Efficacy and safety of ridinilazole compared with vancomycin for the treatment of Clostridium difficile infection: a phase 2, randomised, double-blind, active-controlled, non-inferiority study

Clostridioides difficile infection: history, epidemiology, risk factors, prevention, clinical manifestations, treatment, and future options

SUMMARYClostridioides difficile infection (CDI) is one of the major issues in nosocomial infections. This bacterium is constantly evolving and poses complex challenges for clinicians, often encountered in real-life scenarios. In the face of CDI, we are increasingly equipped with new therapeutic strategies, such as monoclonal antibodies and live biotherapeutic products, which need to be thoroughly understood to fully harness their benefits. Moreover, interesting options are currently under study for the future, including bacteriophages, vaccines, and antibiotic inhibitors. Surveillance and prevention strategies continue to play a pivotal role in limiting the spread of the infection. In this review, we aim to provide the reader with a comprehensive overview of epidemiological aspects, predisposing factors, clinical manifestations, diagnostic tools, and current and future prophylactic and therapeutic options for C. difficile infection.

Comparison of fidaxomicin, metronidazole and vancomycin for initial episode and recurrence of Clostridioides difficile infection - An observational cohort study

Objectives

The main aim of this study was to compare the clinical outcomes of patients attended in our area with Clostridioides difficile infection (CDI) (sustained cure, recurrence or death) in relation to treatment to normal or hypervirulent C. difficile as a risk factor and to describe the resistance profile to metronidazole and vancomycin antibiotics in our hospital over a one-year period.

Methods

A retrospective, cross-sectional and observational study was conducted between June 2022 and June 2023 to compare the clinical cure and/or recurrence of CDI in adult patients treated in a Spanish secondary Hospital depending on the prescribed antibiotic treatment. In addition, we performed an antimicrobial susceptibility study to vancomycin and metronidazole in all C. difficile isolated in bacterial culture.

Results

Out of 194 selected patients the treatments were as follow: 43.81 % vancomycin, 21.65 % metronidazole, 8.25 % a combination of both, 6.70 % fidaxomicin and 19.59 % were untreated. Vancomycin and fidaxomicin patients had higher odds ratio of prolonged hospitalization (p = 0.041 and p = 0.040, respectively). Fidaxomicin had increased odds of suffering another episode of C. difficile (p = 0.009) and it was inferior to metronidazole for recurrent CDI (rCDI) (p = 0.035).Resistance profile for C. difficile was 4.07 % for vancomycin and 3.49 % for metronidazole. Hypervirulent C. difficile was identified in 17 (8.76 %) patients with 29.41 % of mortality (5/17; p > 0.05).

Conclusion

Fidaxomicin treated patients had statistically increased odds of rCDI. Compared to other treatments, fidaxomicin was inferior to metronidazole for rCDI in our cohort;Hypervirulent C. difficile was not associated with death.Vancomycin resistance of C. difficile statistically decreased, whereas metronidazole resistance did not vary during the studied period.

Fighting against Clostridioides difficile infection: Current medications

Clostridioides difficile (formerly Clostridium difficile) has been regarded as an 'urgent threat' and a significant global health problem, as life-threatening diarrhoea and refractory recurrence are common in patients with C. difficile infection (CDI). Unfortunately, the available anti-CDI drugs are limited. Recent guidelines recommend fidaxomicin and vancomycin as first-line drugs to treat CDI, bezlotoxumab to prevent recurrence, and faecal microbiota transplantation for rescue treatment. Currently, researchers are investigating therapeutic antibacterial drugs (e.g. teicoplanin, ridinilazole, ibezapolstat, surotomycin, cadazolid, and LFF571), preventive medications against recurrence (e.g. Rebyota, Vowst, VP20621, VE303, RBX7455, and MET-2), primary prevention strategies (e.g. vaccine, ribaxamase, and DAV132) and other anti-CDI medications in the preclinical stage (e.g. Raja 42, Myxopyronin B, and bacteriophage). This narrative review summarises current medications, including newly marketed drugs and products in development against CDI, to help clinicians treat CDI appropriately and to call for more research on innovation.

A Randomized, Double-Blind, Phase 3 Safety and Efficacy Study of Ridinilazole Versus Vancomycin for Treatment of Clostridioides difficile Infection: Clinical Outcomes With Microbiome and Metabolome Correlates of Response

BACKGROUND

Exposure to antibiotics predisposes to dysbiosis and Clostridioides difficile infection (CDI) that can be severe, recurrent (rCDI), and life-threatening. Nonselective drugs that treat CDI and perpetuate dysbiosis are associated with rCDI, in part due to loss of microbiome-derived secondary bile acid (SBA) production. Ridinilazole is a highly selective drug designed to treat CDI and prevent rCDI.

METHODS

In this phase 3 superiority trial, adults with CDI, confirmed with a stool toxin test, were randomized to receive 10 days of ridinilazole (200 mg twice daily) or vancomycin (125 mg 4 times daily). The primary endpoint was sustained clinical response (SCR), defined as clinical response and no rCDI through 30 days after end of treatment. Secondary endpoints included rCDI and change in relative abundance of SBAs.

RESULTS

Ridinilazole and vancomycin achieved an SCR rate of 73% versus 70.7%, respectively, a treatment difference of 2.2% (95% CI: -4.2%, 8.6%). Ridinilazole resulted in a 53% reduction in recurrence compared with vancomycin (8.1% vs 17.3%; 95% CI: -14.1%, -4.5%; P = .0002). Subgroup analyses revealed consistent ridinilazole benefit for reduction in rCDI across subgroups. Ridinilazole preserved microbiota diversity, increased SBAs, and did not increase the resistome. Conversely, vancomycin worsened CDI-associated dysbiosis, decreased SBAs, increased Proteobacteria abundance (∼3.5-fold), and increased the resistome.

CONCLUSIONS

Although ridinilazole did not meet superiority in SCR, ridinilazole greatly reduced rCDI and preserved microbiome diversity and SBAs compared with vancomycin. These findings suggest that treatment of CDI with ridinilazole results in an earlier recovery of gut microbiome health. Clinical Trials Registration.Ri-CoDIFy 1 and 2: NCT03595553 and NCT03595566.

