Legionella

• Gram negative aerobe
• L. pneumophila: associated with two distinct syndromes: pneumonia (legionnaires disease) and Pontiac Fever
• Infection typically occurs via inhalation of aerosolized contaminated water or aspiration of contaminated water
  • Outbreaks often associated with cooling towers, hot tubs, medical equipment
  • Increased incidence with hot, humid, weather and thundershowers
• Most commonly found in patients age > 50 years, smokers, immunocompromised.[1]
  • However, likely underestimated in children[2]

• Pontiac fever[3]
  • Fever, mild flu-like illness
  • Absence of pneumonia
• Legionnaires disease[4]
  • High mortality
  • Incubation 2-10d[5]
  • Fever, often high
  • Cough
  • Respiratory distress
    • Respiratory failure in ~10% of all cases[6]
  • Relative [[bradycardia (relative to temperature)
• Gastrointestinal symptoms (e.g. nausea/vomiting, diarrhea)
• Neurologic symptoms
  • Headache
  • Tremor
  • Seizure
  • Guillain-barre
  • Chorea
  • Acute cerebellar ataxia

Gastrointestinal symptoms Neurologic symptoms Can cause tremor, seizures, Guillain-Barre, and chorea. Has been linked to cases of Acute Cerebellar Ataxia. [Nigro, 1983] Respiratory failure occurs in ~10% of all cases.

Severe case of Legionellosis on CXR

• Sputum sample for culture
• Urine legionella antigen
• Na: Low in CAP but mostly frequently associated with Legionella
• AST/ALT: Mildly increased 2-5x normal
• Phosphate: Decreased
• CK: Increased
• CRP: > 35
• Ferritin: Increased >2x normal

• Reportable disease, notify appropriate health department[8]
• First line
  • Azithromycin
• Alternatives:
  • Doxycycline
  • Tigecycline
  • Respiratory fluoroquinolone for severe disease[9]

• Microbiology (Main)