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Physiology 1 : GI > Introduction to microbiology of the gut > Flashcards

Introduction to microbiology of the gut Flashcards

1
Q

What types of flora are there?

A

→Resident flora - for life,commensal organisms

→Transient flora - temporarily reduced - carried or changes

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2
Q

Why do the color and texture of babies feces change a lot?

A

→change in organisms of the baby’s gut

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3
Q

What do the organisms from a babys gut change from and to?

A

→facultative anaerobes to obligate anaerobes

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4
Q

What does bifidobacter produce and what does it prevent?

A

→produces lactic acid

→prevents the growth of gram negative bacteria

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5
Q

Once a baby starts to wean what happens to the bifidobacter?

A

→bifdobacter decreases and becomes

→bacteroides, clostridia and eubacteria

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6
Q

How many bacteria are there in the stomach?

A

→There are few bacteria due to the acidic conditions

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7
Q

When do the bacteria increase?

A

→ As you go into the jejunum and duodenum

→ Mainly lactobacillus

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8
Q

What are obligate anaerobes?

A

→bacteroides
→ bifidobacter
→clostridia

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9
Q

What are facultative anaerobes?

A

→E.Coli

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10
Q

What kind of bacteria is E.Coli?

A

→gram negative

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11
Q

How many bacteria per gram are there in feces?

A

→10x11 bacteria per gram

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12
Q

Going from the top to the bottom of the GI how do bacteria change?

A

→number and complexity of the species increases.

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13
Q

What two types of bacteria does a normal gut usually have?

A

→bacteroides

→firmicutes

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14
Q

What diseases are associated with microbiome alterations?

A 
→Crohn’s disease 
→Inflammatory bowel disease 
→Clostridium difficile 
→Colon cancer
→Allergy 
→Celiac disease 
→Diabetes type I and II 
→Obesity (bacteroidetes/firmicute ratios) 
→Mental health and depression
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15
Q

How do scientists find bacteria in the gut?

A

→targeting and sequencing 16S rRNA is how scientists find the bacteria in the gut.

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16
Q

What are the host defences against pathogens?

A

→Structural
Seamless epithelium, tight junctions, sloughing/turnover

→Mechanical
Peristalsis, chewing, fluid movement

→Biochemical
Gastric acid, bile, mucus

→Immunological
Secretory IgA, intraepithelial lymphocytes

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17
Q

What are the 4 benefits of gut flora?

A

→Colonization resistance - blocks pathogens
→Metabolites of benefit to host
→Normal development of immunity
→Aids digestion

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18
Q

How do gut flora produce gut metabolites?

A

→Vitamin K, B12, organic acids
→Enhanced utilization of amino acids
→Butyrate for colonocytes - maintain anerobiasis

19
Q

How do gut flora aid digestion?

A

→Fermentation of sugars (10% of energy), H2 or methane, regulation of fat storage

20
Q

What do probiotic organisms produce?

A

→lactic acid and organic acids

21
Q

What do probiotic organisms do?

A

→get 10% absorbable energy from dietary fibre.

22
Q

What is the function of microbial antagonism?

A

→Maintains flora through complex interactions - competition between flora
→Limits the growth of competitors and pathogens

23
Q

How does gut flora prevent colonization?

A 
→Bacteriocins (peptides that kill other bacteria) 
→Reduced numbers of available epithelial receptors 
→Keeps pH low 
→Controls oxidative potential 
→Limits pathogen growth 
→Occupy all niches 
→High numbers 
Waste products
24
Q

What does loss of flora lead to?

A

→ Bacterial or pathogen overgrowth

25
Q

What effects does ciprofloxacin have on flora and when does this return to normal?

A

→decrease in diversity with significant effects on 1/3rd of taxa
→ returns to normal in 4 weeks

26
Q

What is diarrhoea defined as?

A

→Defined as watery or liquid stools

→Increase in stool weight above 200g per day

27
Q

What are clinical consequences of diarrhoea?

A 
→Can lead to severe dehydration 
→Excessive fluid and electrolyte loss 
→Hypovolaemia, hypokalaemia 
→Organ failure
→Long term morbidity and reduced growth
28
Q

What is the global impact of diarrhoea?

A

→3 billion episodes per year

→1.3 million deaths per year due to dehydration

29
Q

What are the organisms that cause diarrhoea?

A 
→Microorganisms 
→Bacteria 
→Viruses 
→Parasites - protozoal and worms 
→Shed in feces and transmission to new hosts
30
Q

What is dysentery and what is it associated with?

A

→Inflammatory disorder of GI tract - usually large intestine
→Often associated with blood and pus

31
Q

What are the symptoms of dysentery?

A

→Pain
→ fever
→abdominal cramps

32
Q

Acute of chronic diarrhoea + blood + pus = ?

A

= dysentery

33
Q

What does chronic diarrhoea or malabsorption lead to?

A

→ steatorrhea

→ fat malabsorption

34
Q

What does infective proctitis lead to?

A

→ ano-rectal STIs

35
Q

What is associated with dyspepsia?

A

→ ulcers

→ H. pYlori

36
Q

What is associated with dysphagia?

A

→oesophagus

→ candida

37
Q

What are the 4 types of damage caused by GI infection?

A

→Pharmacological action of bacterial toxins

→Local inflammation in response to superficial microbial invasion

→Deep invasion to blood and lymphatics and dissemination of the organism to other body sites

→Perforation/ ulceration of mucosal epithelium
Peritonitis, intra abdominal abscess

38
Q

What causes watery diarrhoea?

A

→ epithelial cells/enterocytes are damaged
→ absorption of fluid is stopped
→villi are damaged
→ crypt cells start hypersecreting

39
Q

What do E.Coli toxins do?

A

→toxin migrates into the cell and causes changes to cAMP
→change protein kinases
→change chloride channels

40
Q

How does changing chloride channels by E.Coli cause diarrhoea

A

→There is hyperchloride secretion

→Causes the osmotic flow of water following the chloride and fluid is secreted leading to diarrhoea.

41
Q

How does EPEC E.COli work?

A

→Enteropathogenic E.Coli binds to the brush border and the microvillus structure is destroyed so the enterocytes no longer works.
→ Adherence

42
Q

How do viruses cause diarrhoea?

A

→Viruses can penetrate the enterocytes which destroy the cells.
→No absorption occurs and malabsorption happens with hypersecretion.
→There is villus atrophy and as a result of this you get crypt hyperplasia, eventually the villi recover.

43
Q

What are the 3 mechanisms of diarrhoea and what organisms cause this?

A

→ Bacterial toxins - E.coli
→ Adherence - E.coli
→ Penetration and iNvasion - Viruses

44
Q

What is the microbiome affected by?

A

→diet
→ antibiotics
→surgery
→genes

Physiology 1 : GI (15 decks)

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