Gut Microbes

Background and AimsThe rising incidence of Crohns disease (CD) in Westernized countries has been linked to changes in diet and increased consumption of food additives, yet the mechanisms by which these factors fuel intestinal inflammation remain unclear. Adherent-invasive Escherichia coli (AIEC), a pathobiont involved in CD pathogenesis, lacks a clear genetic hallmark but exhibits intestinal colonization and virulence traits, raising questions about the evolutionary forces promoting its emergence among select individuals. Here, we investigated how chronic exposure to two common dietary emulsifiers, carboxymethylcellulose (CMC) and polysorbate 80 (P80), along with host inflammation, drives AIEC genomic evolution and pathogenic potential. MethodsWild-type and Il10-deficient mice were monocolonized with AIEC and chronically exposed to CMC, P80, or water. Bacterial isolates were collected and analyzed for genomic diversification, mutations, and phenotype both in vitro and in vivo. ResultsEmulsifiers accelerated AIEC genomic diversification and selected for mutations linked to increased motility, invasion, and pro-inflammatory activity. Moreover, dietary emulsifier-evolved strains displayed a marked fitness advantage in vivo, outcompeting their counterparts in murine hosts, with the greatest advantage observed when evolution occurred under inflammatory conditions. Notably, evolutionary pathways and phenotypic outcomes were shaped by both emulsifier and the hosts inflammatory status, highlighting synergy between diet and host genetics in fostering pro-inflammatory pathobionts. ConclusionThese findings provide an evolutionary framework connecting modern dietary habits to the emergence of pathogenic AIEC strains, and underscore the importance of dietary interventions in individuals at risk for inflammatory bowel disease.

Background: The enterotype concept proposed that gut microbiomes cluster into discrete types, but subsequent critiques demonstrated that such clustering depends on methodological choices, that the number of clusters is not fixed, and that faecal samples cannot capture spatial heterogeneity along the gastrointestinal tract. The stomach remains particularly understudied, and no systematic classification exists for gastric microbial community types. Methods: We assembled a multi-cohort dataset of 566 gastric mucosal samples spanning healthy controls to gastric cancer, with both Helicobacter pylori (HP)-negative and HP-positive individuals. Critically, we applied the key methodological lessons of the enterotype debate: we used a variational autoencoder (VAE) for dimensionality reduction to learn a continuous latent representation without forcing discrete structure, determined the optimal number of clusters using the Silhouette index (an absolute validation measure) across K=2 to K=10 rather than arbitrarily selecting a cluster number, and performed transparent evaluation of multiple clustering solutions. This VAE-plus-silhouette workflow directly addresses the critiques leveled against the original enterotype analysis. Results: Four gastotypes were identified, with K=4 achieving the highest mean silhouette score, indicating good cluster cohesion and separation. Two gastotypes (Variovorax-type and Trabulsiella-type) were significantly enriched in HP-positive samples, while two gastotypes (Bacteroides-type and Streptococcus-type) were significantly enriched in HP-negative samples. Random Forest and Gradient Boosting achieved excellent baseline performance for predicting HP infection (AUC = 0.990 and 0.993). Conclusions: The VAE-plus-silhouette workflow provides a robust, data-driven approach for identifying gastotypes without forcing discrete structure or arbitrarily fixing cluster numbers. Using this framework, we identified four gastotypes with significantly different HP infection rates. Variovorax-type and Trabulsiella-type showed strong HP-positive enrichment, while Bacteroides-type and Streptococcus-type showed strong HP-negative enrichment. These findings demonstrate that methodological advances from the enterotype controversy can be successfully transferred to the stomach, offering a reproducible taxonomy for stratifying HP infection status with potential clinical utility.

BackgroundA major hurdle in probiotic development for inflammatory bowel disease (IBD) is the inability to disentangle their direct effects on the host from those mediated through the resident microbiota. Here, we establish a reverse screening platform in gnotobiotic zebrafish to overcome this limitation. ResultsWe isolated Bacillus velezensis (B. velezensis) GFZF-23 from long-surviving gnotobiotic zebrafish and demonstrated its potent protective effects against DSS-induced colitis. The strain significantly attenuated intestinal damage and inflammatory responses in both germ-free and conventional hosts. Multi-omics analysis revealed that B. velezensis GFZF-23 employs environment-specific strategies. In the presence of a microbiome, it restored community homeostasis by enriching beneficial taxa, such as Faecalibacterium. Strikingly, in germ-free conditions, GFZF-23 did not simply reverse disease-associated markers but actively reprogrammed host metabolism, with particular enrichment in the linoleic acid pathway. Functional assays confirmed that {beta}-sitosterol serves as a critical effector metabolite driving this protection. ConclusionsThis work establishes B. velezensis as a promising therapeutic candidate and provides a robust framework for deconvoluting the direct and indirect effects of potential probiotics. Our findings highlight metabolic reprogramming as a vital, underappreciated mechanism in precision microbiome therapeutics. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/710680v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@10868e6org.highwire.dtl.DTLVardef@11f1532org.highwire.dtl.DTLVardef@1a88631org.highwire.dtl.DTLVardef@1020b33_HPS_FORMAT_FIGEXP M_FIG C_FIG