European Practice for CDI Treatment

Clostridioides difficile infection (CDI) remains a significant cause of morbidity and mortality worldwide. Historically, two antibiotics (metronidazole and vancomycin) and a recent third (fidaxomicin) have been used for CDI treatment; convincing data are now available showing that metronidazole is the least efficacious agent. The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) management guidance for CDI were updated in 2021. This guidance document outlines the treatment options for a variety of CDI clinical scenarios and for non-antimicrobial management (e.g., faecal microbiota transplantation, FMT). One of the main changes is that metronidazole is no longer recommended as first-line CDI treatment. Rather, fidaxomicin is preferred on the basis of reduced recurrence rates with vancomycin as an acceptable alternative. Recommended options for recurrent CDI now include bezlotoxumab as well as FMT.A 2017 survey of 20 European countries highlighted variation internationally in CDI management strategies. A variety of restrictions were in place in 65% countries prior to use of new anti-CDI treatments, including committee/infection specialist approval or economic review/restrictions. This survey was repeated in November 2022 to assess the current landscape of CDI management practices in Europe. Of 64 respondents from 17 countries, national CDI guidelines existed in 14 countries, and 11 have already/plan to incorporate the ESCMID 2021 CDI guidance, though implementation has not been surveyed in 6. Vancomycin is the most commonly used first-line agent for the treatment of CDI (n = 42, 66%), followed by fidaxomicin (n = 30, 47%). Six (9%) respondents use metronidazole as first-line agent for CDI treatment, whereas 22 (34%) only in selected low-risk patient groups. Fidaxomicin is more likely to be used in high-risk patient groups. Availability of anti-CDI therapy influenced prescribing in six respondents (9%). Approval pre-prescription was required before vancomycin (n = 3, 5%), fidaxomicin (n = 10, 6%), bezlotoxumab (n = 11, 17%) and FMT (n = 10, 6%). Implementation of CDI guidelines is rarely audited.Novel anti-CDI agents are being evaluated; it is not yet clear what will be the roles of these agents. The treatment of recurrent CDI is particularly troublesome, and several different live biotherapeutics are being developed, in addition to FMT.

Pathogenicity and virulence of Clostridioides difficile

Clostridioides difficile is the most common cause of nosocomial antibiotic-associated diarrhea, and is responsible for a spectrum of diseases characterized by high levels of recurrence, morbidity, and mortality. Treatment is complex, since antibiotics constitute both the main treatment and the major risk factor for infection. Worryingly, resistance to multiple antibiotics is becoming increasingly widespread, leading to the classification of this pathogen as an urgent threat to global health. As a consummate opportunist, C. difficile is well equipped for promoting disease, owing to its arsenal of virulence factors: transmission of this anaerobe is highly efficient due to the formation of robust endospores, and an array of adhesins promote gut colonization. C. difficile produces multiple toxins acting upon gut epithelia, resulting in manifestations typical of diarrheal disease, and severe inflammation in a subset of patients. This review focuses on such virulence factors, as well as the importance of antimicrobial resistance and genome plasticity in enabling pathogenesis and persistence of this important pathogen.

BioAct-Het: A Heterogeneous Siamese Neural Network for Bioactivity Prediction Using Novel Bioactivity Representation

Drug failure during experimental procedures due to low bioactivity presents a significant challenge. To mitigate this risk and enhance compound bioactivities, predicting bioactivity classes during lead optimization is essential. The existing studies on structure-activity relationships have highlighted the connection between the chemical structures of compounds and their bioactivity. However, these studies often overlook the intricate relationship between drugs and bioactivity, which encompasses multiple factors beyond the chemical structure alone. To address this issue, we propose the BioAct-Het model, employing a heterogeneous siamese neural network to model the complex relationship between drugs and bioactivity classes, bringing them into a unified latent space. In particular, we introduce a novel representation for the bioactivity classes, called Bio-Prof, and enhance the original bioactivity data sets to tackle data scarcity. These innovative approaches resulted in our model outperforming the previous ones. The evaluation of BioAct-Het is conducted through three distinct strategies: association-based, bioactivity class-based, and compound-based. The association-based strategy utilizes supervised learning classification, while the bioactivity class-based strategy adopts a retrospective study evaluation approach. On the other hand, the compound-based strategy demonstrates similarities to the concept of meta-learning. Furthermore, the model's effectiveness in addressing real-world problems is analyzed through a case study on the application of vancomycin and oseltamivir for COVID-19 treatment as well as molnupiravir's potential efficacy in treating COVID-19 patients. The data and code underlying this article are available on https://github.com/CBRC-lab/BioAct-Het. However, data sets were derived from sources in the public domain.

A US-based national surveillance study for the susceptibility and epidemiology of Clostridioides difficile isolates with special reference to ridinilazole: 2020-2021

We have previously reported on the susceptibility and epidemiology of Clostridioides difficile isolates from six geographically dispersed medical centers in the United States. This current survey was conducted with isolates collected in 2020-2021 from six geographically dispersed medical centers in the United States, with specific attention to susceptibility to ridinilazole as well as nine comparators. C. difficile isolates or stools from patients with C. difficile antibiotic-associated diarrhea were collected and referred to a central laboratory. After species confirmation of 300 isolates at the central laboratory, antibiotic susceptibilities were determined by the agar dilution method [M11-A9, Clinical and Laboratory Standards Institute (CLSI)] against the 10 agents. Ribotyping was performed by PCR capillary gel electrophoresis on all isolates. Ridinilazole had a minimum inhibitory concentration (MIC) 90 of 0.25 mcg/mL, and no isolate had an MIC greater than 0.5 mcg/mL. In comparison, fidaxomicin had an MIC 90 of 0.5 mcg/mL. The vancomycin MIC 90 was 2 mcg/mL with a 0.7% resistance rate [both CLSI and European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria]. The metronidazole MIC 90 was 1 mcg/mL, with none resistant by CLSI criteria, and a 0.3% resistance rate by EUCAST criteria. Among the 50 different ribotypes isolated in the survey, the most common ribotype was 014-020 (14.0%) followed by 106 (10.3%), 027 (10%), 002 (8%), and 078-126 (4.3%). Ridinilazole maintained activity against all ribotypes and all strains resistant to any other agent tested. Ridinilazole showed excellent in vitro activity against C. difficile isolates collected between 2020 and 2021 in the United States, independent of ribotype.

Therapeutics for Clostridioides difficile infection: molecules and microbes

INTRODUCTION

Clostridioides difficile infection (CDI) is a major healthcare problem in the developed world, and effective management of recurrent infection remains one of the biggest challenges. Several advances have occurred in the management of CDI, and in the last 15 years, multiple new agents have been tested. Since 2011, four new products have been approved by the US FDA for treatment of CDI or prevention of recurrent CDI.

AREAS COVERED

This review focuses on therapeutics of CDI and includes sections on primary prevention, management of active infection, and prevention of recurrent CDI. Specifically, data are included on fecal microbiota transplantation and live biotherapeutics. A comprehensive search of several databases including Ovid MEDLINE(R) and Epub Ahead of Print, In-Process & Other Non-Indexed Citations, and Daily, Ovid EMBASE, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Database of Systematic Reviews, and Scopus from inception to 1 May 2023 was conducted.

