Antibiotic Management for Intra-Abdominal Abscess
For intra-abdominal abscesses, combine source control (percutaneous drainage or surgery) with broad-spectrum antibiotics covering gram-negative aerobes, anaerobes, and gram-positive cocci; treat for 4 days in immunocompetent patients with adequate drainage, or up to 7 days in critically ill or immunocompromised patients. 1
Patient Stratification and Antibiotic Selection
Immunocompetent, Non-Critically Ill Patients with Adequate Source Control
Duration: 4 days of antibiotic therapy 1
First-Line Regimens:
- Piperacillin-tazobactam: 3.375 g IV every 6 hours (or 4.5 g every 6 hours for severe infection) 1, 2
- Ertapenem: 1 g IV every 24 hours 1
- Eravacycline: 1 mg/kg IV every 12 hours 1
Alternative Single-Agent Options:
- Moxifloxacin with metronidazole 1
- Cefoxitin 1
- Tigecycline: 100 mg loading dose, then 50 mg every 12 hours 1
Combination Regimens:
- Ceftriaxone or cefotaxime PLUS metronidazole 1
- Cefepime 2 g IV every 8-12 hours PLUS metronidazole 1, 3
Critically Ill or Immunocompromised Patients
Duration: Up to 7 days based on clinical response and inflammatory markers 1
With Adequate Source Control:
- Piperacillin-tazobactam: 6 g/0.75 g loading dose, then 4 g/0.5 g every 6 hours OR 16 g/2 g continuous infusion 1
- Eravacycline: 1 mg/kg IV every 12 hours 1
With Inadequate/Delayed Source Control or High ESBL Risk:
Septic Shock
Use one of the following carbapenems with extended or continuous infusion: 1
- Meropenem: 1 g every 6 hours by extended/continuous infusion 1
- Doripenem: 500 mg every 8 hours by extended/continuous infusion 1
- Imipenem-cilastatin: 500 mg every 6 hours by extended infusion 1
- Eravacycline: 1 mg/kg every 12 hours 1
Special Considerations
Beta-Lactam Allergy
- Eravacycline: 1 mg/kg IV every 12 hours 1
- Tigecycline: 100 mg loading dose, then 50 mg every 12 hours 1
- Ciprofloxacin PLUS metronidazole (only if local E. coli susceptibility ≥90%) 1
Abscess Size-Specific Management
Small Abscesses:
- Antibiotics alone for 7 days may be sufficient 1
Large Abscesses:
- Percutaneous drainage PLUS antibiotics for 4 days 1
- Higher antibiotic doses may be needed for adequate abscess penetration; piperacillin-tazobactam, cefepime, and metronidazole achieve adequate concentrations except in the largest abscesses 4
Health Care-Associated Infections
Empiric therapy must be driven by local resistance patterns 1
Broad-Spectrum Coverage Required:
- Meropenem, imipenem-cilastatin, doripenem, or piperacillin-tazobactam 1
- Add vancomycin if MRSA suspected 1
- Consider aminoglycoside if ≥20% resistant Pseudomonas aeruginosa locally 1
Critical Pitfalls to Avoid
Do NOT Use:
- Ampicillin-sulbactam: High E. coli resistance rates 1
- Cefotetan or clindamycin: Increasing Bacteroides fragilis resistance 1
- Fluoroquinolones if local E. coli resistance >10-20% 1
Enterococcal Coverage:
- NOT routinely needed for community-acquired infections 1
- IS recommended for health care-associated infections, postoperative infections, or patients with prior cephalosporin exposure 1
Antifungal Coverage:
- NOT routinely needed for community-acquired infections 1
- Consider if Candida isolated from cultures in severe/health care-associated infections 1
- Fluconazole requires higher doses for adequate abscess penetration 4
Duration and De-escalation
- Reassess at 7 days: Patients with ongoing infection beyond 7 days warrant diagnostic investigation 1
- Tailor therapy based on culture results when available 1, 5
- Obtain intraoperative cultures routinely, as resistant organisms at second intervention are significantly more common without comprehensive initial coverage 6