What is the treatment for Acinetobacter infections?

Treatment of Acinetobacter Infections

For Acinetobacter infections, polymyxins (colistin or polymyxin B) are recommended as the primary treatment for carbapenem-resistant strains, while carbapenems remain the first-line therapy for susceptible isolates. 1

First-Line Treatment Options

For Carbapenem-Susceptible Strains:

• Carbapenems: First-line therapy for susceptible isolates
  • Meropenem: 2g every 8 hours (extended infusion recommended) 2
  • Imipenem: 0.5-1g every 6 hours 2, 3
  • Doripenem: Standard dosing

For Carbapenem-Resistant Strains:

• Polymyxins: First-line therapy
  • Colistin: Loading dose 6-9 million IU, then 9 million IU/day in 2-3 doses 2
  • Polymyxin B: Loading dose 2-2.5 mg/kg, then 1.5-3 mg/kg/day in 2 doses 2

Alternative Agents:

• Sulbactam: 9-12g/day in 3-4 doses (4-hour infusion recommended) 2
• Tigecycline:
  • Standard dose: 100mg loading, then 50mg q12h
  • High dose: 200mg loading, then 100mg q12h 2

Treatment Approach Based on Infection Site

Ventilator-Associated Pneumonia (VAP):

• Consider combination therapy with two active agents 1, 2
• For VAP, nebulized antibiotics (colistin or aminoglycosides) may be added to systemic therapy 1
• Nebulized colistin: 2-6 million IU daily, preferably using a vibrating plate nebulizer 1

Bloodstream Infections:

• Combination therapy may be beneficial for severe bacteremia 2
• Monitor for clinical response within 48-72 hours of treatment initiation 2

Skin/Soft Tissue Infections:

• Imipenem is FDA-approved for Acinetobacter skin and soft tissue infections 3
• Consider local wound care in addition to systemic antibiotics

Combination Therapy Considerations

• Combination therapy should be considered for:

  • Severe infections (severe sepsis or septic shock) 1
  • Infections with highly resistant strains 2
  • Clinical failures with monotherapy 1

• Potential combinations:

  • Polymyxin + tigecycline
  • Polymyxin + sulbactam
  • Carbapenem + sulbactam (for borderline susceptible isolates)
  • Polymyxin + rifampin (though routine use not recommended) 1

Treatment Duration

• For severe infections such as VAP or bacteremia: 14 days 1, 2
• For less severe infections: Shorter durations may be acceptable 1
• Duration should be based on clinical response and source control 1

Important Caveats and Pitfalls

1. Avoid inappropriate empiric therapy: Mortality increases threefold with ineffective initial therapy 4

2. Do not use:

   • Tetracyclines as monotherapy, even if reported as susceptible in vitro 2
   • Ertapenem (lacks activity against Acinetobacter) 2
   • Combination of colistin with glycopeptides (no proven benefit) 1

3. Monitor for toxicity:

   • Renal function with polymyxins
   • Neurotoxicity with high-dose polymyxins

4. Resistance development:

   • Resistance can emerge during therapy, particularly with colistin and tigecycline 1
   • Consider combination therapy to prevent resistance development

5. Susceptibility testing:

   • Verify MICs for all antibiotics before finalizing treatment plan
   • Local susceptibility patterns should guide empiric therapy

The treatment of Acinetobacter infections remains challenging due to increasing resistance patterns, and therapy must be guided by local susceptibility data and individualized based on infection severity and patient factors 1, 5.