Bezlotoxumab for Prevention of Recurrent Clostridium difficile Infection

Metronidazole-ursodeoxycholic acid bifunctional antibacterial: A promising strategy to combat Clostridium difficile infection and prevent recurrence

Current treatments against Clostridium difficile infection (CDI), such as vancomycin and metronidazole, frequently lead to severe recurrence due to disruption of gut microbiota balance, which results in a pressing need for new chemical entities to treat CDI. Bile acids, such as UDCA, have been demonstrated to inhibit the growth and spore germination of C. difficile, and regulate the structure of the intestinal flora. This study involved the synthesis of eight bile acid-metronidazole hybrids. Among them, the most promising hybrid, SCUT1-2, effectively killed the vegetative cells of C. difficile with a minimum inhibitory concentration (MIC) of 0.06-0.50 μg/mL, and inhibited spore germination in vitro. The absolute bioavailability of SCUT1-2 (F = 56.8 %) indicated that approximately half of SCUT1-2 was absorbed systemically, while a considerable portion remained in the gastrointestinal tract in its original form, laying a solid foundation for its effective action in vivo. SCUT1-2 could effectively alleviate the symptoms of weight loss and diarrhea in mice caused by CDI and effectively reduce the relevant expressions of inflammatory factors, outperforming metronidazole. Furthermore, SCUT1-2 demonstrated a favorable therapeutic effect in reducing mortality and disease symptoms in CDI mice by killing C. difficile cells and regulating the composition and structure of the intestinal flora. Notably, SCUT1-2 could effectively prevent recurrent CDI. This work provides a potential clinical lead for the development of CDI therapies and highlights hybrid medication as a new strategy.

The efficacy and underlying mechanisms of berberine in the treatment of recurrent Clostridioides difficile infection

Recurrent Clostridioides difficile infection (rCDI) is a global health threat that has received considerable attention. Berberine (BBR), a natural pentacyclic isoquinoline alkaloid, has been used as a cost-effective treatment for intestinal infections in Asia for many years. However, the effect of BBR on rCDI is not clear. The efficacy and underlying mechanisms of BBR were evaluated in a vancomycin-dependent rCDI mouse model and an intestinal organoids model. The study findings showed that BBR treatment alleviated the severity of infection and increased survival rate in rCDI mice. Mechanistically, BBR alleviated intestinal epithelial damage with higher Occludin expression, suppressed some inflammatory pathways and reduced the level of inflammatory factors in both the caecum and serum. Moreover, 16S rRNA sequencing analysis indicated that BBR reshaped the gut microbiota by increasing the abundance of Firmicutes and reducing the abundance of Proteobacteria. At genus level, BBR treatment increased levels of Blautia and Bilophila, and reduced levels of Proteus. In addition, acetic acid, one of the short-chain fatty acids (SCFAs), was also increased after BBR treatment in rCDI mice. Collectively, BBR exerted a protective effect in rCDI via multiple underlying mechanisms and is a potential drug candidate for alleviating rCDI, but further research is needed in this area.

Fulminant Clostridioides difficile Infection: A Journey into the Unknown!

Clostridioides difficile is 1 of the 5 urgent antibiotic resistance threats in the United States as reported by the Centers for Disease Control and Prevention. Fulminant C difficile infection (CDI), characterized by hallmarks of critical illness such as hypotension, shock, or megacolon, has been difficult to define and treat. In this article, we describe the diagnostic criteria for fulminant CDI, clinical factors and inflammatory markers. We review the currently recommended treatment modalities including antibiotics and surgical interventions, colectomy, and diverting loop ileostomy. We also included treatment approaches that are still investigational such as intestinal microbiota transplant, tigecycline, and intravenous immunoglobulin.

Evaluating Vancomycin Monotherapy and Dual Therapy with Nifuroxazide for Medium-Severe Clostridioides Difficile Infection

BACKGROUND

All currently used therapeutic protocols and drugs for Clostridioides difficile infection (CDI) treatment do not have a satisfying success and usually cost a lot.

OBJECTIVES

To compare the efficacy of vancomycin monotherapy vs modified dual therapy with vancomycin + nifuroxazide as a therapeutic protocol for a medium-severe form of CDI. In addition, the effects of a modified therapeutic protocol with standard monotherapy on the number of stools and stool consistency in a medium-severe CDI will be compared.

MATERIALS AND METHODS

A prospective, randomized, controlled clinical trial that included 60 patients divided into two groups was conducted. One group of patients was treated with vancomycin monotherapy. The other group was treated with the modified therapeutic protocol (vancomycin + nifuroxazide).

RESULTS

The modified therapy with vancomycin + nifuroxazide demonstrated enhanced pharmacological efficacy in the management of CDI compared to the standard vancomycin monotherapy. Patients treated with dual therapy reported a significantly lower number of stools in first, second and third control; first control (4.47 ± 2.20 compared to 5.70 ± 1.91 in vancomycin group (p = 0.024)), second control (2.37 ± 0.85 compared to 3.13 ± 0.90 in vancomycin group (p = 0.001)), and third control (1.53 ± 0.51 compared to 1.80 ± 0.61 in vancomycin group (p = 0.035)). Also, the first and third controls noted significant improvements in stool consistency, measured as a decrease in the number of completely watery stools (p = 0.011 and p < 0.001, respectively).

CONCLUSIONS

Nifuroxazide and vancomycin have demonstrated accelerated improvement in patient status and hold promise as a novel dual therapeutic regimen for managing patients diagnosed with a medium-severe form of CDI.

Allosterically switchable network orients β-flap in Clostridioides difficile toxins

Allosteric proteins exhibit a functional response upon ligand binding far from the active site. Clostridioides difficile toxins use allosteric binding by the endogenous cofactor myo-inositol hexakisphosphate to orchestrate self-cleavage from within the target cell. This binding event induces a conformational shift, primarily effecting a lever-like β-flap region, with two known orientations. We uncovered a mechanism for this allosteric transition using extensive atomistic molecular dynamics simulations and computational and experimental mutagenesis. The mechanism relies on a switchable interaction network. The most prominent interaction pair is K600-E743, with K600 interactions explaining ∼70% of the allosteric effect. Rather than gradually morphing between two end states, the interaction network adopts two mutually exclusive configurations in the active and inactive state. Similar switchable networks may explain allostery more broadly. This mechanism in particular could aid in drug development targeting the C. difficile toxins autoproteolysis.

The evolving landscape of live biotherapeutics in the treatment of Clostridioides difficile infection

Clostridioides difficile (C. difficile) infection (CDI) is common after antibiotic exposure and presents significant morbidity, mortality and healthcare costs worldwide. The rising incidence of recurrent CDI, driven by hypervirulent strains, widespread antibiotic use and increased community transmission, has led to an urgent need for novel therapeutic strategies. Conventional antibiotic treatments, although effective, face limitations due to rising antibiotic resistance and high recurrence rates, which can reach up to 60% after multiple infections. This has prompted exploration of alternative therapies such as fecal microbiota-based therapies, including fecal microbiota transplantation (FMT) and live biotherapeutics (LBPs), which demonstrate superior efficacy in preventing recurrence. They are aimed at restoring the gut microbiota. Fecal microbiota, live-jslm and fecal microbiota spores, live-brpk have been approved by the U.S. Food and Drug Administration in individuals aged 18 years or older for recurrent CDI after standard antimicrobial treatment. They have demonstrated high efficacy and a favorable safety profile in clinical trials. Another LBP under study includes VE-303, which is not derived from human donor stool. This review provides a comprehensive overview of the current therapeutic landscape for CDI, including its epidemiology, pathophysiology, risk factors, diagnostic modalities and treatment strategies. The review delves into the emerging role of live biotherapeutics, with a particular focus on fecal microbiota-based therapies. We explore their development, mechanisms of action, clinical applications and potential to revolutionize CDI management.

