Efficacy and safety of fecal microbiota transplantation in the treatment of ulcerative colitis: a systematic review and meta-analysis

Mucosal Bacterial Immunotherapy Attenuates the Development of Experimental Colitis by Reducing Inflammation Through the Regulation of Myeloid Cells

Ulcerative colitis is a chronic relapsing-remitting and potentially progressive form of inflammatory bowel disease in which there is extensive inflammation and mucosal damage in the colon and rectum as a result of an abnormal immune response. MV130 is a mucosal-trained immunity-based vaccine used to prevent respiratory tract infections in various clinical settings. Additionally, MV130 may induce innate immune cells that acquire anti-inflammatory properties and promote tolerance, which could have important implications for chronic inflammatory diseases such as ulcerative colitis. This work demonstrated that the prophylactic administration of MV130 substantially mitigated colitis in a mouse model of acute colitis induced by dextran sulphate sodium. MV130 downregulated systemic and local inflammatory responses, maintained the integrity of the intestinal barrier by preserving the enterocyte layer and goblet cells, and reduced the oedema and fibrosis characteristic of the disease. Mechanistically, MV130 significantly reduced the infiltration of neutrophils and pro-inflammatory macrophages in the intestinal wall of the diseased animals and favoured the appearance of M2-polarised macrophages. These results suggest that MV130 might have therapeutic potential for the treatment of ulcerative colitis, reducing the risk of relapse and the progression of disease.

Diet and Microbiota Modulation for Chronic Pouchitis: Evidence, Challenges, and Opportunities

Chronic pouchitis occurs in about 50% of patients undergoing a restorative proctocolectomy for ulcerative colitis. This affection represents a significant therapeutic challenge, particularly for symptomatic patients who do not respond to antibiotic treatments and biologic therapies. Several dietary approaches, including low FODMAP diets and the Mediterranean diet, have shown promising results in improving symptoms and disease burden. The rationale for dietary intervention lies in the reduction in inflammation and modulation of gut microbiota. However, conflicting results and methodological heterogeneity jeopardize the transition of these approaches from the field of research to clinical practice. Together with a nutritional approach, innovative methods of microbiota modulation, including probiotics and fecal microbiota transplantation, are emerging as safe and effective strategies in managing chronic pouchitis. This narrative review analyzes recent advancements in nutritional therapies and microbiota modulation as innovative and complementary approaches for managing chronic pouchitis. After examining microbiota modulation strategies, specifically the effectiveness of probiotics, prebiotics, and fecal microbiota transplantation in restoring microbial diversity and their potential role in alleviating symptoms, the review assesses the available clinical evidence concerning dietary interventions and their impact on gut microbiota. A comprehensive understanding of interventions aimed at modulating the microbiota is crucial for enhancing the effectiveness of conventional therapies. Such strategies may lead to significant improvements in patients' quality of life and their perception of the disease. However, the variability in microbiota composition, the use of restrictive diets, and the lack of standardized methods for evaluating these interventions remain significant challenges. Future research is essential to improve our understanding of the underlying mechanisms and optimize clinical application.

MaAsLin 3: Refining and extending generalized multivariable linear models for meta-omic association discovery

A key question in microbial community analysis is determining which microbial features are associated with community properties such as environmental or health phenotypes. This statistical task is impeded by characteristics of typical microbial community profiling technologies, including sparsity (which can be either technical or biological) and the compositionality imposed by most nucleotide sequencing approaches. Many models have been proposed that focus on how the relative abundance of a feature (e.g. taxon or pathway) relates to one or more covariates. Few of these, however, simultaneously control false discovery rates, achieve reasonable power, incorporate complex modeling terms such as random effects, and also permit assessment of prevalence (presence/absence) associations and absolute abundance associations (when appropriate measurements are available, e.g. qPCR or spike-ins). Here, we introduce MaAsLin 3 (Microbiome Multivariable Associations with Linear Models), a modeling framework that simultaneously identifies both abundance and prevalence relationships in microbiome studies with modern, potentially complex designs. MaAsLin 3 also newly accounts for compositionality with experimental (spike-ins and total microbial load estimation) or computational techniques, and it expands the space of biological hypotheses that can be tested with inference for new covariate types. On a variety of synthetic and real datasets, MaAsLin 3 outperformed current state-of-the-art differential abundance methods in testing and inferring associations from compositional data. When applied to the Inflammatory Bowel Disease Multi-omics Database, MaAsLin 3 corroborated many previously reported microbial associations with the inflammatory bowel diseases, but notably 77% of associations were with feature prevalence rather than abundance. In summary, MaAsLin 3 enables researchers to identify microbiome associations with higher accuracy and more specific association types, especially in complex datasets with multiple covariates and repeated measures.

