What is the treatment for Legionnaires' pneumonia (Legionella pneumonia)?

From the Guidelines

Legionnaires' pneumonia should be treated with azithromycin or a fluoroquinolone, such as levofloxacin, as these antibiotics have been shown to be effective in targeting the Legionella bacteria and improving patient outcomes. The treatment guidelines recommend azithromycin 500 mg once daily for 5-10 days or levofloxacin 750 mg once daily for 7-14 days as the first-line treatment options 1. For severe cases requiring hospitalization, intravenous antibiotics may be necessary initially, followed by oral therapy once the patient improves. Fluoroquinolones like levofloxacin are particularly effective because they achieve high concentrations in lung tissue and within macrophages where Legionella bacteria multiply. Macrolides like azithromycin work by inhibiting bacterial protein synthesis.

Some key points to consider when treating Legionnaires' pneumonia include:

• The importance of prompt treatment, even before laboratory confirmation, if Legionnaires' disease is suspected based on clinical presentation and risk factors 1
• The need for supportive care, including oxygen therapy, adequate hydration, and respiratory support, in addition to antibiotic therapy
• The ineffectiveness of beta-lactam antibiotics (penicillins and cephalosporins) against Legionella, as they cannot penetrate the cells where the bacteria reside
• The potential for severe cases to require longer treatment durations, up to 21 days, especially in immunosuppressed patients 1

It is essential to note that the treatment guidelines are based on the most recent and highest-quality evidence available, and azithromycin or a fluoroquinolone should be used as the first-line treatment for Legionnaires' pneumonia, as recommended by the guidelines 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 [see Dosage and Administration (2.1) and Clinical Studies (14.2)]. 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 Chlamydia pneumoniae, Haemophilus influenzae, Legionella pneumophila, Moraxella catarrhalis, Mycoplasma pneumoniae, Staphylococcus aureus, or Streptococcus pneumoniae in patients who require initial intravenous therapy

Legionella pneumophila treatment can be done with:

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

From the Research

Treatment Options for Legionnaire Pneumonia

• Erythromycin has been traditionally used as the first-line treatment for Legionnaire pneumonia, with an intravenous dosage of 1g every 6 hours as initial therapy 4.
• However, newer macrolides/azalides such as clarithromycin and azithromycin have excellent in vitro activity against Legionella and fewer adverse effects than erythromycin 5.
• Fluoroquinolones, particularly levofloxacin, are also highly effective against Legionella pneumonia 5, 6.
• Other treatment options include doxycycline, rifampicin, and trimethoprim-sulfamethoxazole, although their efficacy may vary 4, 5.

Treatment Recommendations

• For outpatient treatment, azithromycin, erythromycin, clarithromycin, telithromycin, doxycycline, or an extended-spectrum fluoroquinolone may be used 7.
• For hospitalized patients, parenteral azithromycin or extended-spectrum fluoroquinolones followed by step-down to oral formulations are recommended 7.
• The duration of treatment typically ranges from 10-21 days, although a shorter course of 7-10 days may be possible for intravenous/oral azithromycin 7.

Comparison of Treatment Outcomes

• A study comparing levofloxacin and azithromycin found no significant differences in outcomes, including time to defervescence, time to achieve clinical stability, and length of hospital stay 8.
• However, patients treated with clarithromycin had longer intravenous antibiotic treatment and longer hospital stay compared to those treated with levofloxacin 8.
• The overall mortality rate was 4.3%, with no significant association between levofloxacin and azithromycin on mortality 8.