Clostridioides difficile infection and recurrence in cancer patients (CIRCA): A multicentre, international study

OBJECTIVES

We aimed to describe the characteristics of Clostridioides difficile infection (CDI) in cancer patients, analysing risk factors for 90-day recurrence and attributable mortality.

METHODS

Retrospective analysis on all CDI episodes from 2020 to 2022 in three Australian hospitals and one Spanish hospital. Logistic regression analyses were performed.

RESULTS

A total of 547 CDI episodes in cancer patients were documented. Treatment predominantly involved vancomycin (81.5%), followed by metronidazole (15.0%) and fidaxomicin (9.1%). Combined antibiotics were used in 61 (11.2%) episodes. The 90-day recurrence rate was 15.6%. Independent risk factors for CDI recurrence were female sex (OR 2.26, 95% CI 1.13-4.52), age >75 years (OR 2.69, 95% CI 1.30-5.59), dialysis (OR 5.15, 95% CI 1.45-18.27), vomiting at presentation (OR 0.06, 95% CI 0.01-0.55), colonic wall thickening in the CT abdomen (OR 2.42, 95% CI 1.06-5.49) and vancomycin therapy (OR 4.60, 95% CI 1.34-15.84). Overall, 90-day mortality was 22.3%, but attributable mortality was 4.9%. Risk factors for mortality attributed to CDI were age >65 years (OR 15.91, 95% CI 2.64-95.80), previous cerebrovascular disease (OR 20.27, 95% CI 3.12-131.84), antibiotic therapy within the last 30 days (OR 0.17, 95% CI 0.05-0.54), high-output diarrhoea (OR 6.68, 95% CI 1.68-26.56), high CRP-levels (OR 11.60, 95% CI 1.90-70.81) and need for treatment change (OR 6.65, 95% CI 2.20-20.08).

CONCLUSIONS

CDI recurrence rates among cancer patients remain significant. Nonetheless, fidaxomicin and other preventive strategies are seldom used. We identified several factors that could inform the implementation of these strategies in cancer patients.

Safety and Immunogenicity of an Adjuvanted Clostridioides difficile Vaccine Candidate in Healthy Adults: A Randomized Placebo-Controlled Phase 1 Study

BACKGROUND

This study investigated the safety, reactogenicity, and immunogenicity in healthy subjects of a Clostridioides difficile vaccine candidate with/without adjuvant, targeting toxins A and B.

METHODS

In this first-in-human, phase 1, observer-blind study, subjects aged 18-45 years were randomized to receive F2 antigen (n = 10) or placebo (n = 10), and subjects aged 50-70 years to receive F2 antigen plus AS01 adjuvant (n = 45), F2 antigen (n = 45), or placebo (n = 30) in 2 doses 1 month apart. A subcohort (n = 40) received a third dose 15 months later. Solicited adverse events (AEs) were recorded for 7 days and unsolicited AEs for 30 days after each dose. Immunogenicity was assessed at baseline and after each dose.

RESULTS

Solicited AEs were transient and most frequent in subjects receiving F2 antigen plus AS01. No serious AEs were considered related to study vaccine. Immunogenicity was substantially higher in subjects receiving F2 antigen plus AS01 than subjects receiving F2 antigen alone. A third dose increased the immune response in subjects with baseline neutralization titers below the assay lower limit of quantitation.

CONCLUSIONS

The GSK C. difficile vaccine candidate was immunogenic, especially when given with AS01, and was well tolerated with an acceptable safety profile.

CLINICAL TRIAL REGISTRATION

NCT04026009.

Improved health-related quality of life in patients with recurrent Clostridioides difficile infection after treatment with faecal microbiota transplantation

BACKGROUND

Clostridioides difficile is a major burden for both healthcare systems and the patients. Faecal microbiota transplantation (FMT) is becoming more common as a treatment since it reduces the risk of recurrent Clostridioides difficile infection (rCDI).

OBJECTIVES

To evaluate how treatment with FMT is affecting the health-related quality of life (HRQoL) in patients with rCDI.

METHODS

A prospective observational cohort study was conducted where patients who were offered FMT as a treatment for rCDI were asked to fill in a questionnaire based on the Short Health Scale (SHS) and EuroQol 5-Dimensions 5-Levels (EQ-5D-5L) about their HRQoL before and after treatment.

RESULTS

Patients with rCDI had poor HRQoL, which improved following FMT.

CONCLUSIONS

Since FMT cures, reduces the risk of new recurrences of CDI and improves the HRQoL of the patients, it should be offered as a treatment for patients with rCDI. Also, SHS is a useful and reliable instrument for measuring HRQoL in patients with rCDI.

Risk Factors for Antibiotic Exposure Post-Fecal Microbiota Transplantation for Recurrent Clostridioides difficile Infection: A Prospective Multicenter Observational Study

Background

Recurrent Clostridioides difficile infection (CDI) is primarily driven by antibiotic-induced disruption of the indigenous intestinal microbiota. Restoration of microbiota through fecal microbiota transplantation (FMT) is effective in preventing subsequent CDI, although this effect is attenuated with additional antibiotic exposure. The aim of this study was to identify the risk factors for recurrent antibiotic administration after FMT.

Methods

This is a prospective cohort of patients who were administered FMT for recurrent CDI from 1 July 2019 through 23 November 2023 across 6 institutions in the United States. Providers collected de-identified data at the time of FMT administration and in the months post-FMT administration.

Results

The analysis included 448 patients. Risk factors for non-CDI antibiotic administration within 2 months of FMT included immunocompromised status (odds ratio [OR], 2.2 [95% confidence interval {CI}, 1.1-4.4]; P = .02), >3 non-CDI antibiotic courses pre-FMT (OR, 3.1 [95% CI, 1.4-6.8]; P = .006), and prior hospitalization for CDI (OR, 2.0 [95% CI, 1.1-3.8]; P = .02). The most common indications for non-CDI antibiotic administration post-FMT were urinary tract infections, respiratory infections, and procedure prophylaxis.

Conclusions

Non-CDI antibiotic exposure significantly increases the risk of CDI recurrence post-FMT. Risk factors for non-CDI antibiotic administration within 2 months of FMT include immunocompromised status, multiple prior non-CDI antibiotics, and prior hospitalization for CDI. These individuals may benefit from additional or modified recurrent CDI prevention strategies.

The always evolving diagnosis and management of Clostridioides difficile colitis: What you need to know

ABSTRACT

The diagnosis, pharmacologic management, and surgical options for Clostridioides difficile infection (CDI) are rapidly evolving, which presents a challenge for the busy surgeon to remain up to date on the latest clinical guidelines. This review provides an evidence-based practical guide for CDI management tailored to the needs of surgeons and surgical intensivists. Historically, the diagnosis of CDI relied on slow cell culture cytotoxicity neutralization assays, but now, the rapidly resulting nucleic acid amplification tests and enzyme immunoassays have become mainstream. In terms of antibiotic therapy, metronidazole and oral vancomycin were the main "workhorse" antibiotics in the early 2000s, but large randomized controlled trials have now demonstrated that fidaxomicin produces superior results. Regarding surgical intervention, total abdominal colectomy was once the only procedure of choice; however, diverting loop ileostomy with colonic lavage is emerging as a viable alternative. Finally, novel adjuncts such as fecal microbiota transplantation and targeted therapy against toxin B (bezlotoxumab) are playing an increasingly important role in the management of CDI.

