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GI AM > Microbiota of the GI tract > Flashcards

Microbiota of the GI tract Flashcards

1
Q

What is the transit time in the mouth?

A

Up to 1 minute

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2
Q

What is the transit time in the oesophagus?

A

4-8 seconds

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3
Q

What is the transit time in the stomach?

A

2-4 hours

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4
Q

What is the transit time in the small intestine?

A

3-5 hours

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5
Q

What is the transit time in the colon?

A

10 hours to several days

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6
Q

What does transit time affect?

A

Bacterial populations

Cell exposure to toxins

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7
Q

What increases moving don the GI tract?

A

Anaerobic conditions
Bacterial density
Dominance of obligate anaerobes

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8
Q

What is the most bacterial dense site of the GI tract?

A

Large intestine

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9
Q

What is the predominant colonisation of the large intestine?

A

Anarobes

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10
Q

What are facultative anaerobes?

A

Can grow in presence or absence or oxygen

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11
Q

What are obligate anaerobes?

A

Cannot grow in the presence of oxygen

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12
Q

What factors affect the dominant bacteria at each site?

A

pH
Transit time
O2 concentration

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13
Q

What is the pH of the mouth?

A

Neutral

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14
Q

What is the pH of the stomach?

A

Acidic

1.5-4

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15
Q

What is the pH of the duodenum?

A

Neutral

7-8.5

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16
Q

What is the pH of the ileum?

A

Acidic

4-7

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17
Q

What is the pH of the colon?

A

5.5-6.5

18
Q

What is the role of the GI microbiota?

A 
Metabolism of dietary components
Production of essential metabolites
Development of immune system
Host signalling
Defence against pathogens
Modifications of host secretions
19
Q

How does the GI microbiota metabolise dietary components?

A

Microbes grow on fibre and convert it to other products

20
Q

What are the benefits of including fibre in the diet?

A

Improves faecal bulking

Contains important phytochemical, antioxidants and vitamins

21
Q

What is the purpose of bacterial fermentation of fibre?

A

Release additional phytochemicals
Maintains slightly acidic pH
Increases commensal bacterial population and resistance to pathogens
Essential supply of short chain fatty acids

22
Q

What short chain fatty acids does fibre supply and what is their purpose?

A

Butyrate- epithelial cell growth and regeneration
Propionate- gluconeogenesis and satiety signalling
Acetate- lipogenesis

23
Q

How do resident bacteria protect against pathogens?

A

Lower pH
Create physical barrier
Prime immune system
Produce active components to ‘kill’ incoming pathogens

24
Q

What is the barrier effect?

A

Large number of indigenous microbiota prevent colonisation by ingested pathogens and inhibit overgrowth of potentially pathogenic bacteria normally resident at low levels

25
Q

What is the gut mucosal immune system?

A

Mucous layer of the gut forms barrier between lumen bacteria and epithelial cells

26
Q

When do autoimmune disease of the gut occur?

A

When immune system can no longer distinguish between harmful pathogens and commensal bacteria

27
Q

How does the breakdown of fibre help with signalling?

A

Short chain fatty acids produced act on receptors on epithelial cells to secrete hormones and have the desired effect

28
Q

What factors influence gut microbiota>

A

Dietary changes- greatest influence
Age
Alcohol intake

29
Q

What is changes in microbiota composition associated with?

A

Disease

This does not mean this is necessarily the cause

30
Q

How might diseases be cause by indigenous microbiota?

A

Overgrowth
Colonisation at a different body site
General dysbiosis

31
Q

What is inflammation in IBD likely caused by?

A

Dysregulated immune response to microbiota

32
Q

What microbiota changes are present in IBD?

A

Reduced bacterial diversity
Reduced stability in bacterial composition
Increased mucosal barrier load

33
Q

What is the treatment of IBD?

A

Broad spectrum antibiotics

Faecal stream diversion

34
Q

Why is it difficult to distinguish between the cause and effect of IBD?

A

Reduced bacterial diversity could be caused by inflammation or antibiotics

35
Q

What are probiotics?

A

Live microorganisms which, when administered in adequate amounts, confer a health benefit

36
Q

What are the different mechanisms of action of probiotics?

A 
Competition
Bioconversion
Production of vitamins
Direct antagonism
Competitive exclusion
Barrier function
Reduce inflammation
Immune stimulation
37
Q

What are probiotics?

A

Selectively fermented food/ingredient that results in specific changes in composition and/or activity of GI microbiota, conferring health benefit on the host

38
Q

What is the effect of antibiotics on microbiota?

A

Kill pathogen but also commensal bacteria

39
Q

What are the consequences of antibiotic therapy?

A

Decreased microbial diversity

Opportunity for pathogen colonisation and pathogen dominant community

40
Q

What happens with C. diff post antibiotic therapy?

A

C. diff expands to occupy empty niches

Overgrowth causes toxin production, fever, abdomen pain, C. diff associated diarrhoea

41
Q

What is the initial treatment of C. diff infection?

A

Antibiotic therapy

42
Q

What is the treatment for recurring C. diff infections?

A

Faecal microbial transplant

GI AM (34 decks)

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