development of frozen and lyophilized FMT preparations that can be prepared at stool banks and shipped to the point of care. Both access and patient acceptance would be enhanced by oral FMT capsules, and there is potential to reduce capsule burden by utilizing colonic release capsules, targeting the site of disease. This review compares the efficacy of different FMT routes of administration: capsules, nasal feeding tubes, enemas, and colonoscopic infusions. FMT is considered investigational by the Food and Drug Administration. In effort to improve access to FMT, physicians may perform FMT outside of an investigational new drug application for treating CDI infections not responsive to standard therapies. The majority of FMT studies report only minor adverse effects; however, there is risk of transmission of infections.

Microbiome Restoration by RBX2660 Does Not Preclude Recurrence of Multidrug-Resistant Urinary Tract Infection Following Subsequent Antibiotic Exposure: A Case Report

A 62-year-old woman received RBX2660, an investigational microbiome restoration therapeutic, for recurrent multidrug-resistant (MDR) urinary tract infection (UTI). RBX2660 increased gut microbiome diversity but did not eliminate uropathogen carriage, and MDR UTI recurred after subsequent antibiotic exposure. Thus, restoration of microbiome diversity does not preclude disease recurrence by residual MDR pathogens.

Strategies to prevent adverse outcomes following Clostridioides difficile infection in the elderly

Introduction: Clostridioides difficile remains the most common cause of healthcare-associated infections in the US, and it disproportionately affects the elderly. Older patients are more susceptible and have a greater risk of adverse outcomes from C. difficile infection (CDI), despite advances in treatment and prevention.Areas covered: The epidemiology and pathogenesis of CDI, as well as risk factors in the aging host, will be reviewed. The importance of antimicrobial stewardship and infection prevention in order to avoid acquisition and transmission will be discussed, as well as strategies to prevent adverse outcomes and recurrent CDI, through optimization of CDI treatment s,election.Expert opinion: Appropriate CDI-prevention strategies to avoid adverse outcomes in this susceptible population involve antimicrobial stewardship and methods to prevent C. difficile transmission in healthcare settings. Management strategies to prevent adverse outcomes include initiation of supportive therapy and proper selection of CDI specific treatments. Many patients may also benefit from adjunctive therapies or additional procedures.

The current novel therapeutic regimens for Clostridium difficile infection (CDI) and the potentials of Traditional Chinese Medicine in treatment of CDI

Clostridium difficile infection (CDI) is featured as the dysbiosis of gut microbiota and consequent mild diarrhoea or severe pseudomembranous colitis. However, the frequent recurrence of CDI following treatment course challenged the antibiotic therapy. Currently, to address the relapse of CDI, several novel therapeutic approaches have emerged, including Bezlotoxumab, SYN-004 (Ribaxamase), RBX2660, and faecal microbial transplant. Traditional Chinese Medicine (TCM) is an old medical system accumulated for thousands of years. Orientated by syndrome-based treatment, TCM functions in a multicomponent and multitarget mode. This old medical system showed superiority over conventional medical treatment, particularly in the treatment of complex disorders, including CDI. In the present review, we will elaborate the TCM intervention in the management of CDI and others disorders via restoring the gut microbiota dysbiosis. We hope that this review will deepen our understanding of TCM as an alternative to CDI treatment. However, more rigorously designed basic researches and randomised controlled trials need to conduct to appraise the function mechanisms and effects of TCM. Finally, it is concluded that the combined therapeutic potentials of TCM and western medicine could be harness to resolve the recurrence and improve the outcome of CDI.

Recent developments in the management of recurrent Clostridioides difficile infection

Clostridioides (formerly Clostridium) difficile is responsible for a substantial burden of nosocomial infection. Recurrent C. difficile infection (rCDI) remains a concern due to its high morbidity, mortality, and cost. Despite the updated 2017 IDSA C. difficile treatment guidelines, there remains a lack of well-studied preventive control measures and treatment modalities for rCDI. There are ongoing efforts to develop novel therapies, such as new antibiotics with a lesser impact on gut microbiota and more targeted therapies, such as bacteriotherapy. This mini review highlights key rCDI management updates, preventive measures and ongoing research on novel treatment strategies including bacteriotherapy.

A network meta-analysis of randomized controlled trials exploring the role of fecal microbiota transplantation in recurrent Clostridium difficile infection

Background

Recurrence remains a challenge in Clostridium difficile infection (CDI), and in this field fecal microbiota transplantation (FMT) has attracted significant interest. Network meta-analysis (NWM) has been established as an evidence-synthesis tool that incorporates direct and indirect evidence in a collection of randomized controlled trials. So far no NWM exists concerning therapeutic interventions for recurrent CDI (rCDI).

