Infectious Diarrhoea

Question 1

Definition of diarrhoea, gastro, dysentery

Answer 1

diarrhoea = subjective: fluidity and frequency
Gastro-enteritis: >/ 3 loose stools/day, accompanying features
Dysentery: obvious large bowel inflammation, bloody stools

Question 2

Bristol Stool Chart

Answer 2

1: separate hard lumps like nuts, hard to pass
2: sausage shaped but lumpy
3: like a sausage but with cracks on surface
4: like a sausage/snake, smooth and soft
5: soft blobs with clear cut edges
6: fluffy pieces with ragged edges, mushy stool
7: watery, no solid pieces

Question 3

Gastroenteritis cause

Answer 3

the contamination of foodstuffs - chicken and campylobacter

often due to poor storage - bacteria proliferate

Question 4

Pathogenic causes of Gastroenteritis

Answer 4

Viral - are the most common cause (norovirus/rotavirus)
Bacterial. Campylobacter = most common bacterial pathogen.Salmonella = most common pathogen that causes hospital admission
Parasitic

Question 5

Example of non-inflammatory/secretory diarrhoea

Answer 5

Cholera: is secretory toxin mediated. increases cAMP levels and Cl secretion. E.coli (travellers diarrhoea) is the most common cause. Water flows into the lumen and leads to dehydration.
Caused by bacterium: Vinrio cholerae

Frequent water stools with little abdominal pain

Rehydration is the main therapy

Question 6

Example of inflammatory diarrhoea

Answer 6

Shigella dysentery (Shigellosis): inflammatory toxin damage. spread via faeces. Often seen in schools and children.
can cause fever and pain
Rehydration alone can be sufficient treatment but sometimes antimicrobials needed.

Question 7

Example of a mix of secretory and inflammatory diarrhoea

Answer 7

C. diff. Often seen in those treated with antibiotics. very infectious. Treat with antibiotics (vancomycin/metronidazole)

Question 8

If diarrhoea symptoms have lasted more than 2 weeks what is it unlikely to be?

Answer 8

Gastro-enteritis

Question 9

Important history questions (4)

Answer 9

Length: >2/52 then unlikely gastro
Exposure risks: diet, contact, travel
Hydration: postural, skin turgor, pulse. in babies: few tears, sunken fontanelle, dry mouth
Inflammation features: WCC, fever

Question 10

Fluid and Electrolyte loss

Answer 10

this can be severe in secretory diarrhoea

Question 11

Investigations for prolonged diarrhoea (5)

Answer 11

stool culture
blood culture
renal function 
blood count - neutrophillia, haemolysis
Abdo XR if abdo distended/tender

Question 12

Differentials of prolonged diarrhoea (4)

Answer 12

IBD
Spurious diarrhoea - secondary to constipation (overflow)
Carcinoma
Diarrhoea and fever can occur with sepsis outside the gut, lack of abdo pain/tenderness goes against gastro

Question 13

Treatment of prolonged diarrhoea

Answer 13

Rehydration - oral- rehydration with salt/sugar solution

IV - saline

Question 14

Campylobacter Gastro

Answer 14

Most common cause of food poisoning. usually isolated cases rather than outbreaks. Up to 7 days incubation therefore dietary history may be unreliable. Stools negative within 6 weeks. Severe abdo pain.
post infection sequelae: guillian-barre, reactive arthritis

Culture: Has specialised conditions. comes from chickens, contaminated milk, puppies.

TREAT: azithromycin

Question 15

Salmonella Gastro

Answer 15

Symptoms usually onset <48 hourrs post exposure
Last less than 10 days
20% still have positive stools at 20 weeks - prolonged carriage may be associated with gallstones. post-infectious irritable bowel common.

Culture: screened out as lactose non-fermenters.
Salmonella enteritidis and typhimurium most common

Treatment: CIPROFLOXACIN

Question 16

E.coli O157

Answer 16

infection from contaminated meat or person to person spread. typically characterised by frequent bloody stools. produces verocyto-toxin.
Stays in the gut but the toxin moves to the blood. toxin can cause haemolytic-uraemic syndrome (HUS) - haemolytic anaemia, renal failure and thrombocytopenia.

Treatment - supportive. ANTIBIOTICS NOT INDICATED

Question 17

Other bacteria

Answer 17

shigella - nurseries etc
staph aureus
bacillus cereus - reheated rice

Question 18

When should antibiotics be given (5)

Answer 18

immunocompromised
severe sepsis/invasive infection
valvular heard disease
chronic illness
diabetes

Question 19

When should antibiotics not be given?

Answer 19

not indicated in healthy patient with non-invasive infection

Question 20

C. diff

Answer 20

Produces spores
Usually a history of antibiotic treatment. severity ranges from diarrhoea to severe colitis.
O2 resistant, heat resistant, alcohol gel resistant
Produces toxins: enterotoxin A and cytotoxin B, c. diff transferase
Positive toxin test doesnt always mean disease - diarrhoea symptoms need to be present for diagnosis

Question 21

4 Cs of antibiotics

Answer 21

Cephalosporins
Co-amoxiclav
Ciprofloxacin (and other quinolones)
Clindamycin

Question 22

Treatment of C.diff

Answer 22

ORAL vancomycin
metronidazole
Fidaxomicin (new and expensive)
Stool transplants
May require surgery

Question 23

C.diff prevention

Answer 23

reduction in antibiotic prescription
avoid 4 Cs
isolate symptomatic patients
wash hands WITH SOAP

Question 24

Parasitology

Answer 24

order stool sample with PCO

Question 25

Giardia lamblia

Answer 25

contaminated water
diarrhoea, malabsorption, failure to thrive
cysts seen on stool microscopy
treat with metronidazole

Question 26

Cryptosporidium parvum

Answer 26

first recognised in AIDS
contaminated water (animal faeces)
Cysts seen on microscopy
no treatment

Question 27

Entamoeba histolytica

Answer 27

amoebic dysentery
can cause liver abscess - may be a long term complication ‘anchovy pus’
treat with metronidazole

Question 28

Viral diarrhoea - causes

Answer 28

rotavirus - children under 5, antigen detection

norovirus - common cause of outbreaks, diagnose via PCR. needs strict infection control