ID Board Review/Bacterial Diseases/Gram-negative Rods (GNR)/Legionella spp
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Histology[edit | edit source]
- Facultative Intracellular Gram-negative bacilli
Pathophysiology[edit | edit source]
Clinical Presentations[edit | edit source]
- Elderly patients, classically nursing home residents
- Risk Factors: Age, Hx of COPD
- Confusion, high fever, bradycardia
- CXR often unilobar infiltrate that progresses to consolidation
- Often failure to respond to broad spectrum/appropriate antibiotics
Natural Environments[edit | edit source]
- Aquatic bodies e.g. lakes, streams, man-made reservoirs, standing water
- "Air conditioners in retirement homes"
Diagnosis[edit | edit source]
- Legionella Urine Antigen test (only detects L. pneumophila serogroup 1)
- Sputum or BAL sample for Legionella Cx
- Hyponatremia, thrombocytopenia, elevated LFTs are all suggestive
Differential Diagnoses[edit | edit source]
Management[edit | edit source]
- Proven, or suspected Legionella PNA requires either:
- Respiratory fluoroquinolone (e.g. Levofloxacin)
- Newer macrolide (e.g. Azithromycin)
NOTE: Both have good lung penetration with potent intracellular activity