History

Fact Explanation
Fever The causative agent in 90% of infections is L.pneumophila. This is one of the earliest symptoms.The fever is a high fever in one thirds of the patients.[1]
Upper respiratory symptoms such as : sneezing, sore throat, runny nose These symptoms are due to inflammation and irritation of the mucosa.This is usually a nonspecific symptom.
Cough This occurs after the onset of fever.This can be a pronounced cough.[1] This can be a nonproductive cough or a purulent one.[1]
Rigors Along with high fever, this occurs as a mechanism to increase the body temperature.
Myalgias This is an early and a nonspecific symptom.This is due to action of inflammatory mediators or this may be a complication of legionella such as rhabdomyolysis. [3]
Dyspnea This is due to the hypoxemia generated by the poor oxygenation (following inflammation of the lung tissue). Worsening of dyspnoea can be a feature of myocarditis.[4]
Pleuritic Chest pain. This can occur either due to the inflammation of the pleura or following intense coughing.
Extrapulmonary: gastro-intestinal symptoms This is prominent in Legionnaires disease. Common complaints are : watery diarrhea, nausea, vomiting and abdominal pain. [1]
Extrapulmonary: neurological symptoms These can be variable according to individual patients. The symptoms are: headache, confusion, obtundation, seizures, hallucinations. They are due to encephalitis.[5] Confusion and agitation can be a cause of rhabdomyolysis. [3]
Extrapulmonary: anuria This is mostly due to rhabdomyolysis.[3]
Hospitalization Pneumonia that develops after 48 hours of hospitalization can occur due to Legionella infections.
Risk factors: environment Aerosol-generating devices( nebulizers, cooling towers, showers, respiratory therapy equipment,air conditioners) can act as modes of spread of the disease.[2] The person to person transmission doesn't occur. Optimal water temperatures for growth is in the range of 20°C to 45°C. [2]
Risk factors: patient factors. Following conditions can have increased risk of Legionnaires disease. Severe immunosuppression (organ transplantation), hematological malignancy, end-stage renal disease, diabetes mellitus, chronic lung disease, non-hematological malignancy, HIV, elderly, smokers. [2]
References
  1. FIELDS BS, BENSON RF, BESSER RE. Legionella and Legionnaires' Disease: 25 Years of Investigation Clin Microbiol Rev [online] 2002 Jul, 15(3):506-526 [viewed 22 June 2014] Available from: doi:10.1128/CMR.15.3.506-526.2002
  2. JOSEPH, Carol .LEE,John, WIJNGAARDEN Jan van DRASAR, Vladimir. European Guidelines for Control and Prevention of Travel Associated Legionnaires’ Disease.The European Surveillance Scheme for Travel Associated Legionnaires’ Disease.2005 Disease and the European Working Group for Legionella Infections.
  3. SAURET JM, MARINIDES G, WANG GK. Rhabdomyolysis. Am Fam Physician [online] 2002 Mar 1, 65(5):907-12 [viewed 19 June 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/11898964
  4. ISHIMARU N, SUZUKI H, TOKUDA Y, TAKANO T. Severe Legionnaires' disease with pneumonia and biopsy-confirmed myocarditis most likely caused by Legionella pneumophila serogroup 6. Intern Med [online] 2012, 51(22):3207-12 [viewed 19 June 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/23154735
  5. ROIG J, RELLO J. Legionnaires' disease: a rational approach to therapy. J Antimicrob Chemother [online] 2003 May, 51(5):1119-29 [viewed 22 June 2014] Available from: doi:10.1093/jac/dkg191

Examination

Fact Explanation
Fever This one of the commonest symptoms.In one third of patients its a high fever[3].
Tachycardia This is a prominent symptom. [3] Hypoxia, Fever, release of catecholamines can induce tachycardia.
Tachypnoea This can be a prominent symptom.[3] Hypoxia and hypercarbia stimulate the respiratory center and induce tachycardia.
Dull percussion note This can be due to either the consolidation or the pleural effusion.
Coarse crackles This is due to the consolidation[3]. The sound is generated by opening of the collapsed airways.
Rhonchi This can be auscultated in some of the patients.This is caused by air flowing through the narrowed airways due to inflammation.
Pleural friction rubs This sign can indicate small pleural effusions.
Hepatomegaly There can be hepatitis in some of the patients.
Splenomegaly This can be present in some patients[4]This is due to the congestion of the Splenic vasculature
Nuchial rigidity This is due to the meningism and there is a spasm of the cervical muscles on passive stretch.
Alteration of GCS This can be due to the encephalitis [1]
Muscle tenderness, swelling This can be a feature of rhabdomyolysis[2]
References
  1. DE LAU LM, SIEPMAN DA, REMMERS MJ, TERWINDT GM, HINTZEN RQ. Acute disseminating encephalomyelitis following legionnaires disease. Arch Neurol [online] 2010 May, 67(5):623-6 [viewed 19 June 2014] Available from: doi:10.1001/archneurol.2010.75
  2. SAURET JM, MARINIDES G, WANG GK. Rhabdomyolysis. Am Fam Physician [online] 2002 Mar 1, 65(5):907-12 [viewed 19 June 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/11898964
  3. NICOLINI A, FERRAIOLI G, SENAREGA R. Severe Legionella pneumophila pneumonia and non-invasive ventilation: presentation of two cases and brief review of the literature. Pneumonol Alergol Pol [online] 2013, 81(4):399-403 [viewed 22 June 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/23744171
  4. HIGA F, FUJITA J, KOIDE M, HARANAGA S, TATEYAMA M. Clinical features of two cases of Legionnaires' disease with persistence of Legionella urinary antigen excretion. Intern Med [online] 2008, 47(3):173-8 [viewed 22 June 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/18239328

