2026 Discussion Groups
Click on the discussion groups below to see full descriptions.
Chairs: Daniel Merenstein MD, Georgetown University Medical Center, Washington, DC, USA and Daniel J. Tancredi, PhD, University of California, Davis, USA
Introduction: We are living in the era of the microbiome. Both popular media and scientific publications frequently highlight its importance to human health. It is common for nutrition articles to recommend an increase of dietary fiber and fermented foods, usually kombucha, yogurt, kefir and such, with the goal of supporting a healthy microbiome. Infant formulas often contain prebiotics and postbiotics usage is greatly increasing. Even as consumer popularity grows, in a clinical setting prescribers must continue to make a rational, informed and evidence-backed decisions about whether to recommend biotics as a first-line therapy to patients. This group examines the level of evidence for biotics compared to mainstream medicine options for a few common biotic indications.
Background: In an ISAPP Discussion Group 2 years ago, the common question of ‘Should everyone take a probiotic?’ was addressed by evaluating the strength of evidence for preventative use of probiotics by the general population. This 2026 group will build on these conclusions by comparing evidence for biotics against commonly used (non-biotic) first-line therapies, for therapeutic, rather than preventative, applications.
Research Question: Are there specific clinical indications where biotics should be used on their own or along with regular treatments/prevention strategies as a first line option?
Hypothesis: There are certain clinical indications where biotics have a robust evidence base that should result in them being recommended for first line independent use or in conjunction with mainstream approaches.
Topics: A brief presentation comprising the traditional and biotic approach will set the stage for each topic. Presenters and discussion group participants will consider the totality of the evidence for each indication. Thus, the discussion will center on NNT (Number Needed to Treat), NNH (Number Needed to Harm), cost, accessibility, and such. We will encourage presenters to utilize systematic reviews where available, while also highlighting high quality trials that might not have yet been included in a systematic review.
Chairs: Maria Marco PhD, University of California, Davis, USA and Michael Gänzle PhD, University of Alberta, Canada
Background: Strain designations of probiotics are critical for fundamental research, clinical studies, and commercial applications. However, the genetic boundaries distinguishing intraspecies strain differences are difficult to define. This problem has accelerated with the emergence of improved DNA sequencing and genomics methods, which have enabled a more complete and detailed resolution of probiotic genotypes than ever before. The Discussion Group will discuss historical and current definitions of microbial strains and the implications of these definitions for probiotics. The outcomes of this discussion group are expected to lead to improved reporting and monitoring of probiotic strains and to a better understanding of strain-level classifications of probiotics between researchers, clinicians, and industry.
Key questions:
- What is the scale (number) and positionality (genomic location) of genetic mutations needed to which distinguish one probiotic strain from another?
- Should there be a general rule for defining a probiotic strain or should this be decided for each microbial species? If the latter, what metrics should be used to delineate strains (for example, mutation rates or intraspecies genetic diversity)?
- How do terms like “variant” and “isolate” relate to the strain concept?
- How frequently do probiotics accumulate mutations during manufacture and after application, such as after ingestion and during passage through the gastrointestinal tract?
- How important is genetic variation when clinical effects and other functionality-relevant traits are preserved?
Chairs: Sarah Lebeer PhD, University of Antwerp, Belgium and Gabriel Vinderola PhD, National University of Litoral and CONICET, Argentina
This discussion group will explore the scientific, clinical, regulatory, and commercial considerations of administering probiotics and prebiotics either orally or vaginally- with a focus on women’s health. Growing advances in vaginal microbiome research increasingly support vaginal delivery as the most direct and biologically plausible route, yet the commercial landscape continues to favor oral supplementation.
Background and Rationale
Oral probiotics have long been used for BV, VVC, and UTIs, yet despite some impact on clinical endpoints and some meta-analyses showing positive trends, supportive evidence for meaningful oral‑to‑vaginal species transfer remains limited. Most women’s health supplements rely on Lacticaseibacillus rhamnosus or Lim. reuteri, species that are not optimal vaginal colonizers compared with Lactobacillus crispatus, and manufacturing constraints continue to limit access to L. crispatus‑based products. Orally administered species must also survive gastrointestinal transit and typically reach the vagina only in very low concentrations, raising questions about dose, mechanism, and expected efficacy.