Objective

In this NWM we assessed the comparative effectiveness of various therapies for rCDI to examine the efficacy rank order and determine the optimum therapeutic approach.

Methods

A Bayesian network meta-analysis was performed to investigate the efficacy rank order of rCDI interventions.

Results

Six eligible RCTs were entered into an NWM. They included 348 rCDI patients, in whom seven therapeutic interventions were used, i.e. donor fecal microbiota transplantation (DFMT), vancomycin, fidaxomicin, vancomycin + DFMT, vancomycin + bowel lavage, autologous FMT and placebo. DFMT showed the highest efficacy in comparison with vancomycin [odds ratio (95% credible interval), 20.02 (7.05-70.03)] and fidaxomicin (22.01 (4.38-109.63)).

Conclusion

This NWM showed that DFMT is the optimum therapeutic approach for rCDI, as it was the most efficacious among various therapeutic interventions, particularly in comparison with commonly used antibiotics such as vancomycin or fidaxomicin.

Fecal Microbiome Characteristics and the Resistome Associated With Acquisition of Multidrug-Resistant Organisms Among Elderly Subjects

Infections caused by multidrug-resistant organisms (MDRO) lead to considerable morbidity and mortality. The elderly population residing in nursing homes are a major reservoir of MDRO. Our objective was to characterize the fecal microbiome of 82 elderly subjects from 23 nursing homes and compare their resistome to that of healthy young persons. Comparisons of microbiome composition and the resistome between subjects who acquired MDRO or not were analyzed to characterize specific microbiome disruption indices (MDI) associated with MDRO acquisition. An approach based on both 16S rRNA amplicon and whole metagenome shotgun (WMS) sequencing data was used. The microbiome of the study cohort was substantially perturbed, with Bacteroides, Firmicutes, and Proteobacteria predominating. Compared to healthy persons, the cohort of elderly persons had an increased number, abundance, and diversity of antimicrobial resistance genes. High proportions of study subjects harbored genes for multidrug-efflux pumps (96%) and linezolid resistance (52%). Among the 302 antimicrobial resistance gene families identified in any subject, 60% were exclusively detected within the study cohort, including Class D beta-lactamase genes. Subjects who acquired MDRO or not had significant differences in bacterial taxa; Odoribacter laneus, and Akkermansia muciniphila were significantly greater among subjects who did not acquire MDRO whereas Blautia hydrogenotrophica predominated among subjects who acquired MDRO. These findings suggest that specific MDI may identify persons at high risk of acquiring MDRO.

Management of Clostridioides (formerly Clostridium) difficile infection (CDI) in solid organ transplant recipients: Guidelines from the American Society of Transplantation Community of Practice

These updated guidelines from the American Society of Transplantation Infectious Diseases Community of Practice address the prevention and management of Clostridium difficile infection in solid organ transplant (SOT) recipients. Clostridioides (formerly Clostridium) difficile infection (CDI) is among the most common hospital acquired infections. In SOT recipients, the incidence of CDI varies by type and number or organs transplanted. While a meta-analysis of published literature found the prevalence of postoperative CDI in the general surgical population to be approximately 0.51%, the prevalence of CDI that is seen in the solid organ transplant population ranges from a low of 3.2% in the pancreatic transplant population to 12.7% in those receiving multiple organ transplants. There are no randomized, controlled trials evaluating the management of CDI in the SOT population. Herein is a review and summary of the currently available literature that has been synthesized into updated treatment guidelines for the management of CDI in the SOT population.

Clostridioides difficile: diagnosis and treatments

Clostridioides difficile (formerly Clostridium) is a major cause of healthcare associated diarrhea, and is increasingly present in the community. Historically, C difficile infection was considered easy to diagnose and treat. Over the past two decades, however, diagnostic techniques have changed in line with a greater understanding of the physiopathology of C difficile infection and the use of new therapeutic molecules. The evolution of diagnosis showed there was an important under- and misdiagnosis of C difficile infection, emphasizing the importance of algorithms recommended by European and North American infectious diseases societies to obtain a reliable diagnosis. Previously, metronidazole was considered the reference drug to treat C difficile infection, but more recently vancomycin and other newer drugs are shown to have higher cure rates. Recurrence of infection represents a key parameter in the evaluation of new drugs, and the challenge is to target the right population with the adapted therapeutic molecule. In multiple recurrences, fecal microbiota transplantation is recommended. New approaches, including antibodies, vaccines, and new molecules are already available or in the pipeline, but more data are needed to support the inclusion of these in practice guidelines. This review aims to provide a baseline for clinicians to understand and stratify their choice in the diagnosis and treatment of C difficile infection based on the most recent data available.