EXPERT OPINION

Metronidazole is no longer advised for management of outpatient CDI. The preferred medication of choice for a first episode is oral vancomycin or fidaxomicin. For those patients who recur after the first episode, vancomycin taper pulse or fidaxomicin can be used. Intravenous bezlotoxumab, a monoclonal antibody, is available to prevent recurrences. There are now two FDA-approved microbiome-based therapies or live biotherapeutics for prevention of recurrent CDI, for any recurrent CDI and not necessarily multiply recurrent C difficile. Fecal microbiota transplantation remains available in limited settings for recurrent CDI.

[Clostridioides difficile - New Insights and Therapy Recommendations]

After an increase in Clostridioides difficile infections (CDI) until 2013 due to epidemic ribotypes such as 027 and 078, CDI incidence in Germany is now declining, as confirmed by recent epidemiological data. Despite this success through antimicrobial stewardship and hospital hygiene, the burden of disease remains high, especially in older patients (>65 years) with comorbidities. The main risk factor for CDI is the use of broad-spectrum antibiotics, which disrupt the gut microbiota, allowing C. difficile colonization. Coinfection with other intestinal pathogens such as enterococci can further increase the virulence of C. difficile. The updated 2021 ESCMID guidelines recommend fidaxomicin instead of vancomycin as the antibiotic of choice for the treatment of CDI because of its lower recurrence rate. Vancomycin remains a good alternative; however, metronidazole should only be used if neither antibiotic is available. In the future, ridinilazole may be available as another therapeutic option that has a narrow spectrum of activity and low intestinal absorption. For the treatment of recurrent CDI, the new guidelines also include the use of the monoclonal antibody bezlotoxumab. In addition, a new oral microbiome therapy, SER-109 (capsules containing purified Firmicutes spores), which showed promising results in a phase 3 study, may provide an easy-to-administer alternative to fecal microbiota transplantation. Hopes for a well-performing toxoid vaccine for primary and secondary prevention of CDI have unfortunately not been fulfilled in the CLOVER trial.

Emerging Options for the Prevention and Management of Clostridioides difficile Infection

Agents in development for the prevention or treatment of Clostridioides difficile infection can be split into three broad categories: antibiotics, microbiome restoration, and vaccines. Given the extensive list of agents currently in development, this narrative review will focus on agents that have progressed into late-stage clinical trials, defined as having a Phase III clinical trial registered on ClinicalTrials.gov. These agents include one antibiotic (ridinilazole), three live biotherapeutic products (LBPs) (CP101, RBX2660, and SER109), and two toxoid vaccines (PF06425090 and a second toxoid vaccine). As new prevention and treatment strategies enter the market, clinicians and administrators will need knowledge of these products to make rational decisions on how best to adopt them into clinical practice.

Microbiome and Metabolome Insights into the Role of the Gastrointestinal-Brain Axis in Parkinson's and Alzheimer's Disease: Unveiling Potential Therapeutic Targets

Neurodegenerative diseases such as Parkinson's (PD) and Alzheimer's disease (AD), the prevalence of which is rapidly rising due to an aging world population and westernization of lifestyles, are expected to put a strong socioeconomic burden on health systems worldwide. Clinical trials of therapies against PD and AD have only shown limited success so far. Therefore, research has extended its scope to a systems medicine point of view, with a particular focus on the gastrointestinal-brain axis as a potential main actor in disease development and progression. Microbiome and metabolome studies have already revealed important insights into disease mechanisms. Both the microbiome and metabolome can be easily manipulated by dietary and lifestyle interventions, and might thus offer novel, readily available therapeutic options to prevent the onset as well as the progression of PD and AD. This review summarizes our current knowledge on the interplay between microbiota, metabolites, and neurodegeneration along the gastrointestinal-brain axis. We further illustrate state-of-the art methods of microbiome and metabolome research as well as metabolic modeling that facilitate the identification of disease pathomechanisms. We conclude with therapeutic options to modulate microbiome composition to prevent or delay neurodegeneration and illustrate potential future research directions to fight PD and AD.

Microbiome and Human Health: Current Understanding, Engineering, and Enabling Technologies

The human microbiome is composed of a collection of dynamic microbial communities that inhabit various anatomical locations in the body. Accordingly, the coevolution of the microbiome with the host has resulted in these communities playing a profound role in promoting human health. Consequently, perturbations in the human microbiome can cause or exacerbate several diseases. In this Review, we present our current understanding of the relationship between human health and disease development, focusing on the microbiomes found across the digestive, respiratory, urinary, and reproductive systems as well as the skin. We further discuss various strategies by which the composition and function of the human microbiome can be modulated to exert a therapeutic effect on the host. Finally, we examine technologies such as multiomics approaches and cellular reprogramming of microbes that can enable significant advancements in microbiome research and engineering.

Ridinilazole: a novel, narrow-spectrum antimicrobial agent targeting Clostridium (Clostridioides) difficile

Clostridium (Clostridioides) difficile infection (CDI) remains an urgent threat to patients in health systems worldwide. Recurrent CDI occurs in up to 30% of cases due to sustained dysbiosis of the gut microbiota which normally protects against CDI. Associated costs of initial and recurrent episodes of CDI impose heavy financial burdens on health systems. Vancomycin and metronidazole have been the mainstay of therapy for CDI for many years; however, these agents continue to cause significant disruption to the gut microbiota and thus carry a high risk of recurrence for CDI patients. Treatment regimens are now turning towards novel narrow spectrum antimicrobial agents which target C. difficile while conserving the commensal gut microbiota, thus significantly reducing risk of recurrence. One such agent, fidaxomicin, has been in therapeutic use for several years and is now recommended as a first-line treatment for CDI, as it is superior to vancomycin in reducing risk of recurrence. Another narrow spectrum agent, ridnilazole, was recently developed and is undergoing evaluation of its potential clinical utility. This review aimed to summarize experimental reports of ridinilazole and assess its potential as a first-line agent for treatment of CDI. Reported results from in vitro assessments, and from hamster models of CDI, show potent activity against C. difficile, non-inferiority to vancomycin for clinical cure and non-susceptibility among most gut commensal bacteria. Phase I and II clinical trials have been completed with ridinilazole showing high tolerability and efficacy in treatment of CDI, and superiority over vancomycin in reducing recurrence of CDI within 30 days of treatment completion. Phase III trials are currently underway, the results of which may prove its potential to reduce recurrent CDI and lessen the heavy health and financial burden C. difficile imposes on patients and healthcare systems.

