Legionellosis is the
infection caused by bacteria of the genus Legionella, including a non-pneumonic
influenza-like syndrome, and
Legionnaires' disease is a more serious illness characterized by
pneumonia.
Legionellosis is becoming increasingly important as a public health problem throughout the world; although it is an underreported disease, studies have consistently documented a high incidence. In addition, health costs associated with the disease are high. Diagnosis of
Legionnaires' disease is based mainly on the detection of Legionella pneumophila serogroup 1
antigen in urine. However, there have been advances in detection tests for patients with
legionellosis. New methodologies show greater sensitivity and specificity, detect more species and serogroups of Legionella spp., and have the potential for use in epidemiological studies. Testing for Legionella spp. is recommended at hospital admission for severe community-acquired
pneumonia, and
antibiotics directed against Legionella spp. should be included early as empirical
therapy. Inadequate or delayed
antibiotic treatment in Legionella
pneumonia has been associated with a worse prognosis. Either a
fluoroquinolone (
levofloxacin or
moxifloxacin) or a
macrolide (
azithromycin preferred) is the recommended first-line
therapy for
Legionnaires' disease; however, little information is available regarding adverse events or complications, or about the duration of
antibiotic therapy and its association with clinical outcomes. Most published studies evaluating
antibiotic treatment for
Legionnaires' disease are observational and consequently susceptible to bias and confounding. Well-designed studies are needed to assess the usefulness of diagnostic tests regarding clinical outcomes, as well as randomized trials comparing
fluoroquinolones and
macrolides or combination
therapy that evaluate outcomes and adverse events.