Normal habitat is water and soil
Can colonise cooling towers and water distribution system
85-90% of infections caused by Legionella pneumophila
Chlorine-tolerant - survives water treatment procedures
Transmission: Inhalation of aerosolised organisms, swimming in contaminated water
Ability to reach the lung (due to decreased cough etc)
-> phagocytosis by alveolar macrophages
-> failure to fuse with lysosome
-> multiply within phagosome
-> cell ruptures, releasing bacteria
Atypical acute lobar pneumonia
Develops in 1-5% of people exposed
Cause 1-5% of community-acquired pneumonia (after S. pneumoniae, H. influenzae, S. aureus)
Mortality rate - 5-30%
Nonspecific
Influenza-like illness
Attack rate 90% in exposed
Recovery - within 1 week.
No specific therapy required.
Facultative intracelluar parasite
Unencapsulated, slender rods
Aerobic
Fastidious, require L-cysteine
Gimenez stain more useful than Gram stain.
Culture using buffered (pH6.9) charcoal yeast extract enriched with L-cysteine, iron, alpha-ketoglutarate
First line: azithromycin (macrolides)
Second line: Levofloxacin (fluoroquinolones)
No treatment needed for Pontiac fever
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Created | 20040402 |