The mechanism of resistance in Escherichia coli to ridinilazole and other antibacterial head-to-head bis-benzimidazole compounds

The appY gene has been characterised as conferring resistance to a novel series of antimicrobial benzimidazole derivatives in E. coli MC1061 cells when expressed in high copy-number. A microarray approach was used to identify genes involved in the mechanism of appY-mediated antibacterial resistance, that were up- or down-regulated following induction of the gene in the appY knockout strain JW0553. In total, expression of 90 genes was induced and 48 repressed greater than 2.5-fold (P < 0.05), 45 min after appY induction. Over half the genes up-regulated following appY expression had confirmed or putative roles in acid resistance (AR) and response to oxidative and antibiotic stresses. These included the genes for MdtE and MdtF, which form a multi-drug transporter with TolC and have been implicated in resistance to several antibiotics including erythromycin. Amongst the acid resistance genes were gadAB and adiAC encoding the glutamate-dependant (AR2) and arginine-dependant (AR3) acid resistance systems respectively, in addition to the transcriptional activators of these systems gadE and gadX. In agreement with earlier studies, appA, appCB and hyaA-F were also up-regulated following induction of appY. This study has also confirmed that over-expression of mdtEF confers resistance to these antibacterial benzimidazoles, indicating that the observation of appY conferring resistance to these compounds, proceeds through an appY-mediated up-regulation of this efflux transporter. To assess the importance of the AppY enzyme to acid stress responses, the percentage survival of bacteria in acidified media (pH ≤ 2) was measured. From an initial input of 1 × 106 CFU/ml, the wild-type strain MG1655 showed 7.29% and 0.46% survival after 2 and 4 h, respectively. In contrast, strain JW0553 in which appY is deleted was completely killed by the treatment. Transformation of JW0553 with a plasmid carrying appY returned survival to wild-type levels (7.85% and 1.03% survival at 2 and 4 h). Further dissection of the response by prior induction of each of the three AR systems has revealed that AR1 and AR3 were most affected by the absence of appY. This work highlights an important and previously unidentified role for the AppY enzyme in mediating the responses to several stress conditions. It is likely that the appY gene fits into a complex transcriptional regulatory network involving σS and gadE and gadX. Further work to pinpoint its position in such a hierarchy and to assess the contribution of appY to oxidative stress responses should help determine its full significance. This work is also consistent with recent studies in C. difficile showing that the mechanism of action of ridinilazole involves AT-rich DNA minor groove binding.

Clostridioides difficile: Current overview and future perspectives

The most common world-wide cause of antibiotic-associated infectious diarrhea and colitis is the toxin producing bacterium, Clostridioides difficile (C. difficile). Here we review the background and characteristics of the bacterium and the toxins produced together with the epidemiology and the complex pathogenesis that leads to a broad clinical spectrum of disease. The review describes the difficulties faced in obtaining a quick and accurate diagnosis despite the range of sensitive and specific diagnostic tools available. We also discuss the problem of disease recurrence and the importance of disease prevention. The high rates of infection recurrence mean that treatment strategies are constantly under review and we outline the diverse treatment options that are currently in use and explore the emerging treatment options of pulsed antibiotic use, microbial replacement therapies and the use of monoclonal antibodies. We summarize the future direction of treatment strategies which include the development of novel antibiotics, the administration of oral polyclonal antibody formulations, the use of vaccines, the administration of competitive non-toxigenic spores and the neutralization of antibiotics at the microbiota level. Future successful treatments will likely involve a combination of therapies to provide the most effective and robust approach to C. difficile management.

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.

Antibiotic Therapies for Clostridioides difficile Infection in Children

While rates of Clostridioides difficile infection (CDI) are increasing among children in the United States, studies assessing CDI treatment in children are severely lacking. Thus, treatment guidelines have historically relied on evidence from limited observational data in children and randomized controlled trials (RCTs) conducted in adults to form recommendations. Currently, the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA) recommend metronidazole and/or vancomycin for pediatric CDI depending on disease severity. Recently however, the first and only RCT of CDI treatment in children demonstrated fidaxomicin to be non-inferior to vancomycin, proving its safety and efficacy in this population. Additionally, observational data published since the IDSA/SHEA guidelines were released suggest metronidazole has lower rates of clinical improvement when compared to vancomycin in hospitalized children with non-severe CDI. Given these recent publications, fidaxomicin and vancomycin, instead of metronidazole, appear to be more appropriate, evidence-based options for the treatment of CDI in children.

Frontiers in antibiotic alternatives for Clostridioides difficile infection

Clostridioides difficile (C. difficile) is a gram-positive, anaerobic spore-forming bacterium and a major cause of antibiotic-associated diarrhea. Humans are naturally resistant to C. difficile infection (CDI) owing to the protection provided by healthy gut microbiota. When the gut microbiota is disturbed, C. difficile can colonize, produce toxins, and manifest clinical symptoms, ranging from asymptomatic diarrhea and colitis to death. Despite the steady-if not rising-prevalence of CDI, it will certainly become more problematic in a world of antibiotic overuse and the post-antibiotic era. C. difficile is naturally resistant to most of the currently used antibiotics as it uses multiple resistance mechanisms. Therefore, current CDI treatment regimens are extremely limited to only a few antibiotics, which include vancomycin, fidaxomicin, and metronidazole. Therefore, one of the main challenges experienced by the scientific community is the development of alternative approaches to control and treat CDI. In this Frontier article, we collectively summarize recent advances in alternative treatment approaches for CDI. Over the past few years, several studies have reported on natural product-derived compounds, drug repurposing, high-throughput library screening, phage therapy, and fecal microbiota transplantation. We also include an update on vaccine development, pre- and pro-biotics for CDI, and toxin antidote approaches. These measures tackle CDI at every stage of disease pathology via multiple mechanisms. We also discuss the gaps and concerns in these developments. The next epidemic of CDI is not a matter of if but a matter of when. Therefore, being well-equipped with a collection of alternative therapeutics is necessary and should be prioritized.

Antibiotic use but not gastrointestinal infection frequently precedes first diagnosis of functional gastrointestinal disorders

INTRODUCTION

While the etiopathogenesis of functional gastrointestinal disorders (FGIDs) is not completely understood, alterations of the intestinal microbiome have been observed. Antibiotics can induce dysbiosis, but whether antibiotics are a risk factor for the onset of FGIDs is uncertain. Antibiotics have been reported as both a risk factor for new onset FGID but also as a therapy for existing FGID. This study aimed to estimate the fraction of cases where antibiotics provoked the onset of FGID.

METHOD

Electronic medical records were obtained from general practices (primary care) in the United Kingdom. Dates of antibiotic prescription (AP) were compared with first date of FGID diagnosis and contrasted across three prevalent FGIDs and controls without gastrointestinal disorders.