Evaluating Bezlotoxumab-Fidaxomicin Combination Therapy in Clostridioides Infection: A Single-Center Retrospective Study from Aichi Prefecture, Japan

Background/Objectives:Clostridioides difficile infection (CDI) poses a significant healthcare challenge, with recurrence rates reaching 30%, leading to substantial morbidity and costs. Fidaxomicin (FDX) and bezlotoxumab (BEZ) have shown potential in reducing recurrence; however, real-world data on the efficacy of their combination in high-risk CDI patients remain limited. This study aimed to evaluate the efficacy and safety of FDX + BEZ compared with FDX alone in CDI patients with recurrence risk factors. Methods: CDI patients with ≥two recurrence risk factors treated with FDX alone or FDX + BEZ were analyzed. Sixteen factors were evaluated as risk factors for recurrent CDI based on findings from previous studies. Patients with FDX treatment duration <10 days or other CDI treatment prior to FDX were excluded. Outcomes included recurrence within 2 months, global and clinical cure rates, and adverse events. Univariate and multivariate analyses were performed to evaluate efficacy. Results: Among 82 patients, the FDX + BEZ group (n = 30) demonstrated significantly higher global (86.7% vs. 65.4%; p < 0.05) and clinical cure rates (90.0% vs. 69.2%; p < 0.05) compared with the FDX-alone group (n = 52), despite more severe cases in the combination group. Recurrence rates were non-significantly lower in the FDX + BEZ group (3.3% vs. 11.5%). Combination therapy also accelerated diarrhea resolution without additional adverse events. Multivariate analysis identified FDX + BEZ as significantly associated with improved clinical cure (adjusted odds ratio 4.167; 95% CI: 1.029-16.885). Conclusions: FDX + BEZ therapy offers superior efficacy and safety in CDI patients with recurrence risk factors, presenting a promising strategy for optimizing CDI management.

Enhanced immunogenicity of a Clostridioides difficile TcdB vaccine adjuvanted with a synthetic dual-TLR ligand adjuvant

We report a comprehensive evaluation of the toxin B (TcdB) vaccine adjuvanted with a dual Toll-like receptor ligand liposome adjuvant for Clostridioides difficile infection (CDI). The vaccine completely protected mice from a lethal infection. Compared to alum adjuvanted TcdB, it generated functionally superior systemic antibodies and supported strong memory B cell and gut IgA responses. This pharmaceutically acceptable adjuvant platform holds promise for developing a next-generation CDI vaccine.

Mechanisms, therapeutic strategies, and emerging therapeutic alternatives for carbapenem resistance in Gram-negative bacteria

Carbapenem-resistant Gram-negative bacteria (CR-GNB) have experienced an alarming surge in prevalence in recent years, escalating into a critical global healthcare crisis. As carbapenems represent the last line of defense against such pathogens, infections caused by CR-GNB have become increasingly challenging to treat, given the restricted therapeutic options and heightened mortality risks. The discovery and development of alternative therapeutic strategies that present novel avenues against multi-drug-resistant organisms are gaining increased attention, presenting a pressing need for innovative solutions. Our comprehensive review delves into the multifaceted landscape of carbapenem resistance in Gram-negative bacteria in response to this urgent challenge. The scope of this review aims to provide an up-to-date and in-depth exploration regarding the mode of action of carbapenem and the resisting mechanisms of carbapenem in GNB. Additionally, it discusses the state of the art of some clinical therapies for the treatment of infections caused by CR-GNB. Moreover, it describes several combinational and alternative therapies to combat CR-GNB, including the computational approach of "molecular docking". In light of the conclusions of this review, we call for the implementation of these strategies to develop comprehensive approaches to mitigate carbapenem resistance in Gram-negative bacteria.

Citrulline Inhibits Clostridioides difficile Infection With Anti-inflammatory Effects

BACKGROUND & AIMS

Clostridioides difficile infection (CDI) causes colitis and diarrhea. C. difficile bacterium produces toxins A and B, which cause intestinal inflammation. A metabolomics analysis discovered fecal metabolites with anti-inflammatory effects in CDI. We aimed to identify an anti-CDI metabolite that can inhibit CDI-mediated colitis and prevent recurrence.

METHODS

Fresh human colonic tissues and primary human cells were used to determine metabolite effects. Humanized C. difficile-infected HuCD34-NCG mice and antibiotics-treated human gut microbiota-treated (ABX + HGM) hamsters were used to simulate the human environment.

RESULTS

High-throughput screening and fecal metabolomics analysis identified anti-inflammatory metabolites. Compared with other tested metabolites, citrulline preserved the mucosal integrity of toxin-exposed fresh human colonic tissues with reduced macrophage inflammatory protein 1 alpha (MIP-1a) and increased interleukin-10 (IL-10) expression. Oral citrulline treatment alleviated cecal inflammation in hamsters infected with C. difficile ribotype 027. This was accomplished by the augmented expression of cecal IL-10 and the diminished level of cecal MIP-1a. Citrulline and vancomycin synergistically prevented recurrence in the infected ABX + HGM hamsters. In C57BL/6J mice infected with C. difficile VPI10463, citrulline ameliorated colitis by reducing colonic Ccl3 mRNA expression. In immunologically humanized HuCD34-NCG mice infected with toxin B-expressing C. difficile ribotype 017, citrulline ameliorated colitis with increased human IL-10 expression in colonic macrophages. Citrulline suppressed MIP-1a secretion and GSK3a/b dephosphorylation in the toxin A-exposed human colonic epithelial cells and promoted IL-10 expression in toxin B-exposed human macrophages and heat shock protein 27 phosphorylation.

CONCLUSION

Citrulline exerts anti-inflammatory effects in the intestines against C. difficile toxins and inhibits CDI recurrence in mice and hamsters.

Diagnosis and Management of Clostridioides difficile in Inflammatory Bowel Disease

Patients with inflammatory bowel disease (IBD) have an increased risk of Clostridioides difficile infection (CDI), which can lead to worse IBD outcomes. The diagnosis of CDI in patients with IBD is complicated by higher C. difficile colonization rates and shared clinical symptoms of intestinal inflammation. Traditional risk factors for CDI, such as antibiotic exposure, may be lacking in patients with IBD because of underlying intestinal microbiota dysbiosis. Although CDI disproportionately affects people with IBD, patients with IBD are typically excluded from CDI clinical trials creating a knowledge gap in the diagnosis and management of these 2 diseases. This narrative review aims to provide a comprehensive overview of the diagnosis, treatment, and prevention of CDI in patients with IBD. Distinguishing CDI from C. difficile colonization in the setting of an IBD exacerbation is important to avoid treatment delays. When CDI is diagnosed, extended courses of anti- C. difficile antibiotics may lead to better CDI outcomes. Regardless of a diagnosis of CDI, the presence of C. difficile in a patient with IBD should prompt a disease assessment of the underlying IBD. Microbiota-based therapies and bezlotoxumab seem to be effective in preventing CDI recurrence in patients with IBD. Patients with IBD should be considered at high risk of CDI recurrence and evaluated for a preventative strategy when diagnosed with CDI. Ultimately, the comanagement of CDI in a patient with IBD requires a nuanced, patient-specific approach to distinguish CDI from C. difficile colonization, prevent CDI recurrence, and manage the underlying IBD.

Management of Recurrent Clostridioides difficile Infection (rCDI): A Systematic Literature Review to Assess the Feasibility of Indirect Treatment Comparison (ITC)

Recurrent Clostridioides difficile infection (rCDI) is a major cause of increased morbidity, mortality, and healthcare costs. Fecal-microbiota-based therapies are recommended for rCDI on completion of standard-of-care (SoC) antibiotics to prevent further recurrence: these therapies include conventional fecal-microbiota transplantation and the US Food and Drug Administration-approved therapies REBYOTA® (RBL) and VOWST Oral Spores™ (VOS). As an alternative to microbiota-based therapies, bezlotoxumab, a monoclonal antibody, is used as adjuvant to SoC antibiotics to prevent rCDI. There are no head-to-head clinical trials comparing different microbiota-based therapies or bezlotoxumab for rCDI. To address this gap, we conducted a systematic literature review to identify clinical trials on rCDI treatments and assess the feasibility of using them to conduct an indirect treatment comparison (ITC). The feasibility analysis determined that trial heterogeneity, particularly relating to inclusion criteria, may significantly compromise ITC and prevent cross-trial comparisons. Our analysis underlines the need to adopt standardized protocols to ensure comparability across trials.

