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

Review article: The epidemiology and management of Clostridioides difficile infection-A clinical update

BACKGROUND

Clostridioides difficile is the most common cause of healthcare-associated infection, and severe cases can result in significant complications. While anti-microbial therapy is central to infection management, adjunctive therapies may be utilised as preventative strategies.

AIM

This article aims to review updates in the epidemiology, diagnosis, and management, including treatment and prevention, of C. difficile infections.

METHODS

A narrative review was performed to evaluate the current literature between 1986 and 2023.

RESULTS

The incidence of C. difficile infection remains significantly high in both hospital and community settings, though with an overall decline in recent years and similar surveillance estimates globally. Vancomycin and fidaxomicin remain the first line antibiotics for treatment of non-severe C. difficile infection, though due to lower recurrence rates, infectious disease society guidelines now favour use of fidaxomicin. Faecal microbiota transplantation should still be considered to prevent recurrent C. difficile infection. However, in the past year the field has had a significant advancement with the approval of the first two live biotherapeutic products-faecal microbiota spores-live brpk, an oral capsule preparation, and faecal microbiota live-jslm-both indicated for the prevention of recurrent C. difficile infection, with additional therapies on the horizon.

CONCLUSION

Although the prevalence of C. difficile infection remains high, there have been significant advances in the development of novel therapeutics and preventative measures following changes in recent practice guidelines, and will continue to evolve in the future.

An insight into the last 5-year patents on Porphyromonas gingivalis and Streptococcus mutans, the pivotal pathogens in the oral cavity

INTRODUCTION

The oral cavity harbors an extensive array of over 700 microorganisms, forming the most complex biome of the entire human body, with bacterial species being the most abundant. Oral diseases, e.g. periodontitis and caries, are strictly associated with bacterial dysbiosis. Porphyromonas gingivalis and Streptococcus mutans stand out among bacteria colonizing the oral cavity.

AREAS COVERED

After a brief overview of the bacterial populations in the oral cavity and their roles in regulating (flora) oral cavity or causing diseases like periodontal and cariogenic pathogens, we focused our attention on P. gingivalis and S. mutans, searching for the last-5-year patents dealing with the proposal of new strategies to fight their infections. Following the PRISMA protocol, we filtered the results and analyzed over 100 applied/granted patents, to provide an in-depth insight into this R&D scenario.

EXPERT OPINION

Several antibacterial proposals have been patented in this period, from both chemical - peptides and small molecules - and biological - probiotics and antibodies - sources, along with natural extracts, polymers, and drug delivery systems. Most of the inventors are from China and Korea and their studies also investigated anti-inflammatory and antioxidant effects, being beneficial to oral health through a prophylactic, protective, or curative effect.

Colorectal Disease and the Gut Microbiome: What a Surgeon Needs to Know

The gut microbiome is defined as the microorganisms that reside within the gastrointestinal tract and produce a variety of metabolites that impact human health. These microbes play an intricate role in human health, and an imbalance in the gut microbiome, termed gut dysbiosis, has been implicated in the development of varying diseases. The purpose of this review is to highlight what is known about the microbiome and its impact on colorectal cancer, inflammatory bowel disease, constipation, Clostridioides difficile infection, the impact of bowel prep, and anastomotic leaks.

Microbiota restoration therapies for recurrent Clostridioides difficile infection reach an important new milestone

Microbiota restoration therapy has become a standard treatment for recurrent Clostridioides difficile infection (rCDI). In this article, we review the studies supporting the licensure of two live biotherapeutic products (LBPs) designed to prevent rCDI and to provide clinicians with a perspective on their differences. PubMed was reviewed on 1 October 2023, for all papers published concerning the current Food and Drug Administration allowance of the use of fecal microbiota transplantation (FMT) and the studies that led to the licensure of RBX2660 (REBYOTA™), generic name, fecal microbiota, live-jslm, and SER-109 (VOWST™), generic name, fecal microbiota spores, live-brpk. OpenBiome continues to produce fecal products for patients with rCDI at their treatment sites, and the American Gastroenterology Association has a National Registry focused on long-term safety of administering fecal microbiota products. The science behind the licensing of fecal microbiota, live-jslm, a consortium of fecal anaerobes found in stool augmented with strains of Bacteroidetes and fecal microbiota spores, live-brpk, a mixture of 50 species of purified Firmicutes spores is reviewed. Both products appear to be safe in clinical trials and effective in reducing rCDI episodes by mechanisms established for FMT, including normalization of α- and β-diversity of the microbiome and by increasing fecal secondary bile acids. The different makeup of the two LBPs suggests that rCDI responds to a variety of engrafting microbiota which explains why nearly all donors in FMT of rCDI are generally effective. Fecal microbiota, live-jslm has also been shown to successfully treat rCDI in elderly patients with advanced comorbidities. With the licensure of two novel LBPs, we are entering a new phase of microbiota replacement therapy. Having standardized manufacturing and proper monitoring of products, harnessing the microbiome to control and prevent disease has a new beginning.

