Gastroenteritis

Semantha Chia Peck Sin
041303015 (Batch 15 - Group B2)

Gastroenteritis

• The most common form of acute gastrointestinal infection.
• Causes diarrhoea with or without vomiting.
• Viral gastroenteritis is a common cause of diarrhoea vomiting in young children but is rarely seen in adults.
• Protozoal and helminthic gut infections are relatively common in developing countries.
• The most common cause of significant adult gastroenteritis world-wide is bacterial infection.

Risk Factors:-

1. Children (Especially those in the developing world)
2. Elderly - A major cause of morbidity.
3. Travellers to developing countries.
4. Homsexual men.
5. Infants in day care facilities.

Mechanisms
Bacteria can cause diarrhoea in 3 different ways:-

(1) Mucosal Adherence:-

• Most bacteria causing diarrhoea must first adhere to specific receptors on the mucosa.
• Different molecular adhesion mechanisms include adhesions at the tip of the pili or fimbriae which protrude from the bacterial surface aid adhesion.
• Mode of Action: Effacement of intestinal mucosa
• Clinical Presentation: Moderate watery diarrhoea
• Eg: Enteropathogenic E. coli (EPEC)

(2) Mucosal Invasion:-

• Mode of Action: Penetration and destruction of mucosa.
• The invasive pathogens then destroy the epithelial cells and produce the symptoms of dysentery: Low-volume bloody diarrhoea, with abdominal pain.
• Clinical Presentation: Dysentry
• Eg: Shigella species, Campylobacter species, Enteroinvasive E. coli (EIEC)

(3) Toxin production:-
(a) Enterotoxin

• Mode of Action: Induces fluid secretion without mucosal damage
• Clinical Presentation: Profuse watery diarrhoea
• Eg: Vibrio cholerae, Salmonella species, Campylobacter species, Enterotoxigenic
  E. coli (ETEC)

(b) Neurotoxin

• Mode of Action: Paralysis of autonomic nervous system
• Clinical Presentation: Variable diarrhoea and vomiting
• Eg: Bacillus cereus, Staphylococcus aureus producing enterotoxin B

(c) Cytotoxin

• Mode of Action: Damage to mucosa and, in some cases, vascular endothelium as
  well.
• Clinical Presentation: Bloody diarrhoea
• Eg: Salmonella species, Campylobacter species, Enterohaemorrhagic E. coli
  (EHEC)

Clinical Syndromes
Bacterial gastroenteritis can be divided on clinical grounds into 2 broad syndromes:-
(1) Watery diarrhoea - Usually due to neurotoxins of enterotoxins, or adherence.
(2) Dysentry - Usually due to mucosal invasion.
** With some pathogens such as Campylobacter jejuni, there may be overlap between the 2
syndromes.

Causes of Watery Diarrhoea and Dysentry

Watery diarrhoea:-

1. Bacillus cereus
2. Staphylococcus aureus
3. Vibrio cholerae
4. Enterotoxigenic Escherichia coli (ETEC)
5. Enteropathogenic Escherichia coli (EPEC)
6. Salmonella species
7. Campylobacter jejuni
8. Clostridium perfringens
9. Clostridium difficile

Dysentry:-

1. Shigella species
2. Salmonella species
3. Campylobacter species
4. Enteroinvasive Escherichia coli (EIEC)
5. Enterohaemorrhagic Escherichia coli (EHEC)
6. Yersinia enterocolitica
7. Vibrio parahaemolyticus
8. Clostridium difficile

Management
Investigations

1. Urea
2. Electrolytes
3. Stool microscopy
4. Stool culture
5. Clostridium difficile toxin
6. Blood culture

Treatment

• In children, untreated diarrhoea has a high mortality due to dehydration, especially in hot climates.
• The mainstay of treatment of all types of gastroenteritis is rehydration.
• IV infusion and fluid balance.
• Antibiotics have a subsidiary role in some cases.

-- Empirical therapy if:-
Dysenteric symptoms
Severely dehydrated
Severe systemic symptoms
Immunosuppressed
Underlying illness
Cholera likely

• Other measures:-

(1) Watch for complications such as renal failure, perforation or septicaemia.
(2) Inform appropriate public health authorities.
(3) Try to trace source.
(4) Avoid anti-motility agents.