Legionella

Aka: Legionella, Legionella pneumophila, Legionella pneumonia, Legionnaire's Disease, Legionellosis, Pontiac Fever

1. See Also
   1. Bacterial Pneumonia
   2. Waterborne Illness
2. Pathophysiology
   1. Aerobic, intracellular, Gram Negative Rod
      1. Virulent organism
      2. More severe disease than other Atypical Pneumonia
   2. Transmission
      1. Optimal conditions for growth
         1. Temperature: 89 to 113 F water
         2. Stagnant water
      2. Waterborne Illness
         1. Freshwater or moist soil near ponds
         2. Air conditioning
         3. Condensers
         4. Cooling towers
         5. Respiratory therapy equipment
         6. Showers or water faucets
         7. Whirlpools
         8. Aeorsolized mist (hot tubs, decorative fountains)
   3. Incubation
      1. Two to ten days
3. Risk Factors
   1. Tobacco Smoking
   2. Chronic Renal Failure
   3. Malignancy
   4. Immunosuppression
   5. Diabetes Mellitus
   6. Chronic Liver Disease
   7. Exposure to recent plumbing work
   8. Overnight stay outside the home
4. Presentations
   1. Legionellosis (severe illness, Pneumonia)
      1. Legionella pneumonia
   2. Pontiac Fever (mild, Influenza-like illness)
5. Symptoms
   1. Prodrome for 12-48 hours
      1. Malaise
      2. Myalgia
      3. Headache
   2. Symptoms for 2-3 days
      1. Fever to 40.5 C persists for 8-10 days
      2. Gastrointestinal symptoms in 20-40% of cases
         1. Nausea or Vomiting
         2. Diarrhea
   3. Later Symptoms: Cough
      1. Minimal to no Sputum production
      2. Slightly blood tinged Sputum
6. Signs
   1. Severe respiratory distress
   2. Confusion
   3. Disorientation
7. Complications
   1. Respiratory Failure (20-40% of cases)
   2. Extrapulmonary complications
      1. Myocarditis or Pericarditis
      2. Prosthetic Valve Endocarditis
      3. Glomerulonephritis
      4. Pancreatitis
      5. Peritonitis
8. Radiology: Chest XRay
   1. Small Pleural Effusions
   2. Unilateral parenchymal infiltrates
      1. Round, fluffy opacities
      2. Spread contiguously to other lobes
      3. Progresses to dense consolidation
      4. Progresses to bilateral infiltrates
9. Labs
   1. Complete Blood Count
      1. Leukocytosis
      2. Leukopenia
   2. Erythrocyte Sedimentation Rate
      1. Elevated markedly
   3. Liver Function Tests increased
   4. Sputum Exam
      1. Fluorescent Antibody studies of Sputum
      2. Legionella can not be seen on Gram Stain
10. Diagnosis
    1. Legionella urine antigen testing
       1. High sensitivity and Specificity for serogroup 1
          1. Serogroup 1 (LP1) causes most U.S. cases (80%)
       2. Sputum Culture required to identify other serogroups
          1. Urine antigen and Sputum Culture all cases
       3. References
          1. Benin (2002) Clin Infect Dis 35:1039-46 [PubMed]
    2. Concurrent Sputum and Blood Culture in all suspected cases (before antibiotics)
       1. Sputum Culture on special medium
    3. Legionella Serologies
       1. Legionella fourfold titer rise to >= 1:128 or
       2. Legionella titer >= 1:256
11. Management (Antibiotic course for 21 days)
    1. Azithromycin IV
    2. Levofloxacin IV
    3. Trovafloxacin IV
    4. Erythromycin IV
       1. Add Rifampin in immunocompromised or severe disease
12. Course
    1. Response to antibiotics may not be seen for 4-5 days
    2. Up to 10-15% mortality in some studies
13. References
    1. Gilbert (2001) Sanford Antimicrobial, p. 28
    2. Akbas (2001) Postgrad Med 109(5):135-47 [PubMed]
    3. File (1998) Infect Dis Clin North Am 12(3):569-92 [PubMed]
    4. Klein (1998) Semin Respir Infect 13(2):140-6 [PubMed]
    5. Perkins (2017) Am Fam Physician 95(9):554-60 [PubMed]
    6. Plouffe (2000) Clin Infect Dis 31:S35-9 [PubMed]
    7. Tan (1999) Can Respir J 6:15A-9A [PubMed]
    8. Waterer (2001) Am J Med 110(1):41-8 [PubMed]