Infections of the GI system

Question 1

Describe ETEC

Answer 1

• Enterotoxic E. coli
• Produces enterotoxins
• Causes watery diarrhoea (travellers and low income countries)

Question 2

Describe EPEC

Answer 2

• Enteropathogenic E. coli
• Produces type 3 secretion system toxins
• Causes non-specific gastro (especially in infants and children)
• Damages brush border

Question 3

Describe EHEC

Answer 3

• Enterohaemorrhagic E. coli
• Produces shiga toxins
• Causes bloody diarrhoea (any age, developed countries)
• Can cause hemolytic uremic syndrome
• Antibiotic use STRONGLY not advised

Question 4

Describe EIEC

Answer 4

• Enteroinvasive E. coli
• Invades into mucosa only
• Causes dysentery (watery, bloody mucous filled diarrhoea)

Question 5

Describe rotavirus:

Answer 5

• Virus invades enterocytes, replicates and causes enterocyte death
• Destroys large amounts of brush border
• Young children that have just ceased breast feeding are especially susceptible

Question 6

Describe giardia lamblia

Answer 6

• Results in chronic diarrhoea (pale, foul smelling)

- Lots of bloating, cramping and gas

Question 7

Describe hepatitis A:

Answer 7

• Acute infection
• Spread through contaminated food/water
• Vaccine preventable
• Incubation period 30 days
• Causes jaundice, vomiting, pale faeces and dark urine
• Large increase in ALT
• Ingested orally -> infects intestinal epithelium -> spreads to blood -> replicates in liver -> shed in bile and faeces
• Can be prevented with serum Ig

Question 8

Describe hepatitis E:

Answer 8

• Acute infection
• Spread through contaminated food/water
• Incubation period 40 days
• Causes jaundice, vomiting, pale faeces and dark urine
• Large increase in ALT
• Ingested orally -> infects intestinal epithelium -> spreads to blood -> replicates in liver -> shed in bile and faeces

Question 9

Describe hepatitis B:

Answer 9

• Spread through sex, IVDU and perinatally
• Penetrates mucosal epithelia -> spreads to blood -> replicates in liver -> shed into blood and secretions
• Leads chronic infection in 30-90% of children under 5, and 2-10% of people >5
• More severe disease = better immune clearance
• Chronic carriers do not develop anti-HBs and remain HBsAg+ (HBeAg+ = active replication)
• Chronic carrier status can lead to cirrhosis and hepatocellular carcinoma
• Can be prevented with vaccine

Question 10

Describe hepatitis D:

Answer 10

• Only infects with conjunction of HBV infection
• Co-infection: Leads to more severe acute disease but less chance of chronicity
• Superinfection into HBV+ patient: generally becomes chronic - high risk of severe liver disease

Question 11

Describe hepatitis C:

Answer 11

• Spread through blood, sex and IVDU (but mainly IVDU)
• Results in chronic infection in 70% of people
• There is no vaccine and poor immunity (no protective Ab)
• Leads to cirrhosis and liver failure

Question 12

What drugs are used to treat hepatitis C?

Answer 12

1. Viral entry inhibitors
2. HCV RNA translation inhibitors
3. Post-translational processing inhibitors
4. HCV replication inhibitors
5. Viral assembly and release inhibitors
   - Curative >95% of people