RESULTS

There were 10,926 GI healthy controls, 4326 IBS alone, 3477 FD alone, 340 chronic constipation and 4402 with overlap of multiple conditions. Both the prevalence of AP and rate were higher in FGID patients and increased with diagnosis of multiple FGIDs. 7%-14% of FGID patients were prescribed their first recorded antibiotic in the 12 months prior to their first FGID diagnosis and 20%-33% were prescribed an antibiotic in the same period. Differences between FGID groups were not accounted for by social deprivation and only rate of AP was moderated by social deprivation. In contrast, only 5%-10% of patients ever had a gastrointestinal infection recorded and only 1.5%-3.5% prior to their first FGID diagnosis.

CONCLUSION

These data indicate that antibiotics are prescribed prior to FGID diagnosis in a significant minority of care-seeking FGID patients, opening the potential for this medication to contribute to the pathophysiology. APs appears to mostly be for non-gastrointestinal conditions.

Antibiotics in the pipeline: a literature review (2017-2020)

Introduction

Antimicrobial resistance (AMR) is an emerging global threat. It increases mortality and morbidity and strains healthcare systems. Health care professionals can counter the rising AMR by promoting antibiotic stewardship and facilitating new drug development. Even with the economic and scientific challenges, it is reassuring that new agents continue to be developed.

Methods

This review addresses new antibiotics in the pipeline. We conducted a review of the literature including Medline, Clinicaltrials.org, and relevant pharmaceutical companies for approved and in pipeline antibiotics in phase 3 or new drug application (NDA).

Results

We found a number of new antibiotics and reviewed their current development status, mode of action, spectra of activity, and indications for which they have been approved. The included studies from phase 3 clinical trials were mainly utilized for the treatment of acute bacterial skin and skin structure infections, community-acquired bacterial pneumonia, and pneumonia acquired in the healthcare settings. The number of these agents is limited against high priority organisms. The identified antibiotics were based mainly on previously known molecules or pre-existing antimicrobial agents.

Conclusion

There are a limited number of antibiotics against high priority organisms such as multi-drug-resistant Pseudomonas aeruginosa, and carbapenem-resistant Enterobacteriaceae. New antimicrobial agents directed against the top priority organisms as classified by the World Health Organization are urgently needed.

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.

Targeted microbiome-sparing antibiotics

A factor in our inability to meet the challenge of clinical antibiotic resistance has been the low productivity of research and development (R&D) efforts, with only incremental improvements on existing broad-spectrum classes coming into clinical use recently. The disappointing returns from this approach have focussed attention on narrower-spectrum antibiotics; such new agents are directed against the pathogen of relevance with the additional benefit of preserving the human microbiome(s). Our knowledge of the gut microbiome and its contribution to health homeostasis increases yearly and suggests that broad-spectrum treatments incur health costs beyond the initial infection. Improved diagnostics, antibiotic stewardship, and the crucial role of the gut microbiome in health indicate targeted agents as a more viable approach for future antibiotic R&D.

Inhibition of spores to prevent the recurrence of Clostridioides difficile infection - A possibility or an improbability?

Clostridioides difficile is one of the most common nosocomial gastrointestinal pathogens, and recurrence is a problematic issue because approximately 20-30% of patients experience at least one episode of recurrence, even after treatment with a therapeutic drug of choice for C. difficile infection (CDI), such as vancomycin. CDI recurrence has a multifactorial complex mechanism, in which gut microbiota disruption coincident with viable C. difficile spores, is considered the most important factor. The effectiveness of an anti-C. difficile antimicrobial agent against CDI cannot guarantee its inhibitory effect on C. difficile spores and vice versa. However, an antimicrobial agent, such as fidaxomicin, which has a good inhibitory effect on both C. difficile vegetative cells and spores is assumed to not only treat CDI but also prevent its recurrence. Prolonged adherence to the exosporium has been proposed as a possible mechanism of inhibiting spores, and as a result, redesigning anti-C. difficile antimicrobial agents with the ability to adhere to the exosporium may provide another pathway for the development of anti-C. difficile spore agents. For example, vancomycin lacks an inhibitory effect against C. difficile spores, but a vancomycin-loaded spore-targeting iron oxide nanoparticle that selectively binds to C. difficile spores has been developed to successfully delay spore germination. Some new antimicrobial agents in phase II clinical trials, including cadazolid and ridinilazole, have shown exceptional anti-C. difficile and spore-inhibiting effects that can be expected to not only treat CDI but also prevent its recurrence in the future.

A Review of Clostridioides difficile Infection and Antibiotic-Associated Diarrhea

Antibiotic-associated diarrhea and Clostridioides difficile infection (CDI) occur frequently among adults. The pathophysiology of CDI is related to disruption of normal gut flora and risk factors include hospitalization, use of antibiotic therapy, and older age. Clinical manifestations can range from mild disease to toxic megacolon. Diagnosis is challenging and is based on a combination of clinical symptoms and diagnostic tests. Therapy includes cessation of antibiotics, or use of other agents depending on the severity of illness. Many novel agents for the treatment and prevention of CDI show promise and are under investigation.

The contribution of bile acid metabolism to the pathogenesis of Clostridioides difficile infection

Clostridioides difficile infection (CDI) remains a major global cause of gastrointestinal infection, with significant associated morbidity, mortality and impact upon healthcare system resources. Recent antibiotic use is a key risk factor for the condition, with the marked antibiotic-mediated perturbations in gut microbiome diversity and composition that underpin the pathogenesis of CDI being well-recognised. However, only relatively recently has further insight been gained into the specific mechanistic links between these gut microbiome changes and CDI, with alteration of gut microbial metabolites - in particular, bile acid metabolism - being a particular area of focus. A variety of in vitro, ex vivo, animal model and human studies have now demonstrated that loss of gut microbiome members with bile-metabolising capacity (including bile salt hydrolases, and 7-α-dehydroxylase) - with a resulting alteration of the gut bile acid milieu - contributes significantly to the disease process in CDI. More specifically, this microbiome disruption results in the enrichment of primary conjugated bile acids (including taurocholic acid, which promotes the germination of C. difficile spores) and loss of secondary bile acids (which inhibit the growth of C. difficile, and may bind to and limit activity of toxins produced by C. difficile). These bile acid changes are also associated with reduced activity of the farnesoid X receptor pathway, which may exacerbate C. difficile colitis throughout its impact upon gut barrier function and host immune/inflammatory response. Furthermore, a key mechanism of efficacy of faecal microbiota transplant (FMT) in treating recurrent CDI has been shown to be restoration of gut microbiome bile metabolising functionality; ensuring the presence of this functionality among defined microbial communities (and other 'next generation' FMT products) designed to treat CDI may be critical to their success.

