Microbiome 2.0: lessons from the 2024 Gut Microbiota for Health World Summit

The 12th Gut Microbiota for Health World Summit (March 2024, Washington, DC), organized by AGA and ESNM, convened clinicians, scientists, regulators, and industry stakeholders to focus on therapeutic manipulation of the gut microbiome in health and disease. The program comprised plenary sessions on improving health via the microbiome, pathways to market for microbiome-based products, transitioning from human-derived microbiome therapies to synthetic communities, and handling big microbiome data, as well as workshops on correcting microbial functional deficits, biomarker identification, personalized nutrition, and future microbiome therapies. Open Q&A and poster sessions emphasized moving beyond correlative studies toward generalizable, actionable strategies to modify the microbiome for prevention and treatment of disease. This report synthesizes recurrent themes and challenges across the meeting to advance microbiome-based therapies: identifying actionable microbial targets, developing effective manipulation strategies, and aligning therapies within real-world clinical paradigms.

Three thematic pillars for advancing microbiome-based therapies were highlighted: (1) Target identification: Cohort-based host–microbiome comparisons are essential but confounded by diet, genetics, medications, geography, sampling, and sequencing/analysis variability. An interlaboratory MOSAIC Standards Challenge (44 labs, 7 shared reference standards) showed substantial methodological impact: 16S sequencing vs shotgun metagenomics could invert Firmicutes/Bacteroidetes ratios, underscoring comparability issues. Proposed solutions include deeper, multi-site cohort phenotyping with dietary biomarkers, app-based outcomes, continuous metabolic monitoring, and preclinical prospective designs (e.g., first-degree relatives of IBD patients) to address causality. Human Fecal Reference Material (NIST) is being introduced to harmonize protocols and benchmark biases. Target validity can be strengthened via preclinical models: IBD-associated Klebsiella pneumoniae strains exacerbate colitis in germ-free, colitis-prone mice; Akkermansia muciniphila strains from lean humans reversed high-fat diet-induced metabolic disorders in obesity models. AI tools such as MDITRE leverage longitudinal microbiome dynamics to identify disease-associated targets. (2) Effective manipulation: Conventional antibiotics, FMT, and standard probiotics face off-target effects, variable efficacy/engraftment, and risk of introducing deleterious microbes. Ecologically directed approaches show promise. Bacteriophage cocktails (e.g., 5-phage mix targeting pathogenic Klebsiella pneumoniae) ameliorated colonic inflammation in IBD-prone mice; engineered phages/bacteria delivering CRISPR-Cas9, postbiotics, and bacteriocins can selectively eliminate pathobionts. Next-generation probiotics: Human-derived strains scaled for trials (Akkermansia muciniphila supplementation in 32 overweight/obese volunteers was safe and improved insulin sensitivity, total cholesterol, body weight, and liver dysfunction); Faecalibacterium prausnitzii is under clinical investigation for IBD. Simple defined consortia (8–12 strains) can outperform single strains: VE303 (8 commensal Clostridia) reduced recurrent Clostridioides difficile infection vs placebo; GUT-108 (11 strains) reduced IL-1β, IFN-γ, TNF-α and reversed colitis in T cell-mediated mouse models. Complex consortia (100+ strains) offer scaffold diversity and functional breadth: Hcom2 (>119 strains, 62 functional pathways) sustainably engrafted in mice in 4 weeks; targeted engineering (plasmid in Bacteroides) increased secondary bile acids and reduced fibrosis in NAFLD models. Manufacturing under anaerobic, humidity-controlled, CGMP conditions and thorough strain characterization (genomics, stability, resistance, potency) are challenging; patient heterogeneity (microbiome, diet, ethnicity, health status) drives variable responses. Regulatory pathway: INDs require detailed product and manufacturing data; FDA approvals of Vowst and Rebyota demonstrate feasibility. (3) Real-world positioning: Clinical benefits of FMT for complex diseases are variable; meta-analysis of 6 RCTs in obesity/metabolic syndrome showed no significant changes in obesity parameters, with negligible improvements in HbA1c, insulin sensitivity, and metabolic profiles; in ulcerative colitis, SER-287 failed prespecified remission outcomes vs placebo. Strategies to optimize efficacy include integrating high-resolution, longitudinal microbiome sequencing in multi-center trials, machine learning to predict donor–recipient complementarity, prioritizing functional metabolic deficits (SCFAs, secondary bile acids, AhR agonists) over taxonomic composition, and matching therapies accordingly (e.g., Lactobacillus reuteri with AhR agonist production capacity). Diet modulates microbiome composition/activity: whole-plant diets increase fermentable fiber delivery and SCFA producers; RCTs of fiber interventions predictably alter microbiome; pairing FMT with anti-inflammatory diets sustained ulcerative colitis remission over 1 year vs standard therapy. The NIH Precision Nutrition Strategic Plan aims to establish evidence for diet–microbiota interactions to guide personalized diets that may support engraftment and efficacy. Positioning within treatment paradigms should consider disease phase: immunosuppressive therapy can improve dysbiosis, potentially enabling microbiome-directed therapies to maintain remission.

The meeting synthesized a pathway for translating microbiome science into therapies that address disease: robust target discovery through deeply phenotyped, multi-site cohorts and harmonized methodologies; preclinical validation to establish causality and mechanism; and diversified manipulation strategies spanning phages, engineered microbes, postbiotics, next-generation probiotics, and microbial consortia. Standardization (reference materials, reporting guidelines) and computational advances (longitudinal modeling, interpretable ML) directly mitigate reproducibility issues and enhance target prioritization. Regulatory clarity (IND requirements, recent product approvals) demonstrates a viable path to market, while real-world considerations—patient heterogeneity, diet, disease phase, and integration with standard therapies—are critical to achieving consistent clinical benefits. Emphasizing functional metabolic correction over taxonomic shifts and leveraging diet as an adjunct may improve engraftment and therapeutic impact, aligning microbiome interventions with personalized medicine paradigms.

Progress in microbiome-directed interventions is accelerating, evidenced by FDA-approved FMT-based products, maturation of next-generation probiotics, and rationally designed microbial consortia. The summit identified actionable steps: improve identification and validation of disease-relevant targets; develop precise, scalable strategies to eliminate pathobionts or introduce beneficial functions; and integrate therapies within personalized, diet-informed, phase-appropriate clinical frameworks. Future research should prioritize standardized sampling and analysis using reference materials, longitudinal multi-center cohorts, mechanistic validation in relevant models, engineering of complex consortia with robust scaffolding and metabolic breadth, biomarker-driven personalization focused on functional deficits, and rigorous trials testing co-deployment with controlled diets and conventional therapies across disease phases to achieve durable, clinically meaningful outcomes.

This is a meeting report without original experimental methodology, so conclusions reflect synthesized insights, cited studies, and expert opinion rather than a single controlled investigation. Translational gaps include variability in sequencing pipelines, cohort heterogeneity (diet, geography, medications), and limited reproducibility across studies. Preclinical validations in mouse models may not generalize to human patients. Manufacturing and regulatory complexities constrain rapid development of complex consortia and next-generation probiotics, and patient-to-patient variability in microbiome composition and health status can lead to inconsistent clinical responses.