What is the recommended antibiotic coverage for peritonitis?

Antibiotic Coverage for Peritonitis

For peritonitis, empiric broad-spectrum antibiotic therapy covering Gram-negative bacteria, Gram-positive bacteria, and anaerobes should be started as soon as peritonitis is diagnosed, with specific regimens determined by patient clinical status and community vs. hospital acquisition. 1, 2

Antibiotic Selection Based on Patient Status

Non-Critically Ill, Immunocompetent Patients with Community-Acquired Peritonitis

• First-line therapy (adequate source control):
  • Amoxicillin/Clavulanate 2 g/0.2 g q8h 1
  • Alternative if beta-lactam allergy: Eravacycline 1 mg/kg q12h or Tigecycline 100 mg loading dose then 50 mg q12h 1

Critically Ill or Immunocompromised Patients

• First-line therapy (adequate source control):
  • Piperacillin/tazobactam 6 g/0.75 g loading dose then 4 g/0.5 g q6h or 16 g/2 g by continuous infusion 1
  • Alternative if beta-lactam allergy: Eravacycline 1 mg/kg q12h 1

Patients with Septic Shock

• First-line therapy:
  • Meropenem 1 g q6h by extended infusion or continuous infusion, OR
  • Doripenem 500 mg q8h by extended infusion or continuous infusion, OR
  • Imipenem/cilastatin 500 mg q6h by extended infusion, OR
  • Eravacycline 1 mg/kg q12h 1

Patients with Risk Factors for ESBL-producing Enterobacterales

• First-line therapy:
  • Ertapenem 1 g q24h or Eravacycline 1 mg/kg q12h 1

Duration of Antibiotic Therapy

• Immunocompetent, non-critically ill patients with adequate source control: 4 days 1
• Immunocompromised or critically ill patients with adequate source control: Up to 7 days based on clinical conditions and inflammatory markers 1
• Patients with ongoing signs of infection beyond 7 days: Warrant diagnostic investigation and multidisciplinary re-evaluation 1

Special Considerations

Secondary Bacterial Peritonitis

• Requires anaerobic coverage in addition to a third-generation cephalosporin 1
• Surgical intervention is necessary for source control 1
• Characteristic findings: PMN count ≥250 cells/mm³, multiple organisms on Gram stain/culture, and at least two of: total protein >1g/dL, LDH greater than upper limit of normal for serum, and glucose <50 mg/dL 1

Spontaneous Bacterial Peritonitis (SBP)

• First-line therapy: Third-generation cephalosporins (e.g., cefotaxime 2 g every 8 hours) 1
• Alternatives include amoxicillin/clavulanic acid or quinolones 2

Hospital-Acquired Peritonitis

• Consider broader coverage for resistant organisms 2
• If MDR bacteria are suspected: Imipenem/cilastatin-relebactam, meropenem/vaborbactam, or ceftazidime/avibactam + metronidazole 1
• A study showed that prior use of broad-spectrum antibiotics between initial intervention and reoperation was the only significant risk factor for MDR bacteria (OR=5.1) 3

Monitoring and Follow-up

• Monitor clinical improvement and normalization of inflammatory markers (WBC, PCT, CRP) 1, 2
• Consider CT imaging to rule out persistent infection or abscess formation 1
• If no improvement after 48 hours, consider antibiotic failure, resistant organisms, or inadequate source control 2

Common Pitfalls to Avoid

1. Delayed initiation of antibiotics: Start antimicrobial therapy as soon as peritonitis is diagnosed or strongly suspected 2
2. Inadequate source control: Surgical intervention is crucial for most forms of peritonitis 2
3. Prolonged antibiotic courses: Short-course therapy (3-5 days) is sufficient with adequate source control 1
4. Overlooking antifungal therapy: Consider in hospital-acquired infections and critically ill or immunocompromised patients 1
5. Failing to adjust therapy based on culture results: De-escalate antibiotics when culture results become available 1

Remember that source control through surgical intervention or drainage procedures remains a cornerstone of peritonitis management alongside appropriate antibiotic therapy.