Microbiota-Based Live Biotherapeutic Products for Clostridioides Difficile Infection- The Devil is in the Details

Clostridioides difficile infection (CDI) remains a significant contributor to healthcare costs and morbidity due to high rates of recurrence. Currently, available antibiotic treatment strategies further disrupt the fecal microbiome and do not address the alterations in commensal flora (dysbiosis) that set the stage for CDI. Advances in microbiome-based research have resulted in the development of new agents, classified as live biotherapeutic products (LBPs), for preventing recurrent CDI (rCDI) by restoring eubiosis. Prior to the LBPs, fecal microbiota transplantation (FMT) was available for this purpose; however, lack of large-scale availability and safety concerns have remained barriers to its widespread use. The LBPs are an exciting development, but questions remain. Some are derived directly from human stool while other developmental products contain a defined microbial consortium manufactured ex vivo, and they may be composed of either living bacteria or their spores, making it difficult to compare members of this heterogenous drug class to one another. None have been studied head-to head or against FMT in preventing rCDI. As a class, they have considerable variability in their biologic composition, biopharmaceutic science, route of administration, stages of development, and clinical trial data. This review will start by explaining the role of dysbiosis in CDI, then give the details of the biopharmaceutical components for the LBPs which are approved or in development including how they differ from FMT and from one another. We then discuss the clinical trials of the LBPs currently approved for rCDI and end with the future clinical directions of LBPs beyond C. difficile.

Gut Microbiota-Gut Metabolites and Clostridioides difficile Infection: Approaching Sustainable Solutions for Therapy

Clostridioides difficile (C. difficile) infection (CDI) is the most common hospital-acquired infection. With the combination of a high rate of antibiotic resistance and recurrence, it has proven to be a debilitating public health threat. Current treatments for CDI include antibiotics and fecal microbiota transplantation, which contribute to recurrent CDIs and potential risks. Therefore, there is an ongoing need to develop new preventative treatment strategies for CDI. Notably, gut microbiota dysbiosis is the primary risk factor for CDI and provides a promising target for developing novel CDI therapy approaches. Along with gut microbiota dysbiosis, a reduction in important gut metabolites like secondary bile acids and short-chain fatty acids (SCFAs) were also seen in patients suffering from CDI. In this review study, we investigated the roles and mechanisms of gut microbiota and gut microbiota-derived gut metabolites, especially secondary bile acids and SCFAs in CDI pathogenesis. Moreover, specific signatures of gut microbiota and gut metabolites, as well as different factors that can modulate the gut microbiota, were also discussed, indicating that gut microbiota modulators like probiotics and prebiotics can be a potential therapeutic strategy for CDI as they can help restore gut microbiota and produce gut metabolites necessary for a healthy gut. The understanding of the associations between gut microbiota-gut metabolites and CDI will allow for developing precise and sustainable approaches, distinct from antibiotics and fecal transplant, for mitigating CDI and other gut microbiota dysbiosis-related diseases.

Bile Acids and Short-Chain Fatty Acids Are Modulated after Onion and Apple Consumption in Obese Zucker Rats

Gut microorganisms are involved in the development and severity of different cardiovascular diseases, and increasing evidence has indicated that dietary fibre and polyphenols can interact with the intestinal microbiota. The study objective was to investigate the effect of onion and apple intake on the major types of microbial-derived molecules, such as short-chain fatty acids (SCFAs) and bile acids (BAs). Obese Zucker rats were randomly assigned (n = eight rats/group) to a standard diet (OC), a standard diet/10% onion (OO), or a standard diet/10% apple (OA). Lean Zucker rats fed a standard diet served as a lean control (LC) group. Faecal samples were collected at baseline, and 8 weeks later, the composition of the microbial community was measured, and BA and SCFA levels were determined using high-performance liquid chromatography-mass spectrometry (HPLC-MS) and gas chromatography-mass spectrometry (GC-MS), respectively. Rats fed onion- and apple-enriched diets had increased abundance of beneficial bacteria, such as Bifidobacterium spp. and Lactobacillus spp., enhanced SCFAs (acetic, propionic, isobutyric, and valeric acids), decreased excretion of some BAs, mainly of the primary (CA, α-MCA, and β-MCA) and secondary type (ω-MCA, HDCA, NCA, DCA, and LCA), and increased amount of taurine- and glycine-conjugated BAs compared to the OC group. The contribution of specific bioactive compounds and their metabolites in the regulation of the microbiome and the pathways linked to SCFA and BA formation and their relationship with some diseases needs further research.