Clostridioides difficile major toxins remodel the intestinal epithelia, affecting spore adherence/internalization into intestinal tissue and their association with gut vitronectin

The most common cause of healthcare-associated diarrhea and colitis in the U.S., is Clostridioides difficile, a spore-forming pathogen. Two toxins, TcdA and TcdB, are major virulence factors essential for disease manifestations, while C. difficile spores are essential for disease transmission and recurrence. Both toxins cause major damage to the epithelial barrier, trigger massive inflammation, and reshape the microbiome and metabolic composition, facilitating C. difficile colonization. C. difficile spores, essential for transmission and recurrence of the disease, persist adhered and internalized in the intestinal epithelia. Studies have suggested that toxin-neutralization in combination with antibiotic during CDI treatment in humans significantly reduces disease recurrence, suggesting a link between toxin-mediated damage and spore persistence. Here, we show that TcdA/TcdB-intoxication of intestinal epithelial Caco-2 cells leads to remodeling of accessible levels of fibronectin (Fn) and vitronectin (Vn) and their cognate alpha-integrin subunits. While TcdB-intoxication of intestinal tissue had no impact in accessible levels of Fn and Vn, but significantly increased levels of intracellular Vn. We observed that Fn and Vn released to the supernatant readily bind to C. difficile spores in vitro, while TcdB-intoxication of intestinal tissue led to increased association of C. difficile spores with gut Vn. Toxin-intoxication of the intestinal tissue also contributes to increased adherence and internalization of C. difficile spores. However, TcdB-intoxicated ligated loops infected of mice treated with Bezlotoxumanb (monoclonal anti-TcdB antibodies) did not prevent TcdB-mediated increased spore adherence and internalization into intestinal tissue. This study highlights the importance of studying the impact of C. difficile toxins of host tissues has in C. difficile interaction with host surfaces that may contribute to increased persistence and disease recurrence.

A Review of Therapies for Clostridioides difficile Infection

Clostridioides difficile is an urgent public health threat that affects approximately half a million patients annually in the United States. Despite concerted efforts aimed at the prevention of Clostridioides difficile infection (CDI), it remains a leading cause of healthcare-associated infections. CDI is associated with significant clinical, social, and economic burdens. Therefore, it is imperative to provide optimal and timely therapy for CDI. We conducted a systematic literature review and offer treatment recommendations based on available evidence for the treatment and prevention of CDI.

Live Biotherapeutic Products for the Prevention of Recurrent Clostridioides difficile Infection

OBJECTIVE

To review the efficacy, safety, and role of live biotherapeutic products (LBPs) in the prevention of recurrent Clostridioides difficile infection (rCDI).

DATA SOURCES

A literature search was performed using PubMed and Google Scholar (through February 2024) with search terms RBX2660, SER-109, and fecal microbiota. Other resources included abstracts presented at recent conferences, national clinical practice guidelines, and manufacturers' websites.

STUDY SELECTION AND DATA EXTRACTION

All relevant studies, trial updates, conference abstracts, and guidelines in the English language were included.

DATA SYNTHESIS

Two LBPs were recently approved by the Food and Drug Administration for the prevention of recurrence in adults following antibiotic treatment for rCDI. Fecal microbiota, live-jslm is administered rectally as a retention enema, whereas fecal microbiota spores, live-brpk is given orally after bowel preparation. Several phase 2 and phase 3 clinical trials have established the safety and efficacy of these LBPs in reducing rates of rCDI compared with placebo. Patients with severe immunosuppression and those with inflammatory bowel disease were largely excluded from these trials.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE IN COMPARISON WITH EXISTING DRUGS

Live biotherapeutic products offer a similar mechanism to conventional fecal microbiota transplant (FMT) in preventing rCDI through microbiota restoration. The primary advantages of LBPs over FMT are their standardized composition and donor stool screening processes for transmissible pathogens. Bezlotoxumab is also available for the prevention of Clostridioides difficile infection; however, there are no clinical data available to compare the efficacy of LBPs with bezlotoxumab, and the benefit of simultaneous use of these preventative therapies is unclear.

CONCLUSIONS

Live biotherapeutic products provide a safe and effective option for the prevention of rCDI and represent an improvement over conventional FMT. Additional studies are needed to further determine their place in therapy relative to bezlotoxumab and in the setting of immunosuppression and inflammatory bowel disease.

The complete catalog of antimicrobial resistance secondary active transporters in Clostridioides difficile: evolution and drug resistance perspective

Secondary active transporters shuttle substrates across eukaryotic and prokaryotic membranes, utilizing different electrochemical gradients. They are recognized as one of the antimicrobial efflux pumps among pathogens. While primary active transporters within the genome of C. difficile 630 have been completely cataloged, the systematical study of secondary active transporters remains incomplete. Here, we not only identify secondary active transporters but also disclose their evolution and role in drug resistance in C. difficile 630. Our analysis reveals that C. difficile 630 carries 147 secondary active transporters belonging to 27 (super)families. Notably, 50 (34%) of them potentially contribute to antimicrobial resistance (AMR). AMR-secondary active transporters are structurally classified into five (super)families: the p-aminobenzoyl-glutamate transporter (AbgT), drug/metabolite transporter (DMT) superfamily, major facilitator (MFS) superfamily, multidrug and toxic compound extrusion (MATE) family, and resistance-nodulation-division (RND) family. Surprisingly, complete RND genes found in C. difficile 630 are likely an evolutionary leftover from the common ancestor with the diderm. Through protein structure comparisons, we have potentially identified six novel AMR-secondary active transporters from DMT, MATE, and MFS (super)families. Pangenome analysis revealed that half of the AMR-secondary transporters are accessory genes, which indicates an important role in adaptive AMR function rather than innate physiological homeostasis. Gene expression profile firmly supports their ability to respond to a wide spectrum of antibiotics. Our findings highlight the evolution of AMR-secondary active transporters and their integral role in antibiotic responses. This marks AMR-secondary active transporters as interesting therapeutic targets to synergize with other antibiotic activity.

Breaking the Cycle of Recurrent Clostridioides difficile Infections: A Narrative Review Exploring Current and Novel Therapeutic Strategies

Clostridioides difficile is a toxin-producing bacteria that is a main cause of antibiotic-associated diarrhea. Clostridioides difficile infections (CDI) are associated with disruptions within the gastrointestinal (GI) microbiota which can be further exacerbated by CDI-targeted antibiotic treatment thereby causing recurrent CDI (rCDI) and compounding the burden placed on patients and the healthcare system. Treatment of rCDI consists of antibiotics which can be paired with preventative therapeutics, such as bezlotoxumab or fecal microbiota transplants (FMTs), if sustained clinical response is not obtained. Newer preventative strategies have been recently approved to assist in restoring balance within the GI system with the goal of preventing recurrent infections.