In contrast, recent work from the VMRC, the Gates Foundation, and several LBP‑focused companies has accelerated interest in targeted vaginal LBPs, which show promise in reducing BV/VVC recurrence and improving reproductive outcomes. However, vaginal delivery is regulated as a drug route in Europe- requiring extensive clinical validation – while in the US some vaginal products remain under cosmetic categories with limited claims. These regulatory differences strongly shape investment decisions. Vaginal LBPs are also significantly more expensive to develop, leading many companies to continue prioritizing oral supplements despite weaker biological plausibility. As a result, only a small number of vaginal LBP trials exist compared with the large number of oral probiotic supplement studies, creating a widening gap between scientific evidence and market offerings.
Key Questions for Discussion
- How do oral versus vaginal routes differ in colonization, efficacy, and immune response?
- What mechanisms of action matter for BV, VVC, and UTIs across routes?
- Which outcomes should be prioritized: microbiome restoration, recurrence reduction, symptoms, systemic effects?
- How do formulation, stability, and host factors influence each route?
- What regulatory and commercial barriers limit vaginal LBP development, and how can they be reduced?
- How can academia and industry collaborate to accelerate innovation and generate high‑quality evidence?
- What dose and formulation parameters are needed to evaluate oral‑to‑vaginal species transfer?
Goal
To identify critical knowledge gaps, harmonize terminology, and develop a roadmap for future research, product development, and regulatory strategy. By bringing together leading scientists and industry innovators, this discussion group aims to clarify where each delivery route is most appropriate, explore opportunities for vaginal LBP development, and strengthen the scientific foundation for women’s health interventions.
Chairs: Jens Walter PhD, University College Cork, Ireland and Dirk Haller PhD, Technical University of Munich, Germany
Scope
Evidence increasingly implicates the gut microbiome as a modifier of cancer therapy outcomes, particularly immune checkpoint inhibitors. At the same time, recent studies indicate that non-targeted microbiome interventions may be ineffective or even detrimental. This ISAPP discussion group will critically evaluate the evidence base, mechanistic rationale, and translational readiness of biotics (including probiotics, prebiotics, synbiotics, postbiotics, live biotherapeutics, and FMT) as adjuncts in cancer therapy.
Key Aims
- Assess causal evidence linking the gut microbiome to cancer treatment efficacy.
- Examine microbiome–immune mechanisms relevant to therapy response.
- Evaluate FMT as a model for targeted microbiome modulation in oncology.
- Critically appraise benefits and risks of current biotic interventions.
- Identify principles for rational strain selection and minimum standards for clinical trials.
Format & Outputs
Half-day discussion group with invited experts and selected participants. Short invited presentations and flash talks will frame discussion. Outputs will include a concise consensus statement and prioritized research recommendations to inform future ISAPP activities.
Chairs: Kristin Verbeke, Pharm, PhD, Katholieke Universiteit Leuven, Anisha Wijeyesekera, PhD, University of Reading, UK and Hannah D. Holscher, PhD RD, University of Illinois Urbana-Champaign, USA
In prebiotic research, while microbiome modulation and clinical health benefits are the most frequently studied endpoints, the mediators of biological activity of prebiotics often remain elusive. SCFAs are frequently hypothesized as a mechanism of action, esp. for traditional fiber-based substrates, however reliable and relevant measures of SCFAs remain a challenge. For emerging non-carbohydrate prebiotics, the need for robust biochemical markers and mechanistic endpoints of prebiotic activity is equally strong. In 2024, ISAPP produced an expert recommendation addressing key research challenges and criteria for the classification of compounds as prebiotics. This group will build on these conclusions, with a focus on identification and measurement of prebiotic biomarkers, exploring methodological approaches and research gaps to guide future efforts in defining and validating prebiotic study outcomes across diverse contexts.
Key questions and discussion points will include:
- Evaluating the feasibility of key microbially derived metabolites (e.g. short chain fatty acids) as biomarkers of prebiotic efficacy
- Identification of other metabolites or panels of compounds, produced following microbial utilisation of emerging and novel prebiotics
- Consideration of specific metabolites reflecting specific health targets (e.g. GABA for mental health, inflammatory markers for metabolic health)
- Evaluating analytical approaches to integrate multi-modal data, in order to capture the full spectrum of prebiotic effects. This is especially relevant for systemic applications, where outcomes depend on complex host-microbiome interactions.