Clostridioides difficile Infection: Landscape and Microbiome Therapeutics

Clostridioides difficile infection (CDI) is the leading cause of hospital-acquired diarrhea and is common in the community. Both younger individuals who may be healthy otherwise and older individuals with comorbid conditions are at risk for developing CDI, with the predominant risk factor being antibiotic use. Unlike other gastrointestinal infections, CDI is not self-limited, requires antimicrobial therapy, and tends to recur at high rates even without additional risk factor exposure. The goals of CDI management include controlling active symptoms and using a recurrence prevention strategy such as a narrow-spectrum antibiotic, tapered and pulsed regimens, antibody- based therapies (directed against toxin B), or microbiome restoration. In recent years, fecal microbiota transplantation (FMT) has been the most used modality to prevent recurrent CDI with high cure rates. Heterogeneity, lack of scalability, and serious adverse events from FMT have led to development of standardized microbiota restoration therapies (MRTs). The US Food and Drug Administration has approved 2 stool-derived MRTs for prevention of recurrent CDI: fecal microbiota, live-jslm, an enema-based therapy; and fecal microbiota spores, live-brpk, an oral therapy. A phase 3 trial for a synthetic oral MRT is underway. This article outlines the pathophysiology and treatment of CDI, focusing primarily on the gut microbiome and standardized MRTs.

Beneficial effects of fecal microbiota transplantation in recurrent Clostridioides difficile infection

Fecal microbiota transplantation (FMT) is highly effective in preventing recurrent Clostridioides difficile infection (rCDI). However, the mechanisms underpinning its clinical efficacy are incompletely understood. Herein, we provide an overview of rCDI pathogenesis followed by a discussion of potential mechanisms of action focusing on the current understanding of trans-kingdom microbial, metabolic, immunological, and epigenetic mechanisms. We then outline the current research gaps and offer methodological recommendations for future studies to elevate the quality of research and advance knowledge translation. By combining interventional trials with multiomics technology and host and environmental factors, analyzing longitudinally collected biospecimens will generate results that can be validated with animal and other models. Collectively, this will confirm causality and improve translation, ultimately to develop targeted therapies to replace FMT.

Shengjiang Xiexin Decoction ameliorates antibiotic-associated diarrhea by altering the gut microbiota and intestinal metabolic homeostasis

BACKGROUND

Antibiotic-associated diarrhea (AAD) has had a significant increase in the last years, with limited available effective therapies. Shengjiang Xiexin Decoction (SXD), a classic traditional Chinese medicine formula for treating diarrhea, is a promising alternative for reducing the incidence of AAD.

PURPOSE

This study aimed to explore the therapeutic effect of SXD on AAD and to investigate its potential therapeutic mechanism by integrated analysis of the gut microbiome and intestinal metabolic profile.

METHODS

16S rRNA sequencing analysis of the gut microbiota and untargeted-metabolomics analysis of feces were performed. The mechanism was further explored by fecal microbiota transplantation (FMT).

RESULTS

SXD could effectively ameliorate AAD symptoms and restore intestinal barrier function. In addition, SXD could significantly improve the diversity of the gut microbiota and accelerate the recovery of the gut microbiota. At the genus level, SXD significantly increased the relative abundance of Bacteroides spp (p < 0.01) and decreased the relative abundance of Escherichia_Shigela spp (p < 0.001). Untargeted metabolomics showed that SXD significantly improved gut microbiota and host metabolic function, particularly bile acid metabolism and amino acid metabolism.

CONCLUSION

This study demonstrated that SXD could extensively modulate the gut microbiota and intestinal metabolic homeostasis to treat AAD.

In Silico Analysis of Changes in Predicted Metabolic Capabilities of Intestinal Microbiota after Fecal Microbial Transplantation for Treatment of Recurrent Clostridioides difficile Infection

IMPORTANCE

Although highly effective in treating recurrent Clostridioides difficile infection (RCDI), the mechanisms of action of fecal microbial transplantation (FMT) are not fully understood.

AIM

The aim of this study was to explore microbially derived products or pathways that could contribute to the therapeutic efficacy of FMT.

METHODS

Stool shotgun metagenomic sequencing data from 18 FMT-treated RCDI patients at 4 points in time were used for the taxonomic and functional profiling of their gut microbiome. The abundance of the KEGG orthology (KO) groups was subjected to univariate linear mixed models to assess the significance of the observed differences between 0 (pre-FMT), 1, 4, and 12 weeks after FMT.

RESULTS

Of the 59,987 KO groups identified by shotgun metagenomic sequencing, 27 demonstrated a statistically significant change after FMT. These KO groups are involved in many cellular processes, including iron homeostasis, glycerol metabolism, and arginine regulation, all of which have been implicated to play important roles in bacterial growth and virulence in addition to modulating the intestinal microbial composition.