Fecal Microbiota Transplantation: Indications, Methods, and Challenges

Over the past two decades, as the importance of gut microbiota to human health has become widely known, attempts have been made to treat diseases by correcting dysbiosis of gut microbiota through fecal microbiota transplantation (FMT). Apart from current knowledge of gut microbiota, FMT to treat disease has a long history, from the treatment of food poisoning in the fourth century to the treatment of Clostridioides difficile infections in the twentieth century. In 2013, FMT was recognized as a standard treatment for recurrent C. difficile because it consistently showed high efficacy. Though recurrent C. difficile is the only disease internationally recognized for FMT efficacy, FMT has been tested for other diseases and shown some promising preliminary results. Different FMT methods have been developed using various formulations and administration routes. Despite advances in FMT, some issues remain to be resolved, such as donor screening, manufacturing protocols, and unknown components in the fecal microbiota. In this review, we discuss the mechanisms, clinical indications, methods, and challenges of current FMT. We also discuss the development of alternative therapies to overcome the challenges of FMT.

Case report: Fecal microbiota transplant for Clostridium difficile infection in a pregnant patient with acute severe ulcerative colitis

Ulcerative colitis (UC) is a chronic colonic mucosal inflammation characterized by reduced gut microbial diversity. Patients with UC at pregnancy are prone to suffer from severe disease progression due to the changes of hormone and immune regulation. Fecal microbiota transplant (FMT) is a promising therapy for UC and recurrent Clostridium difficile infection (CDI). However, acute severe ulcerative colitis (ASUC) treatment especially in patients at pregnancy is clinically challenging. Herein, we report a 34-year-old pregnant woman who manifested with numerous bloody stools and markedly elevated serological inflammatory indicators and was diagnosed with ASUC and concurrent CDI. The use of intravenous injection steroids and anti-TNF-α therapy failed to improve her condition. Frozen encapsulated FMT therapy was finally performed to this patient with clearly improved symptoms and indications of safe delivery without UC flares or complications, and markedly increased diversity of the gut microbiota was also shown in this patient after FMT. This report firstly describes FMT as a safe salvage therapy for a pregnant patient with CDI and ASUC refractory to intravenous steroids and anti-TNF therapy.

Editorial for the Special Issue "Gut Dysbiosis: Molecular Mechanisms and Therapies 2.0"

Gut homeostasis depends on maintaining a fine equilibrium between the intestinal epithelial barrier, the microbiota, and the host's immune system [...].

Beyond Antibiotics: What the Future Holds

The prevalence of multidrug resistance (MDR) and stagnant drug-development pipelines have led to the rapid rise of hard-to-treat antibiotic-resistant bacterial infections. These infectious diseases are no longer just nosocomial but are also becoming community-acquired. The spread of MDR has reached a crisis level that needs immediate attention. The landmark O'Neill report projects that by 2050, mortality rates associated with MDR bacterial infections will surpass mortality rates associated with individuals afflicted with cancer. Since conventional antimicrobials are no longer very reliable, it is of great importance to investigate different strategies to combat these life-threatening infectious diseases. Here, we provide an overview of recent advances in viable alternative treatment strategies mainly targeting a pathogen's virulence capability rather than viability. Topics include small molecule and immune inhibition of virulence factors, quorum sensing (QS) quenching, inhibition of biofilm development, bacteriophage-mediated therapy, and manipulation of an individual's macroflora to combat MDR bacterial infections.

Integrating multi-omics to unravel host-microbiome interactions in inflammatory bowel disease

The gut microbiome is crucial for nutrient metabolism, immune regulation, and intestinal homeostasis with changes in its composition linked to complex diseases like inflammatory bowel disease (IBD). Although the precise host-microbial mechanisms in disease pathogenesis remain unclear, high-throughput sequencing have opened new ways to unravel the role of interspecies interactions in IBD. Systems biology-a holistic computational framework for modeling complex biological systems-is critical for leveraging multi-omics datasets to identify disease mechanisms. This review highlights the significance of multi-omics data in IBD research and provides an overview of state-of-the-art systems biology resources and computational tools for data integration. We explore gaps, challenges, and future directions in the research field aiming to uncover novel biomarkers and therapeutic targets, ultimately advancing personalized treatment strategies. While focusing on IBD, the proposed approaches are applicable for other complex diseases, like cancer, and neurodegenerative diseases, where the microbiome has also been implicated.