Management of Clostridioides difficile colitis: insights for the gastroenterologist

Clostridioides difficile infection (CDI) is a common cause of diarrhea in both inpatient and outpatient settings. The last few years have seen major changes in the treatment spectrum of CDI, most notably, recommendations against using metronidazole for initial CDI, the addition of fidaxomicin and bezlotoxumab, and emergence of microbial replacement therapies. Several other therapies are undergoing clinical trials. This narrative review focuses on the treatment of CDI with a summary of literature on the newer modalities and the treatment guidelines issued by Infectious Diseases Society of America and European Society of Clinical Microbiology and Infectious Diseases.

Restoration of Bacterial Microbiome Composition and Diversity Among Treatment Responders in a Phase 2 Trial of RBX2660: An Investigational Microbiome Restoration Therapeutic

Background

RBX2660 is an investigational microbiota restoration therapy in phase 3 clinical development for preventing recurrent Clostridioides difficile infections (CDIs). In a randomized, double-blinded placebo-controlled phase 2B trial, RBX2660 was effective at preventing CDI recurrence. The current study was performed to characterize the fecal bacterial microbiome before and after treatment among RBX2660- or placebo-treated responders in that trial.

Methods

Samples were sequenced using 16S methods, and the resulting relative abundance data were fit to a Dirichlet-multinomial distribution to determine group mean relative taxonomic abundance and overdispersion at the class level. Alpha diversity was determined for all samples. Biostatistical tools, including effect size and repeated-measures analysis, were applied to evaluate the statistical significance of observed changes.

Results

At study entry, subjects' microbiomes were dominated by Gammaproteobacteria and Bacilli, with low abundance of Bacteroidia and Clostridia. After treatment, Bacteroidia, Clostridia, and alpha diversity increased among RBX2660 responders, concomitant with a decrease of Gammaproteobacteria and Bacilli. The resulting compositions differed significantly from baseline compositions, and the changes among RBX2660 responders differed significantly from those in placebo responders, in whom Bacteroidia or Gammaproteobacteria abundance did not change as much. Repeated-measures analyses indicated more rapid and extensive microbiome remodeling among RBX2660 responders compared with placebo responders, and effect size analyses revealed that RBX2660 responders' microbiomes became more similar to the RBX2660 composition, also compared with placebo responders.

Conclusions

Prevention of recurrent CDI with RBX2660 was associated with restorative microbiome changes that may help resist C. difficile colonization and recurrence. RBX2660 was more effective than placebo at restoring participant microbiomes.

Emerging drugs for the treatment of clostridium difficile

INTRODUCTION

Clostridium difficile or Clostridioides difficile (C. difficile) infection represents the most common cause of healthcare-associated infection. Over the last decades, the incidence and severity of C. difficile infection is rapidly increasing, with a significant impact on morbidity and mortality, and burden on health care system. Orally administered vancomycin and fidaxomicin are the therapeutic options of choice for initial C. difficile infection and fecal microbiota transplant for the recurrence infection. Furthermore, in recent years several new antibiotics with narrow-spectrum activity and low intestinal resorption have been developed, including surotomycin, cadazolid, and ridinilazol, and novel toxoid vaccines are expected to be efficacious in the prevention of C. difficile infection. Areas covered: Literature review was performed to select publications about current guidelines and phase-II/III trials on emerging drugs. These include novel antibiotics, monoclonal antibodies, vaccines, and fecal microbiota transplantation. Expert opinion: We have today a wide spectrum of promising therapeutic possibilities against infection. Pivotal future clinical trials may be crucial in developing effective strategies to optimize outcomes, mainly in high-risk population.

Fecal microbiota transplantation: Review and update

Fecal microbiota transplantation (FMT) is a method to directly change the recipient's gut microbiota to normalize the composition and gain a therapeutic benefit. The history of FMT has been traced back to the 4th century and has been highly regarded since 2013, when the United States Food and Drug Administration approved FMT for treating recurrent and refractory Clostridium difficile infection. Since then, the range of FMT applications extended rapidly and broadly not only in gastrointestinal disorders, but also in extra-gastrointestinal diseases. Donor selection with questionnaire, interview, blood tests, and stool examinations should be strictly performed before FMT to reduce and prevent occurrence of any adverse events. Step-by-step cautious fecal and recipient preparation along with adequately choosing delivery methods based on individual clinical situations are key points of the FMT process. Although current evidence deems FMT as a generally safe therapeutic method with few adverse effects, the long-term outcomes of FMT have not been completely elucidated. Therefore, establishing periodicity and length of regular follow-up after FMT to monitor the clinical efficacy and long-term adverse events are other essential issues. In the future, we will look forward to personalized FMT for different patients and conditions according to varied hosts and diseases.