Infectious diarrhoea Flashcards Preview

Infections Year 3 > Infectious diarrhoea > Flashcards

Flashcards in Infectious diarrhoea Deck (26)
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1
Q

What is the Bristol Stool Chart

A

The Bristol stool scale is a diagnostic medical tool designed to classify the form of human faeces into seven categories

2
Q

What are the 7 types of the Bristol Stool Chart?

A
3
Q

Epidemiology of gastro-enteritis

A
  • 25% of population have infectious intestinal disorder each year
  • 2% of the population visit GP because of GI infection each year
  • For each reported case there are 10 GP consults and 147 community that are unreported
  • Viruses are the commonest cause with campyolobacter being the commonest bacterial pathogen
4
Q

What is the most common foodborne pathogen?

A

Campylobacter

  • With about 280,000 cases each year
5
Q

What pathogen causes the most hospital admissions?

A

Salmonella

  • About 2500 each year
6
Q

What food is linked to the most cases of food poisoning each year?

A

Poultry meat

  • Estimated 244,000 cases each year
7
Q

What are defences against enteric infections?

A
  • Hygiene
  • Stomach acidity
    • antacids and infection
  • Normal gut flora
    • Cl. difficile diarrhoea
  • Immunity
    • HIV + salmonella
8
Q

What are clinical features of diarrhoeal illness?

A
  • Non-inflammatory/secretory
    • e.g. cholera
  • Inflammatory
    • e.g. shigella dysentery
  • Mixed picture e.g. C. difficile
9
Q

What is the mechanism of diarrhoea in cholera?

A

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

10
Q

What are clinical features of non-inflammatory diarrhoeal illness?

A
  • Secretory toxin-mediated
    • cholera - increases cAMP levels and Cl secretion
    • enterotoxigenic E.coli (travellers’ diarrhoea)
  • Frequent watery stools with little abdo pain
  • Rehydration mainstay of therapy
11
Q

Clinical features of inflammatory diarrhoeal illness

A
  • Inflammatory toxin damage and mucosal destruction => pain and fever
  • Bacterial infection/amoebic dysentery
  • Antimicrobials may be appropriate but rehydration alone is often sufficient
12
Q

What would you take into account when assessing the patient?

A
  • Symptoms and their duration
    • >2/52 unlikely to be infective gastroenteritis
  • Risk of food poisoning
    • Dietary, contact, travel history
  • Assess hydration
    • postural BP, skin turgor, pulse
  • Features of inflammation (SIRS)
    • fever, raised WCC
13
Q

What are clinical features of dehydration in infants?

A

Sunken eyes and cheeks

Decreased skin turgor

Sunken fontanelle

Few or no tears

Dry mouth or tongue

14
Q

How much fluid and electrolyte loss can there be with secretory diarrhoea?

A
  • 1-7 litres fluid per day containing 80-100 mmol Na
  • 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)
15
Q

What investigations would you do for diarrhoea?

A

Stool culture +/- molecular or Ag testing

Blood culture

Renal function

Blood count - neutrophilia, haemolysis (E.Coli O157)

Abdominal X-ray/CT if abdomen distended, tender

16
Q

Differential diagnoses for diarrhoea

A

Inflammatory bowel disease

Spurious diarrhoea - secondary to constipation

Carcinoma

Diarrhoea and fever can occur with sepsis outside the gut

17
Q

What is treatment for gastro-enteritis?

A

Rehydration

  • Oral rehydration with salt/sugar solution
  • IV saline
18
Q

Features of Campylobacter gastroenteritis

A

Up to 7 days incubation so dietary history may be unreliable

Stools negative within 6 weeks

Abdominal pain can be severe

<1% invasive

Post-infection seqelae

19
Q

Features of Salmonella gastroenteritis

A

Symptom onset usually <48 hrs after exposure

Diarrhoea usually lasts <10 days

<5% positive blood cultures

20% patients still have positive stools at 20/52

Post-infectious irritable bowel is common

20
Q

What are the 2 main species in genus of Salmonella?

A

S. enterica

S. bongori

21
Q

What are the commonest salmonella isolates in the UK?

A

Salmonella enteritidis

Salmonella typhimurium

22
Q

Features of E.coli O157

A

Infection from e.g. contaminated meat or person-to-person spread

Typical illness characterised by frequent bloody stools

E.coli produces Shiga toxin

Avoid antibiotic use for E.coli O157

23
Q

What is so dangerous about E.coli O157?

A

E.coli O157 stays in the gut but the toxin gets into the blood

Toxin can cause haemolytic-uraemic (HUS) syndrome (haemolytic anaemia and renal failure)

  • Antibiotics can make this worse
24
Q

What occurs in haemolytic-uraemic syndrome?

A

Toxin stimulates platelet activation => micro-angiopathy results

It is characterised by the triad of microangiopathic haemolytic anaemia, thrombocytopenia, and acute kidney injury.

25
Q

When should I give antibiotics?

A

Indicated in gastroenteritis for:

  • Immunocompromised
  • Severe sepsis or invasive infection
  • Chronic illness e.g. malignancy

Not indicated for a healthy patient with non-invasive infection

26
Q
A