Application of Microbiome Management in Therapy for Clostridioides difficile Infections: From Fecal Microbiota Transplantation to Probiotics to Microbiota-Preserving Antimicrobial Agents

Oral vancomycin and metronidazole, though they are the therapeutic choice for Clostridioides difficile infections (CDIs), also markedly disturb microbiota, leading to a prolonged loss of colonization resistance to C. difficile after therapy; as a result, their use is associated with a high treatment failure rate and high recurrent rate. An alternative for CDIs therapy contains the delivery of beneficial (probiotic) microorganisms into the intestinal tract to restore the microbial balance. Recently, mixture regimens containing Lactobacillus species, Saccharomyces boulardii, or Clostridium butyricum have been extensively studied for the prophylaxis of CDIs. Fecal microbiota transplantation (FMT), the transfer of (processed) fecal material from healthy donors to patients for treating CDIs, combined with vancomycin was recommended as the primary therapy for multiple recurrent CDIs (rCDIs). Either probiotics or FMT have been utilized extensively in preventing or treating CDIs, aiming at less disturbance in the microbiota to prevent rCDIs after therapy cessation. Otherwise, many newly developed therapeutic agents have been developed and aim to preserve microbiota during CDI treatment to prevent disease recurrence and might be useful in clinical patients with rCDIs in the future.

Protecting the Microbiota

We examine 3 different approaches to protecting the gut microbiome: highly targeted antibiotics, antibiotic destruction, and antibiotic binding. Each approach shows promise to prevent the off-target effects of antibiotics on the gut microbiome.

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.

<em>Clostridium difficile</em> infection in pediatric patients of oncological hospital: cultivation of anaerobic intestinal flora and treatment

In recent years, the number of infectious diseases caused by Clostridium difficile in the world has grown with a significant increase in relapses and mortality in patients, particularly among the cancer patients in hospitals. There is also observed an increase in the resistance of Clostridium difficile to the first-line drugs, namely metronidazole and vancomycin, which makes the search for new methods of treatment and prevention of this infection even more urgent. In this review, we analyze the recent data on the methods of cultivation and isolation of the pure bacterial culture of Clostridium difficile and other anaerobic enteropathogens over the course of enterocolitis treatment with antimicrobial drugs in pediatric patients with oncopathology. Novel approaches to the therapy of this infection are discussed. 

Clostridioides Difficile Infection: A comprehensive review for primary providers

Clostridioides Difficile infection (CDI) is an issue of great concern due to its rising incidence, recurrence, morbidity and impact on healthcare spending. Treatment guidelines have changed in the last few years, and new therapies are being considered. This is a practical review for the primary care practitioner of the latest guidelines for CDI diagnosis, treatment and emerging therapies.

Risk factors for development of initial Clostridioides difficile infection

OBJECTIVES

The purpose of this study was to identify risk factors for initial complicated Clostridioides difficile infection (CDI).

METHODS

This retrospective cross-sectional study included adult patients with initial episodes of CDI who received ≥72 h of CDI-active antimicrobials. Patients were categorised into one of two groups: complicated CDI or uncomplicated CDI. A total of 513 patients were screened for inclusion, with complicated CDI patients exhibiting abnormal abdominal CT findings or experiencing death within 30 days post-CDI diagnosis.

RESULTS

A total of 203 patients met the inclusion criteria, comprising 143 (70.4%) with uncomplicated CDI and 60 (29.6%) with complicated CDI. Complicated CDI patients were more likely to have been exposed to fluoroquinolones (48.3% vs. 30.8%; P = 0.017) and to carbapenems for a longer duration prior to CDI diagnosis (7 days vs. 3 days; P = 0.019). They were more likely to receive oral vancomycin (65.0% vs. 46.9%; P = 0.018) and rectal vancomycin (5.0% vs. 0%; P = 0.025) compared with uncomplicated CDI patients. Logistic regression identified previous fluoroquinolone exposure increased the risk of complicated CDI, while previous abdominal surgery decreased the risk.

CONCLUSION

Almost one-third of included patients experienced a complicated episode of CDI as their initial episode. Further research is warranted to elucidate the extent of influence of prior antibiotics on the development of complicated CDI.

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.

Recent developments in antimicrobial therapy for gastrointestinal infections

PURPOSE OF REVIEW

This focused, narrative review summarizes human clinical trial data for direct-acting antimicrobials in development for the treatment of gastrointestinal infections that were published in the past 18 months (1 January 2019 to 30 June 2020).

RECENT FINDINGS

Antimicrobial agents for Clostridioides difficile infection (n = 6), cryptosporidiosis (n = 1), cytomegalovirus infection (n = 3) and Helicobacter pylori infection (n = 1) have completed and/or are undergoing human clinical trials.

SUMMARY

Although this review highlights significant advances in four disease states, many common gastrointestinal pathogens have no antimicrobials in human clinical trials, emphasizing the need for continued prioritization in this field of study.

Immunotherapy and vaccination against infectious diseases

Due to the overuse of antibiotics, infections, in particular those caused by multidrug-resistant bacteria, are becoming more and more frequent. Despite the worldwide introduction of antibiotic therapy, vaccines and constant improvements in hygiene, the burden of multidrug-resistant bacterial infections is increasing and is expected to rise in the future. The development of monoclonal therapeutic antibodies and specific immunomodulatory drugs represent new treatment options in the fight against infectious diseases. This article provides a brief overview of recent advances in immunomodulatory therapy and other strategies in the treatment of infectious disease.