Microbiota restoration for recurrent Clostridioides difficile infection

Since the publication of the recent North American and European guidelines on management of Clostridioides difficile infection (CDI), new evidence describing the epidemiology, testing and treatment of CDI has emerged. Despite all advances in infection control and antibiotic stewardship, the incidence and burden of CDI in the hospitals and the community remains at a stable high. Coupled with the incidence of primary CDI, there is a stable high incidence of recurrent CDI. Testing for primary and recurrent CDI remains a clinical challenge owing to high sensitivity of the PCR (leading to false positives) and somewhat limited sensitivity of EIA for toxin. The pathophysiology of recurrent CDI involves an ongoing disruption of the microbiota owing to the infection and the treatment of CDI employed. Broad spectrum antibiotics such as vancomycin leads to further disruption of microbiota compared to fidaxomicin which has a lower disruption of the microbiota and leads to fewer recurrences. Owing to these data fidaxomicin is considered as the first line antibiotic for recurrent CDI. Intravenous bezlotoxumab is a monoclonal antibody that reduces the risk of recurrence in high-risk patients but does not restore the microbiota. Experimental fecal microbiota transplantation (FMT) has been available for more than a decade. Owing to the success of FMT, two new non-invasive donor dependent Food and Drug Administration (FDA) approved therapies have been available since late 2022. This review summarizes all these conundrums regarding CDI and provides clinical pearls to use in day-to-day practice.

Early geriatric assessment and management in older patients with Clostridioides difficile infection in Denmark (CLODIfrail): a randomised trial

BACKGROUND

Clostridioides difficile infection causes diarrhoea and colitis. Older patients with C difficile infection are often frail and have comorbidities, leading to high mortality rates. The frailty burden in older people might restrict access to treatments, such as C difficile infection-specific antibiotics and faecal microbiota transplantation. We aimed to investigate the clinical effects of early comprehensive geriatric assessment (CGA) and frailty evaluation, including home visits and assessment for faecal microbiota transplantation, in older patients with C difficile infection.

METHODS

In this randomised, quality improvement trial with a pragmatic design, patients from the Central Denmark Region aged 70 years or older with a positive PCR test for C difficile toxin were randomly assigned (1:1) to CGA or standard care, both with equal access to faecal microbiota transplantation. Patients and investigators were unmasked to treatment. The primary outcome was 90-day mortality, and was compared in the study groups according to the intention-to-treat principle. The study is registered with ClinicalTrials.gov, NCT05447533.

FINDINGS

Between Sept 1, 2022, and May 3, 2023, we randomly assigned 217 patients to CGA (n=109) or standard care (n=108). The median patient age was 78 years (IQR 74-84). 116 (53%) of 217 patients were female and 101 (47%) were male. 16 (15%; 95% CI 9-23) of 109 patients in the CGA group and 22 (20%; 14-29) of 108 patients in the standard-care group died within 90 days (odds ratio 0·66, 95% CI 0·32-1·38. No serious adverse events or deaths related to patient assessment or faecal microbiota transplantation were recorded in either group. Deaths directly attributable to C difficile infection were lower in the CGA group (seven [44%] of 16 deaths vs 18 [82%] of 22 deaths in the standard-care group; p=0·020).

INTERPRETATION

Older patients who received CGA had a 90-day mortality rate similar to that of patients who received standard care, but with fewer deaths directly attributable to C difficile infection.

FUNDING

Innovation Fund Denmark, Novo Nordisk Foundation, and Helsefonden.

Enhanced immunogenicity of a Clostridioides difficile TcdB vaccine adjuvanted with a synthetic dual-TLR ligand adjuvant

We report a comprehensive evaluation of the toxin B (TcdB) vaccine adjuvanted with a dual Toll-like receptor ligand liposome adjuvant for Clostridioides difficile infection (CDI). The vaccine completely protected mice from a lethal infection. Compared to alum adjuvanted TcdB, it generated functionally superior systemic antibodies and supported strong memory B cell and gut IgA responses. This pharmaceutically acceptable adjuvant platform holds promise for developing a next-generation CDI vaccine.

mRNA-based platform for preventing and treating Staphylococcus aureus by targeted staphylococcal enterotoxin B

Staphylococcus aureus (S. aureus) possesses numerous virulence factors, with the increasing prevalence of drug-resistant strains heightening the threat posed by this pathogen. Staphylococcal enterotoxin B (SEB), a highly conserved toxin secreted by S. aureus, is also recognized as a potential bioweapon with super-antigenic activity. SEB represents a promising target in efforts to combat infections caused by S. aureus. We developed mRNA-based vaccine and antibody targeting SEB for both prophylactic and therapeutic purposes in varying S. aureus infection conditions. The mSEB mRNA vaccine (10 μg per mouse) induces more robust and persistent immune responses, including higher antibody titers and specific cellular immune responses, compared to immunization with 30 μg of mSEB protein adjuvanted with aluminum phosphate. Additionally, the anti-SEB mRNA antibody maintains secretion of anti-SEB monoclonal antibody (mAb) with a dosage that is 10 times lower than purified protein administration. The mRNA-based antibody exhibits superior pharmacokinetic profiles compared to its protein counterparts, efficiently neutralizing SEB and clearing S. aureus from circulation. Both the mRNA vaccine and mRNA antibody demonstrate preventive and therapeutic effects by eliciting specific immune responses and generating high-affinity antibodies in mice. We have laid the groundwork for the development and evaluation of mRNA-based vaccines and antibodies targeting SEB produced by S. aureus. Our studies demonstrate that these approaches are more effective than traditional protein-based vaccines and antibodies in terms of inducing immune responses, pharmacokinetics, and their prophylactic or therapeutic efficacy against S. aureus infections.

Designing a simple and efficient phage biocontainment system using the amber suppressor initiator tRNA

Multidrug-resistant infections are becoming increasingly prevalent worldwide. One of the fastest-emerging alternative and adjuvant therapies being proposed is phage therapy. Naturally isolated phages are used in the vast majority of phage therapy treatments today. Engineered phages are being developed to enhance the effectiveness of phage therapy, but concerns over their potential escape remain a salient issue. To address this problem, we designed a biocontained phage system based on conditional replication using amber stop codon suppression. This system can be easily installed on any natural phage with a known genome sequence. To test the system, we individually mutated the start codons of three essential capsid genes in phage φX174 to the amber stop codon (UAG). These phages were able to efficiently infect host cells expressing the amber initiator tRNA, which suppresses the amber stop codon and initiates translation at TAG stop codons. The amber phage mutants were also able to successfully infect host cells and reduce their population on solid agar and liquid culture but could not produce infectious particles in the absence of the amber initiator tRNA or complementing capsid gene. We did not detect any growth-inhibiting effects on E. coli strains known to lack a receptor for φX174 and we showed that engineered phages have a limited propensity for reversion. The approach outlined here may be useful to control engineered phage replication in both the lab and clinic.

IL-33 protects from recurrent C. difficile infection by restoration of humoral immunity

Clostridioides difficile infection (CDI) recurs in one of five patients. Monoclonal antibodies targeting the virulence factor TcdB reduce disease recurrence, suggesting that an inadequate anti-TcdB response to CDI leads to recurrence. In patients with CDI, we discovered that IL-33 measured at diagnosis predicts future recurrence, leading us to test the role of IL-33 signaling in the induction of humoral immunity during CDI. Using a mouse recurrence model, IL-33 was demonstrated to be integral for anti-TcdB antibody production. IL-33 acted via ST2+ ILC2 cells, facilitating germinal center T follicular helper (GC-Tfh) cell generation of antibodies. IL-33 protection from reinfection was antibody-dependent, as μMT KO mice and mice treated with anti-CD20 mAb were not protected. These findings demonstrate the critical role of IL-33 in generating humoral immunity to prevent recurrent CDI.

Novel and emerging therapeutics for antimicrobial resistance: A brief review

A pandemic known as anti-microbial resistance (AMR) poses a challenge to contemporary medicine. To stop AMR's rise and quick worldwide spread, urgent multisectoral intervention is needed. This review will provide insight on new and developing treatment approaches for AMR. Future therapy options may be made possible by the development of novel drugs that make use of developments in "omics" technology, artificial intelligence, and machine learning. Vaccines, immunoconjugates, antimicrobial peptides, monoclonal antibodies, and nanoparticles may also be intriguing options for treating AMR in the future. Combination therapy may potentially prove to be a successful strategy for combating AMR. To lessen the impact of AMR, ideas like drug repurposing, antibiotic stewardship, and the one health approach may be helpful.

