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Microbiome Dysbiosis

An astronomical number of bacteria live in our guts. The average adult human has been estimated to harbor 38 trillion (3.8 x 1013) bacterial cells. Ninety-seven percent of these bacteria inhabit the colon whereas much lower numbers of bacteria are present in the stomach (107 bacteria) and small intestine (1011 bacteria).1

The gut microbiome is rich and diverse with more than 5000 bacterial species present.2 Together these bacteria produce a wealth of molecules as part of their metabolism, e.g. vitamins, nutrients, or neurotransmitters.3, 4 Some metabolites are able to penetrate into the intestinal mucosa where they have local effects,5, 6 while others enter blood circulation and can affect organs such as the liver, or the brain.4, 7

A close relationship between the diet and the composition of the microbiome determines the types of metabolites being produced in the gut.3, 8, 9 The homeostatic relationship between diet, microbiome and host contributes to human well-being and long-term health.10, 11, 12, 13

The natural gut homeostasis may be disturbed resulting in an unbalanced, or dysbiotic microbiome14 with loss of diversity, keystone species, or pathogenic overgrowth.15 Ultimately this may have consequences for human health.16, 17, 18

Although the adult microbiome is relatively stable, it is sensitive to lifestyle factors such as diet,9 psychological stress,19 or medication.20 Use of antibiotics may cause severe dysbiosis and the effect on the microbiome may be long-lasting.21

Studies have shown that some probiotics may help maintain a healthy balance in the microbiome therefore, reducing the risk of antibiotic associated diarrhea. In these studies, Bifidobacterium, BB-12® and Lactobacillus acidophilus, LA-5® demonstrated effectiveness at reducing the duration of this condition.22, 23 One mechanism by which BB-12® and LA-5® may exert this effect is through their bactericidal action, i.e. the probiotic bacteria compete with harmful bacteria by producing substances that are toxic to the pathogens.24, 25 Many probiotics have been shown to produce bioactive molecules with anti-bacterial effects, including BB-12®,24 LA-5®,26 Lactobacillus rhamnosus, LGG®,27 to stimulate the body’s own antibacterial molecules, Lactobacillus paracasei, L. CASEI 431®,28 to inhibit the adhesion of pathogens to the epithelium, BB-12®,29 LGG®,30 Lactobacillus rhamnosus, GR-1®,31 or to displace adhering pathogens, LGG®.32

BB-12®, LA-5®, LGG®, L. CASEI 431®, and GR-1® are registered trademarks of Chr. Hansen A/S.

The article is provided for informational purposes regarding probiotics and is not meant to suggest that any substance referenced in the article is intended to diagnose, cure, mitigate, treat, or prevent any disease.


