Lec 19 - Probiotics and prebiotics Flashcards
List the 6 mechanisms describing how commensal bacteria form colonisation resistance
- Enhancement of epithelial barrier
- Increased adhesion to intestinal mucosa
- Inhibition of pathogen adhesion by outcompeting receptors
- Competitive exclusion of pathogenic MCOs
- Production of anti-MCO substances
- Modulation of the immune system
What were the effects noted from antibiotic use in early life when conducted in mouse studies?
- Increased type-1 diabetes
- Reduced anti-inflammatory immune cells
- Increased adiposity
- Increased risk of asthma
Describe how the effects of antibiotics can be reversed
- Spontaneous recovery
- Probiotics
- Faecal microbiota transplant (FMT)
In an unweighted unifrac, which of the following 3 methods demonstrated the best recovery of the original microbiota?
- Spontaneous recovery
- Probiotics
- FMT
- Spontaneous recovery = fairly good
- Probiotics = worst bc different bacteria
- FMT = almost complete recovery (best)
What is Clostridium difficile and how does it effect the microbiota? How is it treated?
- Gram positive rod
- Pathobiont
- Spores germinate in gut to vegetative cells which produce enterotoxin
- Colon inflammation, diarrhoea, pseudomembrane entercolitis
- Treated by FMT
Describe what happens to the immune system in germ-free animal studies
Lymphoid organ development deficiency and reduced immune cell activity
What was the original hygiene hypothesis?
David Strachan 1989 = children with older siblings had less hay fever and eczema
Early life exposure to infections drives immune response favourably to reduce allergies
What is the reviewed hygiene hypothesis?
Protection from allergic diseases is mediated by early life exposure to healthy commensals rather than pathogens
Describe the typical features of symbiosis
- Functional epithelia with mucus production, PRRs, antimicrobials and secretory IgA
- Small PAMP leakage activating Tregs which produce IL-10 and TGF-beta for immune suppression and IgA production
- Tolerance = decreased inflammation
Describe the typical features of dysbiosis
- Pathobiont overgrowth and toxins
- Loss of epithelia
- More PAMPs = proinflammatory cytokines in Th1 and Th17 responses producing IgG
- No tolerance = increased inflammation = further dmg
What are the 3 types of xenobiotics? Provide examples
- Dietary compounds eg carcinogenic cyclamate to cyclohexylamine
- Industrial chemicals and pollutants eg methylmercury to secretable mercury
- Pharmaceuticals eg chemotherapeutic oxaliplatin with reduced effectiveness if antibiotics used
Describe which species of Staphylococcus produced an antibiotic
Skin commensal Staphylococcus lugdunensis produces lugdunin which inhibits S. aureus
What are the roles of fungi, viruses and archaea in the microbiota?
- Fungi = much less abundant, mouth and genital tracts, 18S rRNA seqeuncing or ribosomal ITS region sequencing
- Viruses = consider eukaryotic and prokaryotic ones, culture or WGS
- Archaea = abundant methanogens associated with peridontal disease, recognised by immunity
What were 2 instances in history of probiotic use?
- 1917 Alfred Nissle found soldier with E. coli strain antagonising bacteria to resist dysentry
- 1910 Elie Metchnikoff found extended age of Balkan peasants due to Lactobacillus in yoghurt
List untargeted interventions for the microbiome and their overall aim
Exercise, diet, FMT, probiotics, prebiotics, synbiotics, postbiotics
Aim = general improvement in microbiota