The intestinal mucus network, primarily composed of O-glycosylated MUC2 mucin polymers, is essential for protecting the gastrointestinal tract from microbial threats. Sialic acid (Sia), a terminal monosaccharide on complex O-glycans, plays a key role in maintaining mucus integrity and is frequently modified by Casd1-dependent O-acetylation (OAc). Despite its prevalence, the biological significance of sialic acid OAc (OAc-Sia) modifications in human and murine mucus remains unclear. We hypothesized that OAc-Sia variants on mucus interact with the microbiota and are required for optimal mucus barrier function and host-microbe homeostasis in the colon. To test this, we profiled OAc-Sia on human and mouse MUC2 in situ using viral-derived probes with bacterial FISH and confocal microscopy; generated intestinal epithelial cell (IEC)-specific Casd1 null mice (IEC Casd1-/-); performed sialylomic and O-glycomic HPLC-MS analyses; assessed microbial communities by 16S rRNA sequencing with quantitative microbial profiling (QMP); and evaluated disease susceptibility using DSS colitis and Citrobacter rodentium infection models. Results revealed that both human and murine mucins are extensively O-acetylated and interact with the microbiota, suggesting biological relevance. IEC Casd1-/- mice were viable and displayed a complete loss of mucin OAc-Sia, indicating Casd1 is the sole contributor to OAc-status. Unexpectedly, mucus function was intact in IEC Casd1-/- mice, with no difference in structure or quality vs. WT co-housed littermates.16S rRNA analysis showed a modest but significant sex-specific reduction of microbial loads in male IEC Casd1-/-mice, and a clear trend toward reduced Turicibacter spp. vs. WT mice in both male and females, without impacting overall short-chain fatty acid (SCFA) production. DSS treatment led to more severe and extensive tissue damage in IEC Casd1-/- mice. C. rodentium infection led to increased damage in the cecum and distal colon of IEC Casd1-/- mice without affecting pathogen load, suggesting that OAc-Sia status has a role in tolerance defense. These findings establish intestinal epithelial Sia O-acetylation as a component dispensable for mucus and host-microbe homeostasis at baseline, but important in limiting damage to mucosal inflammatory insults.

Liraglutide, a GLP-1 receptor agonist, is used to induce weight loss. However, limited information exists on liraglutides effects on the gut bacterial community and their restoration after washout. We investigated liraglutides effect on the gut bacterial community in diet-induced obese (DIO) mice and whether these changes persist after washout. Twenty-four male C57BL/6J mice on high-fat (HFC) or low-fat (LFC) diets were monitored for 21 days. A subgroup of high-fat mice received daily liraglutide for 14 days (HFL), followed by a 7-day washout. Liraglutide induced significant weight loss by Day 4, which persisted during treatment and partially reversed post-treatment. For bacterial community analysis, 7.1 million 16S rRNA gene sequences were retrieved using Illumina paired-end sequencing. We observed distinct shifts in gut bacterial community structure during liraglutide treatment, which mostly returned to baseline after the 7-day washout. Using SIMPER analysis, 21 amplicon sequence variants (ASVs) were identified as major contributors. Nine ASVs, related to Lactobacillus gasseri, L. paragasseri, L. johnsonii, and Leptogranulimonas caecicola, significantly increased during treatment and declined post-washout. The remaining 12 ASVs, associated with protein- and carbohydrate-fermenting bacteria (Romboutsia, Faecalicatena, Oscillibacter), decreased during treatment. Comparison across all groups identified 29 ASVs, clustering into seven phylogenetic groups, highlighting liraglutides enrichment of bile-acid- and mucin-associated taxa and suppression of carbohydrate-fermentative genera. These findings demonstrate that liraglutide induces rapid, diet-dependent, yet reversible shifts in the gut microbiome, favoring lactic acid-producing bacteria while reducing fermentative taxa. Such microbial changes may contribute to liraglutides metabolic effects and provide insight into host- microbiome interactions in obesity treatment. IMPORTANCEObesity and overweight states are intricately linked to the gut bacterial community, yet the effects of common obesity treatments such as GLP-1 receptor agonists on gut bacteria remain unclear. Here, we show that liraglutide, a GLP-1 analog, reshapes the gut bacterial community in diet-induced obese mice relative to untreated obese and lean controls. By including baseline samples when mice were at a normal weight, we distinguished bacterial changes due to the drug from those due to obesity progression, as well as how the community structure is affected during a washout period. Liraglutide treatment selectively increased beneficial gut bacteria (e.g., Lactobacillaceae) under high-fat conditions. These bacterial shifts during GLP-1 therapy may contribute to its metabolic benefits and broaden our understanding of host bacterial interactions in the context of diet and weight management.

