What is the role of antimicrobial therapy in the treatment of Legionella infection?

Updated: Nov 13, 2018
  • Author: Mobeen H Rathore, MD, CPE, FAAP, FIDSA; Chief Editor: Russell W Steele, MD  more...
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Antimicrobial therapy for Legionella disease

  • Specific therapy includes antibiotics capable of achieving high intracellular concentrations (eg, macrolides, quinolones, ketolides, tetracyclines, rifampin). The reported rank order of in vitro and intracellular activity against L pneumophila is quinolones, then ketolides, and then macrolides [34] . Beta-lactams and aminoglycosides have activity against Legionella species in vitro but are not clinically effective.

  • No prospective randomized studies have been performed regarding antibiotic effectiveness in patients with Legionella disease. Recommendations are based on retrospective reviews and experimental (laboratory and animal) studies.

  • Azithromycin is the drug of choice for children with suspected or confirmed Legionella disease. [1] With rare exceptions, the initial course should be intravenously administered. After a good clinical response is observed, it can be switched to the oral route. In patients with severe disease or who appear to be unresponsive to monotherapy, the addition of rifampin is recommended.

  • Certain fluoroquinolones (eg, levofloxacin, moxifloxacin) are effective and are recommended for adults with severe disease. [35] Because macrolides may interfere with drugs metabolized by cytochrome P450 (CYP) 3A4 isoenzyme (eg, cyclosporine), the quinolones mentioned above are suitable alternatives to treat Legionnaires disease in patients taking cyclosporine or other CYP3A4 substrates. An older fluoroquinolone, ciprofloxacin, does inhibit CYP3A4. Although the US Food and Drug Administration (FDA) has not approved fluoroquinolones for persons younger than 18 years (because of concerns about arthropathy in studies of juvenile animals), they have been successfully used to treat children with Legionnaires disease [3, 36, 13] and may be used in children in special circumstances.

  • Other alternatives include doxycycline or trimethoprim (TMP) and sulfamethoxazole (SMZ).

  • The recommended duration of therapy is 5-10 days if azithromycin is used. If other drugs are used, the duration should be 2-3 weeks. For patients with severe disease or immunocompromise, prolonged courses may be required.

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