CONCLUSION

Our findings suggest potential changes in key KO groups post-FMT, which may contribute to FMT efficacy beyond the restored microbial composition/diversity and metabolism of bile acids and short-chain fatty acids. Future larger studies that include a fecal metabolomics analysis combined with animal model validation work are required to further elucidate the molecular mechanisms.

Cytotoxic synergism of Clostridioides difficile toxin B with proinflammatory cytokines in subjects with inflammatory bowel diseases

Clostridioides difficile (C. difficile) is progressively colonizing humans and animals living with humans. During this process, hypervirulent strains and mutated toxin A and B of C. difficile (TcdA and TcdB) are originating and developing. While in healthy subjects colonization by C. difficile becomes a risk after the use of antibiotics that alter the microbiome, other categories of people are more susceptible to infection and at risk of relapse, such as those with inflammatory bowel disease (IBD). Recent in vitro studies suggest that this increased susceptibility could be due to the strong cytotoxic synergism between TcdB and proinflammatory cytokines the tumor necrosis factor-alpha and interferon-gamma (CKs). Therefore, in subjects with IBD the presence of an inflammatory state in the colon could be the driver that increases the susceptibility to C. difficile infection and its progression and relapses. TcdB is internalized in the cell via three receptors: chondroitin sulphate proteoglycan 4; poliovirus receptor-like 3; and Wnt receptor frizzled family. Chondroitin sulphate proteoglycan 4 and Wnt receptor frizzled family are involved in cell death by apoptosis or necrosis depending on the concentration of TcdB and cell types, while poliovirus receptor-like 3 induces only necrosis. It is possible that cytokines could also induce a greater expression of receptors for TcdB that are more involved in necrosis than in apoptosis. Therefore, in subjects with IBD there are the conditions: (1) For greater susceptibility to C. difficile infection, such as the inflammatory state, and abnormalities of the microbiome and of the immune system; (2) for the enhancement of the cytotoxic activity of TcdB +Cks; and (3) for a greater expression of TcdB receptors stimulated by cytokines that induce cell death by necrosis rather than apoptosis. The only therapeutic approach currently possible in IBD patients is monitoring of C. difficile colonization for interventions aimed at reducing tumor necrosis factor-alpha and interferon-gamma levels when the infection begins. The future perspective is to generate bacteriophages against C. difficile for targeted therapy.

Human Fecal Bile Acid Analysis after Investigational Microbiota-Based Live Biotherapeutic Delivery for Recurrent Clostridioides difficile Infection

Microbiome-based therapeutics are increasingly evaluated as a strategy to reduce recurrent Clostridioides difficile infection (rCDI), with proposed mechanisms including restoration of the microbiota and microbiota-mediated functions, such as bile acid (BA) metabolism. This study reports a quantitative and sensitive assay for targeted metabolomic assessment, and the application of the assay to profile BA composition in a Phase 2 trial of the investigational microbiota-based live biotherapeutic RBX2660 for reduction of rCDI. A liquid chromatography tandem mass spectrometry method was developed to extract and quantify 35 BAs from 113 participant stool samples from 27 RBX2660-treated rCDI participants in the double-blinded, placebo-controlled clinical trial. The results demonstrate a high-confidence assay as represented by sensitivity, linearity, accuracy, and precision. Furthermore, the assay enabled the observation of primary BAs as the dominant BA species at baseline in stool samples from clinical trial participants, consistent with the expected loss of commensals after broad-spectrum antibiotic treatment. After RBX2660 administration, there was a significant drop in primary BAs concurrent with increased secondary BAs that sustained through 24 months post-RBX2660. Taken together, we describe a robust assay that demonstrates altered BA metabolism in rCDI patients treated with RBX2660 administration.

Bile acids as modulators of gut microbiota composition and function

Changes in the composition of gut-associated microbial communities are associated with many human illnesses, but the factors driving dysbiosis remain incompletely understood. One factor governing the microbiota composition in the gut is bile. Bile acids shape the microbiota composition through their antimicrobial activity and by activating host signaling pathways that maintain gut homeostasis. Although bile acids are host-derived, their functions are integrally linked to bacterial metabolism, which shapes the composition of the intestinal bile acid pool. Conditions that change the size or composition of the bile acid pool can trigger alterations in the microbiota composition that exacerbate inflammation or favor infection with opportunistic pathogens. Therefore, manipulating the composition or size of the bile acid pool might be a promising strategy to remediate dysbiosis.

Assessing the clinical value of faecal bile acid profiling to predict recurrence in primary Clostridioides difficile infection

BACKGROUND

Factors influencing recurrence risk in primary Clostridioides difficile infection (CDI) are poorly understood, and tools predicting recurrence are lacking. Perturbations in bile acids (BAs) contribute to CDI pathogenesis and may be relevant to primary disease prognosis.

