Acute Bacterial Gastroenteritis Diagnosis and Management

Key Differential Diagnoses

The combination of loose stools, abdominal pain, high-grade fever, and headache most strongly suggests acute bacterial gastroenteritis, particularly Campylobacter, Salmonella, Shigella, or Yersinia species, which characteristically present with this constellation of symptoms 1, 2
Campylobacter, Salmonella, Shigella, Yersinia: These pathogens classically cause abdominal pain with high-grade fever 1, 2
Shiga toxin-producing E. coli (STEC): Presents with severe abdominal pain and often grossly bloody stools, though patients are typically NOT febrile at presentation (important distinguishing feature) 1
Non-cholera Vibrio species: Consider if patient has exposure to salty/brackish waters or consumed raw/undercooked shellfish 1
Clostridioides difficile: Must be considered if recent antibiotic exposure within 8-12 weeks 1, 3

Obtain focused history on: Stool characteristics: presence of blood, mucus, or watery consistency 1, 3
Recent antibiotic use (within 8-12 weeks) to assess C. difficile risk 1, 3
Food exposures: raw/undercooked meat, shellfish, unpasteurized dairy 1
Travel history: recent travel to endemic areas 1, 4
Immune status: HIV, transplant, chemotherapy, chronic steroids 1, 6
Outbreak setting: multiple people with similar symptoms 1
Stool testing is indicated for: Fever with diarrhea 4
Severe abdominal cramping or tenderness 4
Signs of sepsis 4
Single diarrheal stool specimen for bacterial pathogens: Salmonella, Shigella, Campylobacter, Yersinia, and STEC 1, 4
Molecular multiplex testing preferred over traditional stool cultures for higher sensitivity 3, 4
C. difficile toxin testing if any antibiotic exposure in past 8-12 weeks 1, 7
Blood cultures if signs of septicemia or patient <3 months old 2, 4
Stool for ova and parasites only if diarrhea persists >14 days 1

Hydration is paramount: Oral rehydration solution (WHO formulation: Na 90 mM, K 20 mM, glucose 111 mM) for all patients able to take oral fluids 3
DO NOT give empiric antibiotics while awaiting test results in immunocompetent patients with bloody diarrhea 2, 3, 4
EXCEPTIONS warranting empiric antibiotics: Infants <3 months with suspected bacterial etiology 2, 4
Documented fever + abdominal pain + bloody diarrhea with presumed bacillary dysentery (Shigella) 2, 3
Immunocompromised patients require broad-spectrum coverage 1, 6
Antibiotic choices when indicated: Adults: Fluoroquinolones (ciprofloxacin) or azithromycin 2
Children: Third-generation cephalosporins or azithromycin 2

NEVER give antibiotics for STEC O157 or Shiga toxin 2-producing STEC due to increased risk of hemolytic uremic syndrome (HUS) 2, 4
Red flags requiring urgent evaluation: Bloody diarrhea with anemia, thrombocytopenia, or renal dysfunction (suspect HUS) 4
Signs of toxic megacolon or peritonitis 5
Severe dehydration or hemodynamic instability 3
Do not miss: C. difficile testing in healthcare-associated diarrhea 4
CMV colitis in immunocompromised patients (requires tissue biopsy with immunohistochemistry for definitive diagnosis) 5
Vibrio species if exposure to brackish water or raw shellfish 1