Ertapenem Lacks Activity Against Acinetobacter baumannii
Ertapenem is not effective against Acinetobacter baumannii infections and should not be used for treatment of this pathogen. 1
Carbapenem Options for A. baumannii
- Carbapenems are traditionally the drugs of choice for A. baumannii infections, but specifically imipenem, meropenem, and doripenem - not ertapenem 1, 2
- Ertapenem lacks activity against A. baumannii and is explicitly excluded from carbapenem options for this pathogen 1
- In areas with low rates of carbapenem resistance, other carbapenems (imipenem, meropenem, doripenem) remain first-line agents for empirical therapy of A. baumannii infections 1, 2
Alternative Treatment Options
When treating A. baumannii infections, the following alternatives should be considered:
- For carbapenem-susceptible isolates: imipenem, meropenem, or doripenem are recommended 2, 3
- For carbapenem-resistant isolates:
- Polymyxins (colistin) are currently the antimicrobials with the greatest level of in vitro activity 1, 4, 5
- Ampicillin-sulbactam at high doses (3g sulbactam every 8 hours as 4-hour infusions) for isolates with MIC ≤4 mg/L 1, 4
- For severe infections, combination therapy with two active agents may be considered 2, 4
Clinical Implications and Pitfalls
- Despite being a carbapenem, ertapenem has a different spectrum of activity compared to other carbapenems and should never be used for suspected or confirmed A. baumannii infections 1
- Using ertapenem for A. baumannii infections would result in treatment failure and potentially increased mortality 1, 5
- Some studies have suggested that ertapenem may be advantageous for treating other multidrug-resistant gram-negative infections (like ESBL-producers) as it might not select for carbapenem-resistant A. baumannii due to its lack of activity against this pathogen 6
- Misidentification of A. baumannii species can lead to inappropriate antibiotic selection; accurate identification using methods like MALDI-TOF MS is recommended 1
Monitoring and Resistance Concerns
- A. baumannii has an impressive propensity for acquiring antibiotic resistance, making empirical treatment challenging 1
- In a recent study, clinical isolates of A. baumannii showed high resistance rates to all carbapenems including ertapenem 7
- Carbapenem resistance in A. baumannii is increasingly reported worldwide, necessitating alternative treatment strategies 3, 8, 5
- Heteroresistance to various antibiotics has been reported in A. baumannii, further complicating treatment 1