AIMS

To define stool BA dynamics in patients with primary CDI and to explore signatures predicting recurrence METHODS: Weekly stool samples were collected from patients with primary CDI from the last day of anti-CDI therapy until recurrence or, otherwise, through 8 weeks post-completion. Ultra-high performance liquid chromatography-mass spectrometry was used to profile BAs. Stool bile salt hydrolase (BSH) activity was measured to determine primary BA bacterial deconjugation capacity. Multivariate and univariate models were used to define differential BA trajectories in patients with recurrence versus those without, and to assess faecal BAs as predictive markers for recurrence.

RESULTS

Twenty (36%) of 56 patients (median age: 57, 64% male) had recurrence; 80% of recurrences occurred within the first 9 days post-antibiotic treatment. Principal component analysis of stool BA profiles demonstrated clustering by recurrence status and post-treatment timepoint. Longitudinal faecal BA trajectories showed recovery of secondary BAs and their derivatives only in patients without recurrence. BSH activity increased over time only among non-relapsing patients (β = 0.056; likelihood ratio test p = 0.018). A joint longitudinal-survival model identified five stool BAs with area under the receiver operating characteristic curve >0.73 for predicting recurrence within 9 days post-CDI treatment.

CONCLUSIONS

Gut BA metabolism dynamics differ in primary CDI patients between those developing recurrence and those who do not. Individual BAs show promise as potential novel biomarkers to predict CDI recurrence.

The role of the gut microbiome in colonization resistance and recurrent Clostridioides difficile infection

The species composition of the human gut microbiota is related to overall health, and a healthy gut microbiome is crucial in maintaining colonization resistance against pathogens. Disruption of gut microbiome composition and functionality reduces colonization resistance and has been associated with several gastrointestinal and non-gastrointestinal diseases. One prime example is Clostridioides difficile infection (CDI) and subsequent recurrent infections that occur after the development of systemic antibiotic-related dysbiosis. Standard-of-care antibiotics used for both acute and recurrent infections do not address dysbiosis and often worsen the condition. Moreover, monoclonal antibodies, recommended in conjunction with standard-of-care antibiotics for the prevention of recurrent CDI in patients at high risk of recurrence, reduce recurrences but do not address the underlying dysbiosis. Fecal microbiota transplantation (FMT) is an evolving therapeutic strategy in which microbes are harvested from healthy donor stool and transplanted into the gut of a recipient to restore the gut microbiome. Although effective in the prevention of recurrent CDI, some existing challenges include screening and the standardization of stool acquisition and processing. Recent safety alerts by the US Food and Drug Administration raised concern about the possibility of transmission of multidrug-resistant organisms or severe acute respiratory syndrome coronavirus 2 via FMT. Increased knowledge that microbes are beneficial in restoring the gut microbiome has led to the clinical development of several newer biotherapeutic formulations that are more regulated than FMT, which may allow for improved restoration of the gut microbiome and prevention of CDI recurrence. This review focuses on mechanisms by which gut microbiome restoration could influence colonization resistance against the pathogen C. difficile.

Plain language summary

The Role of the Gut Microbiome in Clostridioides difficile Infection Introduction: A rich and diverse gut microbiome is key to immune system regulation and colonization resistance against pathogens.A disruption in the gut microbiome composition can make the gut more vulnerable to diseases such as Clostridioides difficile infection (CDI), caused by the bacterium C. difficile.CDI management presents a therapeutic dilemma, as it is usually treated with antibiotics that can treat the infection but also can damage the microbiome.Treatment of CDI using antibiotics can further reduce microbial diversity and deplete beneficial bacteria from the gut leading to a condition called dysbiosis.Antibiotic treatment can be followed by therapies that restore the gut microbiota, boost colonization resistance, and prevent the development of antimicrobial resistance.It is important to evaluate treatment options to determine their safety and effectiveness. Methods: The researchers provided an overview of the mechanisms that the gut microbiome uses to prevent colonization of the gut by pathogens.They subsequently reviewed the efficacy and shortcomings of the following treatments for CDI: - Antibiotics- Monoclonal antibodies- Fecal microbiota transplantation (FMT) Results: Commensal intestinal bacteria prevent colonization of the gut by pathogens using mechanisms such as: - Competition for key nutrients- Production of inhibitory bile acids- Short-chain fatty acid production- Lowering the luminal pH- Production of bacteriocinsAntibiotic therapy is recommended as a standard treatment for CDI. However, patients are vulnerable to recurrent CDI after discontinuation of the therapy.Monoclonal antibodies that inactivate C. difficile toxins may be recommended along with antibiotics to prevent recurrent CDI. However, this approach does not restore the microbiome.FMT is one method of microbial restoration, where stool is harvested from a healthy donor and transplanted into a patient's colon.Although FMT has shown some efficacy in the treatment of recurrent CDI, the procedure is not standardized.Safety concerns have been raised about the possibility of transmission of multidrug-resistant pathogens via FMT. Conclusion: Treatment methods that can efficiently restore the diversity of the gut microbiome are crucial in preventing recurrence of CDI.