Long-distance microbial mechanisms impacting cancer immunosurveillance

The intestinal microbiota determines immune responses against extraintestinal antigens, including tumor-associated antigens. Indeed, depletion or gross perturbation of the microbiota undermines the efficacy of cancer immunotherapy, thereby compromising the clinical outcome of cancer patients. In this review, we discuss the long-distance effects of the gut microbiota and the mechanisms governing antitumor immunity, such as the translocation of intestinal microbes into tumors, migration of leukocyte populations from the gut to the rest of the body, including tumors, as well as immunomodulatory microbial products and metabolites. The relationship between these pathways is incompletely understood, in particular the significance of the tumor microbiota with respect to the identification of host and/or microbial products that regulate the egress of bacteria and immunocytes toward tumor beds.

Current Pharmacologic Options and Emerging Therapeutic Approaches for the Management of Ulcerative Colitis: A Narrative Review

Introduction

Ulcerative colitis (UC) is a chronic inflammatory bowel disorder (IBD) with periods of relapse and remission. Current advancements in clinical research have led to the development of more refined and effective medical therapy for UC.

Summary of the Evidence

Traditional therapeutic agents such as 5-aminosalicylates (5-ASAs), sulfasalazine (SASP), corticosteroids, and immunomodulatory drugs have remained the gold standard for decades. However, their novel formulations and dosage regimens have changed their sequences in the medical management of UC. Several other novel drugs are in the final phases of clinical development or have recently received regulatory approval designed to target specific mechanisms involved in the inflammatory cascade for UC.

Conclusions

This narrative review sought to provide a comprehensive knowledge of the potential benefits of standard and emerging therapies, including novel formulations, new chemical entities, and novel therapeutic approaches in managing UC. Keywords: Ulcerative colitis, 5- Aminosalicylic acid, sulfasalazine, corticosteroids, biologics, immunomodulators, novel formulations.

Targeting microbial pathogenic mechanisms as a novel therapeutic strategy in IBD

BACKGROUND

Current therapy for patients suffering from inflammatory bowel diseases (IBD) is focused on inflammatory mechanisms exclusively and not the dysbiotic microbiota, despite growing evidence implicating a role for intestinal microbes in disease.

MAIN BODY

Ongoing research into the intestinal microbiota of IBD patients, using new technologies and/or deeper application of existing ones, has identified a number of microorganisms whose properties and behaviors warrant consideration as causative factors in disease. Such studies have implicated both bacteria and fungi in the pathogenesis of disease. Some of these organisms manifest mechanisms that should be amenable to therapeutic intervention via either conventional or novel drug discovery platforms. Of particular note is a deeper characterization of microbial derived proteases and their destructive potential.

CONCLUSION

Given the steady progress on the mechanistic role of the microbiota in inflammatory diseases, it is reasonable to anticipate a future in which therapeutics targeting microbial derived pathogenic factors play an important role in improving the lives of IBD patients.

DAMP-ing IBD: Extinguish the Fire and Prevent Smoldering

In inflammatory bowel diseases (IBD), the most promising therapies targeting cytokines or immune cell trafficking demonstrate around 40% efficacy. As IBD is a multifactorial inflammation of the intestinal tract, a single-target approach is unlikely to solve this problem, necessitating an alternative strategy that addresses its variability. One approach often overlooked by the pharmaceutically driven therapeutic options is to address the impact of environmental factors. This is somewhat surprising considering that IBD is increasingly viewed as a condition heavily influenced by such factors, including diet, stress, and environmental pollution-often referred to as the "Western lifestyle". In IBD, intestinal responses result from a complex interplay among the genetic background of the patient, molecules, cells, and the local inflammatory microenvironment where danger- and microbe-associated molecular patterns (D/MAMPs) provide an adjuvant-rich environment. Through activating DAMP receptors, this array of pro-inflammatory factors can stimulate, for example, the NLRP3 inflammasome-a major amplifier of the inflammatory response in IBD, and various immune cells via non-specific bystander activation of myeloid cells (e.g., macrophages) and lymphocytes (e.g., tissue-resident memory T cells). Current single-target biological treatment approaches can dampen the immune response, but without reducing exposure to environmental factors of IBD, e.g., by changing diet (reducing ultra-processed foods), the adjuvant-rich landscape is never resolved and continues to drive intestinal mucosal dysregulation. Thus, such treatment approaches are not enough to put out the inflammatory fire. The resultant smoldering, low-grade inflammation diminishes physiological resilience of the intestinal (micro)environment, perpetuating the state of chronic disease. Therefore, our hypothesis posits that successful interventions for IBD must address the complexity of the disease by simultaneously targeting all modifiable aspects: innate immunity cytokines and microbiota, adaptive immunity cells and cytokines, and factors that relate to the (micro)environment. Thus the disease can be comprehensively treated across the nano-, meso-, and microscales, rather than with a focus on single targets. A broader perspective on IBD treatment that also includes options to adapt the DAMPing (micro)environment is warranted.