The incidence of colorectal cancer (CRC) has been increasing in Taiwan and is associated with multiple risk factors, including aging, obesity, and dietary habits. Increasing evidence suggests that gut microbiota dysbiosis contributes to CRC development. This study aimed to characterize microbial and metabolic alterations across premalignant and malignant colorectal lesions and to identify potential microbiome-associated biomarkers. Individuals undergoing colonoscopy for screening or surveillance at Taipei Veterans General Hospital were enrolled. Gut microbial composition was analyzed using full-length 16S rRNA gene sequencing to achieve high-resolution taxonomic profiling. Predicted functional pathways were inferred from microbial communities, and targeted metabolomic profiling was performed to evaluate microbial metabolic outputs. A total of 122 individuals were included, comprising 62 healthy controls, 15 adenoma cases, and 45 CRC cases. Progressive shifts in microbial composition and predicted functional pathways were observed along the adenoma-carcinoma sequence. Several bacterial taxa, including Phocaeicola dorei, Anaerotignum faecicola, Negativibacillus massiliensis, and Dysosmobacter segnis, were enriched in CRC. At the functional level, CRC samples showed enrichment of pathways associated with energy metabolism and bacterial stress responses. Metabolomic analysis further revealed increased levels of tauro-ursocholanic acid in CRC samples, whereas short-chain fatty acids (SCFAs) were reduced compared with controls. Integrative analysis combining full-length 16S sequencing, functional pathway prediction, and metabolomic profiling revealed coordinated microbial and metabolic alterations across the adenoma-carcinoma sequence. These findings provide insight into microbiome-associated processes in colorectal tumorigenesis and suggest potential microbial and metabolic biomarkers for CRC. ImportanceColorectal cancer (CRC) develops through a adenoma-carcinoma sequence, yet the microbial and metabolic alterations accompanying this progression remain incompletely understood. In this study, we integrated full-length 16S rRNA gene sequencing with metabolomic profiling to characterize taxonomic, functional, and metabolic changes across healthy controls, adenoma, and CRC. Our results reveal synchronized shifts in specific microbial taxa, predicted metabolic pathways, and fecal metabolites along the adenoma-carcinoma sequence. Several bacterial species, including Phocaeicola dorei, Anaerotignum faecicola, and Dysosmobacter segnis, increased in CRC, whereas short-chain fatty acids decreased progressively from controls to adenoma and CRC. Functional pathway analysis further indicated alterations in microbial fermentation, amino acid metabolism, and energy-related pathways. Together, these findings highlight the potential role of microbiome-associated metabolic changes in colorectal tumorigenesis and suggest candidate microbial and metabolic markers that may aid in understanding disease development and improving risk stratification.

The microbiome-gut-brain axis is a mediator of stress-related disorders. The number of preclinical studies exploring the potential causal mechanism of this connection using fecal microbiota transplantation (FMT) is growing. However, the most common method for delivering fecal transplants in rodent models is still oral gavage, which creates an adverse experience that may confound stress-related outcomes. Here, we establish an alternative methodology for FMT that decreases stress induced by traditional experimental procedures. We first used preference and anxiety behavior assays to identify antibiotic therapies having maximal tolerability and minimal anxiolytic properties. We then collected feces from donor mice and homogenized them with a microbe-stabilizing buffer to create a slurry, which was frozen into pellets ("poopsicles") for subsequent FMT. Recipient mice voluntarily consumed the pellets, and blood was collected to compare corticosterone levels relative to traditional gavage FMT. Plasma corticosterone levels were found to be significantly lower in mice receiving FMT via pellets compared to oral gavage. Furthermore, relative to gavage FMT, microbial signatures of mice receiving FMT via pellets were more similar to those of the donor pellets at one week following final FMT and were sustained for up to six weeks, as assessed by comparing Bray-Curtis beta-diversity distances. Together, these results establish effective antibiotic and FMT methods that minimize treatment-induced stress, while effectively transplanting fecal microbes between murine conspecifics.

