What is the treatment for Acinetobacter lwoffii infections?

Treatment of Acinetobacter lwoffii Infections

For Acinetobacter lwoffii infections, carbapenems are the first-line treatment in areas with low carbapenem resistance, while polymyxins (colistin) should be used in areas with high carbapenem resistance. 1

Initial Antibiotic Selection Algorithm

Step 1: Assess Local Resistance Patterns

• Determine local carbapenem resistance rates for Acinetobacter species
• Review patient's previous colonization status with resistant Acinetobacter

Step 2: Select Empiric Therapy Based on Resistance Patterns

1. In areas with low carbapenem resistance:

   • First choice: Imipenem or meropenem 1, 2
   • Dosage: Imipenem 500 mg IV every 6 hours or 1000 mg every 8 hours 2

2. In areas with high carbapenem resistance:

   • First choice: Polymyxin (colistin) 1
   • Consider combination therapy for severe infections

Step 3: Adjust Therapy Based on Susceptibility Testing

• Once susceptibility results are available, narrow therapy to the most appropriate agent
• For A. lwoffii specifically, studies show highest sensitivity to:
  • Imipenem (57%)
  • Cotrimoxazole (32%)
  • Ciprofloxacin (21%) 3

Treatment Options by Susceptibility

Carbapenem-Susceptible A. lwoffii

• Preferred: Imipenem or meropenem 1, 2
• Alternative: Ampicillin-sulbactam (if susceptible) 1
  • Dosage: 9-12 g/day of sulbactam component in 3 divided doses 1

Carbapenem-Resistant A. lwoffii

• Preferred: Intravenous polymyxin (colistin or polymyxin B) 1
• Consider: Adjunctive inhaled colistin for respiratory infections 1

Special Considerations

For Respiratory Infections

• Consider adjunctive inhaled colistin with systemic therapy for ventilator-associated pneumonia 1
• Nebulized antibiotics may improve outcomes in respiratory infections 1

For Severe Infections

• Duration of therapy: 2 weeks for severe infections such as bacteremia or pneumonia 1
• Shorter durations may be acceptable for less severe infections 1

Important Clinical Pearls

1. Heteroresistance concern: A. lwoffii may develop resistance during therapy, particularly to colistin. Monitor clinical response carefully 1

2. Combination therapy: While routine combination therapy is not recommended, consider it for:

   • Clinical failures
   • Isolates with MICs at the upper limit of susceptibility 1

3. Avoid monotherapy with:

   • Tigecycline
   • Aminoglycosides 1

4. Risk factors for A. lwoffii infection:

   • Prior colonization
   • Immunosuppression
   • Previous antimicrobial therapy
   • Multiple invasive procedures 1
   • Premature and very low birth weight in neonates 3

Treatment Pitfalls to Avoid

1. Inadequate dosing: Ensure appropriate dosing based on site of infection and renal function 1, 2

2. Delayed therapy: Prompt initiation of appropriate antibiotics is crucial for survival 1

3. Overlooking susceptibility testing: Always obtain susceptibility testing to guide definitive therapy 1

4. Inappropriate empiric coverage: Consider A. lwoffii coverage empirically only during outbreaks, in endemic situations, or in previously colonized patients 1

5. Ignoring local resistance patterns: Treatment should be guided by local susceptibility patterns 4