The Science, Microbes & Health Podcast

International Scientific Association for Probiotics and Prebiotics (ISAPP)
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This podcast covers emerging topics and challenges in the science of probiotics, prebiotics, synbiotics, postbiotics and fermented foods. This is the podcast of The International Scientific Association for Probiotics and Prebiotic (ISAPP), a nonprofit scientific organization dedicated to advancing the science of these fields.

  1. 16H AGO

    Inflammatory microbes on the skin, with Dr. Nathan Archer PhD

    This episode features Dr. Nathan Archer PhD from Johns Hopkins Medicine (USA), speaking about the skin microbiome and particular microorganisms that cause inflammation. The skin is a dynamic organ with the main functions of keeping moisture in and keeping the environment out. Overall, the skin environment is not very welcoming to microorganisms but some have adapted to thrive in the low pH environment. His research has found that certain bacteria that are normally considered commensals can become pathogenic when they start producing specific proteases that instigate inflammation on the skin. Acute inflammation that removes a bacterial exposure from the skin is beneficial, but chronic inflammation can be a major problem. Staphylococcus aureus is a bacterium that predominates in many inflammatory skin diseases and benefits from an inflammatory environment and disruption in the skin barrier; in turn, S. aureus is proinflammatory and uses proteases to drive skin inflammation. His lab is interested in understanding the connection between skin microorganisms and the ‘atopic march’ (progression of allergic diseases, including atopic dermatitis, through infancy and childhood). They found that S. aureus on the skin can exacerbate allergic reactions in the lungs, driving hard-to-treat neutrophilic asthma. His group is contributing to several strategies for preventing / treating skin and allergic diseases, including a vaccine for S. aureus; so far, vaccines against this bacterium have not succeeded because S. aureus has so many tools for avoiding human immune responses. However, a multivalent vaccine targeting multiple toxins that affect the immune system is currently being developed and is in Phase 1 clinical trials. Episode abbreviations and links: Paper on the contribution of microorganisms to normal skin function: Commensal Staphylococcus epidermidis contributes to skin barrier homeostasis by generating protective ceramides Research on the mechanisms of how S. aureus triggers skin inflammation: Staphylococcus aureus proteases trigger eosinophil-mediated skin inflammation Study on the mechanisms by which S. aureus causes epithelial barrier damage: Quorum sensing between bacterial species on the skin protects against epidermal injury in atopic dermatitis Review article on how S. aureus contributes to skin inflammation: Staphylococcus aureus Proteases: Orchestrators of Skin Inflammation Connection of skin microbes to allergic diseases: Epicutaneous Staphylococcus aureus initiates cross-tissue IL-36R signaling for neutrophilic lung inflammation in a model of the atopic march Treatment approach for atopic dermatitis: Development of a human skin commensal microbe for bacteriotherapy of atopic dermatitis and use in a phase 1 randomized clinical trial About Dr. Nathan Archer PhD: Dr. Nathan Archer is an Associate Professor at the Johns Hopkins School of Medicine Department of Dermatology. Dr. Archer’s research involves uncovering how skin microbes, especially the major human pathogen Staphylococcus aureus, exacerbate inflammatory skin diseases such atopic dermatitis as well as how host immunity protects against bacterial skin infections. His work involves the incorporation of immunological and “omic” approaches with preclinical models and clinical samples to reveal mechanistic insights with translational relevance to human disease. His long-term research goals are to develop novel host-directed therapies for the treatment of inflammatory skin disorders and skin infections. Dr. Archer has received funding from the NIH as well as from foundation and industry sources, including the Dermatology Foundation, LEO Foundation, and Pfizer. He has been an invited speaker at numerous international and national conferences with a focus on dermatology, immunology, and microbiology.

