GI Infections Flashcards by Ella Knight

What are the GI defences against infection?

Saliva - antibacterial enzyme
Gastric acid - low pH
Anaerobic environment
Gut biome

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How does the gut microbiome act as a defence?

Competes with harmful bacterial

Produces antimicrobial substances

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What does the microbiome produce?

Vitamin K
Butyrate
Acetate
Propionate

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What is the role of butyrate?

Energy source for colonocytes

Helps regulate gut environment

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What is the role of acetate?

Involved in cholesterol metabolism

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What is the role of propionate?

Helps regulate satiety

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What are the common bacterial infections of the gut?

Salmonella 
Campylobacter
Shigella 
E.coli 
Clostridium dificile

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What type of organism is salmonella?

Gram negative rod

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What are the symptoms of salmonella infection?

Nausea
V+D - non bloody
Fever
Abdo cramping

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What is the pathogenesis of salmonella?

Gain entry to enterocytes
Move to submucosa - encounter macrophages
Macrophages transfer salmonella to RES
Causes lymphoid hyperplasia

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What is the incubation period for salmonella?

1-2 days

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What type of organism is campylobacter?

Gram negative rod - S shaped

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What is the incubation period of campylobacter?

1-7 days

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What are the symptoms of a campylobacter infection?

Fever
Abdo cramp
Diarrhoea

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What is the pathogenesis of campylobacter?

Releases a cytotoxin

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What type of organism is shigella?

Gram negative rod

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What are the symptoms of a shigella infection?

Bloody diarrhoea

Abdo cramping

What is the pathogenesis of shigella?

Invades large intestine colonocytes

Kills colonocytes + forms abscesses

What type of organism is E.coli?

Gram negative rod

What is the symptoms of E.coli infection?

Watery diarrhoea

Traveller’s diarrhoea

What is the pathogenesis of E.coli?

Invades enterocytes
Produces enterotoxins
Cause hypersecretion of Cl-
Na+ + water follows

What type of organism is c.diff?

Gram positive spore forming bacillus

When is c.diff infection likely?

Following a course of antibiotics

What is the pathogenesis of c.diff?

Toxin A - enterotoxin that results in excessive secretion

Toxin B - cytotoxin

What is a potential complication of c.diff infection?

Pseudomembranous colitis

What is pseudomembranous colitis?

Inflammatory condition with elevated yellow plaques that form a pseudomembrane

What are viral causes of GI infections?

Rota virus | Norovirus

What type of organism is rotavirus?

Double stranded RNA virus

What are the symptoms of rotavirus?

Commonly in children Vomiting with fever Diarrhoea

What is the pathogenesis of rotavirus?

SGLT1 disruption - reduced movement of Na/glucose - higher osmotic load Chloride secretion - Na + water follow Reduced brush border enzyme function - malabsorption

What type of organism is norovirus?

RNA virus

What is the pathogenesis of norovirus?

Infects small intestion | Damages microvilli

What are the symptoms of norovirus?

Vomiting Watery diarrhoea Fever

What are common protozoa affecting the GI system?

Cryptosporidium Giardia lamblia Entamoeba

How is cryptosporidium spread?

Faecal-oral route - large bodies of water

What is the pathogenesis of cryptosporidium?

Ingestion of oocyst Reproduces inside epithelial cells of distal small intestine Affects brush border enzymes

What are the symptoms of cryptosporidium?

Watery diarrhoea

How is giardia spread?

Faecal-oral - water sources

What are the symptoms of giardia?

Persistent diarrhoea | Abdo cramps

What is the pathogenesis of giardia?

Cyst ingested Multiples in small intestine Damages proximal small intestine

What are the symptoms of Entamoeba infection?

Bloody diarrhoea

What is the pathogenesis of Entamoeba?

Ingestion of cyst | Trophozoites invade mucosa in colon