Legionella

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

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II. 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

III. 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

IV. Presentations

  1. Legionellosis (severe illness, Pneumonia)
    1. Legionella pneumonia
  2. Pontiac Fever (mild, Influenza-like illness)

V. 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

VI. Signs

  1. Severe respiratory distress
  2. Confusion
  3. Disorientation

VII. 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

VIII. 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

IX. 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

X. 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

XI. 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

XII. Course

  1. Response to Antibiotics may not be seen for 4-5 days
  2. Up to 10-15% mortality in some studies

XIII. 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]

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