9. GI Infections

Question 1

What are the GI defences to infection?

Answer 1

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

Question 2

What are the benefits of gut microbiome?

Answer 2

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

Question 3

How can less gut microbiota affect our health?

Answer 3

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

Question 4

What do bacteria in colon produce?

Answer 4

SCFAs - acetate, propionate, butyrate

Question 5

What is the role of butyrate?

Answer 5

Energy source for colonocytes, helps regulate gut environment

Question 6

What is the role of acetate?

Answer 6

Involved in cholesterol metabolism

Question 7

What is the role of propionate?

Answer 7

Helps regulate satiety

Question 8

What is a faecal microbiota transplant?

Answer 8

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

Question 9

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

Answer 9

Salmonella
Campylobacter
Shigella
Enterotoxigenic E.coli

Question 10

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

Answer 10

Clostridium difficile

Question 11

What are the symptoms of salmonella infection?

Answer 11

Nausea, vomiting, watery diarrhoea, fever, abdominal cramping

Question 12

How does salmonella affect the body?

Answer 12

-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

Question 13

How is salmonella spread?

Answer 13

Ingesting contaminated food or water

Question 14

How s campylobacter spread to humans?

Answer 14

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

Question 15

What are the symptoms of campylobacter infection?

Answer 15

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

Question 16

How long does campylobacter usually last?

Answer 16

Incubation period 1-7 days

Can last days to weeks, generally self limiting

Question 17

What is the treatment for campylobacter infection?

Answer 17

Fluid/electrolyte replacement

Consider antibiotics if bloody diarrhoea

Question 18

How is shigella spread?

Answer 18

Spread from infected stools, person to person

Only needs a small dose to cause infection

Question 19

How does shigella affect the body?

Answer 19

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

Question 20

How is enterotoxigenic E.coli spread?

Answer 20

Spread by faecal oral route by contaminated water

Common cause of travellers diarrhoea

Question 21

How does enterotoxigenic E.coli affect the body?

Answer 21

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

Question 22

Following antibiotic therapy, what happens with C.diff?

Answer 22

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

Question 23

What are the symptoms of C.diff?

Answer 23

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

Question 24

What is pseudomembranous colitis?

Answer 24

Inflammatory condition

Elevated yellow plaques join to form pseudomembrane

Question 25

What is the treatment for C.diff?

Answer 25

Remove offending antibiotic Fluid resuscitation Metronidazole/vancomycin

Question 26

What is rotavirus?

Answer 26

Very common cause of gastroenteritis in the under 5’s | Double stranded RNA virus

Question 27

What are the symptoms of rotavirus?

Answer 27

Vomiting with a fever | Diarrhoea - lasts up to a week

Question 28

What is the treatment for rotavirus?

Answer 28

Managing dehydration

Question 29

How does rotavirus affect the body?

Answer 29

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

Question 30

What is norovirus?

Answer 30

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

Question 31

What are the symptoms of norovirus?

Answer 31

Vomiting, water diarrhoea, fever

Question 32

How does norovirus affect the body?

Answer 32

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

Question 33

What is the treatment for norovirus?

Answer 33

Oral rehydration

Question 34

What are 3 parasitic causes of gastroenteritis?

Answer 34

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

Question 35

How is cryptosporidium spread?

Answer 35

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

Question 36

What is cryptosporidium?

Answer 36

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

Question 37

What are the symptoms of cryptosporidium?

Answer 37

Water diarrhoea that is normally self limiting | - malabsorption and chloride secretion

Question 38

What is the treatment for cryptosporidium?

Answer 38

Fluids | Occasionally anti-parasitic treatment in at risk groups - AIDS

Question 39

How is giardia spread?

Answer 39

Faecal oral route with water supplies often affected in developing countries

Question 40

What are the symptoms of giardia?

Answer 40

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

Question 41

What are the 2 stages in giardias life cycle?

Answer 41

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

Question 42

What is the treatment for giardia?

Answer 42

Antibiotics and fluid rehydration therapy

Question 43

What is common post giardia infection?

Answer 43

Lactase deficiency is common - lactose intolerance

Question 44

What are the symptoms of entamoeba histolytica?

Answer 44

Most cases are asymptomatic | Diarrhoea, liver abscesses (rare)

Question 45

How is entamoeba histolytica spread?

Answer 45

Faecal-oral route from contaminated food or water

Question 46

Who does entamoeba histolytica most commonly affect?

Answer 46

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

Question 47

How does entamoeba histolytica affect the body?

Answer 47

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

Question 48

What is the treatment for entamoeba histolytica?

Answer 48

Anti-protozoals/metronidazole | Severe colitis/toxic megacolon may require surgery