What is the antibiotic of choice for diverticulitis?

Antibiotic Selection for Diverticulitis

For uncomplicated diverticulitis in immunocompetent patients, conservative treatment without antibiotics is recommended; when antibiotics are needed, first-line options include ertapenem, piperacillin/tazobactam, or eravacycline. 1, 2

Classification and Treatment Approach

Uncomplicated Diverticulitis

• Conservative treatment without antibiotics is recommended for immunocompetent patients with CT-confirmed uncomplicated diverticulitis 1
• Antibiotic therapy (when indicated) should be limited to 7 days in immunocompromised or elderly patients 1

When to Use Antibiotics in Uncomplicated Cases

Antibiotics should be considered in patients with:

• Symptoms lasting >5 days
• Pain score >7
• Vomiting
• Systemic comorbidities
• Elevated white blood cell count
• High C-reactive protein levels
• CT findings showing pericolic extraluminal air/fluid
• Immunocompromised status
• Advanced age
• Pregnancy
• Poorly controlled chronic medical conditions 2

Antibiotic Regimens by Patient Category

For Immunocompetent, Non-critically Ill Patients

• Duration: 4 days if source control is adequate 1, 2
• Options:
  • Piperacillin/tazobactam 4g/0.5g q6h
  • Eravacycline 1 mg/kg q12h 1

For Immunocompromised or Critically Ill Patients

• Duration: Up to 7 days based on clinical condition 1, 2
• Options:
  • Piperacillin/tazobactam 6g/0.75g LD then 4g/0.5g q6h (or 16g/2g continuous infusion)
  • Eravacycline 1 mg/kg q12h 1

For Patients with Risk of ESBL-producing Bacteria

• Ertapenem 1g q24h
• Eravacycline 1 mg/kg q12h 1

For Patients in Septic Shock

• Meropenem 1g q6h (extended/continuous infusion)
• Doripenem 500mg q8h (extended/continuous infusion)
• Imipenem/cilastatin 500mg q6h (extended infusion)
• Eravacycline 1 mg/kg q12h 1

For Patients with Beta-lactam Allergy

• Eravacycline 1 mg/kg q12h
• Tigecycline 100mg LD then 50mg q12h 1

For Outpatient Treatment (Oral Antibiotics)

• Amoxicillin/clavulanic acid
• Ciprofloxacin plus metronidazole 3

Special Considerations

Complicated Diverticulitis Management

• Small abscesses: Antibiotic therapy alone for 7 days
• Large abscesses: Percutaneous drainage plus antibiotics for 4 days
• If drainage not feasible:
  • Non-critically ill/immunocompetent: antibiotics alone
  • Critically ill/immunocompromised: surgical intervention 1

Monitoring Response

• Patients with ongoing signs of infection beyond 7 days of antibiotic treatment require further diagnostic investigation 1
• Follow-up within 4-7 days of starting treatment to confirm symptom improvement 4

Diagnostic Approach

• CT scan with IV contrast is the preferred diagnostic test (sensitivity 98%, specificity 99%) 1, 2
• Key findings include:
  • Intestinal wall thickening
  • Pericolonic fat inflammation
  • Thickening of lateroconal fascia
  • Signs of perforation (if present) 1

Common Pitfalls to Avoid

1. Overuse of antibiotics in uncomplicated cases where conservative management would suffice
2. Inadequate duration of antibiotics in immunocompromised patients
3. Failure to recognize progression to complicated disease
4. Inappropriate antibiotic selection not accounting for local resistance patterns
5. Delayed source control in cases with large abscesses or perforation

The most recent guidelines emphasize a more selective approach to antibiotic use in uncomplicated diverticulitis, reserving them for patients with specific risk factors or signs of systemic illness 2.