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Infectious colitis/diarrhoea
Infectious colitis/diarrhoea

Infectious colitis/diarrhoea

Pathophysiology

Gastroenteritis is a common cause of diarrhoea and vomiting that is caused by ingestion of bacteria, viruses or toxins. It is also common whilst travelling abroad and may be termed traveller’s diarrhoea.

🦠 Causative agents

Bacterial

  • E. Coli - we will discuss E. coli further later. Most common bacterial cause.
  • Staph aureus - usually in cooked meat and cream products.
  • Bacillus cereus - mainly in reheated rice.
  • Clostridium perfringens - mainly in reheated meat.
  • Campylobacter
  • Salmonella
  • Shigella
  • Listeria monocytogenes - in deli meats.
☠️
Food poisoning:

Typically caused by:

  1. S. Aureus
  2. Bacillus cereus
  3. Clostridium perfringens

It is a notifiable disease in the UK.

Viral

  • Rotavirus - most common cause of infantile gastroenteritis.
  • Norovirus - most common cause of viral gastroenteritis among all ages in the UK.
  • Adenoviruses

We will cover these in the viral gastroenteritis CCC.

🧼
Norovirus prevention is crucial in hospitals, nursing homes etc. It is done by handwashing with soap and warm water.

Parasitic

  • Giardia intestinalis
  • Cryptosporidium
  • Entamoeba histolytica
🔪
Escherichia coli subtypes:

E. coli is an anaerobic, gram-negative rod which is normally found in the gut as commensal bacteria.

It can be classified according to its antigens:

  1. O antigen - LPS layer
  2. K antigen - capsular layer
  3. H antigen - flagellin

Let’s now look at the subtypes of E. coli and their different mechanism:

  • Enterohaemorrhagic E. coli (EHEC) - attaches to enterocytes of the colon and releases virulence factors, such as Shiga-like toxin. This disrupts protein synthesis and causes cell death → bloody diarrhoea. Importantly it has the E. coli O157:H7 serotype which is severe and it can lead to systemic toxicity and cause haemolytic uraemic syndrome. It is often spread by contaminated ground beef.
  • Enteropathogenic E. coli (EPEC) - binds to small bowel epithelial cells → damage of microvilli.
  • Enteroinvasive E. coli (EIEC) - resembles Shigella infection as it causes a secretory diarrhoea/dysentery. It invades into cells and replicates within the cell.
  • Enterotoxigenic E. coli (ETEC) - non-invasive strain that binds to the small bowel enterocytes and produces enterotoxins that are heat-stable or heat-labile. Most common cause of traveller’s diarrhoea. It is the only one in which antibiotic therapy is considered.
  • Enteroaggregative E. coli (EAEC) - another non-invasive strain that binds to the intestinal mucosa and creates a thick biofilm and also later on releases enterotoxins and cytotoxic so.
  • Diffusely adherent E. coli (DAEC) - colonises the small bowel and causes development of finger-like projections that wrap around the bacteria.
image

😷 Presentation

Diarrhoea of course is the main presentation. Gastroenteritis is defined as at least 3 loose/watery stools in 24 hours.

It may/may not be accompanied by:

  • Abdominal cramps
  • Fever
  • Nausea
  • Vomiting
  • Bloody stool

🔍 Investigations

🏆 Clinical diagnosis is often made.

🥇 Stool cultures should be sent for patients with moderate-severe symptoms. It is mandatory with bloody diarrhoea or signs of systemic toxicity.

FBC + U&Es should be sent if there is suspicion of haemolytic uraemic syndrome.

🧰 Management

💧
Gastroenteritis management:

It is usually managed conservatively with fluid replacement and supportive therapy.

  • 🥇 Fluid replacement or oral hydration sachets. Glucose-containing fluids are preferred as glucose promoted sodium absorption, and as a result, water.
  • Bismuth subsalicylate (pepto-bismol) can be given as adjunctive treatment. However, in children <12 it is not recommended as it may cause Reye’s syndrome.
🔪
Antibiotic therapy:

Antibiotics are indicated if the patient is:

  1. Systemically unwell
  2. Immunosuppressed patient
  3. Elderly patient
  • Enterotoxigenic E. coli (ETEC) - ciprofloxacin
  • Salmonella and shigella - ciprofloxacin
  • Campylobacter - macrolides e.g. erythromycin
  • Cholera - tetracycline

🚨 Complications

  • Haemolytic uraemic syndrome (HUS)
  • Dehydration
🦠
Infection specific presentations:
  1. Escherichia coli - it is common amongst travellers.
    1. Watery stools
    2. Abdominal cramps
    3. Nausea
  1. Giardiasis
    1. Prolonged non-bloody diarrhoea
    2. Foul-smelling stools
  2. Cholera
    1. Profuse rice-water diarrhoea
    2. Severe dehydration
  1. Shigella
    1. Bloody diarrhoea
    2. Vomiting
    3. Abdominal pain
  2. Staphylococcus aureus
    1. Severe vomiting
    2. Short incubation period
    3. Found in milk, pudding, pastries, sliced meats.
  1. Campylobacter - may mimic appendicitis. Associated with undercooked chicken.
    1. Flu-like prodrome
    2. Abdominal cramps
    3. Fever
    4. Diarrhoea may be bloody
    5. Seagull shape under microscopy.
  1. Bacillus cereus
    1. Vomiting within 6 hours (especially after eating reheated rice)
    2. Diarrhoea after 6 hours
  1. Amoebiasis
    1. Gradual onset
    2. Bloody diarrhoea
    3. Abdominal pain that may last a few weeks.
    4. May cause liver or colonic abscess which has contents that anchovy sauce.