    30 min

  2. MAR 25

    The skin microbiome’s role in atopic dermatitis, with Dr. Maria Teresa García-Romero, MD MPH

    This episode features Dr. Maria Teresa García-Romero, MD MPH from the National Institute of Pediatrics in Mexico City, talking about the skin microbiome and how it relates to atopic dermatitis. The skin microbiome varies widely at different sites on the body, but in general, increased diversity is associated with healthy skin. In atopic dermatitis, Staphylococcus aureus becomes abundant and skin microbiome diversity decreases, correlating with inflammatory responses. Treatments have the effect of reducing Staphylococcus aureus. These bacteria are now established to have a role in the pathophysiology of the disease. The caution with antibiotic treatment is that a systematic review and meta-analysis from Dr. García-Romero’s group found Staphylococcus aureus isolates from people with atopic dermatitis had suboptimal susceptibility to commonly used antimicrobials, especially in lower middle-income and upper middle-income countries. Mechanistically, Staphylococcus aureus decrease natural antimicrobial molecules in the skin, stimulate the innate immune response, and likely reduce beneficial bacteria. New treatments are urgently needed because atopic dermatitis is very prevalent (affecting 20-30% of the population), with far-reaching effects in children’s and families’ lives. Two ingested probiotics are commercially available for atopic dermatitis, backed by clinical data, whereas topical probiotic treatments require further research. Episode abbreviations and links: Paper showing how treatments for atopic dermatitis help the skin microbiome more closely resemble healthy controls: The Skin Microbiome of Patients With Atopic Dermatitis Normalizes Gradually During Treatment Systematic Review and Meta-Analysis looking at susceptibility of atopic-dermatis associated Staphylococcus aureus to antibiotics in different regions of the world: Global Antimicrobial Susceptibility Patterns of Staphylococcus aureus in Atopic Dermatitis About Dr. Maria Teresa García-Romero: Dr. Maria Teresa García-Romero is a medical doctor graduated from Tec de Monterrey School of Medicine, magna cum laude. She has a Specialty in Dermatology and Diploma in Medical Mycology from UNAM, Mexico City. Dr. García-Romero completed a Fellowship in Pediatric Dermatology at the University of Toronto, and a Master’s degree in Public Health and Quantitative methods of research at Harvard University Chan School of Public Health.  She has received meritorious awards including the Mexican Foundation for Health (FUNSALUD), Harvard University Presidential Award, Society for Pediatric Dermatology Fellow Award, among others; and funding for research projects by prestigious international organizations such as MIT (Massachusetts Institute for Technology) seed funds and EB Research Partnership.  She is currently an attending physician in the Dermatology Department of the National Institute of Pediatrics in Mexico City and a member of the National System of Researchers level II. She has more than 150 articles published in national and international magazines, supervised multiple postgraduate theses and has presented in multiple forums worldwide. Dr. García-Romero is a member of the Editorial Committee of JAMA Dermatology, Pediatric Dermatology and other high impact journals. Her research interests include the skin microbiome, atopic dermatitis, vascular anomalies and autoimmune disease.

    30 min

  3. MAR 13

    An introduction to skin microbiome research, with Dr. Aayushi Uberoi PhD

    This episode features Dr. Aayushi Uberoi PhD from Washington University in St. Louis (USA), speaking about the skin microbiome and various techniques for studying it. The skin is a reactive interface that protects the body, with the skin on various parts of the body looking very different because of stratifications in the epithelial layers and the local nutritional landscape. The skin microbiome in general is nutrient sparse and varies at different body sites. Research has shown that epithelial development, stratification, and differentiation are altered in the absence of the microbiota, showing the active role of the skin microbiota in regulating skin function. Microbes that inhabit the skin are shown to elicit unique immune responses with systemic effects. Communication between skin microbes and human body cells may be happening via metabolites. When conducting skin microbiome experiments, controls are important; the low biomass samples are susceptible to contamination. In the future, knowing more about the nutritional needs of the skin microbes could help guide the development of prebiotics for skin. Episode abbreviations and links: Paper showing a humanized mouse model for studying the skin microbiome: Commensal-derived tryptophan metabolites fortify the skin barrier: insights from a 50-species gnotobiotic model of human skin microbiome Paper on the skin microbiome’s contributions to wound healing: The wound microbiota: microbial mechanisms of impaired wound healing and infection Paper investigating mechanisms of how skin microbes influence skin function: Commensal Microbiota Regulates Skin Barrier Function And Repair Via Signaling Through The Aryl Hydrocarbon Receptor Review by Belkaid and Segre: Dialogue between skin microbiota and immunity About Dr. Aayushi Uberoi PhD: Aayushi Uberoi is an Assistant professor of Pathology & Immunology and Medicine (Dermatology) in Washington University School of Medicine in Saint Louis. Her lab studies the host-microbe-environment interactions in regulating skin barrier. She  has studied interactions between microbes and skin since her Ph.D. research on cutaneous papillomaviruses in Dr. Paul Lambert’s lab at the University of Wisconsin-Madison. While traditional studies of infectious skin diseases have typically focused on singular pathogens within the host, skin is colonized by a diverse array of microbes, which likely exert significant influence on epithelial characteristics. Motivated by this question, Aayushi’s postdoctoral research at the University of Pennsylvania in Dr. Elizabeth Grice’s lab explored the role of the commensal microbiome in regulating the function of the cutaneous barrier. In the lab, Aayushi wears several hats such as conducting research, developing protocols and assays, writing, and making sure the lab has fun equipment.  Aayushi is a recipient of K99/R00 Pathway to Independence award from National Institute of Arthritis & Musculoskeletal & Skin Diseases (NIAMS/NIH), innovator award from Society of Investigative Dermatology, fellowships from Prevent Cancer Foundation and Dermatology Foundation and a Young Investigator Award from the Wound Healing Society.

