Clinical Setting

    • Community or hospital-acquired pneumonia, extrapulmonary infections (e.g., endocarditis) occur but are rare
    • Despite cough, patients with pneumonia may produce small amounts of mucoid non-purulent sputum
    • Risk factors: Immunocompromised patient, smoking, co-morbidities.
    • Associated clinical findings with pneumonia (although nonspecific):
      • Diarrhea, other gastrointestinal symptoms
      • Confusion
      • Relative bradycardia
      • Hyponatremia
      • Elevated hepatic enzymes
      • Elevated BUN and creatinine
      • Elevated ferritin levels. Range of peak levels: 591-5990 (Clin Infect Dis 46:1789, 2008)

    Diagnosis

    • Culture (requires selective media) or PCR: detects multiple serotypes.
    • Antigen assay, direct fluorescent antibody, or serology detects L. pneumophila serotype 1 strains only (for review of diagnostics see Clin Microbiol Rev 28:95, 2015).

    Classification

    • Gram negative bacilli
    • Legionella pneumophila (60-80% of cases)
    • Legionella (tatlockia)   micdadei
    • Legionella wadsworthii
    • ~40 species identified, most rarely associated with human disease

    Primary Regimens

    • Pneumonia
      • Levofloxacin 750 mg IV/po q24h or Moxifloxacin 400 mg IV/po q24 
      • Azithromycin 500 mg IV/po q24h 
      • No proven benefit of Rifampin combination therapy (and drug interactions are a major issue in many patients) or combination of Azithromycin + fluoroquinolone
    • Endocarditis: above (see Comments)

    Alternative Regimens

    Antimicrobial Stewardship

    • Duration of therapy.
      • 7-10 days of IV/po therapy depending on clinical response is appropriate for immunocompetent patients with legionella pneumonia.
      • 14-21 days of therapy with IV/po therapy depending on clinical response is recommended for immunocompromised patients.
      • Duration of therapy not well defined, but prolonged therapy, up to 5 months, has been used

    Comments

    • For endocarditis
      • Advise microbiology laboratory when considering the diagnosis of Legionella spp. endocarditis as it is possible to isolate the organism in blood culture media with special handling..
      • Infectious Diseases consultation recommended
      • Several Legionella spp have been reported as causes of endocarditis.
      • Most patients reported in the literature have undergone valve replacement in addition to medical therapy.
      • Treatment recommendations based on anecdotal case reports.
      • References: J Infect 51:e256, 2005,  Clin Micro Rev 2001; 14:177, Circulation. 2015;132:1435-1486.
    • Macrolides and fluoroquinolones are probably equally effective (Clin Infect Dis 2021;72:1979).
    • TMP-SMP also probably effective but less data to support its efficacy
    • Reference on diagnosis and treatment: Infect Dis Ther. 2022; 11:973-986.
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