Current and future microbiome-based therapies in inflammatory bowel disease

PURPOSE OF REVIEW

The role of the microbiome and dysbiosis is increasingly recognized in the pathogenesis of inflammatory bowel disease (IBD). Intestinal microbiota transplant (IMT), previously termed fecal microbiota transplant has demonstrated efficacy in restoring a healthy microbiome and promoting gut health in recurrent Clostridioides difficile infection. Several randomized trials (RCTs) highlighted IMT's potential in treating ulcerative colitis, while smaller studies reported on its application in managing Crohn's disease and pouchitis.

RECENT FINDINGS

This review delves into the current understanding of dysbiosis in IBD, highlighting the distinctions in the microbiota of patients with IBD compared to healthy controls. It explores the mechanisms by which IMT can restore a healthy microbiome and provides a focused analysis of recent RCTs using IMT for inducing and maintaining remission in IBD. Lastly, we discuss the current knowledge gaps that limit its widespread use.

SUMMARY

The body of evidence supporting the use of IMT in IBD is growing. The lack of a standardized protocol impedes its application beyond clinical trials. Further research is needed to identify patient profile and disease phenotypes that benefit from IMT, to delineate key donor characteristics, optimize the delivery route, dosage, and frequency.

Siderophore-harboring gut bacteria and fecal siderophore genes for predicting the responsiveness of fecal microbiota transplantation for active ulcerative colitis

BACKGROUND

Predictive markers for fecal microbiota transplantation (FMT) outcomes in patients with active ulcerative colitis (UC) are poorly defined. We aimed to investigate changes in gut microbiota pre- and post-FMT and to assess the potential value in determining the total copy number of fecal bacterial siderophore genes in predicting FMT responsiveness.

METHODS

Patients with active UC (Mayo score ≥ 3) who had undergone two FMT procedures were enrolled. Fecal samples were collected before and 8 weeks after each FMT session. Patients were classified into clinical response and non-response groups, based on their Mayo scores. The fecal microbiota profile was accessed using metagenomic sequencing, and the total siderophore genes copy number via quantitative real-time polymerase chain reaction. Additionally, we examined the association between the total siderophore genes copy number and FMT efficacy.

RESULTS

Seventy patients with UC had undergone FMT. The clinical response and remission rates were 50% and 10% after the first FMT procedure, increasing to 72.41% and 27.59% after the second FMT. The cumulative clinical response and clinical remission rates were 72.86% and 25.71%. Compared with baseline, the response group showed a significant increase in Faecalibacterium, and decrease in Enterobacteriaceae, consisted with the changes of the total bacterial siderophore genes copy number after the second FMT (1889.14 vs. 98.73 copies/ng, P < 0.01). Virulence factor analysis showed an enriched iron uptake system, especially bacterial siderophores, in the pre-FMT response group, with a greater contribution from Escherichia coli. The total baseline copy number was significantly higher in the response group than non-response group (1889.14 vs. 94.86 copies/ng, P < 0.01). A total baseline copy number cutoff value of 755.88 copies/ng showed 94.7% specificity and 72.5% sensitivity in predicting FMT responsiveness.

CONCLUSIONS

A significant increase in Faecalibacterium, and decrease in Enterobacteriaceae and the total fecal siderophore genes copy number were observed in responders after FMT. The siderophore genes and its encoding bacteria may be of predictive value for the clinical responsiveness of FMT to active ulcerative colitis.