The gut microbiome is a key regulator of metabolic homeostasis and contributes to obesity progression through effects on immune signaling, gut barrier integrity, and systemic inflammation. Microbiome-targeted strategies are therefore being explored as complementary approaches to conventional weight-loss therapies. Here, we investigated the probiotic yeast Saccharomyces boulardii in a murine model of diet-induced obesity (DIO) using an integrated multi-omics framework combining metabolic phenotyping, gut microbiome profiling, cecal metabolomics, colonic transcriptomics, and portal cytokine analysis. S. boulardii reduced food intake, attenuated weight gain, and increased energy expenditure without major changes in circulating metabolic hormone levels. Microbial diversity remained largely preserved, but selective enrichment of Bacteroidales lineages, including Muribaculaceae, was observed alongside functional remodeling of microbial pathways. Cecal metabolomics revealed increased B-vitamins, betaine, and GABA, with reduced stress-associated metabolites. Colonic transcriptomics showed attenuation of TNF/NF-{kappa}B signaling and enrichment of interferon and epithelial programs, while portal cytokine profiling indicated reduced inflammatory chemokines with trends toward increased IL-17A and IL-22. Integrated multi-omics analysis identified coordinated host-microbe interactions across metabolic, transcriptional, and immune layers. Collectively, these findings demonstrate that S. boulardii modulates the gut-immune-metabolic axis in obesity, supporting microbiome-based interventions as potential adjunct strategies targeting metabolic inflammation.

AbstractO_ST_ABSBackgroundC_ST_ABSShort-chain fatty acids (SCFAs) are widely used as functional readouts of gut microbial activity in vivo. The growing adoption of decentralised study designs and self-collection protocols has amplified the need for reliable room-temperature storage and shipment strategies. However, SCFAs volatility and the persistence of post-collection microbial metabolism raise concerns regarding pre-analytical stability and the interpretability of measured concentrations. MethodsWe assessed the temporal stability of fatty acids (FAs) across intestinal and systemic matrices under room-temperature storage. Untreated stool was compared with two nucleic acid stabilisation devices (eNAT and OMNIgene-GUT), while whole blood, plasma and dried blood spots (DBS) were evaluated as minimally invasive systemic sampling strategies. Profiles were quantified using complementary GC-MS and LC-MS/MS workflows. ResultsUntreated stool showed fermentation-driven increases in major SCFAs, whereas immediate freezing preserved baseline profiles. eNAT maintained faecal FA stability for up to 21 days, while OMNIgene-GUT exhibited baseline and time-dependent alterations. In systemic matrices, plasma and whole blood showed upward drift, whereas DBS declined initially before stabilising after approximately 14 days. ConclusionsFA measurements are highly matrix- and device-dependent. Our findings provide practical guidance for the selection of sampling strategies in microbiome-associated FA studies and emphasise the need for controlled pre-analytical conditions in decentralised microbiome studies.