Differences in Patient Access to Newly Approved Antibacterial Drugs in EU/EEA Countries

The introduction of antibiotics in the beginning of the 20th century was one of the most important scientific breakthroughs in history. However, in recent decades, the growing threat of antimicrobial resistance (AMR) has shown the limitations of the current research and development programs for new antimicrobial drugs. In the last decade, 20 antibiotics, 7 β-lactam/β-lactamase inhibitor (BL/BLI) combinations and 4 non-traditional antibacterial drugs have been launched worldwide.

METHODS

This study aimed to assess the time to patient access for new antibacterial drugs in countries in the European Union and the European Economic Area (EU/EEA). Time differences in marketing authorization from the U.S. Food and Drug Agency (FDA) and the European Medicines Agency (EMA) were also described, as well as the availability of each drug in the countries in the EU/EEA according to the national competent authorities.

RESULTS

Substantial differences between countries were observed, with no or only one new drug available in some countries.

CONCLUSIONS

Improving pricing and reimbursement timelines and fostering collaboration between national health authorities and market authorization holders can enhance timely and equitable patient access to new antibacterial treatments in Europe. Equitable and sustainable access to antibacterial drugs is a cornerstone in the battle against AMR.

Novel approaches for bacterial toxin neutralization; current advances and future perspectives

This review outlines diverse strategies for neutralizing bacterial toxins which are a significant threat to human health. Effective toxin neutralization is crucial in preventing and treating bacterial infections, especially those caused by antibiotic-resistant strains. Promising approaches include using monoclonal antibodies that target toxins and combining them with agents that directly target bacteria. Aptamers, synthetic molecules that bind to specific targets, provide a rapid and tailored method for inhibiting toxin activity and detecting pathogens. Cell-membrane-coated nanoparticles mimic host cells and effectively neutralize toxins by diverting them and stimulating immune responses. These advancements have the potential to combat bacterial infections and alleviate the associated public health burden.

Expert consensus on antimicrobial resistance research priorities to focus development and implementation of antibacterial vaccines and monoclonal antibodies

To reduce antimicrobial resistance (AMR), pathogen-specific AMR burden data are crucial to guide target selection for research and development of vaccines and monoclonal antibodies (mAbs). We identified knowledge gaps through previously conducted systematic reviews, which informed a Delphi expert consultation on future AMR research priorities and harmonisation strategies to support data-driven decision-making. Consensus (≥80% agreement) on importance and feasibility of research topics was achieved in two rounds, involving 24 of 39 and 19 of 24 invited experts, respectively. Priority pathogens and resistance profiles for future research were identified: third generation cephalosporin-resistant Klebsiella pneumoniae and Escherichia coli, for bloodstream and urinary tract infections, respectively, and meticillin-resistant Staphylococcus aureus for surgical-site infections. Prioritised high-risk populations included surgical, haemato-oncological and transplant patients. Mortality and resource use were prioritised as health-economic outcomes. The importance of age-stratified data and inclusion of a non-infected comparator group were highlighted. This agenda provides guidance for future research to fill knowledge gaps and support data-driven selection of target pathogens and populations for new preventive and treatment strategies, specifically vaccines and mAbs, to effectively address the AMR burden in Europe. These research priorities are also relevant to improve the evidence base for future AMR burden estimates.

Fc-FcγR interactions during infections: From neutralizing antibodies to antibody-dependent enhancement

Advances in antibody technologies have resulted in the development of potent antibody-based therapeutics with proven clinical efficacy against infectious diseases. Several monoclonal antibodies (mAbs), mainly against viruses such as SARS-CoV-2, HIV-1, Ebola virus, influenza virus, and hepatitis B virus, are currently undergoing clinical testing or are already in use. Although these mAbs exhibit potent neutralizing activity that effectively blocks host cell infection, their antiviral activity results not only from Fab-mediated virus neutralization, but also from the protective effector functions mediated through the interaction of their Fc domains with Fcγ receptors (FcγRs) on effector leukocytes. Fc-FcγR interactions confer pleiotropic protective activities, including the clearance of opsonized virions and infected cells, as well as the induction of antiviral T-cell responses. However, excessive or inappropriate activation of specific FcγR pathways can lead to disease enhancement and exacerbated pathology, as seen in the context of dengue virus infections. A comprehensive understanding of the diversity of Fc effector functions during infection has guided the development of engineered antiviral antibodies optimized for maximal effector activity, as well as the design of targeted therapeutic approaches to prevent antibody-dependent enhancement of disease.

Emerging trends and therapeutic applications of monoclonal antibodies

Monoclonal antibodies (mAbs) are being used to prevent, detect, and treat a broad spectrum of malignancies and infectious and autoimmune diseases. Over the past few years, the market for mAbs has grown exponentially. They have become a significant part of many pharmaceutical product lines, and more than 250 therapeutic mAbs are undergoing clinical trials. Ever since the advent of hybridoma technology, antibody-based therapeutics were realized using murine antibodies which further progressed into humanized and fully human antibodies, reducing the risk of immunogenicity. Some of the benefits of using mAbs over conventional drugs include a drastic reduction in the chances of adverse reactions, interactions between drugs, and targeting specific proteins. While antibodies are very efficient, their higher production costs impede the process of commercialization. However, their cost factor has been improved by developing biosimilar antibodies, which are affordable versions of therapeutic antibodies. Along with biosimilars, innovations in antibody engineering have helped to design bio-better antibodies with improved efficacy than the conventional ones. These novel mAb-based therapeutics are set to revolutionize existing drug therapies targeting a wide spectrum of diseases, thereby meeting several unmet medical needs. In the future, mAbs generated by applying next-generation sequencing (NGS) are expected to become a powerful tool in clinical therapeutics. This article describes the methods of mAb production, pre-clinical and clinical development of mAbs, approved indications targeted by mAbs, and novel developments in the field of mAb research.

Comparative effectiveness of treatments for recurrent Clostridioides difficile infection: a network meta-analysis of randomized controlled trials

Background

Clostridioides difficile infection (CDI) is the most common cause of healthcare-associated infectious diarrhea. A major clinical challenge is recurrent CDI (rCDI) without effective standard drug-based therapy. Additionally, a comprehensive comparison of various therapy effectiveness in rCDI patients is still under investigation.

Methods

A Bayesian network meta-analysis (NMA) of randomized control trials up to March 2024 was performed to investigate the efficacy of rCDI interventions.

Results

Seventeen trials were included, comprising 4,148 CDI patients with ten interventions, including fecal microbiota transplantation (FMT) by lower gastrointestinal (LGI), FMT by upper gastrointestinal (UGI), Autologous FMT (AFMT), vancomycin + FMT, vancomycin, placebo, fidaxomicin, Vowst (SER109), Rebyota (RBX2660), and monoclonal antibody. NMA showed that FMT by LGI had the highest efficacy in treating rCDIs with an odds ratio (95% confidence interval) of 32.33 (4.03, 248.69) compared with placebo. FMT by UGI also showed high efficacy, whereas the efficacy comparison between FMT by LGI and UGI was not statistically significant (ORs) (95% CI), 1.72 (0.65, 5.21). The rankogram and surface under the cumulative ranking curve (SUCRA) also showed FMT by LGI ranked at the top and FMT by UGI ranked second in the curative effect.

Conclusion

NMA demonstrates FMT's significant efficacy in rCDI management, regardless of administration route (lower or upper gastrointestinal). Despite its significant benefits, FMT's safety is a concern due to the lack of standardized FDAcompliant manufacturing and oversight. Microbiota-based therapies also exhibit potential. However, limited research mandates further clinical exploration. Antibiotics, in contrast, display comparatively reduced efficacy in rCDI, potentially linked to disruptions in native gut microflora balance.