Current and Future Therapeutic Options for Irritable Bowel Syndrome with Diarrhea and Functional Diarrhea

Irritable bowel syndrome with diarrhea and functional diarrhea are disorders of gut-brain interaction presenting with chronic diarrhea; they have significant impact on quality of life. The two conditions may exist as a continuum and their treatment may overlap. Response to first-line therapy with antispasmodics and anti-diarrheal agents is variable, leaving several patients with suboptimal symptom control and need for alternative therapeutic options. Our aim was to discuss current pharmacologic options and explore alternative therapeutic approaches and future perspectives for symptom management in irritable bowel syndrome with diarrhea and functional diarrhea. We conducted a search of PubMed, Cochrane, clinicaltrial.gov, major meeting abstracts for publications on current, alternative, and emerging drugs for irritable bowel syndrome with diarrhea and functional diarrhea. Currently approved therapeutic options for patients with first-line refractory irritable bowel syndrome with diarrhea and functional diarrhea include serotonin-3 receptor antagonists, eluxadoline and rifaximin. Despite their proven efficacy, cost and availability worldwide impact their utilization. One-third of patients with disorders of gut-brain interaction with diarrhea have bile acid diarrhea and may benefit from drugs targeting bile acid synthesis and excretion. Further understanding of underlying pathophysiology of irritable bowel syndrome with diarrhea and functional diarrhea related to bile acid metabolism, gastrointestinal transit, and microbiome has led to evaluation of novel therapeutic approaches, including fecal microbiota transplantation and enterobacterial "crapsules". These opportunities to treat disorders of gut-brain interaction with diarrhea should be followed with formal studies utilizing large samples of well-characterized patients at baseline and validated response outcomes as endpoints for regulatory approval.

A systematic review on omics data (metagenomics, metatranscriptomics, and metabolomics) in the role of microbiome in gallbladder disease

Microbiotas are the range of microorganisms (mainly bacteria and fungi) colonizing multicellular, macroscopic organisms. They are crucial for several metabolic functions affecting the health of the host. However, difficulties hamper the investigation of microbiota composition in cultivating microorganisms in standard growth media. For this reason, our knowledge of microbiota can benefit from the analysis of microbial macromolecules (DNA, transcripts, proteins, or by-products) present in various samples collected from the host. Various omics technologies are used to obtain different data. Metagenomics provides a taxonomical profile of the sample. It can also be used to obtain potential functional information. At the same time, metatranscriptomics can characterize members of a microbiome responsible for specific functions and elucidate genes that drive the microbiotas relationship with its host. Thus, while microbiota refers to microorganisms living in a determined environment (taxonomy of microorganisms identified), microbiome refers to the microorganisms and their genes living in a determined environment and, of course, metagenomics focuses on the genes and collective functions of identified microorganisms. Metabolomics completes this framework by determining the metabolite fluxes and the products released into the environment. The gallbladder is a sac localized under the liver in the human body and is difficult to access for bile and tissue sampling. It concentrates the bile produced in the hepatocytes, which drains into bile canaliculi. Bile promotes fat digestion and is released from the gallbladder into the upper small intestine in response to food. Considered sterile originally, recent data indicate that bile microbiota is associated with the biliary tract’s inflammation and carcinogenesis. The sample size is relevant for omic studies of rare diseases, such as gallbladder carcinoma. Although in its infancy, the study of the biliary microbiota has begun taking advantage of several omics strategies, mainly based on metagenomics, metabolomics, and mouse models. Here, we show that omics analyses from the literature may provide a more comprehensive image of the biliary microbiota. We review studies performed in this environmental niche and focus on network-based approaches for integrative studies.