    30 min

  4. FEB 22

    ISAPP’s scientific consensus definition of gut health

    This episode features two guests from the ISAPP board of directors who led the recently published consensus definition of gut health: Prof. Maria Marco PhD from UC Davis (USA), and Prof. Eamonn Quigley MD from Houston Methodist Hospital (USA). In the paper, the group defines gut health as: “a state of normal gastrointestinal function without active gastrointestinal disease and gut-related symptoms that affect quality of life”. Gut health is a commonly used term that previously had no scientific definition. Initially the group of experts (both scientists and physicians) that met to discuss it had a lot of skepticism, but they became more enthusiastic and engaged as the discussion proceeded and were finally able to reach consensus. The group identified 6 distinct domains that are encompassed under gut health: gut microbiome, gut barrier, gastrointestinal physiology (primarily intestinal secretions and motility), gut-brain axis, immune function, and metabolism. The group hopes it will provide clarity over time about which aspect(s) of gut health are being assessed in a given study (as it’s not realistic to look at all aspects in a single study). One difficulty is that some of the tests available to measure these domains are quite limited and/or invasive. Nor do consistent correlations exist between symptoms and objective measures of the 6 domains. Determinants of gut health are also discussed in the paper, with diet being important among these. Episode abbreviations and links: Gut health consensus definition paper: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of gut health Earlier publication on gut health by Bischoff: ‘Gut health’: a new objective in medicine? About Prof. Maria Marco PhD: Dr. Maria Marco PhD, is President of ISAPP’s board of directors and Professor in the Department of Food Science and Technology at the University of California, Davis. She earned her PhD in microbiology at the University of California, Berkeley. Prof. Marco started her lactic acid bacteria and gut health laboratory at UC Davis in 2008 and has built an internationally-recognized, NIH, USDA, and NSF funded research program on probiotics, fermented foods, and dietary modulation of the gut microbiome. She is currently a fellow in the American Academy of Microbiology. About Prof. Eamonn Quigley MD: Dr. Eamonn M M Quigley MD FRCP FACP MACG FRCPI MWGO is David M Underwood Chair of Medicine in Digestive Disorders and Chief of the Division of Gastroenterology and Hepatology at Houston Methodist Hospital. A native of Cork, Ireland, he graduated in medicine from University College Cork. He trained in internal medicine in Glasgow, completed a two-year research fellowship at the Mayo Clinic, and training in gastroenterology in Manchester, UK. He joined the University of Nebraska Medical Center in 1986 where he rose to become Chief of Gastroenterology and Hepatology. Returning to Cork in 1998 he served as Dean of the Medical School and a PI at the Alimentary Pharmabiotic Center. He served as president of the American College of Gastroenterology and the WGO and as editor-in-chief of the American Journal of Gastroenterology.