Vitamin B2 (riboflavin) is a key redox cofactor that may modulate gut microbial ecology, yet conventional supplements are absorbed proximally and have limited colonic exposure. We evaluated whether colon-targeted riboflavin alters microbiome composition, function and network structure as well as host biomarkers in healthy older adults. In a randomized, double-blind, placebo-controlled, parallel-group clinical trial (N=348; 50-70 years), participants received colon-targeted riboflavin (1.4, 10, or 75 mg/day) or placebo for 12 weeks. The primary endpoint was the change in fecal microbial composition, while secondary endpoints encompassed microbiome function, host health biomarkers, and clinical outcomes. Shotgun metagenomics and fecal/blood biomarkers were assessed at baseline, week 4, and week 12. Although no significant changes were observed between groups in overall community-wide diversity metrics (alpha and beta diversity), colon-delivered riboflavin significantly altered the relative abundance of several microbial taxa compared with placebo. The most pronounced effects on microbiome composition, function, and network structure were observed with the 10 mg dose at week 12, reflected by within-group increases in alpha diversity, the largest rise in total species counts, higher HACK index values indicating greater community resilience, and distinct shifts in KEGG module abundance, including enhanced potential for riboflavin biosynthesis. Supplementation with 75 mg riboflavin led to higher fecal butyrate concentrations at week 4 versus placebo, while the lowest dose (1.4 mg) significantly reduced the dysbiosis index within groups and modestly improved network structure across groups. All three doses (1.4, 10, and 75 mg) influenced keystone species abundance. No between-group differences were observed for gastrointestinal symptoms, quality-of-life measures, fecal pH, high-sensitivity C-reactive protein (hs-CRP), calprotectin, or soluble CD14, except for an increase in plasma riboflavin concentrations at 75 mg after 12 weeks, indicating colonic absorption. The product was safe and well-tolerated across all doses. These findings indicate that colon-targeted riboflavin can act as a functional modulator of the human gut microbiome, with the most consistent effects observed at 10 mg and additional dose-specific effects at 1.4 mg and 75 mg. Future studies are warranted to establish related health benefits, either as a standalone intervention or in combination with classical pre-, pro-, or postbiotics, particularly in target populations such as individuals with IBS, stress, mild cognitive decline, or early metabolic or inflammatory alterations.

The gut ecosystem is shaped by multiple factors with the immune system being one of the major determinants in shaping its composition in health and disease. On the other hand, the immune system regulates its responses through the action of the sympathetic nervous system (SNS) in part through beta-adrenergic receptors 1/2 (ADRB1/2). In the past years, a clear link has been established between the immune system, SNS, and the modification of nutrient absorption by the gut microbiota in the development of diet-induced obesity. We have previously shown in male mice transplanted with bone marrow cells ADRB1/2 knock-out mice (KD) showed mild immunosuppression and microbiota changes. Post-recovery, mice were challenged with high-fat diet (HFD) for two weeks ad libitum. Our findings show that KD mice are protected against diet-induced adiposity and weight gain. Additionally, these mice showed an increase in residual calorific values and a decreased expression of the fatty acid transporter FAT/CD36. Suggesting a decreased absorption of lipids in the KD mice. Gut microbiota analysis showed that KD microbiota composition on a HFD remained stable with a significant enrichment in the Bacteroidetes phylum, which is depleted in obesity. This was associated with a switch from triglycerides to diglyceride fecal profile. Moreover, microbiome culture showed a decrease in triglycerides after an incubation with 0.1% of HFD lipid extract. Suggesting a potential role of the Bacteroidetes phylum in the metabolism of these lipids. Our findings demonstrate not only that the gut microbiota can modify nutrient absorption and susceptibility to diet-induced obesity but also that the immune system contributes to selective depletion of microbial members that would otherwise thrive on dietary lipids. Revealing a novel mechanism by which host immunity sculpts the gut ecosystem in ways that influence metabolic outcomes.

The human gut microbiome is a complex community that plays an important role in health, where perturbations can result in dysbiosis and disease. Bacteriophages (phages) can provide treatment for bacterial gastrointestinal disease, and commercial preparations such as the Intesti bacteriophage cocktail can be taken orally to target bacterial pathogens. However, interactions between these phages and the native gut microbiota are understudied. To investigate the impact of phage treatment, we used simulated gut models seeded with healthy donor microbiota from three individuals, sequenced the DNA, and analysed the bacterial and viral portion from samples obtained over time. Each donor had a unique bacterial composition which diverged with time. When comparing phage treated to control samples, we observed that Escherichia coli abundance accounted for the largest portion of bacterial community variance and was more associated with the controls. The lower abundance in phage treated samples may have resulted from the lytic action of phages from the cocktail. Additionally, our analyses of the viral portion revealed a phage bloom exclusive to phage treated samples. A highly abundant phage in this bloom was matched with the Intesti bacteriophage cocktail, showed similarity to Enterobacteria phage phi92, and provided evidence of productive infection within the model. While we did observe fluctuations in relative abundance of additional viral sequences in the presence of the phage cocktail, these changes were often transient. Furthermore, we detected only slight differences to typical members of the virome, and low numbers of active prophages. Our experiments suggest that the phage cocktail had minimal interruption to the native gut microbiota within the model. Impact statementBacteriophages are increasingly investigated and tested for their efficacy in treating infections and are a key component in fight against antimicrobial resistant bacterial infections. Because of their specificity, it has become almost a dogma to state that they do not alter the gut microbiome. We have now tested this in an in vitro study using a commercially available cocktail and real human faecal microbiota. We show minimal effects on the composition of the healthy microbiota with an individual-specific effect on Escherichia coli caused by productive infection of one phage in the cocktail.