Systematic Review

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=368435, Identifier CRD42022368435.

Comparing rates of recurrent infection for first occurrence of Clostridioides difficile between tapered oral vancomycin and standard vancomycin: a retrospective, propensity matched cohort study

OBJECTIVE

To compare rates of Clostridioides difficile infection (CDI) recurrence following initial occurrence treated with tapered enteral vancomycin compared to standard vancomycin.

DESIGN

Retrospective cohort study.

SETTING

Community health system.

PATIENTS

Adults ≥18 years of age hospitalized with positive C. difficile polymerase chain reaction or toxin enzyme immunoassay who were prescribed either standard 10-14 days of enteral vancomycin four times daily or a 12-week tapered vancomycin regimen.

METHODS

Retrospective propensity score pair matched cohort study. Groups were matched based on age < or ≥ 65 years and receipt of non-C. difficile antibiotics during hospitalization or within 6 months post-discharge. Recurrence rates were analyzed via logistic regression conditioned on matched pairs and reported as conditional odds ratios. The primary outcome was recurrence rates compared between standard vancomycin versus tapered vancomycin for treatment of initial CDI.

RESULTS

The CDI recurrence rate at 6 months was 5.3% (4/75) in the taper cohort versus 28% (21/75) in the standard vancomycin cohort. The median time to CDI recurrence was 115 days versus 20 days in the taper and standard vancomycin cohorts, respectively. When adjusted for matching, patients in the taper arm were less likely to experience CDI recurrence at 6 months when compared to standard vancomycin (cOR = 0.19, 95% CI 0.07-0.56, p < 0.002).

CONCLUSIONS

Larger prospective trials are needed to elucidate the clinical utility of tapered oral vancomycin as a treatment option to achieve sustained clinical cure in first occurrences of CDI.

Immunosenescence: How Aging Increases Susceptibility to Bacterial Infections and Virulence Factors

The process of aging leads to a progressive decline in the immune system function, known as immunosenescence, which compromises both innate and adaptive responses. This includes impairments in phagocytosis and decreased production, activation, and function of T- and B-lymphocytes, among other effects. Bacteria exploit immunosenescence by using various virulence factors to evade the host's defenses, leading to severe and often life-threatening infections. This manuscript explores the complex relationship between immunosenescence and bacterial virulence, focusing on the underlying mechanisms that increase vulnerability to bacterial infections in the elderly. Additionally, it discusses how machine learning methods can provide accurate modeling of interactions between the weakened immune system and bacterial virulence mechanisms, guiding the development of personalized interventions. The development of vaccines, novel antibiotics, and antivirulence therapies for multidrug-resistant bacteria, as well as the investigation of potential immune-boosting therapies, are promising strategies in this field. Future research should focus on how machine learning approaches can be integrated with immunological, microbiological, and clinical data to develop personalized interventions that improve outcomes for bacterial infections in the growing elderly population.

Forced randomization: the what, why, and how

BACKGROUND

When running a randomized controlled trial (RCT), a clinical site may face a situation when an eligible trial participant is to be randomized to the treatment that is not available at the site. In this case, there are two options: not to enroll the participant, or, without disclosing to the site, allocate the participant to a treatment arm with drug available at the site using a built-in feature of the interactive response technology (IRT). In the latter case, one has employed a "forced randomization" (FR). There seems to be an industry-wide consensus that using FR can be acceptable in confirmatory trials provided there are "not too many" instances of forcing. A better understanding of statistical properties of FR is warranted.

METHODS

We described four different IRT configurations with or without FR and illustrated them using a simple example. We discussed potential merits of FR and outlined some relevant theoretical risks and risk mitigation strategies. We performed a search using Cortellis Regulatory Intelligence database (IDRAC) ( www.cortellis.com ) to understand the prevalence of FR in clinical trial practice. We also proposed a structured template for development and evaluation of randomization designs featuring FR and showcased an application of this template for a hypothetical multi-center 1:1 RCT under three experimental settings ("base case", "slower recruitment", and "faster recruitment") to explore the effect of four different IRT configurations in combination with three different drug supply/re-supply strategies on some important operating characteristics of the trial. We also supplied the Julia code that can be used to reproduce our simulation results and generate additional results under user-specified experimental scenarios.

RESULTS

FR can eliminate refusals to randomize patients, which can cause frustration for patients and study site personnel, improve the study logistics, drug supply management, cost-efficiency, and recruitment time. Nevertheless, FR carries some potential risks that should be reviewed at the study planning stage and, ideally, prospectively addressed through risk mitigation planning. The Cortellis search identified only 9 submissions that have reported the use of FR; typically, the FR option was documented in IRT specifications. Our simulation evidence showed that under the considered realistic experimental settings, the percentage of FR is expected to be low. When FR with backfilling was used in combination with high re-supply strategy, the final treatment imbalance was negligibly small, the proportion of patients not randomized due to the lack of drug supply was close to zero, and the time to complete recruitment was shortened compared to the case when FR was not allowed. The drug overage was primarily determined by the intensity of the re-supply strategy and to a smaller extent by the presence or absence of the FR feature in IRT.

CONCLUSION

FR with a carefully chosen drug supply/re-supply strategy can result in quantifiable improvements in the patients' and site personnel experience, trial logistics and efficiency while preventing an undesirable refusal to randomize a patient and a consequential unblinding at the site. FR is a useful design feature of multi-center RCTs provided it is properly planned for and carefully implemented.

De novo design of mini-protein binders broadly neutralizing Clostridioides difficile toxin B variants

Clostridioides difficile toxin B (TcdB) is the key virulence factor accounting for C. difficile infection-associated symptoms. Effectively neutralizing different TcdB variants with a universal solution poses a significant challenge. Here we present the de novo design and characterization of pan-specific mini-protein binders against major TcdB subtypes. Our design successfully binds to the first receptor binding interface (RBI-1) of the varied TcdB subtypes, exhibiting affinities ranging from 20 pM to 10 nM. The cryo-electron microscopy (cryo-EM) structures of the mini protein binder in complex with TcdB1 and TcdB4 are consistent with the computational design models. The engineered and evolved variants of the mini-protein binder and chondroitin sulfate proteoglycan 4 (CSPG4), another natural receptor that binds to the second RBI (RBI-2) of TcdB, better neutralize major TcdB variants both in cells and in vivo, as demonstrated by the colon-loop assay using female mice. Our findings provide valuable starting points for the development of therapeutics targeting C. difficile infections (CDI).

Integrated Safety and Efficacy Analyses of Phase 3 Trials of a Microbiome Therapeutic for Recurrent CDI

INTRODUCTION

Recurrent Clostridioides difficile infection (rCDI) often occurs after standard-of-care antibiotics. VOWST oral spores (VOS, previously SER-109), an FDA-approved orally administered microbiome therapeutic, is indicated to prevent rCDI following antibiotics for rCDI.

OBJECTIVE, DESIGN, AND PATIENTS

To evaluate safety and efficacy of VOS from two phase 3 trials, (randomized, placebo-controlled [ECOSPOR III: NCT03183128] and open-label, single arm [ECOSPOR IV: NCT03183141]) of 349 adults with rCDI and prevalent comorbidities.

METHODS

VOS or placebo [ECOSPOR III only] (4 capsules once daily for 3 days). Integrated analysis of treatment-emergent adverse events (TEAEs) collected through week 8; serious TEAEs and TEAEs of special interest collected through week 24; and rates of rCDI (toxin-positive diarrhea requiring treatment) evaluated through weeks 8 and 24.