Functional and Metagenomic Evaluation of Ibezapolstat for Early Evaluation of Anti-Recurrence Effects in Clostridioides difficile Infection

Reduction of Clostridioides difficile infection (CDI) recurrence is an essential endpoint for CDI-directed antibiotic development that is often not evaluated until Phase III trials. The purpose of this project was to use a functional and metagenomic approach to predict the potential anti-CDI recurrence effect of ibezapolstat, a DNA polymerase IIIC inhibitor, in clinical development for CDI. As part of the Phase I ibezapolstat clinical study, stool samples were collected from 22 healthy volunteers, who were given either ibezapolstat or vancomycin. Stool samples were evaluated for microbiome changes and bile acid concentrations. Ibezapolstat 450 mg and vancomycin, but not ibezapolstat 300 mg, showed statistically significant changes in alpha diversity over time compared to that of a placebo. Beta diversity changes confirmed that microbiota were significantly different between study groups. Vancomycin had a more wide-ranging effect on the microbiome, characterized by an increased proportion of Gammaproteobacteria. Ibezapolstat demonstrated an increased proportion of Actinobacteria, including the Bifidobacteriaceae family. Using a linear regression analysis, vancomycin was associated with significant increases in primary bile acids as well as primary:secondary bile acid ratios. An overabundance of Enterobacteriaceae was most highly correlated with primary bile acid concentrations (r = 0.63; P < 0.0001). Using Phase I healthy volunteer samples, beneficial changes suggestive of a lower risk of CDI recurrence were associated with ibezapolstat compared to vancomycin. This novel omics approach may allow for better and earlier prediction of anti-CDI recurrence effects for antibiotics in the clinical development pipeline.

The Emerging Role of Bile Acids in the Pathogenesis of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic immune-mediated inflammatory disorder of the gastrointestinal tract that arises due to complex interactions between host genetic risk factors, environmental factors, and a dysbiotic gut microbiota. Although metagenomic approaches have attempted to characterise the dysbiosis occurring in IBD, the precise mechanistic pathways interlinking the gut microbiota and the intestinal mucosa are still yet to be unravelled. To deconvolute these complex interactions, a more reductionist approach involving microbial metabolites has been suggested. Bile acids have emerged as a key class of microbiota-associated metabolites that are perturbed in IBD patients. In recent years, metabolomics studies have revealed a consistent defect in bile acid metabolism with an increase in primary bile acids and a reduction in secondary bile acids in IBD patients. This review explores the evolving evidence that specific bile acid metabolites interact with intestinal epithelial and immune cells to contribute to the inflammatory milieu seen in IBD. Furthermore, we summarise evidence linking bile acids with intracellular pathways that are known to be relevant in IBD including autophagy, apoptosis, and the inflammasome pathway. Finally, we discuss how novel experimental and bioinformatics approaches could further advance our understanding of the role of bile acids and inform novel therapeutic strategies in IBD.

Impact of Primary and Secondary Bile Acids on Clostridioides difficile Infection

Primary bile acids (BAs), synthesized from cholesterol in the liver, after their secretion with bile into the intestinal lumen, are transformed by gut microbiota to secondary BAs. As natural detergents, BAs play a key role in the digestion and absorption of lipids and liposoluble vitamins. However, they have also been recognized as important signaling molecules involved in numerous metabolic processes. The close bidirectional interactions between BAs and gut microbiota occur since BAs influence microbiota composition, whereas microbiota determines BA metabolism. In particular, it is well established that BAs modulate Clostridioides difficile life cycle in vivo. C. difficile is a cause of common nosocomial infections that have become a growing concern. The aim of this review is to summarize the current knowledge regarding the impact of BAs on the pathogenesis, prevention, and treatment of C. difficile infection.

Multi-omics investigation of Clostridioides difficile-colonized patients reveals pathogen and commensal correlates of C. difficile pathogenesis

Clostridioides difficile infection (CDI) imposes a substantial burden on the health care system in the United States. Understanding the biological basis for the spectrum of C. difficile-related disease manifestations is imperative to improving treatment and prevention of CDI. Here, we investigate the correlates of asymptomatic C. difficile colonization using a multi-omics approach. We compared the fecal microbiome and metabolome profiles of patients with CDI versus asymptomatically colonized patients, integrating clinical and pathogen factors into our analysis. We found that CDI patients were more likely to be colonized by strains with the binary toxin (CDT) locus or strains of ribotype 027, which are often hypervirulent. We find that microbiomes of asymptomatically colonized patients are significantly enriched for species in the class Clostridia relative to those of symptomatic patients. Relative to CDI microbiomes, asymptomatically colonized patient microbiomes were enriched with sucrose degradation pathways encoded by commensal Clostridia, in addition to glycoside hydrolases putatively involved in starch and sucrose degradation. Fecal metabolomics corroborates the carbohydrate degradation signature: we identify carbohydrate compounds enriched in asymptomatically colonized patients relative to CDI patients. Further, we reveal that across C. difficile isolates, the carbohydrates sucrose, rhamnose, and lactulose do not serve as robust growth substrates in vitro, consistent with their enriched detection in our metagenomic and metabolite profiling of asymptomatically colonized individuals. We conclude that pathogen genetic variation may be strongly related to disease outcome. More interestingly, we hypothesize that in asymptomatically colonized individuals, carbohydrate metabolism by other commensal Clostridia may prevent CDI by inhibiting C. difficile proliferation. These insights into C. difficile colonization and putative commensal competition suggest novel avenues to develop probiotic or prebiotic therapeutics against CDI.