Both preclinical and clinical studies have revealed the indisputable importance of intestinal bacterial community composition in pathogenesis of various disease states, from obesity to neurodegeneration. Diet remains one of the most important factors shaping human intestinal microbiota composition. In this study, we investigated diet-microbiome interactions in a healthy cohort of 88 participants from Atlanta and Calgary. We examine microbial composition (16S rRNA sequencing) with dietary records using Spearman Correlation tests with Benjamini-Hochberg multiple hypothesis correction to make community-level comparisons between dietary scores and microbial diversity index scores. Predictive models were used for molecular-level comparisons between microbial gene pathways and molecules. Among generalized dietary and microbial indices, we identified a negative association between dietary whole grain consumption and a microbial dysbiosis score. Comparisons between dietary food groups and bacterial family abundance reveal significant associations between dairy consumption and Lactobacillaceae abundance, dietary unsaturated to saturated fatty acid ratio and Clostridia Cluster Family XIII, salt intake and Lachnospiraceae, and consumption of greens and beans and Veillonellaceae. Predictive models of microbial gene pathways and molecules reveal significant positive associations between several dietary fatty acids and microbial short-chain fatty acid fermentation pathways, and between dietary lignans and archaeal methanogenesis pathways. Overall, these associations may inform future explorations on specific dietary interventions to impact the gut microbiome. IMPORTANCEIn this study, we compare dietary records and composition of intestinal microbes in a cohort of 88 participants. We identified associations between dietary consumption of dairy and the presence of dairy-consuming bacteria called Lactobacteriaceae and between consumption of dietary fats and the presence of fat-consuming bacteria called Clostridia. Using predictive analysis, we identify specific fatty acids associated with specific biochemical pathways found in Clostridia that might underlie these associations, in addition to an association between archaeal microbes and dietary consumption of estrogen-binding molecules called lignans, which are commonly found in whole grains and vegetables. Overall, our study generates useful associations between diet and intestinal microbes that can be tested in experiments that may help scientists use diet to control intestinal microbes in order to improve human health.

Background: Irritable bowel syndrome (IBS) is characterized by heterogeneous symptom trajectories and high treatment discontinuation rates. Traditional analyses examine longitudinal outcomes and time-to-event endpoints separately, potentially missing informative dropout and the association between symptom dynamics and treatment persistence. Objective: To jointly model patient-reported IBS symptom trajectories and time-to-treatment discontinuation using shared random effects, characterizing the association between individual symptom dynamics and treatment persistence in a large Canadian prospective cohort. Methods: We analyzed 2,847 adults with Rome IV diagnosed IBS enrolled in the Canadian Gut Project (2018 to 2024) across 14 gastroenterology centres in Alberta, British Columbia, and Ontario. The longitudinal submodel used linear mixed-effects regression for the IBS Severity Scoring System (IBS-SSS) measured at baseline and months 3, 6, 12, 18, and 24. The survival submodel used a Weibull proportional hazards model for time-to-treatment discontinuation. The joint model linked both processes through shared random effects (random intercept and slope), estimated via maximum likelihood with adaptive Gauss-Hermite quadrature (15 nodes). We conducted sensitivity analyses using Bayesian estimation, alternative association structures (current value, time-dependent slopes), and multiple imputation for intermittent missingness. Results: Mean baseline IBS-SSS was 298.4 (SD 72.1). Over 24 months, 1,042 participants (36.6%) discontinued treatment. The longitudinal submodel revealed a mean IBS-SSS decline of -8.7 points/month (95% CI: -10.2, -7.1) with substantial between-person heterogeneity in both intercepts (STD = 4,218.3) and slopes (STD = 12.4). The association parameter linking the shared random intercept to the hazard of discontinuation was = 0.0034 (95% CI: 0.0021, 0.0047; p < 0.001), indicating that each 10-point increase in individual-specific baseline severity increased the hazard of discontinuation by 3.5%. The shared slope association parameter was 2 = -0.187 (95% CI: -0.264, -0.110; p < 0.001), demonstrating that individuals with steeper symptom improvement had lower discontinuation hazards. IBS-D subtype (HR = 1.41; 95% CI: 1.18, 1.69), concurrent anxiety (HR = 1.28; 95% CI: 1.09, 1.50), and social media health information use (HR = 0.82; 95% CI: 0.71, 0.95) were significant predictors in the survival submodel. Conclusion: Joint longitudinal-survival modelling reveals that IBS symptom trajectories and treatment discontinuation are dynamically linked through individual-level latent processes. Higher baseline severity and slower improvement trajectories significantly predict earlier discontinuation. These findings support personalized treatment monitoring approaches that use real-time symptom trajectory data to identify patients at risk of discontinuation.