RESULTS

TEAEs were mostly mild or moderate and gastrointestinal. Most common treatment-related TEAEs were flatulence, abdominal pain and distension, fatigue, and diarrhea. There were 11 deaths (3.2%) and 48 patients (13.8%) with serious TEAEs, none treatment-related. The rCDI rate through week 8 was 9.5% (95% CI 6.6-13.0) and remained low through 24 weeks (15.2%; 95% CI 11.6-19.4). Safety and rCDI rates were consistent across subgroups including age, renal impairment/failure, diabetes, and immunocompromise/immunosuppression.

CONCLUSIONS

VOS was well tolerated and rates of rCDI remained low through week 24 including in those with comorbidities. These data support the potential benefit of VOS following antibiotics to prevent recurrence in high-risk patients.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT03183128 and NCT03183141.

Healthcare as a driver, reservoir and amplifier of antimicrobial resistance: opportunities for interventions

Antimicrobial resistance (AMR) is a global health challenge that threatens humans, animals and the environment. Evidence is emerging for a role of healthcare infrastructure, environments and patient pathways in promoting and maintaining AMR via direct and indirect mechanisms. Advances in vaccination and monoclonal antibody therapies together with integrated surveillance, rapid diagnostics, targeted antimicrobial therapy and infection control measures offer opportunities to address healthcare-associated AMR risks more effectively. Additionally, innovations in artificial intelligence, data linkage and intelligent systems can be used to better predict and reduce AMR and improve healthcare resilience. In this Review, we examine the mechanisms by which healthcare functions as a driver, reservoir and amplifier of AMR, contextualized within a One Health framework. We also explore the opportunities and innovative solutions that can be used to combat AMR throughout the patient journey. We provide a perspective on the current evidence for the effectiveness of interventions designed to mitigate healthcare-associated AMR and promote healthcare resilience within high-income and resource-limited settings, as well as the challenges associated with their implementation.

Antibiotic Resistance in the Elderly: Mechanisms, Risk Factors, and Solutions

Antibiotic resistance presents a critical challenge in healthcare, particularly among the elderly, where multidrug-resistant organisms (MDROs) contribute to increased morbidity, mortality, and healthcare costs. This review focuses on the mechanisms underlying resistance in key bacterial pathogens and highlights how aging-related factors like immunosenescence, frailty, and multimorbidity increase the burden of infections from MDROs in this population. Novel strategies to mitigate resistance include the development of next-generation antibiotics like teixobactin and cefiderocol, innovative therapies such as bacteriophage therapy and antivirulence treatments, and the implementation of antimicrobial stewardship programs to optimize antibiotic use. Furthermore, advanced molecular diagnostic techniques, including nucleic acid amplification tests and next-generation sequencing, allow for faster and more precise identification of resistant pathogens. Vaccine development, particularly through innovative approaches like multi-epitope vaccines and nanoparticle-based platforms, holds promise in preventing MDRO infections among the elderly. The role of machine learning (ML) in predicting resistance patterns and aiding in vaccine and antibiotic development is also explored, offering promising solutions for personalized treatment and prevention strategies in the elderly. By integrating cutting-edge diagnostics, therapeutic innovations, and ML-based approaches, this review underscores the importance of multidisciplinary efforts to address the global challenge of antibiotic resistance in aging populations.

Structure-Activity Relationship of Inositol Thiophosphate Analogs as Allosteric Activators of Clostridioides difficile Toxin B

Clostridioides difficile is a bacterium that causes life-threatening intestinal infections. Infection symptoms are mediated by a toxin secreted by the bacterium. Toxin pathogenesis is modulated by the intracellular molecule, inositol-hexakisphosphate (IP6). IP6 binds to a cysteine protease domain (CPD) on the toxin, inducing autoproteolysis, which liberates a virulence factor in the cell cytosol. We developed second-generation IP6 analogs designed to induce autoproteolysis in the gut lumen, prior to toxin uptake, circumventing pathogenesis. We synthesized a panel of thiophosphate-/sulfate-containing IP6 analogs and characterized their toxin binding affinity, autoproteolysis induction, and cation interactions. Our top candidate was soluble in extracellular cation concentrations, unlike IP6. The IP6 analogs were more negatively charged than IP6, which improved affinity and stabilization of the CPD, enhancing toxin autoproteolysis. Our data illustrate the optimization of IP6 with thiophosphate biomimetic which are more capable of inducing toxin autoproteolysis than the native ligand, warranting further studies in vivo.

Fecal microbiota spores, live-brpk (VOWST™/VOS) for prevention of recurrent Clostridioides difficile infection

Clostridioides difficile infection (CDI) is a health crisis comprising a majority of healthcare-associated infections and is now being seen in the community. Persistent dysbiosis despite treatment with standard-of-care antibiotics increases risk of recurrent infections. Fecal microbiota transplantation has been an effective way of addressing dysbiosis, but the studies have lacked standardization, which makes outcome and safety data difficult to interpret. Standardized microbiome therapies have demonstrated efficacy and safety for recurrent CDI and have been approved to prevent recurrent infection. In this review, we discuss the data behind and the practice use of fecal microbiota spores, live-brpk (VOWST™ / VOS), a US FDA approved live biotherapeutic for the prevention of recurrent CDI.

Loratadine as an Anti-inflammatory Agent Against Clostridium difficile Toxin B

BACKGROUND

Clostridium difficile infection (CDI) is a debilitating nosocomial infection. C. difficile produces toxins A and B, which cause inflammation. Existing therapies have issues with recurrence, cost, and safety. We aim to discover a safe, effective, and economical nonmicrobiological therapeutic approach against CDI.

METHODS

We included human primary peripheral blood mononuclear cells (PBMCs), fresh human colonic explants, and humanized HuCD34-NCG mice. Toxin A+B+ VPI 10463 and A-B+ ribotype 017 C. difficile strains were used. We used single-cell RNA profiling and high-throughput screening to find actionable toxin B-dependent pathways in PBMCs.

RESULTS

Histamine 1 receptor-related drugs were found among the hit compounds that reversed toxin-mediated macrophage inflammatory protein (MIP) 1α expression in PBMCs. We identified loratadine as the safest representative antihistamine for therapeutic development. Loratadine inhibited toxin B-induced MIP-1α secretion in fresh human colonic tissues. Oral loratadine (10 mg/kg/d) maintained survival, inhibited intestinal CCl3 messenger RNA expression, and prevented vancomycin-associated recurrence in the VPI 10463-infected mice and ribotype 017-infected hamsters. Splenocytes from loratadine-treated mice conferred anti-inflammatory effects to the VPI 10463-infected T/B-cell--deficient Rag-/- mice. Oral loratadine suppressed human MIP-1α expression in monocytes/macrophages in toxin B-expressing ribotype 017-infected humanized HuCD34-NCG mice.

CONCLUSIONS

Loratadine may be repurposed to optimize existing therapies against CDI.

Adaptation mechanisms of Clostridioides difficile to auranofin and its impact on human gut microbiota

Auranofin (AF), a former rheumatoid polyarthritis treatment, gained renewed interest for its use as an antimicrobial. AF is an inhibitor of thioredoxin reductase (TrxB), a thiol and protein repair enzyme, with an antibacterial activity against several bacteria including C. difficile, an enteropathogen causing post-antibiotic diarrhea. Several studies demonstrated the effect of AF on C. difficile physiology, but the crucial questions of resistance mechanisms and impact on microbiota remain unaddressed. We explored potential resistance mechanisms by studying the impact of TrxB multiplicity and by generating and characterizing adaptive mutations. We showed that if mutants inactivated for trxB genes have a lower MIC of AF, the number of TrxBs naturally present in clinical strains does not impact the MIC. All stable mutations isolated after AF long-term exposure were in the anti-sigma factor of σB and strongly affect physiology. Finally, we showed that AF has less impact on human gut microbiota than vancomycin.