Navigating changes in Clostridioides difficile prevention and treatment

Clostridioides difficile (C. difficile, previously known as Clostridium difficile) infections are a major health care concern. The Centers for Disease Control and Prevention (CDC) estimates that C. difficile causes almost half a million illnesses in the United States yearly, and approximately 1 in 5 patients with a C. difficile infection (CDI) will experience 1 or more recurrent infections. The incidence of infection has risen dramatically in recent years, and infection severity has increased due to the emergence of hypervirulent strains. There have been noteworthy advances in the development of CDI prevention and treatment, including a growth in the understanding of the role a patient's gut microbiome plays. The 2017 Infectious Diseases Society of America (IDSA) guidelines made a significant change in treatment recommendations for first time CDI episodes by recommending the use of oral vancomycin or fidaxomicin in place of metronidazole as a first-line treatment. The guidelines also included detailed recommendations on the use of fecal microbiota transplant (FMT) in those patients who experience 3 or more recurrent CDI episodes. A number of novel therapies for the treatment of CDI are in various stages of development. Treatments currently in phase 3 trials include the antibiotic ridinilazole, the microbiome products SER-109 and RBX2660, and a vaccine. All of these agents have shown promise in phase 1 and 2 trials. Additionally, several other antibiotic and microbiome candidates are currently in phase 1 or phase 2 trials. A qualitative review and evaluation of the literature on the cost-effectiveness of treatments for CDI in the U.S. setting was conducted, and the summary provided herein. Due to the higher cost of newer agents, cost-effectiveness evaluations will continue to be critical in clinical decision making for CDI. This paper reviews the updated CDI guidelines for prevention and treatment, the role of the microbiome in new and recurrent infections, pipeline medications, and comparative effectiveness research (CER) data on these treatments. DISCLOSURES: Durham and Le have nothing to disclose. Cassano reports consulting fees from Baxter Healthcare. Peer reviewers Drs. Ami Gopalan and Mark Rubin and Ms. Kathleen Jarvis have nothing to disclose. Planners Dr. Christine L. Cooper and Ms. Susan Yarbrough have nothing to disclose.

Recent advances in the treatment of Clostridioides difficile infection: the ever-changing guidelines

Clostridioides difficile infection (CDI), formerly known as Clostridium difficile, continues to be the most common healthcare-associated infection worldwide. With the shifting epidemiology towards higher a incidence of community-acquired CDI and the continued burden on the healthcare system posed by high rates of CDI recurrence, there has been an impetus to advance the diagnostic testing and treatment strategies. Recent advancements over the past decade have led to rapidly changing guidelines issued by the Infectious Diseases Society of America and European Society of Clinical Microbiology and Infectious Diseases. With our comprehensive review, we aim to summarize the latest advances in diagnosing and treating CDI and thus attempt to help readers guide best practices for patient care. This article also focusses on cost-effectiveness of various therapies currently available on the market and provides an analysis of the current evidence on a relatively new monoclonal antibody therapy, Bezlotoxumab, to treat recurrent CDI.

Antimicrobial innovation: a current update and perspective on the antibiotic drug development pipeline

As bacteria continue to develop resistance to our existing treatment options, antibiotic innovation remains overlooked. If current trends continue, then we could face the stark reality of a postantibiotic era, whereby routine bacterial infections could once again become deadly. In light of a warning signaled by the WHO, a number of new initiatives have been established in the hope of reinvigorating the antibiotic drug development pipeline. In this perspective, we aim to summarize some of these initiatives and funding options, as well as providing an insight into the predicament that we face. Using clinical trials data, company website information and the most recent press releases, a current update of the antibiotic drug development pipeline is also included.

Investigational Treatment Agents for Recurrent Clostridioides difficile Infection (rCDI)

Clostridioides difficile infection (CDI) is a major cause of nosocomial diarrhea that is deemed a global health threat. C. difficile strain BI/NAP1/027 has contributed to the increase in the mortality, severity of CDI outbreaks and recurrence rates (rCDI). Updated CDI treatment guidelines suggest vancomycin and fidaxomicin as initial first-line therapies that have initial clinical cure rates of over 80%. Unacceptably high recurrence rates of 15–30% in patients for the first episode and 40% for the second recurrent episode are reported. Alternative treatments for rCDI include fecal microbiota transplant and a human monoclonal antibody, bezlotoxumab, that can be used in patients with high risk of rCDI. Various emerging potential therapies with narrow spectrum of activity and little systemic absorption that are in development include 1) Ibezapolstat (formerly ACX-362E), MGB-BP-3, and DS-2969b-targeting bacterial DNA replication, 2) CRS3213 (REP3123)-inhibiting toxin production and spore formation, 3) ramizol and ramoplanin-affecting bacterial cell wall, 4) LFF-571-blocking protein synthesis, 5) Alanyl-L-Glutamine (alanylglutamine)-inhibiting damage caused by C. difficile by protecting intestinal mucosa, and 6) DNV3837 (MCB3681)-prodrug consisting of an oxazolidinone–quinolone combination that converts to the active form DNV3681 that has activity in vitro against C. difficile. This review article provides an overview of these developing drugs that can have potential role in the treatment of rCDI and in lowering recurrence rates.

Ridinilazole, a narrow spectrum antibiotic for treatment of Clostridioides difficile infection, enhances preservation of microbiota-dependent bile acids

Antibiotic treatment is a standard therapy for Clostridioides difficile infection, but dysbiosis of the gut microbiota due to antibiotic exposure is also a major risk factor for the disease. Following an initial episode of C. difficile infection, a relentless cycle of recurrence can occur, where persistent treatment-related dysbiosis predisposes the patient to subsequent relapse. This study uses a longitudinal study design to compare the effects of a narrow-spectrum (ridinilazole) or broad-spectrum antibiotic (vancomycin) on intestinal bile acid profiles and their associations with gut bacteria over the course of C. difficile infection treatment. At the end of treatment (day 10), subjects receiving vancomycin showed a nearly 100-fold increase in the ratio of conjugated to secondary bile acids in their stool compared with baseline, whereas subjects receiving ridinilazole maintained this ratio near baseline levels. Correlation analysis detected significant positive associations between secondary bile acids and several Bacteroidales and Clostridiales families. These families were depleted in the vancomycin group but preserved at near-baseline abundance in the ridinilazole group. Enterobacteriaceae, which expanded to a greater extent in the vancomycin group, correlated negatively and positively with secondary and conjugated primary bile acids, respectively. Bile acid ratios at the end of treatment were significantly different between those who recurred and those who did not. These results indicate that a narrow-spectrum antibiotic maintains an intestinal bile acid profile associated with a lowered risk of recurrence.NEW & NOTEWORTHY This is the first study to demonstrate in humans the relationships between Clostridioides difficile antibiotic treatment choice and bile acid metabolism both during therapy and after treatment cessation. The results show a microbiota- and metabolome-preserving property of a novel narrow-spectrum agent that correlates with the agent's favorable sustained clinical response rates compared with broad-spectrum antibiotic treatment.

Prevention and treatment of recurrent Clostridioides difficile infection

PURPOSE OF REVIEW

Clostridioides difficile infection (CDI) is a significant burden on the health system, especially due to high recurrence rates. Since the beginning of the CDI epidemic in early 2000s, many strategies for combatting recurrence have been explored, with moderate success so far. This review will focus on the most recent developments in recurrent CDI prevention and treatment.

