• Clinical science

Bacterial gastroenteritis


Bacterial gastroenteritis is caused by a variety of organisms, including Campylobacter, Salmonella, Shigella, Yersinia, Vibrio cholerae, Staphylococcus aureus, diarrheagenic Escherichia coli, Clostridium difficile, Clostridium perfringens, and noncholera Vibrio species. Infection may be foodborne, fecal-oral, or involve direct or indirect animal transmission. Clinical features can be mild, manifesting as abdominal pain and diarrhea, or severe, including vomiting and watery or inflammatory diarrhea, fever, and hypotension. Stool analysis may reveal leukocytes or blood in certain cases. Stool cultures may be considered in severe gastroenteritis. Bacterial gastroenteritis is usually self-limiting and only requires supportive therapy. However, antibiotics are indicated when supportive therapy does not suffice or in immunosuppressed patients. Adequate food and water hygiene is crucial for preventing disease.


Overview of bacterial gastroenteritis
Pathogen Pathophysiology Associations Stool findings
Secretory diarrhea
Bacillus cereus
  • Enterotoxin or bacterial invasion shifts water and electrolyte excretion/absorption in proximal small intestine → watery diarrhea
  • Rice, vomiting
  • WBC negative
  • No blood
  • Recent travel (e.g., Asia, Africa, the Middle East, Mexico, Central, and South America)
Clostridium perfringens
  • Undercooked meat and raw legumes
Staphylococcus aureus
  • Inadequately refrigerated food
Vibrio cholerae
Invasive diarrhea
  • Pathogens penetrate the mucosa and invade the reticuloendothelial system of the distal small intestine → enteric fever
  • WBC positive (fecal mononuclear leukocytes)
  • Blood may be present
Salmonella typhi or paratyphi
  • Poultry/eggs
Inflammatory diarrhea
  • Bacteria or cytotoxins damage the colonic mucosa → blood in stool and fever
  • Most common bacterial organism pathogen responsible for foodborne gastroenteritis in the US
  • WBC positive (fecal polymorphonuclear leukocytes)
  • Blood present
  • Undercooked meat; most common association with hemolytic-uremic syndrome (HUS)
Clostridium difficile
  • Second most common association with hemolytic-uremic syndrome (HUS)
Noncholera Vibrio species
  • Shellfish
Salmonellaa (non-typhoidal)
  • Poultry/eggs


Campylobacter enteritis (campylobacteriosis)

  • Pathogen
    • Campylobacter jejuni, Campylobacter coli
    • Curved, gram-negative, oxidase-positive rods with polar flagella
    • Most common pathogen responsible for foodborne gastroenteritis in the US
    • Highly contagious; low infective dose required (> 500 pathogens)
  • Transmission
    • Fecal-oral
    • Foodborne (undercooked meat; , and unpasteurized milk; ) and contaminated water
    • Direct contact with infected animals (cats and dogs)/animal products
  • Incubation period: 2–4 days
  • Clinical features
    • Duration: up to a week
    • High fever, aches, dizziness
    • Inflammatory (bloody) diarrhea (50% of cases)
    • Severe abdominal pain may present as pseudoappendicitis or colitis
  • Treatment: : (in severe cases) macrolides (e.g., erythromycin or azithromycin)
  • Complications (more common and severe in HIV-positive patients)


Salmonellosis (Salmonella gastroenteritis)


Shigellosis (bacillary dysentry)



  • Pathogen: Vibrio cholerae
    • Rare in developed countries
    • Gram-negative, oxidase positive, curved bacterium with a single polar flagellum produces cholera toxin
      • Cholera toxin stimulates adenylate cyclase via activation of Gs → increased cyclic AMP → increased ion secretion (mainly chloride)
  • Transmission
    • Fecal-oral
    • Undercooked seafood or contaminated water (e.g., non-segregated drinking water and sewage systems)
  • Incubation period: 0–2 days
  • Infectivity
    • Acid-labile (grows well in an alkaline medium); High infective dose required (over 108 pathogens)
  • Clinical features
    • Moderate diarrhea or asymptomatic course (occurs in > 90% of cases)
    • Low-grade fever, vomiting
    • Profuse 'rice-water' stools
  • Diagnosis: dipstick (rapid test; initial test); and stool culture (confirmatory)
  • Treatment
  • Complications




Clostridium perfringens enterocolitis

  • Pathogen: Clostridium perfringens
    • Gram-positive, anaerobic, spore-forming rod-shaped bacterium → produce exotoxins
    • Also causes gas gangrene
    • High dose required (108 pathogens)
  • Transmission: foodborne (undercooked or poorly refrigerated meat, legumes)
  • Incubation period: 6–24 hours
  • Clinical features
    • Duration: < 24 hours
    • Severe abdominal cramping
    • Watery diarrhea
  • Diagnosis: toxin detection in stool cultures
  • Treatment: supportive therapy only
  • Complications: clostridial necrotizing enteritis (∼ 40% mortality rate; related to ingestion of a high burden of C. perfringens contaminated food, usually pork)


Noncholera Vibrio infection