What is the appropriate antibiotic (abx) treatment for an adult patient with suspected bacterial gastroenteritis?

Antibiotic Treatment for Bacterial Gastroenteritis in Adults

Most adults with acute gastroenteritis do NOT require antibiotics, as the majority of cases are viral or self-limited bacterial infections that resolve without antimicrobial therapy.

When to Consider Antibiotics

Antibiotics should be reserved for specific clinical scenarios where bacterial gastroenteritis is suspected and the patient meets high-risk criteria 1, 2:

Indications for Empiric Antibiotic Therapy

Initiate empiric antibiotics when patients present with:

• Severe or bloody diarrhea with fever (suggesting invasive bacterial pathogens like Shigella, Campylobacter, or invasive Salmonella) 3, 4
• Signs of systemic toxicity or sepsis (high fever, hemodynamic instability, severe dehydration) 5
• Immunocompromised status (cancer patients, transplant recipients, HIV/AIDS) 5
• Moderate to severe cramping, nausea, vomiting, and diminished performance status 5

Empiric Antibiotic Choices

For suspected bacterial gastroenteritis requiring empiric treatment:

• Fluoroquinolones (ciprofloxacin 400 mg IV every 12 hours or 500 mg PO twice daily) are first-line for empiric coverage of common enteric pathogens 5, 4
• Azithromycin (500 mg PO daily for 3 days) is preferred when Campylobacter or Shigella is suspected, particularly given rising fluoroquinolone resistance 3, 4
• Metronidazole (500 mg every 8-12 hours) should be added if C. difficile or anaerobic infection is suspected 5, 4

Targeted Therapy Based on Pathogen

Once stool cultures identify a specific pathogen, narrow therapy accordingly:

• Shigella: Azithromycin is preferred 3
• Campylobacter: Azithromycin for severe cases, particularly if treated early in the disease course 3
• Salmonella: Ceftriaxone or ciprofloxacin only for severe cases, bacteremia, or high-risk patients (immunocompromised, extremes of age, prosthetic devices) 3
• C. difficile: Metronidazole or vancomycin per standard protocols 5

Critical Clinical Considerations

Avoid Antibiotics in Most Cases

Do not prescribe antibiotics for:

• Mild, watery diarrhea without fever or blood 1, 2
• Suspected viral gastroenteritis 3
• Non-severe Salmonella gastroenteritis in immunocompetent patients (antibiotics may prolong carrier state) 3

Obtain Stool Studies Before Treatment

When antibiotics are being considered:

• Send stool for culture, C. difficile testing, and fecal leukocytes/lactoferrin 5
• Blood cultures if patient appears septic 5
• However, do not delay antibiotics in septic or severely ill patients while awaiting results 5, 1

Duration of Therapy

Treatment duration should be:

• 3-5 days for most bacterial gastroenteritis when antibiotics are indicated 3
• Adjust based on clinical response and pathogen identified 5

Common Pitfalls to Avoid

• Do not use empiric antibiotics for uncomplicated, self-limited diarrhea – this promotes resistance and provides no clinical benefit 1, 4
• Do not prescribe fluoroquinolones blindly – resistance rates are rising, particularly for Campylobacter (azithromycin preferred) 3, 4
• Do not treat non-typhoidal Salmonella gastroenteritis routinely – antibiotics are only indicated for severe disease or high-risk patients 3
• Do not forget to consider C. difficile – particularly in patients with recent antibiotic exposure or healthcare contact 5

Special Populations

For cancer patients or immunocompromised individuals with complicated diarrhea:

• Hospitalize and treat aggressively with broad-spectrum coverage 5
• Consider piperacillin-tazobactam (3.375 g IV every 6 hours) or cefepime (2 g IV every 8-12 hours) plus metronidazole for neutropenic enterocolitis 5
• Add vancomycin if MRSA or resistant gram-positive organisms suspected 5
• Evaluate for fungal infection if no response to antibacterial agents 5