RECENT FINDINGS

There are two main mechanisms of CDI recurrence: alteration in microbiome and poor antibody response. Development of new antibiotics aims to minimize damage to the microbiome. Fecal transplant or other microbiome replacement therapies seek to replenish the missing elements in the microbiome. Fecal microbiota transplant is the most effective treatment for prevention of CDI recurrenceso far, but is difficult to standardize and regulate, leading to efforts to develop microbiome-derived therapeutics. A deficiency in developing antibodies to C. difficile toxins is another mechanism of recurrence. Active immunization using toxoid vaccines or passive immunization using mAbs address this aspect.

SUMMARY

There are promising new treatments for recurrent CDI in development. Fecal microbiota transplant remains the most effective therapy for multiply recurrent CDI. New antibiotics, microbiome-derived therapeutics, and immunologic therapies are in development.

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.

Recommendations for the diagnosis and treatment of Clostridioides difficile infection: An official clinical practice guideline of the Spanish Society of Chemotherapy (SEQ), Spanish Society of Internal Medicine (SEMI) and the working group of Postoperative Infection of the Spanish Society of Anesthesia and Reanimation (SEDAR)

This document gathers the opinion of a multidisciplinary forum of experts on different aspects of the diagnosis and treatment of Clostridioides difficile infection (CDI) in Spain. It has been structured around a series of questions that the attendees considered relevant and in which a consensus opinion was reached. The main messages were as follows: CDI should be suspected in patients older than 2 years of age in the presence of diarrhea, paralytic ileus and unexplained leukocytosis, even in the absence of classical risk factors. With a few exceptions, a single stool sample is sufficient for diagnosis, which can be sent to the laboratory with or without transportation media for enteropathogenic bacteria. In the absence of diarrhoea, rectal swabs may be valid. The microbiology laboratory should include C. difficile among the pathogens routinely searched in patients with diarrhoea. Laboratory tests in different order and sequence schemes include GDH detection, presence of toxins, molecular tests and toxigenic culture. Immediate determination of sensitivity to drugs such as vancomycin, metronidazole or fidaxomycin is not required. The evolution of toxin persistence is not a suitable test for follow up. Laboratory diagnosis of CDI should be rapid and results reported and interpreted to clinicians immediately. In addition to the basic support of all diarrheic episodes, CDI treatment requires the suppression of antiperistaltic agents, proton pump inhibitors and antibiotics, where possible. Oral vancomycin and fidaxomycin are the antibacterials of choice in treatment, intravenous metronidazole being restricted for patients in whom the presence of the above drugs in the intestinal lumen cannot be assured. Fecal material transplantation is the treatment of choice for patients with multiple recurrences but uncertainties persist regarding its standardization and safety. Bezlotoxumab is a monoclonal antibody to C. difficile toxin B that should be administered to patients at high risk of recurrence. Surgery is becoming less and less necessary and prevention with vaccines is under research. Probiotics have so far not been shown to be therapeutically or preventively effective. The therapeutic strategy should be based, rather than on the number of episodes, on the severity of the episodes and on their potential to recur. Some data point to the efficacy of oral vancomycin prophylaxis in patients who reccur CDI when systemic antibiotics are required again.

Update on Treatment of Clostridioides difficile Infection

Clostridioides difficile infection (CDI) is the leading cause of health care-associated infections in the United States. The increasing incidence and recurrence rates of CDI together with its associated morbidity and mortality are great concerns. Newer treatment methods, such as narrow-spectrum antibiotics, monoclonal antibodies, and microbial replacement therapies, are being developed and implemented. We searched PubMed to identify published literature from 2010 to 2018 using the following keywords: Clostridium difficile, treatment, and therapy. Cited references were also used to identify relevant literature. This review focuses on the current standard of therapy and emerging therapies for CDI and summarizes the updated guidelines on treatment of CDI.

Treatment of Clostridioides (Clostridium) difficile infection

Clostridioides (formerly: Clostridium) difficile infection (CDI) is a major cause of diarrhoea for inpatients as well as outpatients. Usually, CDI is healthcare-associated but the number of community-acquired infections is increasing. CDI is generally associated with changes in the normal intestinal microbiota caused by administration of antibiotics. Elderly and immunocompromised patients are at greater risk for CDI and CDI recurrence. Recently, the treatment options of CDI have undergone major changes: current recommendations speak against using metronidazole for primary CDI, fidaxomicin and bezlotoxumab have been added to the treatment armamentarium and microbial replacement therapies have emerged. Several other therapies are undergoing clinical trials. In this article, we review current treatment guidelines, present the most recent data on the options to treat CDI and glance towards future developments.KEY MESSAGESThe cornerstones for the treatment of CDI are vancomycin and fidaxomicin. Metronidazole should be used only in mild-to-moderate disease in younger patients who have no or only few risk factors for recurrence.In recurrent CDI, bezlotoxumab infusion (a monoclonal antibody against C. difficile toxin B) may be considered as an adjunctive therapeutic strategy in addition to the standard care provided to patients with several risk factors for recurrence.Faecal microbiota transplantation (FMT) should be offered to patients with frequently recurring CDI.

Multiple-Ascending-Dose Phase 1 Clinical Study of the Safety, Tolerability, and Pharmacokinetics of CRS3123, a Narrow-Spectrum Agent with Minimal Disruption of Normal Gut Microbiota

CRS3123 is a novel small molecule that potently inhibits methionyl-tRNA synthetase of Clostridioides difficile, inhibiting C. difficile toxin production and spore formation. CRS3123 has been evaluated in a multiple-ascending-dose placebo-controlled phase 1 trial. Thirty healthy subjects, ages 18 to 45 years, were randomized into three cohorts of 10 subjects each, receiving either 200, 400, or 600 mg of CRS3123 (8 subjects per cohort) or placebo (2 subjects per cohort) by oral administration twice daily for 10 days. CRS3123 was generally safe and well tolerated, with no serious adverse events (SAEs) or severe treatment-emergent adverse events (TEAEs) reported. All subjects completed their assigned treatment and follow-up visits, and there were no trends in systemic, vital sign, or laboratory TEAEs. There were no QTcF interval changes or any clinically significant changes in other electrocardiogram (ECG) intervals or morphology. CRS3123 showed limited but detectable systemic uptake; although absorption increased with increasing dose, the increase was less than dose proportional. Importantly, the bulk of the oral dose was not absorbed, and fecal concentrations were substantially above the MIC90 value of 1 μg/ml at all dosages tested. Subjects receiving either of the two lower doses of CRS3123 exhibited minimal disruption of normal gut microbiota after 10 days of twice-daily dosing. CRS3123 was inactive against important commensal anaerobes, including Bacteroides, bifidobacteria, and commensal clostridia. Microbiome data showed favorable differentiation compared to other CDI therapeutics. These results support further development of CRS3123 as an oral agent for the treatment of CDI. (This study has been registered at Clinicaltrials.gov under identifier NCT02106338.).