7. Gut Microbiota and Immunity

Question 1

Physical/ innate host defences in the GI tract

Answer 1

• Mouth
• Oesophagus
• Stomach
• Small intestine
• Large intestine

Question 2

4 features of the mouth as a host defence

Answer 2

• Flow of liquids
• Saliva
• Antimicrobials
• Normal microbiota

Question 3

2 features of oesophagus as a host defence

Answer 3

• Flow of liquids

* Peristalsis

Question 4

3 features of the stomach as a host defence?

Answer 4

Acid pH
Antimicrobial
Mucus

Question 5

7 features of SI as a host defence

Answer 5

• Flow of gut contents
• Peristalsis
• Mucus
• Bile
• Secretory IgA
• Antimicrobial peptides
• Normal bacterial microbiota

Question 6

4 features of large intestine as a host defence

Answer 6

• Normal microbiota
• Peristalsis
• Mucus
• Shedding and replication of epithelium

Question 7

Name the 3 host-bacteria relationships and the host/bacteria attitude

Answer 7

Commensal:
Host =Unaffected
Bacteria =Happy

Symbiotic:
Host = Happy
Bacteria = Happy

Parasitic = Unhappy
Bacterium = Happy

Question 8

Probiotics:
Name 3?
Action?
Produce what?

Answer 8

E.g.
• Lactobacillus spp.
• Bifidobacterium spp.
• Bacteroides spp

Action: Alters pH but producing lactic acid

Question 9

What are prebiotics?

Answer 9

Non-deigestible food ingredients

Stimulate growth / activity of gut microbiota

Question 10

Functions of probiotics and probiotics?

Answer 10

Development of mucosal barrier
Synthesis of vitamins
Metabolism of bile acids
Production of short-chain fatty acids
Reduction of pH in large bowel
Immune system activation

Question 11

Role of gut microbiota (5)

Answer 11

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

Question 12

A flourishing gut/ecosystem –> Devastation by ______ —> Left alone –> Prebitiocs, probiotics, ______ —> Restored ecosystem

Answer 12

A flourishing gut/ecosystem –> Devastation by ANTIBIOTICS —> Left alone –> Prebitiocs, probiotics, BACTERIOTHERAPY —> Restored ecosystem

Question 13

Factors Controlling Gut Microflora (7)

Answer 13

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

Question 14

Primary immune organ in the body?

Answer 14

GI tract

GI microbiota has a strong influence on the development of the local and systemic immunity and in the regulation of immune functions

Question 15

Name 4 features associated with pathogen recognition?

Answer 15

1. PAMPs / MAMPs: pathogen / microbe associated molecular patterns
2. TLRs: Toll-like receptors
3. NODs: nucleotide-binding oligomerization
   domain-containing proteins
4. NLRs: NOD-like receptors

Question 16

What are the gut microbiota- gut mucosa interactions?

Answer 16

Commensals and pathogens can induce local immune response.
Stimulates release of NK-kB
–>
Transciption of pro-inflammatory genes
–> Secretion of cytokines and chemokine such as TNF and IFN-gamma

NF-κB is a protein complex that controls transcription of DNA, cytokine production and cell survival

Question 17

Diarrhoea:
What is it?
Cause?
Results in?

Answer 17

What is it? Abnormal faecal discharge characterised by frequent and/or fluid stool.

Cause? Result of disease in small intestine

Results in? Involves increased fluid and electrolyte loss

Question 18

Dysentery:
What is it?
Due to?
Associated symptoms?

Answer 18

What is it?
Inflammation disorder of GI tract

Due to:
Disease of large intestine / infection

Associated symptoms:

• Blood and pus in the faeces
• Pain
• Fever
• Abdominal cramps

Question 19

Classification method for stools?

Answer 19

Bristol stool chart

Type 1-7 (hard small lumps –> entirely liquid)

Question 20

Acquisition of intestinal infection

Answer 20

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

Question 21

What are the symptoms of gastroenteritis? 4

Answer 21

Nausea
Vomiting
Diarrhoea
Abdominal discomfort

Question 22

What is enterocolitis?

Answer 22

Inflammation involving the mucosa of both and large intestine