Long-Term Safety Following Faecal Microbiota Transplantation as a Treatment for Recurrent Clostridioides difficile Infection Compared with Patients Treated with a Fixed Bacterial Mixture: Results from a Retrospective Cohort Study

Faecal microbiota transplantation (FMT) is the recommended treatment for recurrent C. difficile infection (rCDI) following a second recurrence. FMT is considered safe in the short term when procedures for the screening of donors and transferred material are followed. However, the long-term safety profile of FMT treatment is largely unknown. In a retrospective cohort study, we assessed the long-term safety of patients treated for rCDI with FMT or a fixed bacterial mixture, rectal bacteriotherapy (RBT). The overall survival, risk of hospital admission, onset of certain pre-specified diseases (cancer, diabetes mellitus, hypertension and inflammatory bowel disease) and risk of being diagnosed with a multidrug-resistant organism were assessed by undertaking a review of the treated patients’ medical records for up to five years following treatment. A total of 280 patients were treated for rCDI with FMT (n = 145) or RBT (n = 135) between 2016 and 2020. In the five years following treatment, there were no differences in survival (adjusted hazard ratio (aHR) 1.03; 95% CI 0.68–1.56), p = 0.89), risk of hospital admission ((aHR 0.92; 95% CI 0.72–1.18), p = 0.5) or onset of any of the analysed diseases. In conclusion, FMT was not associated with increased mortality, risk of hospital admission or onset of disease following treatment when compared with RBT.

Functional profile of host microbiome indicates Clostridioides difficile infection

Clostridioides difficile infection (CDI) is a gastro-intestinal (GI) infection that illustrates how perturbations in symbiotic host-microbiome interactions render the GI tract vulnerable to the opportunistic pathogens. CDI also serves as an example of how such perturbations could be reversed via gut microbiota modulation mechanisms, especially fecal microbiota transplantation (FMT). However, microbiome-mediated diagnosis of CDI remains understudied. Here, we evaluated the diagnostic capabilities of the fecal microbiome on the prediction of CDI. We used the metagenomic sequencing data from ten previous studies, encompassing those acquired from CDI patients treated by FMT, CDI-negative patients presenting other intestinal health conditions, and healthy volunteers taking antibiotics. We designed a hybrid species/function profiling approach that determines the abundances of microbial species in the community contributing to its functional profile. These functionally informed taxonomic profiles were then used for classification of the microbial samples. We used logistic regression (LR) models using these features, which showed high prediction accuracy (with an average A U C ≥ 0.91 ), substantiating that the species/function composition of the gut microbiome has a robust diagnostic prediction of CDI. We further assessed the confounding impact of antibiotic therapy on CDI prediction and found that it is distinguishable from the CDI impact. Finally, we devised a log-odds score computed from the output of the LR models to quantify the likelihood of CDI in a gut microbiome sample and applied it to evaluating the effectiveness of FMT based on post-FMT microbiome samples. The results showed that the gut microbiome of patients exhibited a gradual but steady improvement after receiving successful FMT, indicating the restoration of the normal microbiome functions.

Invisible steps for a global endemy: molecular strategies adopted by Clostridioides difficile

Clostridioides difficile infection (CDI) is on the rise worldwide and is associated with an increase in deaths and socio-health burden. C. difficile has become ubiquitous in anthropized environments because of the extreme resistance of its spores. Based on the epidemiological data and knowledge of molecular pathogenesis of C. difficile, it is possible to predict its progressive colonization of the human population for the following reasons: first, its global spread is unstoppable; second, the toxins (Tcds) produced by C. difficile, TcdA and TcdB, mainly cause cell death by apoptosis, but the surviving cells acquire a senescence state that favours persistence of C. difficile in the intestine; third, proinflammatory cytokines, tumour necrosis factor-α and interferon-γ, induced during CDI, enhance the cytotoxicity of Tcds and can increase the survival of senescent cells; fourth, Tcds block mobility and induce apoptosis in immune cells recruited at the infection site; and finally, after remission from primary infection or relapse, C. difficile causes functional abnormalities in the enteric glial cell (EGC) network that can result in irritable bowel syndrome, characterized by a latent inflammatory response that contributes to C. difficile survival and enhances the cytotoxic activity of low doses of TcdB, thus favouring further relapses. Since a 'global endemy' of C. difficile seems inevitable, it is necessary to develop an effective vaccine against Tcds for at-risk individuals, and to perform a prophylaxis/selective therapy with bacteriophages highly specific for C. difficile. We must be aware that CDI will become a global health problem in the forthcoming years, and we must be prepared to face this menace.