1.Fermentable fibres such as inulin can support metabolic health but may exacerbate gastrointestinal symptoms in individuals with irritable bowel syndrome (IBS) due to rapid fermentation and gas production. The gel-forming fibre psyllium improves IBS symptoms, although the underlying mechanisms remain unclear. We hypothesised that fibre gelation alters fermentation by modulating microbial access to substrates. To test this, we compared psyllium with methylcellulose, a chemically modified, gel-forming fibre, to determine the effects of gelation on inulin fermentation. Inulin alone or combined with psyllium or methylcellulose was fermented for 48 hrs in a colonic fermentation model inoculated with healthy human faeces. Gas production, metabolite profiles, microbial community composition and microbial localisation within fibre gels were assessed. Bioactivity of fermentation products was evaluated in STC-1 cells. Psyllium co-fermentation significantly accelerated fermentation and enhanced production of metabolites, while methylcellulose had minimal effects. Psyllium maintained higher diversity and enriched polysaccharide-degrading taxa including Bacteroides and Phoecaeicola species, which were strongly associated with metabolic activity. Bacterial penetration into the psyllium matrix was observed but not into methylcellulose. Fermentation products from psyllium but not methylcellulose stimulated GLP-1 and 5-HT secretion in STC-1 cells. These findings demonstrate that delayed-onset fermentable gel-forming fibres enhance microbial access to entrapped substrates, driving metabolic and hormonal responses.

Enteroaggregative Escherichia coli (EAEC) is a leading cause of persistent diarrhea in children in low- and middle-income countries, and the emergence of multidrug-resistant (MDR) strains necessitates non-antibiotic therapeutic strategies. This study evaluates Lactobacillus johnsonii, previously characterized by our group, as a probiotic candidate against a clinically confirmed MDR EAEC isolate resistant to ampicillin, ciprofloxacin, azithromycin, amoxicillin, and gentamicin. L. johnsonii demonstrated robust gastrointestinal resilience, high cell surface hydrophobicity, phenol tolerance, and rapid autoaggregation reaching 80.4 {+/-} 2.3% by 4 hours, collectively supporting mucosal colonization potential. In antimicrobial assays, L. johnsonii produced zones of inhibition against MDR EAEC substantially exceeding those of gentamicin, reduced viable biofilm-associated EAEC by over 80%, and displaced pre-adhered EAEC from HCT-116 intestinal epithelial cells in a time-dependent manner. L. johnsonii also attenuated MDR EAEC-induced gas production and reduced nitric oxide levels by 67.7% in infected RAW 264.7 macrophages, suggesting immunomodulatory activity. Nutrient competition did not appear to contribute to EAEC suppression under tested conditions, indicating inhibition is predominantly secretome-dependent. Fractionation of the L. johnsonii cell-free supernatant by fast protein liquid chromatography yielded five fractions below 75 kDa; fractions S5 and S6 exhibited sustained bactericidal activity at 6 hours. Gram staining confirmed that both fractions reduced viable EAEC cell numbers, with S6 producing a greater reduction than S5, indicating quantitatively distinct bactericidal potencies. These in vitro findings support the potential of L. johnsonii as a biotherapeutic candidate for antibiotic-resistant enteric infections. In vivo validation and chemical characterization of active fractions remain important next steps.