The association between dietary patterns and disease severity in patients with ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory disease involving the colon and rectum. One of the most modifiable environmental factors affecting UC severity is the patient's dietary pattern. Although the role of dietary patterns on UC aetiology has been investigated previously, its relationship with disease severity has not yet been elucidated. This study examined the association between UC patients' dietary patterns and disease severity. This cross-sectional study was conducted in 340 UC patients. Using an FFQ, food patterns were assessed. Twenty-five food categories were categorised based on the similarity of the nutrient composition of the food using the factor analysis method. A simple clinical colitis activity index was used to determine disease severity. Three dietary patterns were identified based on the factor analysis: healthy, unhealthy and Western dietary pattern. After adjusting for potential confounding factors, patients who were in the highest tertile of healthy dietary pattern compared with the lowest tertile were 92 % less likely to have severe UC (OR: 0·08; 95 % CI: 0·03, 0·22). Also, those in the highest tertile of the Western dietary pattern were 3·86 times more likely to have severe UC than those in the lowest tertile (OR: 3·86; 95 % CI: 1·86, 8·00). Even after controlling for confounding variables, unhealthy dietary pattern did not increase the risk of severe UC. Our data indicate the beneficial role of healthy dietary pattern in amelioration of disease severity in UC patients. To confirm this association, more studies are needed, especially prospective cohort studies.

Yerba Mate (Ilex paraguariensis) Reduces Colitis Severity by Promoting Anti-Inflammatory Macrophage Polarization

Yerba Mate (YM) (Ilex paraguariensis) is a natural herbal supplement with a well-described anti-inflammatory capacity and beneficial effects in different inflammatory contexts such as insulin resistance or obesity. However, whether YM could improve other inflammatory conditions such as colitis or the immune cell population that can be modulated by this plant remains elusive. Here, by using 61 male and female C57BL/6/J wild-type (WT) mice and the dextran sodium sulfate (DSS)-induced acute colitis model, we evaluated the effect of YM on colitis symptoms and macrophage polarization. Our results showed that the oral administration of YM reduces colitis symptoms and improves animal survival. Increasing infiltration of anti-inflammatory M2 macrophage was observed in the colon of the mice treated with YM. Accordingly, YM promoted M2 macrophage differentiation in vivo. However, the direct administration of YM to bone marrow-derived macrophages did not increase anti-inflammatory polarization, suggesting that YM, through an indirect mechanism, is able to skew the M1/M2 ratio. Moreover, YM consumption reduced the Eubacterium rectale/Clostridium coccoides and Enterobacteriaceae groups and increased the Lactobacillus/Lactococcus group in the gut microbiota. In summary, we show that YM promotes an immunosuppressive environment by enhancing anti-inflammatory M2 macrophage differentiation, reducing colitis symptoms, and suggesting that YM consumption may be a good cost-effective treatment for ulcerative colitis.

Probiotics for inflammatory bowel disease: Is there sufficient evidence?

Inflammatory bowel disease (IBD) refers to chronic inflammatory disorders of the gut. Ulcerative colitis (UC) and Crohn's disease (CD) are two subtypes of IBD. Evidence suggests that the intestinal microbiota plays a role in the pathogenesis of IBD, so probiotics have garnered a lot of interest as a potential treatment or prevention for IBD. However, clinical evidence of the efficacy of probiotics is still debatable. We performed a literature review. An advanced search considered clinical studies on probiotic for IBD from inception to 2023 in PubMed, Embase, Cochrane Library, and Web of Science. In the treatment of UC with probiotics, only Escherichia coli Nissle 1917 for maintenance treatment of UC in remission, and Bifidobacterium and VSL#3 for induction of remission in patients with mild to moderately active UC have shown strong evidence. Currently, there are no definitive conclusions regarding the effectiveness of probiotics in CD. The mechanism of probiotic treatment for IBD may be related to reducing oxidative stress, repairing the intestinal barrier, regulating intestinal flora balance, and modulating intestinal immune response. Differences in the benefits of probiotics between CD and UC may be attributable to the different lesion extent and immune-mediated pathophysiology. More robust randomized clinical trials are required to validate the efficacy and safety of diverse probiotic strains in IBD.

Optimal Management of Refractory Crohn's Disease: Current Landscape and Future Direction

Refractory Crohn's disease, defined as ongoing inflammation despite the trial of multiple advanced therapies, impacts a number of individuals with Crohn's disease, and leads to significant burden in quality of life and cost. Interventions such as early implementation of advanced therapies, optimization of current therapies prior to switching to an alternative, as well as understanding the overlapping pathophysiology between immune-mediated disorders, however, can help shift the current landscape and reduce the number of patients with refractory disease. As such, in this review we summarize the key takeaways of the latest research in the management of moderate-to-severe Crohn's disease, focusing on maximization of our currently available medications, while also exploring topics such as combination advanced therapies. We also describe evidence for emerging and alternative therapeutic modalities, including fecal microbiota transplant, exclusive enteral feeding, hyperbaric oxygen, stem cell therapy, bone marrow transplant, and posaconazole, with a focus on both the potential impact and specific indications for each.

