Gut Microbiota and Immunity Flashcards
What are the three levels of gut defence?
- Physical - skin
- Innate immunity - non-specific
- Acquired immunity - B-cells and T cells
What are the 5 main host defences in the GI tract?
- mouth
- oesophagus
- stomach
- small intestine
- large intestine
What are the host defences of the mouth?
- Flow of liquids
- Saliva
- Antimicrobials
- Microbiota
What are the host defences of the oesophagus?
- flow of liquids
- peristalsis
What are the host defences of the stomach?
- acid pH
- antimicrobials
- mucus (goblet cells)
What are the host defences of the small intestine?
- flow of gut contents
- peristalsis
- mucus
- bile (acidic)
- secretory IgA
- Antimicrobial peptides
- Microbiota
What are the host defences of the large intestine?
- microbiota
- peristalsis
- mcus
- shedding and replication of epithelium
Describe a commensal relationship?
- host = ok
- bacteria = happy
Describe a symbiotic relationship
- host = happy
- bacteria = happy
Describe a parasitic relationship
- host = unhappy
- bacteria = happy
What are the three main probiotic bacteria?
- Lactobacillusspp.
- Bifidobacteriumspp.
- Bacteroidesspp.
What is the meaning of probiotic?
greek “for life”
“friendly bacteria”
What is the action of probiotics?
produce bacteriocins - end product of cabohydrate fermentation
What are the main benefits of prebiotics and probiotics?
- synthesis of vitamins
- metabolism of bile acids
- production of short-chain fatty acids
- reduction in pH of large bowel
- immune system activation
- development of mucosal barrier
What is the role of gut microbtioa?
- Prevent colonisation by pathogens
- Excrete useful metabolites
- Ferment unused energy substrates
- Synthesise and excrete vitamins
- Produce hormones
Draw a diagram indicating the factors that contribute to a healthy gut microbiota
What are the main factors controlling gut microbiota?
- Physiological status
- Underlying disease
- Intestinal secretions
- Intestinal motility
- Immune mechanisms
- Environmental factors
- Use of antibiotics
What is the primary immune organ in the body?
GI tract
contains 60% of total immunoglobulins and >10million lymphocytes per gram tissue
What has a strong influence on the development of the local systemic immunity and the regulation of immune functions?
GI microbiota
What four main pathogen recognition receptors?
- PAMPs / MAMPs: pathogen / microbe associated molecular patterns
- TLRs: Toll-like receptors
- NODs: nucleotide-binding oligomerization domain-containing proteins
- NLRs: NOD-like receptors
How are most GI tract infections acquired?
faceal-oral route
When does infection occur?
when a pathogen causes ill health
What must pathogens overcome to cause infection?
host defences and compete with microbiota
What can become pathogenic if the conditions are right?
commensals
What are common ways to acquire an intestinal infection?
- Ingestion of infected food and water
- Ingestion of bacterial toxins
- Use of oral antibiotics
What are the main symtpoms of gastroenteritis?
- Nausea
- Vomiting
- Diarrhoea
- Abdominal discomfort
What is enterocolitis?
Inflammation involving the mucosa of both small and large intestine.
What is diarrhoea?
abnormal faecal discharge characterised by frequent and/or fluid stool
What is diarrhoea a result of?
disease in the small intestine
involves increased fluid and electrolyte loss
What is dysentery of the GI tract?
inflammation disorder of the GI tract
What does desentery result from?
disease of the large intestine
often associated with blood and pus in faeces
accompanied by pain, fever and abdominal cramps
What are the clinical effects of pathological invasion of the 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 spp.
- Campylobacter spp.
- Listeria spp.
- Clostridium perfringens
- Bacillus cereus
- Yersinia enterocolitica
- tapeworm
Examples of gut pathogens acquired from water
- Escherichia coli
- Salmonellaspp.
- Campylobacterspp.
- Shigellaspp.
- Vibriocholerae
- rotavirus
Examples of gut pathogens acquired from animal resovoirs
- Escherichia coli
- Salmonella spp.
- Campylobacter spp.
- Clostridium perfringens
• Yersinia enterocolitica
Common toxin-producing pathogens
– Bacillus cereus
– Clostridium botulinum
– Clostridium perfringens
– Escherichia coli (enterotoxigenic – ETEC)
– Vibrio cholerae