The study of human enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) has been limited by the inability of these pathogens to effectively colonize murine models without prior antibiotic treatment. Because it mimics key features of human EPEC and EHEC infection, Citrobacter rodentium, a natural mouse pathogen that colonizes the lower intestine, has become the primary model for investigating these organisms. C57BL/6 mice are most commonly used for C. rodentium research, however, unless they carry specific genetic mutations, they typically develop only mild disease and clear the infection within weeks. As a result, models of severe disease in genetically unmodified hosts are lacking. Here, we describe the development of a non-genetically modified C57BL/6 mouse line with an undisturbed intestinal microbiota, highly susceptible to severe C. rodentium infection. Early infection in these mice was marked by significantly elevated cecal bacterial burdens and tissue pathology. Immune profiling revealed broad reductions in multiple lymphoid subsets, indicating impaired early mucosal activation. Although overall cytokine expression patterns were similar between groups, ceca of susceptible mice exhibited elevated baseline and early post-infection IL-18, as well as increased G-CSF at day 1. Microbiota analyses showed broadly comparable communities with wildtype controls, with some altered groups, such as Lachnospiraceae, Prevotellaceae, Desulfovibrionaceae, and Erysipelotrichaceae. Together, these findings characterize a robust C57BL/6 model that reproducibly develops severe C. rodentium-induced disease. This phenotype is driven by microbiota-associated alterations and impaired early cecal immunity, providing a valuable system for studying host-microbiota interactions in enteric infections.

Clostridioides difficile infection (CDI) is a leading healthcare-associated diarrhea with high recurrence rates, partially due to antibiotic-induced dysbiosis and dysregulated host inflammation. Specialized pro-resolving mediators (SPMs), such as Lipoxin A4 (LXA4), offer promise in controlling excessive inflammation and promoting tissue repair, yet their role in CDI remains unexplored. Here, we developed a compact, gas-tight gut-on-a-chip (GOC) system that reconciles the anaerobic requirements of C. difficile with the oxic needs of human intestinal epithelium, enabling physiologically relevant co-culture within a standard incubator. A CDI in vitro model was established based on this GOC system. Using the model, we demonstrated that prophylactic administration of LXA4 significantly preserved epithelial barrier integrity, attenuated pro-inflammatory cytokine secretion (IL-8 and IFN-{gamma}), and reduced bacterial colonization. Transcriptomic analysis revealed that LXA4 pretreatment upregulated genes involved in cell junction organization while downregulated immune activation pathways. These protective effects were validated in a murine CDI model, where LXA4 pretreatment reduced weight loss, pathological damage, and fecal bacterial burden. Furthermore, prophylactic administration of LXA4 synergized with vancomycin treatment further enhanced antibiotic efficacy while allowing a 50% dose reduction without compromising therapeutic outcomes. Our study establishes a robust approach for CDI research and highlights the prophylactic and adjuvant potential of inflammation-resolving strategies, offering a novel approach to mitigate CDI incidence and improve treatment outcomes.

Clostridioides difficile infection (CDI) is a severe antibiotic associated disease and a major cause of morbidity and mortality worldwide. CDI is thought to arise from the loss of protective gut microbes that mediate functions such as secondary bile acid metabolism and nutrient competition, yet the relative contributions of these mechanisms remain unclear. To determine how these processes influence C. difficile growth, virulence, and disease, we performed in vitro and in vivo experiments using two Clostridia strains previously associated with colonization resistance against C. difficile. Neither organism prevented colonization or growth through nutrient competition alone. In contrast, secondary bile acid metabolism significantly reduced toxin-mediated disease in vivo in a strain dependent manner. These findings demonstrate that secondary bile acid modulation is an important component of CDI prevention independent of nutrient competition and suggest that attenuating virulence, in addition to limiting colonization, may represent a key strategy for next-generation CDI therapeutics.

The role of gut microbiome in regulating vertebrate metabolism has been well-recognized. However, the effects of gut bacteria on growth have been less studied. Bacillus is a prevalent genus in the gut microbiota of human and animals. In this study, the effect of gut-derived Bacillus velezensis T23 on growth was investigated in zebrafish. B. velezensis T23 improved the growth of zebrafish and promoted IGF1 production in the liver and muscle, with a concomitant activation of the AKT/mTOR signaling pathway. The growth-promoting effect of B. velezensis T23 was not dependent on lipopeptides and polyketides. Cell wall peptidoglycan isolated from B. velezensis T23, as well as muramyl dipeptide (MDP), was sufficient to stimulate IGF1 signaling and growth. Further, the effect of B. velezensis T23 on growth and IGF1 production was abrogated in nod2-/- zebrafish, confirming that B. velezensis T23 promoted growth via MDP-NOD2 signaling. Gut transcriptomic analysis indicated that B. velezensis T23 promoted renewal and differentiation of intestinal cells, suggesting an involvement of gut-liver axis in the effect of B. velezensis T23 on systemic IGF1 production. Together, our results revealed an effect of gut Bacillus-derived muropeptide on growth via NOD2-IGF1 signaling, and provided novel mechanistic insights in the beneficial effect of Bacillus spp. as probiotics.