Infectious Diarrhoea

Question 1

What is dysentery?

Answer 1

Large bowel inflammation, bloody stools

Question 2

Causes of gastro-enteritis

Answer 2

Contamination of foodstuffs (intensively farmed chicken and campylobacter)
Poor storage of produce (Bacterial proliferation at room temperature)
Travel-related infections (salmonella)
Person-to-person spread (norovirus)

Question 3

What is the most common bacterial pathogen in GI infection?

Answer 3

Campylobacter

Question 4

Which pathogen causes most hospital admissions?

Answer 4

Salmonella

Question 5

Defences against enteric infections

Answer 5

Hygiene
Stomach acidity (antacids and infection)
Normal gut flora (C. difficile diarrhoea)
Immunity (HIV + salmonella)

Question 6

What are the types of clinical features of diarrhoeal illness?

Answer 6

Non-inflammatory/secretory (cholera)
Inflammatory (shigella dysentery)
Mixed picture (C. diff)

Question 7

Non-inflammatory diarrhoeal illness

Answer 7

Secretory toxin-mediated

Frequent watery stools with little abdo pain

Rehydration mainstay of therapy

Question 8

Mechanism of diarrhoea in cholera

Answer 8

Increased cAMP results in loss of Cl from cells along with Na and K

Osmotic effect leads to massive loss of water from the gut

Question 9

Inflammatory diarrhoeal illness

Answer 9

PAIN AND FEVER

Inflammatory toxin damage and mucosal destruction

Bacterial infection/amoebic dysentery

Antimicrobials may be appropriate but rehydration alone is often sufficient

Question 10

Fluid and electrolyte losses in secretory diarrhoea

Answer 10

Hyponatraemia due to Sodium loss with fluid replacement by hypotonic solutions

Hypokalaemia due to K loss in stool (40-80mmol/l of K in stools)

Question 11

Infectious diarrhoea differential diagnosis

Answer 11

IBD
Spurious diarrhoea (secondary to constipation)
Carcinoma

Question 12

Treatment of infectious diarrhoea

Answer 12

Oral rehydration with salt/sugar solution

IV saline

Question 13

Campylobacter gastroenteritis post-infective sequelae

Answer 13

Guillain-Barre syndrome

Reactive arthritis

Question 14

Routine bacterial culture

Answer 14

Difficult to find pathogen in the midst of complex normal flora

Selective and enrichment methods of culture necessary - variety of media and incubation conditions

Takes 3 days to complete all tests

Question 15

Which two species of campylobacter are responsible for most infections?

Answer 15

C. jejuni

C. coli

Question 16

What is prolonged carriage of salmonella associated with?

Answer 16

Gallstones

Question 17

How long after exposure to salmonella is symptom onset?

Answer 17

Usually <48hrs

Question 18

How long does diarrhoea last with salmonella gastroenteritis?

Answer 18

Usually <10 days

Question 19

What are the two species in the salmonella genus?

Answer 19

S. enterica

S. bongori

Question 20

How is E. coli illness typically characterised?

Answer 20

Frequent bloody stools

Question 21

What toxin is produced by E. coli?

Answer 21

Shiga toxin (also produced by shigella spp)

Question 22

Pathophysiology of E. coli infection

Answer 22

E. coli stays in the gut but the toxin travels to the blood which can cause haemolytic-uraemic syndrome (HUS)

Question 23

How is HUS characterised

Answer 23

Haemolytic anaemia
Renal failure
Thrombocytopenia

Question 24

Treatment of HUS

Answer 24

Supportive

Antibiotics NOT indicated

Question 25

When are antibiotics appropriate in gastroenteritis?

Answer 25

Immunocompromised Severe sepsis or invasive infection Chronic illness e.g. malignancy (Not indicated for healthy patient with non-invasive infection)

Question 26

Treatment of C. diff

Answer 26

Metronidazole Oral vancomycin Fidaxomicin (new and expensive) Stool transplants Surgery may be required

Question 27

Presentation of C. diff infection

Answer 27

From mild diarrhoea to severe colitis

Question 28

What are the 4 C antibiotics that result in CDI?

Answer 28

Cephalosporins Co-amoxiclav Clindamycin Ciprofloxacin

Question 29

UK protozoa

Answer 29

Giardia duodenalis Cryptosporidium parvum Entamoeba histolytica

Question 30

Long term complication of amoeba

Answer 30

Amoebic liver abscess

Question 31

WHat are the signs that diarrhoea is caused by sepsis outside of the gut?

Answer 31

Lack of abdo pain/tenderness goes against gastroenteritis No blood/mucus in stools

Question 32

Which bacterial gastroenteritis presents most quickly?

Answer 32

Salmonella - <48 hrs after exposure | Campylobacter - up to 7 days