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GI System > 9. GI Infections > Flashcards

9. GI Infections Flashcards

1
Q

What are the GI defences to infection?

A 
Sight, smell, memory
Saliva (bacteriostatic secretions)
Gastric acid
Small intestinal secretions (bile)
Colonic mucus
Anaerobic environment
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2
Q

What are the benefits of gut microbiome?

A

Harmful bacteria cannot compete for nutrients
Microbiome produces antimicrobial substances
Helps to develop newborns immune system
Produce certain nutrients (vit K)

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3
Q

How can less gut microbiota affect our health?

A

Obesity - seems to be less diverse population of bacteria
IBD - less diversity
Microbiome composition affects response to chemotherapy
Microbiome composition affects insulin response to food

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4
Q

What do bacteria in colon produce?

A

SCFAs - acetate, propionate, butyrate

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5
Q

What is the role of butyrate?

A

Energy source for colonocytes, helps regulate gut environment

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6
Q

What is the role of acetate?

A

Involved in cholesterol metabolism

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7
Q

What is the role of propionate?

A

Helps regulate satiety

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8
Q

What is a faecal microbiota transplant?

A

Faecal transfer from healthy donors to the sick in order to treat disease
Used to treat pseudomembranous colitis (C.diff)
Via NG tube, upper GI endoscopy, colonoscopy, put into caecum

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9
Q

What are gram negative rods that can cause infections of gut?

A

Salmonella
Campylobacter
Shigella
Enterotoxigenic E.coli

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10
Q

What is a gram positive bacteria that can cause GI infection?

A

Clostridium difficile

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11
Q

What are the symptoms of salmonella infection?

A

Nausea, vomiting, watery diarrhoea, fever, abdominal cramping

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12
Q

How does salmonella affect the body?

A

-Ingested salmonella enter small intestinal cells by endocytosis
In 5%:
-Salmonella pass through endothelial cells to submucosa, where they are taken up by macrophages
-macrophages carry salmonella to reticuloendothelial system, causing lymphoid hyperplasia and hypertrophy

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13
Q

How is salmonella spread?

A

Ingesting contaminated food or water

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14
Q

How s campylobacter spread to humans?

A

Present in chicken GI system, spread via faeco-oral route

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15
Q

What are the symptoms of campylobacter infection?

A

Fever, abdominal cramping, perfuse diarrhoea (can be bloody)

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16
Q

How long does campylobacter usually last?

A

Incubation period 1-7 days

Can last days to weeks, generally self limiting

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17
Q

What is the treatment for campylobacter infection?

A

Fluid/electrolyte replacement

Consider antibiotics if bloody diarrhoea

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18
Q

How is shigella spread?

A

Spread from infected stools, person to person

Only needs a small dose to cause infection

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19
Q

How does shigella affect the body?

A

Invades large intestine colonocytes, multiplies in cells and invades neighbouring cells
This kills colonocytes and forms abscesses in the mucosa
Gives bloody diarrhoea with mucus and abdominal cramping

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20
Q

How is enterotoxigenic E.coli spread?

A

Spread by faecal oral route by contaminated water

Common cause of travellers diarrhoea

21
Q

How does enterotoxigenic E.coli affect the body?

A

Adheres to enterocytes, produces enterotoxins
These cause the hypersecretion of chloride ions
Water leaves cells into the gut lumen
Gives watery diarrhoea

22
Q

Following antibiotic therapy, what happens with C.diff?

A 
Can colonise gut and release toxins
Toxins A (enterotoxigenic resulting in excessive secretion and inflammation) and B (cytotoxin)
23
Q

What are the symptoms of C.diff?

A

Most asymptomatic
Varying degrees of diarrhoea (rarely bloody)
Abdominal cramping
In a few cases - pseudomembranous colitis, toxic megacolon (surgery)

24
Q

What is pseudomembranous colitis?

A

Inflammatory condition

Elevated yellow plaques join to form pseudomembrane

25
Q

What is the treatment for C.diff?

A

Remove offending antibiotic
Fluid resuscitation
Metronidazole/vancomycin

26
Q

What is rotavirus?

A

Very common cause of gastroenteritis in the under 5’s

Double stranded RNA virus

27
Q

What are the symptoms of rotavirus?

A

Vomiting with a fever

Diarrhoea - lasts up to a week

28
Q

What is the treatment for rotavirus?

A

Managing dehydration

29
Q

How does rotavirus affect the body?

A

Chloride secretion - gradient for Na, then water moves into gut
SGLT1 disruption - reduced movement of Na/glucose into enterocyte, higher osmotic load in gut, water moves into gut
Brush border dysfunction - general malabsorption

30
Q

What is norovirus?

A

Most common cause of non-bacterial gastroenteritis in world, affects any age
Only requires small dose
Incubation 1-2 days and symptoms last 1-3 days

31
Q

What are the symptoms of norovirus?

A

Vomiting, water diarrhoea, fever

32
Q

How does norovirus affect the body?

A

Infects small intestine and damages microvilli
Anion secretion, so movement of water into gut lumen
Vomiting is due to delayed gastric emptying

33
Q

What is the treatment for norovirus?

A

Oral rehydration

34
Q

What are 3 parasitic causes of gastroenteritis?

A

Cryptosporidium - sporozoan (non-motile)
Giardia lamblia - flagellate
Entamoeba - amoeba

35
Q

How is cryptosporidium spread?

A

Transmitted by faecal-oral route but can also survive and spread via bodies of wate (infected by animal faeces)

36
Q

What is cryptosporidium?

A

Disease caused by ingestion of oocyst - reproduces inside epithelial cells of distal small intestine

37
Q

What are the symptoms of cryptosporidium?

A

Water diarrhoea that is normally self limiting

- malabsorption and chloride secretion

38
Q

What is the treatment for cryptosporidium?

A

Fluids

Occasionally anti-parasitic treatment in at risk groups - AIDS

39
Q

How is giardia spread?

A

Faecal oral route with water supplies often affected in developing countries

40
Q

What are the symptoms of giardia?

A

Most are asymptomatic but symptoms are more common in children
Diarrhoea, abdominal cramping
Common cause of persistent diarrhoea

41
Q

What are the 2 stages in giardias life cycle?

A

Cyst is ingested - stomach acid/pancreatic enzymes release parasite from cyst, damages proximal small intestine causing symptoms, villus atrophy occurs
Parasite then goes back into cyst stage in colon

42
Q

What is the treatment for giardia?

A

Antibiotics and fluid rehydration therapy

43
Q

What is common post giardia infection?

A

Lactase deficiency is common - lactose intolerance

44
Q

What are the symptoms of entamoeba histolytica?

A

Most cases are asymptomatic

Diarrhoea, liver abscesses (rare)

45
Q

How is entamoeba histolytica spread?

A

Faecal-oral route from contaminated food or water

46
Q

Who does entamoeba histolytica most commonly affect?

A

People who have travelled to tropical places that have poor sanitary conditions
People who live in institutions that have poor sanitary conditions
Men who have sex with men

47
Q

How does entamoeba histolytica affect the body?

A

Infection follows ingestion of cysts
Excystation occurs in colon where trophozoites invade mucosa
Infection can also spread to live
Can cause bloody diarrhoea and inflammatory changes

48
Q

What is the treatment for entamoeba histolytica?

A

Anti-protozoals/metronidazole

Severe colitis/toxic megacolon may require surgery

GI System (26 decks)

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