16 Gut microbiota and immunity Flashcards
What are the levels of gut defences?
- Physical
- Innate immunity
- Acquired immunity
Physical/ innate host defences in the GI tract?
- Mouth
- Oesophagus
- Stomach
- Small intestine
- Large intestine
4 features of the mouth as a host defence
- Flow of liquids
- Saliva
- Antimicrobials
- Normal microbiota
2 features of the oesophagus as a host defence
- Flow of liquids
* Peristalsis
3 features of the stomach as a host defence
- Acid pH
- Antimicrobials
- Mucus
7 features of the stomach as a host defence
- Flow of gut contents
- Peristalsis
- Mucus
- Bile
- Secretory IgA
- Antimicrobial peptides
- Normal bacterial microbiota
4 features of the large intestine as a host defence
- Normal microbiota
- Peristalsis
- Mucus
- Shedding and replication of epithelium
Name the 3 host-bacteria relationships and the host/bacteria attitude
- Commensal:
• Host = Unaffected
• Bacterium = Happy - Symbiotic:
• Host = Happy
• bacterium = Happy - Parasitic:
• Host = Unhappy
• Bacterium = Happy
Probiotics:
Name 3?
Action?
Produce what?
- Lactobacillus spp.
- Bifidobacterium spp.
- Bacteroides spp.
• Alters pH but lactic acid-producing “friendly” bacteria
What are prebiotics?
- Non-digestible food ingredients
* Stimulate growth/ activity of gut microbiota
Function of probiotics and prebiotics?
- Development of mucosal barrier
- Synthesis of vitamins
- Metabolism of bile acids
- Production of short-chain fatty acids
- Reduction in pH in large bowel
- Immune system activation
What bacteria is present in oesophagus and stomach?
Lactobacilli
What bacteria are present in duodenum/ jejunum?
- Lactobacilli
* Steptococci
What bacteria are present in jejunum/ ileum?
- Enterobacteria
* Bacteroides spp.
What bacteria are present in large bowel?
Frequency (highest to lowest):
100%: • Bacteroides spp. • Fusobacterium spp. • Step. faecalis • Escherichia coli
25-75% • Enterobacteria • Klebsiella spp. • Eubacteria • Bifidobacteria
10-25%:
• Lactobacillus
• Staph. aureus
• Clostridium spp.
<10%:
• Streptocci
• Pseudomonas
• Salmonella
What bacteria are present in focal material?
Frequency:
100%:
• Bacteroides spp.
• Bifidobacteria
• Eubacteria
<10%:
• Coliforms
• Strep. faecalis
Role of gut microbiota (5)
- Prevent colonisation by pathogens
- Excrete useful metabolites
- Ferment unused energy substrates
- Synthesiss and excrete vitamins
- Produce hormones
Once a flourishing gut ecosystem is devastated by antibiotics, or left alone, what substances can restore the ecosystem?
- Probiotics
- Prebiotics
- Bacteriotherapy
Factors controlling gut microbiota (7)
- Physiological status
- Underlying disease
- Intestinal secretions
- Intestinal motility
- Immune mechanisms
- Environmental factors
- Use of antibiotics
Primary immune organ in the body?
- GI tract
- Contains 60% of total immunoglobulins and >10 million lymphocytes per gram tissue
- GI microbiota has a strong influence on the development of the local and systemic immunity and in the regulation of immune functions
Name 4 features associated with pathogen recognition
- PAMPs/ MAMPs: pathogen/ microbe associated molecular patterns
- TLRs: toll-like receptors
- NODs: nucleotide-binding oligomerisation domain-containing proteins
- NLRs: NOD-like receptors
What are the gut microbiota- gut mucosa interactions?
Commensals and pathogens can induce local immune responses:
- ->Stimulates release of NK-kB
- ->Transciption of pro-inflammatory genes
- -> Secretion of cytokines and chemokine e.g. TNF and IFN-gamma
What is NF-κB?
A protein complex that controls transcription of DNA, cytokine production and cell survival
Infections of the GI tract
- Most infections acquired via the faecal-ral route
- Pathogens have to overcome the host defences and compete with the microbiota
- Infection occurs when micro-organism causes ill-health
- Commensals may become pathogenic under right circumstances
Acquisition of intestinal infection?
- Ingestion of infected food and water
- Ingestion of bacterial toxins
- Use of oral antibiotics
What are the symptoms of gastroenteritis?
- Nausea
- Vomiting
- Diarrhoea
- Abdominal discomfort
What is enterocolitis?
Inflammation involving the mucosa of both small and large intestine
Diarrhoea:
• What is it?
• Cause?
• Results in?
- Abnormal faecal discharge characterised by frequent and/ to fluid stool
- Result of disease in small intestine
- Involves increased fluid and electrolyte loss
Dysentery:
• What is it?
• Due to?
• Associated symptoms?
- Inflammation disorder of the GI tract
- Usually resulting from disease of the large intestine
- Often associated with blood and pus in the faeces
- Often accompanied by pain, fever and abdominal cramps
Classification method for stool?
Bristol Stool Chart:
- Type 1 - separate hard lumps
- Type 2 - sausage-shaped but lumpy
- Type 3 - like a sauste with cracks on surface
- Type 4 - like a sausage, smooth and soft
- Type 5 - soft blobs with clear-cut edges
- Type 6 - fluffy pieces with ragged edges, a mushy stool
- Type 7 - watery, no solid pieces. Entirely liquid
Clinical effects of pathogenic invasion of GI tract?
- Diarrhoea/ dysentery
- Malaena
- Blood in faeces
- Pus in faeces
- Abdominal cramps
- Fever
- Sepsis
Examples of gut pathogens acquired from food
- Escherichia coli
- Salmonella sp.
- Campylobacter sp.
- Listeria sp.
- Clostridium perfringens
- Bacillus cereus
- Yersinia entercolitica
- Tapeworm
Examples of gut pathogens acquired from water
- Escherichia coli
- Salmonella sp.
- Campylobacter sp.
- Shigella sp.
- Vibrio cholerae
- Rotavirus
Examples of gut pathogens acquired from animals
- Escherichia coli
- Salmonella sp.
- Campylobacter sp.
- Clostridium perfringens
- Yersinia enterocolitica
Common toxin-producing pathogens in GI? Frequently associated with?
- Bacillus cereus
- Clostridium botulinum
- Clostridium perfringens
- Escherichia coli (enterotoxigenic - ETEC)
- Vibrio cholerae
• Frequently associated with abdominal cramps