    30 min

  5. 12/18/2025

    2025 highlights in biotic science

    This special year-end episode, which covers 2025’s highlights in biotic science, features three of the academic scientists who serve on the ISAPP board of directors: Prof. Maria Marco PhD from University of California, Davis (USA), Prof. Sarah Lebeer PhD from University of Antwerp (Belgium), and Dr. Gabriel Vinderola PhD from National University of Litoral (Argentina). After a brief review of ISAPP’s activities, the host, Prof. Colin Hill PhD from University College Cork (Ireland) asks the three guests about the talks that stood out from the ISAPP annual meeting. The guests cited talks by Prof. Howard Bauchner MD on publishing and the scientific communication ecosystem; Dr. Carolina Tropini PhD on factors affecting the gut microbial environment and engineering gut microbes as biosensors; and Dr. Peijun Tian PhD on a microbial metabolite that can signal to the brain to relieve depression through the gut-brain axis. The guests also described some stand-out papers published this year (linked below). Finally, they discussed how science is informing regulatory issues in different parts of the world, and shared some research from their own labs that they’re particularly excited about. Episode abbreviations and links: Paper from Dr. Peijun Tian PhD showing a microbial metabolite that signals through the gut-brain axis: Bifidobacteria with indole-3-lactic acid-producing capacity exhibit psychobiotic potential via reducing neuroinflammation NiMe diet paper: Cardiometabolic benefits of a non-industrialized-type diet are linked to gut microbiome modulation (also see this podcast episode) Paper on a host colonization factor in L. plantarum: A conserved bacterial genetic basis for commensal-host specificity Research presented at a congress this year on maternal feces given to infants: Eating a tiny bit of mom’s poop could give C-section babies an immune ‘primer’ Paper from Marco lab on microbial metabolites in sauerkraut: The fermented cabbage metabolome and its protection against cytokine-induced intestinal barrier disruption of Caco-2 monolayers

    30 min

  6. 12/04/2025

    Trials on probiotics and prebiotics in infant formula, with Prof. Yvan Vandenplas MD PhD

    This episode features Prof. Yvan Vandenplas MD PhD from the University Hospital Brussels and Vrije Universiteit Brussel (Belgium), speaking about the science on probiotics and prebiotics in infant formula. Over the past 20 years in this field, awareness of the importance of the gastrointestinal microbiota has grown, and biotics have been employed to try to shape the gut microbiota of infants formula-fed to resemble that of breastfed infants. In particular, human milk oligosaccharides (HMOs) are prebiotics that are shown to change the microbiota composition, although the clinical benefits of these changes are not yet clear. What clinical benefits are achievable for infants who receive formula with added probiotics or prebiotics? Looking closely at the trials, it’s evident that probiotics and prebiotics are associated with a decrease in infections and antibiotic prescriptions, but researchers need to use these as primary endpoints in their trials to increase the strength of the evidence. In a recent European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) recommendations paper, the probiotic recommendations were challenging because for each specific probiotic intervention the group had difficulty finding two clinical trials with a similar design, limiting their ability to make conclusions. Prof. Vandenplas says more trials need to be done independently to strengthen the evidence. Long-term outcomes from probiotic or prebiotic supplementation in infant formula are possible as well, but much larger longitudinal trials are necessary to establish these outcomes. Episode abbreviations and links: ESPGHAN recommendations paper: Recommendations on the health outcomes of infant formula supplemented with biotics by the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition Special Interest Group on Gut Microbiota and Modifications Trial showing positive outcomes of an infant probiotic and prebiotic intervention in a region with high prevalence of infectious disease: A randomized synbiotic trial to prevent sepsis among infants in rural India About Prof. Yvan Vandenplas MD PhD: Yvan Vandenplas did his medical studies at the ”Vrije Universiteit Brussel” (Free University of Brussels) and trained in pediatrics (1981-1986) at the same University. He became Head of the Unit for Pediatric Gastroenterology and Nutrition in 1987 and created the Pediatric Hospital, the KidZ Health Castle, at the University Hospital Brussels (UZ Brussel) of the same university, where he had the Chair of Pediatrics since 1994 up to 2021. He is now Prof. Emeritus and consultant at the same hospital. He is associate editor of Nutrients.