Exposure to prescribed medication in early life and impacts on gut microbiota and disease development

The gut microbiota during early life plays a crucial role in infant development. This microbial-host interaction is also essential for metabolism, immunity, and overall human health in later life. Early-life pharmaceutical exposure, mainly referring to exposure during pregnancy, childbirth, and infancy, may change the structure and function of gut microbiota and affect later human health. In this Review, we describe how healthy gut microbiota is established in early life. We summarise the commonly prescribed medications during early life, including antibiotics, acid suppressant medications and other medications such as antidepressants, analgesics and steroid hormones, and discuss how these medication-induced changes in gut microbiota are involved in the pathological process of diseases, including infections, inflammatory bowel disease, metabolic diseases, allergic diseases and neurodevelopmental disorders. Finally, we review some critical methods such as dietary therapy, probiotics, prebiotics, faecal microbiota transplantation, genetically engineered phages, and vagus nerve stimulation in early life, aiming to provide a new strategy for the prevention of adverse health outcomes caused by prescribed medications exposure in early life.

A comprehensive guide to assess gut mycobiome and its role in pathogenesis and treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is an immune mediated chronic inflammatory disorder of gastrointestinal tract, which has underlying multifactorial pathogenic determinants such as environmental factors, susceptibility genes, gut microbial dysbiosis and a dysregulated immune response. Human gut is a frequent inhabitant of complex microbial ecosystem encompassing bacteria, viruses, parasites, fungi and other microorganisms that have an undisputable role in maintaining balanced homeostasis. All of these microbes interact with immune system and affect human gut physiology either directly or indirectly with interaction of each other. Intestinal fungi represent a smaller but crucial component of the human gut microbiome. Besides interaction with bacteriome and virome, it helps in balancing homoeostasis between pathophysiological and physiological processes, which is often dysregulated in patients with IBD. Understanding of gut mycobiome and its clinical implications are still in in its infancy as opposed to bacterial component of gut microbiome, which is more often focused. Modulation of gut mycobiome represents a novel and promising strategy in the management of patients with IBD. Emerging mycobiome-based therapies such as diet interventions, fecal microbiota transplantation (FMT), probiotics (both fungal and bacterial strains) and antifungals exhibit substantial effects in calibrating the gut mycobiome and restoring dysbalanced immune homeostasis by restoring the core gut mycobiome. In this review, we summarized compositional and functional diversity of the gut mycobiome in healthy individuals and patients with IBD, gut mycobiome dysbiosis in patients with IBD, host immune-fungal interactions and therapeutic role of modulation of intestinal fungi in patients with IBD.

Candida tropicalis-derived vitamin B3 exerts protective effects against intestinal inflammation by promoting IL-17A/IL-22-dependent epithelial barrier function

Candida tropicalis-a prevalent gut commensal fungus in healthy individuals - contributes to intestinal health and disease. However, how commensal C. tropicalis influences intestinal homeostasis and barrier function is poorly understood. Here, we demonstrated that the reference strain of C. tropicalis (MYA-3404) ameliorated intestinal inflammation in murine models of chemically induced colitis and bacterial infection. Intestinal colonization of C. tropicalis robustly upregulated the expression of IL-17A and IL-22 to increase barrier function and promote proliferation of intestinal epithelial cells in the mouse colon. Metabolomics analysis of fecal samples from mice colonized with C. tropicalis revealed alterations in vitamin B3 metabolism, promoting conversion of nicotinamide to nicotinic acid. Although nicotinamide worsened colitis, treatment with nicotinic acid alleviated disease symptoms and enhanced epithelial proliferation and Th17 cell differentiation. Oral gavage of C. tropicalis mitigated nicotinamide-induced intestinal dysfunction in experimental colitis. Blockade of nicotinic acid production with nicotinamidase inhibitors lowered the protective effects against colitis in mice treated with C. tropicalis. Notably, a clinical C. tropicalis strain isolated from patients with candidemia lacked the protective effects against murine colitis observed with the reference strain. Together, our results highlight a novel role for C. tropicalis in resolving intestinal inflammation through the modulation of vitamin B3 metabolism.