What are the primary causes of bacterial gastroenteritis?

Primary Causes of Bacterial Gastroenteritis

The most common bacterial causes of gastroenteritis are Campylobacter, Salmonella, Shigella, and pathogenic Escherichia coli, with Campylobacter and Salmonella accounting for the highest percentage of bacterial cases at approximately 10% and 3% respectively. 1

Major Bacterial Pathogens

Campylobacter

• Most common bacterial cause of gastroenteritis (approximately 10% of bacterial cases) 1
• Transmitted through contaminated food and water
• Associated with more severe tissue injury compared to viral agents 1
• Can lead to post-infectious irritable bowel syndrome (PI-IBS)

Salmonella

• Second most common bacterial cause (approximately 3% of bacterial cases) 1
• Clinical presentation:
  • Can cause acute watery diarrhea that may mimic cholera 2
  • Associated with longer duration of diarrhea (average 12.3 days) compared to viral causes 3
  • Higher rates of associated manifestations and complications 3
• Transmission:
  • Primarily through consumption of contaminated animal-derived products, especially poultry and pig products 4
  • Fecal-oral route 5
• Risk factors:
  • Immunocompromised status increases risk of bacteremia 2
  • Gastric achlorhydria (reduced stomach acid) allows more bacteria to survive 2
  • Higher risk of complications in young and malnourished children 3

Shigella

• Major cause of bacterial dysentery 2
• Very low infectious dose required for infection 6
• Requires compulsive attention to hygiene to prevent spread 6

Pathogenic E. coli

• Various strains can cause different types of diarrheal illness
• Generally associated with less severe manifestations compared to Salmonella 3

Clostridium difficile

• Recently recognized as a cause of post-infectious IBS in up to 25% of cases 1

Vibrio cholerae

• Associated with post-infectious IBS development in 16.5% of cases 1

Yersinia

• Less common but important cause of bacterial colitis 5

Transmission Routes

• Primary transmission route: fecal-oral spread 5
• Common sources:
  • Contaminated food and water 5
  • Person-to-person contact
  • Inadequate hand hygiene after potential contact with fecal material 2
  • Unprotected sexual practices that might result in fecal-oral exposure 2

Clinical Features and Complications

• Bacterial gastroenteritis typically presents as inflammatory-type diarrhea characterized by bloody, purulent, and mucoid stool 5
• Associated symptoms include fever, tenesmus, and severe abdominal pain 5
• Pathologic changes range from superficial exudative enterocolitis to transmural enterocolitis with ulceration 5
• Bacterial infections are associated with higher risk of post-infectious irritable bowel syndrome (PI-IBS) compared to viral infections 1
• Bacterial gastroenteritis can lead to:
  • Longer duration of symptoms compared to viral causes 3
  • Higher rates of complications, especially with Salmonella 3
  • Potential for bacteremia and systemic spread, particularly in immunocompromised hosts 6

Diagnostic Considerations

• Stool culture remains the definitive diagnostic method for bacterial gastroenteritis 5
• Additional tests include histology and identification of specific bacterial toxins 5
• Blood cultures should be considered in:
  • Infants under 1 year of age with suspected Salmonella 6
  • Immunocompromised patients 6
  • Patients appearing more toxic than their state of dehydration would suggest 6

Prevention

• Proper hand hygiene, especially after potential contact with fecal material 2
• Safe food handling practices to avoid cross-contamination 4
• Thorough cooking of food, particularly animal-derived products 4
• Comprehensive approach at farm, manufacturing, distribution, and consumer levels 4

Important Clinical Considerations

• Bacterial causes should be strongly suspected in patients who:
  • Progress rapidly from secretory to inflammatory diarrhea 6
  • Have diarrhea persisting beyond 5-6 days 6
  • Appear more toxic than their state of dehydration would suggest 6
• While many bacterial infections are self-limiting, antibiotic treatment may be warranted in:
  • High-risk patients (immunocompromised, extremes of age) 5
  • Patients with complicated disease 5
  • Cases where eradication of the organism is epidemiologically important 7