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Microbiome dysbiosis

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Surviving the stomach

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Mucus layer

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Immune system

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Intestinal barrier

References Open Close

  1. Sender R, et al. Revised Estimates for the Number of Human and Bacteria Cells in the Body. PLoS Biol. 2016;14(8):e1002533. (PubMed)
  2. Rice BL, et al. Extensive Unexplored Human Microbiome Diversity Revealed by Over 150,000 Genomes from Metagenomes Spanning Age, Geography, and Lifestyle. Cell. 2019;176(3):649-662.e20.(PubMed)
  3. Yuan C, et al. Mucosal Microbiota and Metabolome along the Intestinal Tract Reveal a Location-Specific Relationship. mSystems. 2020;5(3):1–11. (PubMed)
  4. Morais LH, et al. The gut microbiota–brain axis in behaviour and brain disorders. Nat Rev Microbiol. 2021;19(4):241-255. (PubMed)
  5. Wong JMW, et al. Colonic health: Fermentation and short chain fatty acids. J Clin Gastroenterol. 2006;40(3):235–43. (PubMed)
  6. Yan F, et al. Soluble Proteins Produced by Probiotic Bacteria Regulate Intestinal Epithelial Cell Survival and Growth. Gasteroenterology. 2007;132(2):562–75. (PubMed)
  7.  Woodhouse C, et al. Modulating the gut – liver axis and the pivotal role of the faecal microbiome in cirrhosis. Clin Med (Lond). 2020;20(5):493–500. (PubMed)
  8. Tang W, et al. In vitro digestion and fermentation of released exopolysaccharides (r-EPS) from Lactobacillus delbrueckii ssp. bulgaricus SRFM-1. Carbohydr Polym. 2020;230:115593. (PubMed)
  9. Redondo-Useros N, et al. Microbiota and lifestyle: A special focus on diet. Nutrients. 2020;12(6):1–54. (PubMed)
  10. Fujimura KES, et al. Role of the gut microbiota in defining human health. Expert Rev Anti Infect Ther. 2010;8(4):435–54.(PubMed)
  11. Nicholson JK, et al. Host-Gut Microbiota Metabolic Interactions. Science. 2012;336:1262–1266. (PubMed)
  12. Ruan W, et al. Healthy Human Gastrointestinal Microbiome: Composition and Function After a Decade of Exploration. Dig Dis Sci. 2020;65(3):695–705. (PubMed)
  13. Kho ZY, Lal SK. The human gut microbiome - A potential controller of wellness and disease. Front Microbiol. 2018;9:1835. (PubMed)
  14. Hooks KB, O’Malley MA. Dysbiosis and its discontents. MBio. 2017;8(5):e01492-17. (PubMed)
  15. Berg G, et al. Microbiome definition re-visited: old concepts and new challenges. Microbiome. 2020; 8(1):103. (PubMed)
  16. Wilkins LJ, et al. Defining Dysbiosis for a Cluster of Chronic Diseases. Sci Rep. 2019;9(1):1–10. (PubMed)
  17. Petersen C, Round JL. Defining dysbiosis and its influence on host immunity and disease. Cell Microbiol. 2014;16(7):1024–33. (PubMed)
  18. Rogers GB, et al. From gut dysbiosis to altered brain function and mental illness: Mechanisms and pathways. Mol Psychiatry. 2016;21(6):738–48. (PubMed)
  19. Cryan JF, et al. The microbiota-gut-brain axis. Physiol Rev. 2019;99(4):1877–2013. (PubMed)
  20. Jackson MA, et al. Gut microbiota associations with common diseases and prescription medications in a population-based cohort. Nat Commun. 2018;9(1):2655. (PubMed)
  21. Palleja A, et al. Recovery of gut microbiota of healthy adults following antibiotic exposure. Nat Microbiol. 2018;3(11):1255-1265. (PubMed)
  22. Chatterjee S, et al. Randomised Placebo-controlled Double Blind Multicentric Trial on Efficacy and Safety of Lactobacillus acidophilus LA-5 and Bifidobacterium BB-12 for Prevention of Antibiotic-Associated Diarrhoea. J Assoc Physicians India. 2013;61:708–12. (PubMed)
  23. De Vrese M, et al. Probiotic lactobacilli and bifidobacteria in a fermented milk product with added fruit preparation reduce antibiotic associated diarrhea and Helicobacter pylori activity. J Dairy Res. 2011;78(4):396–403. (PubMed)
  24. Martins FS, et al. Comparative study of Bifidobacterium animalis, Escherichia coli, Lactobacillus casei and Saccharomyces boulardii probiotic properties. Arch Microbiol. 2009;191(8):623–30. (PubMed)
  25. Fooks LJ, Gibson GR. Mixed culture fermentation studies on the effects of synbiotics on the human intestinal pathogens Campylobacter jejuni and Escherichia coli. Anaerobe. 2003;9(5):231–42. (PubMed)
  26. Tabasco R, et al. Lactobacillus acidophilus La-5 increases lactacin B production when it senses live target bacteria. Int J Food Microbiol. 2009;132(2–3):109–16. (PubMed)
  27. Lu R, et al. Isolation, Identification, and Characterization of Small Bioactive Peptides From Lactobacillus GG Conditional Media That Exert Both Anti-Gram-negative and Gram-positive Bactericidal Activity. J Pediatr Gastroenterol Nutr. 2009;49:23–30. (PubMed)
  28. Cazorla SI, et al. Oral administration of probiotics increases Paneth cells and intestinal antimicrobial activity. Front Microbiol. 2018;9:736. (PubMed)
  29. Collado MC, et al. Role of commercial probiotic strains against human pathogen adhesion to intestinal mucus. Lett Appl Microbiol. 2007;45(4):454–60. (PubMed)
  30. Tytgat HLP, et al. Lactobacillus rhamnosus GG Outcompetes Enterococcus faecium via Mucus-Binding Pili: Evidence for a Novel and Heterospecific Probiotic Mechanism. Appl Environ Microbiol.2016;82(19):5756–5762. (PubMed)
  31. Petrova MI, et al. The lectin-like protein 1 in Lactobacillus rhamnosus GR-1 mediates tissue-specific adherence to vaginal epithelium and inhibits urogenital pathogens. Sci Rep. 2016;6:37437. (PubMed)
  32. Collado MC, et al. Protection mechanism of probiotic combination against human pathogens: In vitro adhesion to human intestinal mucus. Asia Pac J Clin Nutr. 2006;15(4):570–5. (PubMed)