What is the diagnosis and treatment of Legionella (Legionnaires' disease) pneumonia?

From the Guidelines

Legionella pneumonia should be treated with azithromycin 500mg IV or orally once daily for 7-10 days, or levofloxacin 750mg IV or orally once daily for 7-10 days, as these are the most effective antibiotics for this condition, according to the most recent and highest quality study 1. The diagnosis of Legionella pneumonia is typically confirmed through urinary antigen testing, sputum culture on specialized media, or PCR testing.

• The clinical presentation of Legionella pneumonia can be severe, with high fever, hyponatremia, CNS manifestations, and lactate dehydrogenase levels of 1700 U/mL, or severe disease, and requires prompt treatment to reduce morbidity and mortality 1.
• The bacteria spread through aerosolized water droplets from contaminated water sources, not person-to-person, so isolation precautions are not required for hospitalized patients.
• Patients with Legionella pneumonia typically require hospitalization, especially those with severe symptoms, respiratory distress, or underlying health conditions, and may need supportive care including oxygen therapy, hydration, and respiratory support.
• The recommended total duration of antibiotics therapy for Legionella pneumonia is 7-10 days, but a longer antibiotic course of 21 days may be considered for immunosuppressed patients who are severely ill at presentation 1.
• Combination therapy with azithromycin plus rifampin 600mg twice daily may be used for severe cases, but the clinical benefit of rifampin combination therapy remains inconclusive based on currently available evidence 1.

From the FDA Drug Label

Levofloxacin tablets are indicated for the treatment of community-acquired pneumonia due to methicillin-susceptible Staphylococcus aureus, Streptococcus pneumoniae (including multi-drug-resistant Streptococcus pneumoniae [MDRSP]), Haemophilus influenzae, Haemophilus parainfluenzae, Klebsiella pneumoniae, Moraxella catarrhalis, Chlamydophila pneumoniae, Legionella pneumophila, or Mycoplasma pneumoniae Azithromycin for Injection, USP is indicated for the treatment of patients with infections caused by susceptible strains of the designated microorganisms in the conditions listed below... Community-acquired pneumonia due to ... Legionella pneumophila

Legionella pneumonia can be treated with:

• Levofloxacin (PO) 2
• Azithromycin (IV) 3

From the Research

Diagnosis of Legionella Pneumonia

• The diagnosis of Legionellosis can be established using antigen-testing in urine by a rapid immunochromatographic test (ICT), which is an easy to handle bedside test that provides a result within 15 minutes 4.
• The sensitivity and specificity of this test reach 80% and 100%, respectively 4.

Treatment of Legionella Pneumonia

• Macrolides, doxycycline, fluoroquinolones, and ketolides are drugs with sufficient activity against Legionella spp. and are appropriate candidates for empirical initial antimicrobial treatment regimen of community-acquired pneumonia 4.
• Macrolides and fluoroquinolones should be the drugs of choice for the treatment of established Legionellosis, with oral macrolides preferred in patients with mild to moderate pneumonia 4.
• Azithromycin has been shown to be efficacious in the treatment of Legionella pneumonia, with a cure rate of 95% in hospitalized patients 5.
• Fluoroquinolones, such as ciprofloxacin, levofloxacin, and moxifloxacin, may also be used as alternative treatments 4.
• A systematic review and meta-analysis found no difference in the effectiveness of fluoroquinolones versus macrolides in reducing mortality among patients with Legionella pneumonia 6.
• A retrospective analysis found that azithromycin appears to have clinical efficacy similar to fluoroquinolones for the treatment of Legionella pneumonia 7.

Choice of Antibiotic

• The choice of antibiotic for the treatment of Legionella pneumonia depends on the severity of the disease and the patient's underlying health conditions 4, 8.
• In severe cases or in immunosuppressed patients, intravenous fluoroquinolones or azithromycin may be preferred 4, 8.
• Combination therapy with azithromycin or fluoroquinolones and rifampin or azithromycin and fluoroquinolone may be considered, but its effectiveness is currently unknown 4.