Infectious diarrhoea Flashcards
What is the Bristol Stool Chart
The Bristol stool scale is a diagnostic medical tool designed to classify the form of human faeces into seven categories
What are the 7 types of the Bristol Stool Chart?
Epidemiology of gastro-enteritis
- 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
What is the most common foodborne pathogen?
Campylobacter
- With about 280,000 cases each year
What pathogen causes the most hospital admissions?
Salmonella
- About 2500 each year
What food is linked to the most cases of food poisoning each year?
Poultry meat
- Estimated 244,000 cases each year
What are defences against enteric infections?
- Hygiene
- Stomach acidity
- antacids and infection
- Normal gut flora
- Cl. difficile diarrhoea
- Immunity
- HIV + salmonella
What are clinical features of diarrhoeal illness?
- Non-inflammatory/secretory
- e.g. cholera
- Inflammatory
- e.g. shigella dysentery
- Mixed picture e.g. C. difficile
What is the mechanism of diarrhoea in cholera?
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
What are clinical features of non-inflammatory diarrhoeal illness?
- 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
Clinical features of inflammatory diarrhoeal illness
- Inflammatory toxin damage and mucosal destruction => pain and fever
- Bacterial infection/amoebic dysentery
- Antimicrobials may be appropriate but rehydration alone is often sufficient
What would you take into account when assessing the patient?
- 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
What are clinical features of dehydration in infants?
Sunken eyes and cheeks
Decreased skin turgor
Sunken fontanelle
Few or no tears
Dry mouth or tongue
How much fluid and electrolyte loss can there be with secretory diarrhoea?
- 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)
What investigations would you do for diarrhoea?
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
Differential diagnoses for diarrhoea
Inflammatory bowel disease
Spurious diarrhoea - secondary to constipation
Carcinoma
Diarrhoea and fever can occur with sepsis outside the gut
What is treatment for gastro-enteritis?
Rehydration
- Oral rehydration with salt/sugar solution
- IV saline
Features of Campylobacter gastroenteritis
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
Features of Salmonella gastroenteritis
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
What are the 2 main species in genus of Salmonella?
S. enterica
S. bongori
What are the commonest salmonella isolates in the UK?
Salmonella enteritidis
Salmonella typhimurium
Features of E.coli O157
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
What is so dangerous about E.coli O157?
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
What occurs in haemolytic-uraemic syndrome?
Toxin stimulates platelet activation => micro-angiopathy results
It is characterised by the triad of microangiopathic haemolytic anaemia, thrombocytopenia, and acute kidney injury.
When should I give antibiotics?
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
