Chloramphenicol Coverage of Acinetobacter
Chloramphenicol is NOT an appropriate treatment for Acinetobacter infections and should never be used for this pathogen. While chloramphenicol has historical use in certain rickettsial diseases, it has no established role in treating Acinetobacter species and is not mentioned in any contemporary guidelines for this indication.
Why Chloramphenicol Should Not Be Used
Intrinsic resistance mechanisms: Acinetobacter baumannii possesses a major facilitator superfamily efflux pump (CraA) that displays strong substrate specificity toward chloramphenicol, conferring intrinsic resistance to this agent 1.
No guideline support: Current treatment guidelines for Acinetobacter infections from the Infectious Diseases Society of America, American Thoracic Society, and European Society of Clinical Microbiology and Infectious Diseases do not include chloramphenicol as a treatment option for any Acinetobacter species 2, 3, 4.
Significant toxicity concerns: Chloramphenicol is associated with adverse hematologic effects including aplastic anemia, which has resulted in its extremely limited use in the United States 5.
Limited availability: Chloramphenicol is no longer available in oral form in the United States, and the intravenous form is not readily available at most institutions 5.
Appropriate Treatment Options for Acinetobacter
For Carbapenem-Susceptible Isolates
- Carbapenems (imipenem, meropenem, doripenem) are the drugs of choice in areas with low carbapenem resistance rates 2.
- Note: Ertapenem lacks activity against Acinetobacter and should never be used 2.
For Carbapenem-Resistant Acinetobacter baumannii (CRAB)
- Ampicillin-sulbactam is the preferred option when sulbactam MIC ≤4 mg/L: administer 3g sulbactam every 8 hours as a 4-hour infusion 2, 4.
- Polymyxins (colistin) should be used if sulbactam-resistant but colistin-susceptible: loading dose of 5 mg CBA/kg IV followed by weight-based maintenance dosing 3.
- Combination therapy with two active agents is mandatory for severe infections or septic shock 2, 3.
Critical Pitfall to Avoid
The question may arise from confusion with chloramphenicol's use in rickettsial diseases, where it serves as an alternative (though suboptimal) agent 5. However, this has absolutely no relevance to Acinetobacter treatment, where the pathogen demonstrates intrinsic resistance mechanisms 1.