Gut Microbiota and Immunity

Question 1

What are the three levels of gut defence?

Answer 1

• Physical - skin
• Innate immunity - non-specific
• Acquired immunity - B-cells and T cells

Question 2

What are the 5 main host defences in the GI tract?

Answer 2

• mouth
• oesophagus
• stomach
• small intestine
• large intestine

Question 3

What are the host defences of the mouth?

Answer 3

• Flow of liquids
• Saliva
• Antimicrobials
• Microbiota

Question 4

What are the host defences of the oesophagus?

Answer 4

• flow of liquids
• peristalsis

Question 5

What are the host defences of the stomach?

Answer 5

• acid pH
• antimicrobials
• mucus (goblet cells)

Question 6

What are the host defences of the small intestine?

Answer 6

• flow of gut contents
• peristalsis
• mucus
• bile (acidic)
• secretory IgA
• Antimicrobial peptides
• Microbiota

Question 7

What are the host defences of the large intestine?

Answer 7

• microbiota
• peristalsis
• mcus
• shedding and replication of epithelium

Question 8

Describe a commensal relationship?

Answer 8

• host = ok
• bacteria = happy

Question 9

Describe a symbiotic relationship

Answer 9

• host = happy
• bacteria = happy

Question 10

Describe a parasitic relationship

Answer 10

• host = unhappy
• bacteria = happy

Question 11

What are the three main probiotic bacteria?

Answer 11

• Lactobacillusspp.
• Bifidobacteriumspp.
• Bacteroidesspp.

Question 12

What is the meaning of probiotic?

Answer 12

greek “for life”

“friendly bacteria”

Question 13

What is the action of probiotics?

Answer 13

produce bacteriocins - end product of cabohydrate fermentation

Question 14

What are the main benefits of prebiotics and probiotics?

Answer 14

• 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

Question 15

What is the role of gut microbtioa?

Answer 15

• Prevent colonisation by pathogens
• Excrete useful metabolites
• Ferment unused energy substrates
• Synthesise and excrete vitamins
• Produce hormones

Question 16

Draw a diagram indicating the factors that contribute to a healthy gut microbiota

Answer 16

Question 17

What are the main factors controlling gut microbiota?

Answer 17

• Physiological status
• Underlying disease
• Intestinal secretions
• Intestinal motility
• Immune mechanisms
• Environmental factors
• Use of antibiotics

Question 18

What is the primary immune organ in the body?

Answer 18

GI tract

contains 60% of total immunoglobulins and >10million lymphocytes per gram tissue

Question 19

What has a strong influence on the development of the local systemic immunity and the regulation of immune functions?

Answer 19

GI microbiota

Question 20

What four main pathogen recognition receptors?

Answer 20

• PAMPs / MAMPs: pathogen / microbe associated molecular patterns
• TLRs: Toll-like receptors
• NODs: nucleotide-binding oligomerization domain-containing proteins
• NLRs: NOD-like receptors

Question 21

How are most GI tract infections acquired?

Answer 21

faceal-oral route

Question 22

When does infection occur?

Answer 22

when a pathogen causes ill health

Question 23

What must pathogens overcome to cause infection?

Answer 23

host defences and compete with microbiota

Question 24

What can become pathogenic if the conditions are right?

Answer 24

commensals

Question 25

What are common ways to acquire an intestinal infection?

Answer 25

• Ingestion of infected food and water
• Ingestion of bacterial toxins
• Use of oral antibiotics

Question 26

What are the main symtpoms of gastroenteritis?

Answer 26

• Nausea
• Vomiting
• Diarrhoea
• Abdominal discomfort

Question 27

What is enterocolitis?

Answer 27

Inflammation involving the mucosa of both small and large intestine.

Question 28

What is diarrhoea?

Answer 28

abnormal faecal discharge characterised by frequent and/or fluid stool

Question 29

What is diarrhoea a result of?

Answer 29

disease in the small intestine

involves increased fluid and electrolyte loss

Question 30

What is dysentery of the GI tract?

Answer 30

inflammation disorder of the GI tract

Question 31

What does desentery result from?

Answer 31

disease of the large intestine

often associated with blood and pus in faeces

accompanied by pain, fever and abdominal cramps

Question 32

What are the clinical effects of pathological invasion of the GI tract?

Answer 32

• Diarrhoea / dysentery
• Malaena
• Blood in faeces
• Pus in faeces
• Abdominal cramps
• Fever
• Sepsis

Question 33

Examples of gut pathogens acquired from food?

Answer 33

• Escherichia coli
• Salmonella spp.
• Campylobacter spp.
• Listeria spp.
• Clostridium perfringens
• Bacillus cereus
• Yersinia enterocolitica
• tapeworm

Question 34

Examples of gut pathogens acquired from water

Answer 34

• Escherichia coli
• Salmonellaspp.
• Campylobacterspp.
• Shigellaspp.
• Vibriocholerae
• rotavirus

Question 35

Examples of gut pathogens acquired from animal resovoirs

Answer 35

• Escherichia coli
• Salmonella spp.
• Campylobacter spp.
• Clostridium perfringens

• Yersinia enterocolitica

Question 36

Common toxin-producing pathogens

Answer 36

– Bacillus cereus
– Clostridium botulinum
– Clostridium perfringens

– Escherichia coli (enterotoxigenic – ETEC)

– Vibrio cholerae