Epidemiology
- Legionella Commonly Infects Immunocompetent Persons: presents as a severe community-acquired pneumonia
Risk Factors
- Anti-Tumor Necrosis Factor-α (Anti-TNFα) Therapy (see Anti-Tumor Necrosis Factor-α Therapy, [[Anti-Tumor Necrosis Factor-α Therapy]]) (Clin Infect Dis, 2006) [MEDLINE]
- Case Series of 10 Patients Reported from France
- Agents
- Relative Risk: Adalimumab > Etanercept/Infliximab
- Exposure in Large Hotel/Cruise Ship: symptoms usually occur weeks later
- Exposure to Water Source
- Condensers
- Grocery Store Misters
- Respiratory Care Devices
- Showers
- Whirlpools
- Corticoteroid/Cytotoxic Administration: increases risk of nosocomial Legionella pneumonia (steroids also increase risk for community-acquired Legionella)
- Previous antibiotic use and decreased consciousness were associated with a lower risk of nosocomial pneumonia
Microbiology
- Legionella Species
- Legionella Pneumophila
- Legionella Maceachernii
- Legionella Micdadei
- Incubation: 2-10 days
Diagnosis
Sputum Gram Stain and Culture
- May Show Numerous Neutrophils, But Few or No Organisms
Urinary Legionella Antigen (RIA or ELISA)
- Technique
- Easy Sample to Obtain
- Rapid Turnaround Time: available within hours
- Sensitivity/Specificity
- 90-95% Sensitive for Culture-Proven Cases of Serogroup-1 Legionella Pneumophila
- Does Not Detect Some Legionella Pneumophila Serogroups and Some Other Legionella Species: therefore, it should not be the only test used
- Highly Specific
- Duration of Urinary Antigen Excretion: antigen excretion can persist after illness is cured
Bronchoalveolar Lavage (BAL) Legionella Culture (see Bronchoscopy, [[Bronchoscopy]])
- Culture is the Single Most Important Test for Legionella
- Technique
- Culture on Buffered Charcoal Yeast Extract (BCYE) Agar
- Requires 3 days for Growth
- Negative Results are Not Reported for 1 Week
- Sensitivity/Specificity
- Detects All Legionella Species and Subgroups
- False-Positive Results are Rare
Bronchoalveolar Lavage (BAL) Legionella DFA (see Bronchoscopy, [[Bronchoscopy]])
- Technique
- Requires Lower Respiratory Tract Specimen
- Results are Available Quickly
- Sensitivity/Specificity
- Monoclonal Reagents are Specific and Detect All Legionella Pneumophila Serogroups (But Not Other Legionella Species)
- Specificity of Polyclonal Reagents Used for Serogroups Other than Legionella Pneumophila is Not Well-Defined
Legionella Serology
- Useful for Epidemiologic and Research Purposes Only: too slow to be useful for clinical purposes
Clinical Manifestations of Pontiac Fever (see Pontiac Fever, [[Pontiac Fever]])
- Exposure: inhalation of aerosols from Legionella-infected water source
- Epidemiology: 36 hrs (much shorter than that for Legionnaires’ disease)
- Diagnosis
- Clinical
- Cough (see Cough, [[Cough]])
- Dyspnea (see Dyspnea, [[Dyspnea]])
- Fever (see Fever, [[Fever]])
- Treatment: self-limited febrile syndrome
Clinical Manifestations of Legionnaires’ Disease
General Comments
- Time Course of Legionnaires’ Disease: while fever may precede the appearance of pulmonary infiltrates in some cases, almost all patients have infiltrates by day 3 of the illness
Cardiovascular
Chest Pain (see Chest Pain, [[Chest Pain]])
- Epidemiology: occurs in 13-35% of cases
Myocarditis/Pericarditis/Prosthetic Valve Endocarditis (see Myocarditis, [[Myocarditis]], Acute Pericarditis, [[Acute Pericarditis]], and Endocarditis, [[Endocarditis]])
- Epidemiology: extrapulmonary disease in Legionnaires’ Disease is extremely rare
- Reported Mainly in Immunocompromised Patients
Gastrointestinal Manifestations
Abdominal Pain (see Abdominal Pain, [[Abdominal Pain]])
Diarrhea (see Diarrhea, [[Diarrhea]])
- Epidemiology: occurs in 21-50% of cases
Elevated Liver Function Tests (LFT’s)
Nausea/Vomiting (see Nausea and Vomiting, [[Nausea and Vomiting]])
- Epidemiology: occurs in 8-49% of cases
Neurologic Manifestations
Headache (see Headache, [[Headache]])
- Epidemiology: occurs in 40-48% of cases
Neurologic Abnormalities
- Epidemiology: occur in 4-53% of cases
- Clinical
Pulmonary Manifestations
Acute Respiratory Distress Syndrome (ARDS) (see Acute Respiratory Distress Syndrome, [[Acute Respiratory Distress Syndrome]])
Alveolar or Interstitial Pneumonia
- Radiographic Patterns
- Patchy Lobar Infiltrate, Which Progresses to Consolidation (see Pneumonia, [[Pneumonia]]): most common pattern
- Cavitation is Uncommon: although may be seen in some immunocompromised cases though
- Diffuse Interstitial Infiltrates (see Interstitial Lung Disease, [[Interstitial Lung Disease]]): has been reported (Chest, 2000) [MEDLINE]
- Other Patterns: have been reported
- Cough (see Cough, [[Cough]])
- Dyspnea (see Dyspnea, [[Dyspnea]])
- Rales
- Streaky Hemoptysis (see Hemoptysis, [[Hemoptysis]]): gross hemoptysis is rare
- Absence of Upper Respiratory Symptoms
Lymphocytic Interstitial Pneumonia (see Lymphocytic Interstitial Pneumonia, [[Lymphocytic Interstitial Pneumonia]])
Pleural Effusion (see Pleural Effusion-Exudate, [[Pleural Effusion-Exudate]])
- Epidemiology: small pleural effusion is noted in 20-50% of cases
Rounded Atelectasis (see Rounded Atelectasis, [[Rounded Atelectasis]])
- Epidemiology: may occur in absence of significant pleural disease
Renal Manifestations
Acute Interstitial Nephritis (see Acute Interstitial Nephritis, [[Acute Interstitial Nephritis]])
Hematuria (see Hematuria, [[Hematuria]])
Hyponatremia (see Hyponatremia, [[Hyponatremia]])
- Epidemiology: occurs more commonly in Legionellosis than in other pneumonias
Proteinuria (see Proteinuria, [[Proteinuria]])
Rheumatologic Manifestations
Arthralgias/Myalgias (see xxxx, [[xxxx]])
- Epidemiology: occur in 20-40% of cases
Other Manifestations
Fever (see xxxx, [[xxxx]])
- Epidemiology
- Fever >38.8ºC: occurs in 88-90% of cases
- Fever >40ºC: occurs in 20-62% of cases
Treatment
Antibiotics
References
- The radiologic manifestations of Legionnaire’s disease. The Ohio Community-Based Pneumonia Incidence Study Group. Chest. 2000;117(2):398 [MEDLINE]
- Emergence of Legionella pneumophila pneumonia in patients receiving tumor necrosis factor-alpha antagonists. Clin Infect Dis 2006; 43:e95-e100 [MEDLINE]