    30 min

  7. 11/26/2025

    Dietary management of chronic constipation, with Dr. Eirini Dimidi PhD RD

    This episode features Dr. Eirini Dimidi PhD RD from King’s College London (UK), speaking about the recently published British Dietetic Association’s guidelines for dietary management of chronic constipation. Constipation can be a major concern for patients, but evidence around some of the most common dietary recommendations for addressing it has remained unclear. After a thorough review of evidence from randomized, controlled trials, Dr. Dimidi and colleagues found evidence for specific foods / beverages improving certain symptoms of constipation. In addition, some supplements such as psyllium, certain probiotics, and magnesium oxide have evidence for efficacy. A high-fiber diet is a commonly recommended dietary strategy for chronic constipation, but the guideline shows that the evidence to date is insufficient to support this recommendation. (However, a high fiber diet has many other benefits.) Probably the effective foods’ key mechanism of action in relieving symptoms of constipation is the fiber they contain, but future studies need to confirm this. Regarding probiotics, so far the evidence is ambiguous around which strains and which durations of treatment are the most effective so the authors were unable to make a confident conclusion. However, for practical reasons they included the expert opinion that patients should be advised to take a probiotic of their choice for at least 4 weeks in addressing chronic constipation. Episode abbreviations and links: 2025 guidelines: British Dietetic Association Guidelines for the Dietary Management of Chronic Constipation in Adults 2019 review on fermented foods & gastrointestinal outcomes: Fermented Foods: Definitions and Characteristics, Impact on the Gut Microbiota and Effects on Gastrointestinal Health and Disease LinkedIn profile for Dr. Dimidi About Dr. Eirini Dimidi PhD RD: Dr Eirini Dimidi is an Associate Professor in Nutritional Sciences at King’s College London. She is a registered dietitian and nutritionist since 2011, after completing a BSc in Nutrition and Dietetics and a MSc in Clinical and Public Health Nutrition. This was followed by the completion of a PhD from King’s College London where she investigated the effectiveness of probiotics in people with chronic constipation. She is leading research on nutrition-based interventions, including fibre, prebiotics, probiotics, plant foods, and plant-based diets in gut function and dysfunction. She is also investigating the mechanisms through which nutritional interventions may affect immune and mental health via the gut microbiome. Dr Dimidi led the development of the first ever UK national dietary guidelines for the management of chronic constipation, which have been endorsed by the British Dietetic Association. Dr Dimidi was awarded the 2023 Cuthbertson Medal by the Nutrition Society, and the 2022 ISAPP Glenn Gibson Early Career Research Prize for her research on the effect of diet in gut health. She also received the 2021 Rising Star and 2020 Elizabeth Washington awards by the British Dietetic Association.

    30 min

  8. 11/07/2025

    How ecological dynamics affect pathogens in the gut, with Prof. Kevin Foster PhD

    This episode features Prof. Kevin Foster PhD from University of Oxford (UK), speaking about his lab’s ecological approach to the gut microbiome and efforts to understand and predict dynamics of different species in the microbiome. They also focus on how these ecological dynamics map onto health outcomes, and how they inform interventions. In a 2023 paper, they explored the concept of colonization resistance in the gut, and why certain bacteria or combinations of bacteria are particularly good at preventing pathogens from thriving. Both diversity and composition are important for determining the extent to which a community resists a pathogen. But a microbiome may equally resist a probiotic that’s introduced because the probiotic microorganism doesn’t have access to a unique nutrient. How bacteria interact with each other can help determine resiliency or stability of the microbiome overall. While it’s true that hundreds of species of bacteria exist in the gut, the scale at which the microbes interact locally is much more limited (on the scale of tens of species). Episode abbreviations and links: 2023 paper examining colonization resistance against 2 pathogens: Microbiome diversity protects against pathogens by nutrient blocking.  About Prof. Kevin Foster PhD: Professor Kevin Foster FRS is the Chair of Microbiology at the Dunn School of Pathology, University of Oxford. Prior to this, he was Professor of Evolutionary Biology in the departments of Biology and Biochemistry at Oxford. Before Oxford, he had a lab at Harvard as a Bauer Fellow in the FAS Center for Systems Biology. He did his undergrad at Cambridge in Natural Sciences and his Ph.D. at the University of Sheffield in evolutionary biology. Professor Foster’s research integrates the traditional fields of ecology and evolution with the latest methods in computation, microbiology, molecular genetics, and the study of the mammalian microbiome. The lab focuses on how bacteria compete and succeed in their communities and seeks to use this to manipulate gut communities for better health.

    30 min
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5
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2 Ratings

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This podcast covers emerging topics and challenges in the science of probiotics, prebiotics, synbiotics, postbiotics and fermented foods. This is the podcast of The International Scientific Association for Probiotics and Prebiotic (ISAPP), a nonprofit scientific organization dedicated to advancing the science of these fields.

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