What is Legionella (Legionnaires' disease)?

From the Guidelines

Legionella infection should be treated with azithromycin or a fluoroquinolone, such as moxifloxacin, gatifloxacin, or levofloxacin, as these are the preferred treatment options for hospitalized patients, according to the most recent guidelines 1. When it comes to Legionella infection, it is essential to consider the severity of the illness, the underlying health of the patient, and patient drug tolerance.

• For patients who do not require hospitalization, acceptable antibiotics include erythromycin, doxycycline, azithromycin, clarithromycin, or a fluoroquinolone 1.
• The duration of treatment should be 10–21 days, but it should be less for azithromycin because of its long half-life 1.
• A delay in therapy is associated with an increased mortality rate, and treatment should be started as soon as possible 1.
• Testing for Legionella species is appropriate for any patient hospitalized with enigmatic pneumonia, and the preferred diagnostic tests are the urinary antigen assay and culture of respiratory secretions on selective media 1.
• It is crucial to note that no laboratory test for legionnaires’ disease detects all patients with the disease, and therapy for legionnaires’ disease should be given or continued even if the results of Legionella-specific tests are negative, in the appropriate clinical and epidemiologic settings 1.
• People become infected by inhaling water droplets containing the bacteria, not through person-to-person contact, and those at highest risk include older adults, smokers, and people with weakened immune systems or chronic lung diseases.
• Prevention focuses on proper maintenance of water systems, including regular cleaning and disinfection, maintaining appropriate water temperatures, and preventing water stagnation.
• Early diagnosis is crucial for effective treatment, typically through urine antigen testing or respiratory culture 1.

From the Research

Overview of Legionella

• Legionella is a type of bacteria that can cause pneumonia, known as Legionnaires' disease, which can range from mild to severe [(2,3)].
• The disease is usually caused by Legionella pneumophila and can be acquired in the community or nosocomially from contaminated water sources [(2,3)].

Treatment of Legionnaires' Disease

• The treatment of Legionnaires' disease typically involves the use of antimicrobial agents, with erythromycin being the first-line treatment in the past 2.
• However, current recommendations suggest the use of other antibiotics such as azithromycin, clarithromycin, telithromycin, doxycycline, or extended-spectrum fluoroquinolones [(3,4,5)].
• The choice of antibiotic and duration of treatment depend on the severity of the disease and the patient's condition, with hospitalized patients requiring parenteral treatment and outpatients receiving oral treatment [(3,6)].

Antibiotic Options

• Azithromycin has been shown to be highly effective in the treatment of Legionnaires' disease, with a cure rate of 95-96% in hospitalized patients 6.
• Other effective antibiotics include levofloxacin, clarithromycin, and doxycycline, with quinolone/macrolide combinations being preferred for immunocompromised patients [(4,5)].
• The duration of treatment typically ranges from 7-21 days, depending on the severity of the disease and the patient's response to treatment [(3,5)].