Legionella Flashcards
Where do Legionella like to grow?
intracellularly within amoebas in the environment or within alveolar macrophages in the body.
What is the most virulent form of Legionella?
serotype 1. It causes 100% of community acquired disease.
Describe the morphology of legionella
gram negative rods
strict aerobes
Catalase +
oxidase +
Do Legionella grow on routine media?
No. They require additional Fe, L-cysteine, and charcoal.
What is Legionella’s favorite habitat?
Warm water systems!
What are common sources of transmission for Legionella?
water cooling towers, faucets, shower heads, respiratory equipment, hot tubs, whirlpool spas, indoor decorative fountains, humidifiers, misters, potting soil.
How is Legionella transmitted?
Aerosols from warm water
What is the most common source of nosocomial infection w/ legionella?
Potable water.
Is there human to human transmission of Legionella?
NO
What are the clinical manifestations f Legionnaires Disease
Acute pneumonia with an incubation period of 2-10 days.
Sx: fever, headache, muscle aches, chills, cough, chest pain, confusion
What is the pathogenesis of Legionnaires Disease?
It is associated with intracellular multiplication in alveolar macrophages, monocytes/macrophages.
What is the clinical manifestation of Pontiac Fever?
Mild-self-limited respiratory disease. No pneumonia or fatalities.
What is the best way to diagnose Legionella?
Not via gram stain or CXT!
Often dx as follow up to lack of PCN response and negative culture.
-Culture on special media, direct fluorescent Ab staining, URINE ANTIGEN, PCR, serology (only for retrospective diagnosis0
Treatment of Legionella
Azithromycin/other macrolide.
FQs show good survival as well.
Prevention of Legionella:
Monitor and disinfect water reservoirs in hospital systems
