Pathogens
Legionella pneumophila

Legionella pneumophila

Susceptibilities

General Information

Culture requires special media which is not commonly available.

Urinary antigen detects L. pneumophila serogroup 1. While most infections (~84%) are from serogroup 1 not all cases of Legionella will be detected by urinary antigen. 

Test Sensitivity (%) Specificity (%)
Culture 20-80 100
Urinary antigen (L. pneumophila serogroup 1) 70-100 95-100
PCR 95-99 >99
Direct Fluorescent Antibody (DFA) 25-75 >95
Paired serology 80-90 >99

Aerobic small gram negative bacillus.

Reservoir is water. Aerosolization by cooling towers, spas, shower heads, etc.

Occurs in outbreaks.

Person-to-person transmission not documented.

  • Pneumonia (Legionnaires disease)

  • Pontiac fever (Self-limited febrile illness)

  • Extrapulmonary infections rare, but include endocarditis

Risk factors include:

  • Outbreak setting
  • Older male
  • Smoker
  • Cardiopulmonary disease
  • Renal disease
  • Immunosuppression

CDC Guidance