Differential Diagnoses

Fact Explanation
Streptococcus pneumoniae There is cute onset, with preceded flu-like symptoms.There is Cough with rust coloured sputum,High fevers, and pleuritic chest pain.[1]
Mycoplasma pneumoniae This is usually a mild disease and it is common in young patients. The extrapulmonary symptoms such as headache, malaise, myalgia, haemolytic anaemia, erythema multiforme, hepatitis, can be present.[1]
Staphylococcus aureus There is a recent history of influenza.This is a severe pneumonia with necrotizing and cavitating lesions.[1]
Chlamydophila pneumoniae This is generally a mild disease but with prolonged prodrome and some extrapulmonary involvement such as menigoencephalitis.[1]
Haemophilus influenzae This is more common in pre-existing lung disease (CF, bronchiectasis, COPD) and in the elderly[1]
Coxiella burnetti (Q fever) This commonly occur in young men. Dry cough and high fever can be present. Endocarditis is a recognized feature.[1]
Klebsiella pneumonia More common in men alcoholics,patients with diabetes and other co-morbidities.There is systemic as well.[1]
Pseudomonas aeruginosa There is cavitation and abscess formation. This is more common in immune suppression and chronic lung disease (cystic fibrosis,bronchiectasis, COPD).[1]
All respiratory viruses Common in elderly and it is usually a mild disease.[1]
Fungal infections This is common in immunocompromised patients and in patients with other lung pathology(Ex-Cavitations)
References
  1. BTS Guidelines for the Management of Community Acquired Pneumonia in Adults Thorax [online] 2001 Dec, 56(Suppl 4):iv1-iv64 [viewed 19 June 2014] Available from: doi:10.1136/thorax.56.suppl_4.iv1

Investigations - for Diagnosis

Fact Explanation
FBC with differential count Leucocytosis[1] is prominent feature.But Leucopenia, thrombocytopenia can be present.
CRP As this is an acute phase protein,the levels are elevated.
CXR There can be unilateral or bilateral involvement [1] Alveolar pattern and lobar,nodular involvement. There can be rarely pleural effusions[1] or cavitations present.
Blood culture, gram staining and antibiogram This is a routine investigation but it may not indicate the pathogen. It often gives no growth in usual medium so special culture is required. The gram staining is gram negative bacili.
Detection of urinary antigen for Legionella pneumophila Urinary antigen detection [2]is by Enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay.
Culture of respiratory specimens(sputum) for Legionella spp. and gram staining .A special media must be used for isolation of the organism. This is a gram negative bacili but usual gram staining may not identify this.[1]
Serologic tests To diagnose the disease, acute and convalescent phase sera ( 2 – 4 weeks apart) are needed[3]
Polymerase chain reaction (PCR) on sputum PCR [2] will identify both non-viable as well as viable organisms
Direct fluorescent antibody (DFA) staining on sputum This is another method of identifying the pathogen but it needs expertise. [3]
References
  1. NICOLINI A, FERRAIOLI G, SENAREGA R. Severe Legionella pneumophila pneumonia and non-invasive ventilation: presentation of two cases and brief review of the literature. Pneumonol Alergol Pol [online] 2013, 81(4):399-403 [viewed 22 June 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/23744171
  2. ZAROGOULIDIS P, ALEXANDROPOULOU I, ROMANIDOU G, KONSTASNTINIDIS TG, TERZI E, SARIDOU S, STEFANIS A, ZAROGOULIDIS K, CONSTANTINIDIS T. Community-acquired pneumonia due to Legionella pneumophila, the utility of PCR, and a review of the antibiotics used Int J Gen Med [online] :15-19 [viewed 19 June 2014] Available from: doi:10.2147/IJGM.S15654
  3. NG V, TANG P, JAMIESON F, GUYARD C, LOW DE, FISMAN DN. Laboratory-based evaluation of legionellosis epidemiology in Ontario, Canada, 1978 to 2006 BMC Infect Dis [online] :68 [viewed 19 June 2014] Available from: doi:10.1186/1471-2334-9-68

Investigations - Fitness for Management

Fact Explanation
Electrolytes Hyponatremia and Hypophosphatemia can be identifed[1]
serum creatinine This can be elevated as there is the risk of rhabdomyolysis[2].
UFR and urinary myoglobin This can indicate rhabdomyolysis[2]
Liver transferases Due to hepatitis, these enzymes can be elevated[1]
ECG ECG showed QT prolongation widespread flat T waves [3] and arrhythmias.
Echocardigraphy Wall hypokinasia and reduced ejection fraction indicates myocarditis and heart failure.[3]
Oxygen saturation by pulse oxymetry. It should be kept above 94%.If it drops below 90% ventilation is needed.[4]
Arterial blood gas level This is done with the additional advantage of knowing the blood pH.[4]
References
  1. MASON, J Robertson. et al ed.MURPHY & NADEL'S TEXTBOOK OF RESPIRATORY MEDICINE.5th ed.Philadelphia:SAUNDERS ELSEVIER.2010.PP.722-724
  2. KELTZ E, KHAN FY, MANN G. Rhabdomyolysis. The role of diagnostic and prognostic factors Muscles Ligaments Tendons J [online] , 3(4):303-312 [viewed 19 June 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3940504
  3. ISHIMARU N, SUZUKI H, TOKUDA Y, TAKANO T. Severe Legionnaires' disease with pneumonia and biopsy-confirmed myocarditis most likely caused by Legionella pneumophila serogroup 6. Intern Med [online] 2012, 51(22):3207-12 [viewed 19 June 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/23154735
  4. BTS Guidelines for the Management of Community Acquired Pneumonia in Adults Thorax [online] 2001 Dec, 56(Suppl 4):iv1-iv64 [viewed 19 June 2014] Available from: doi:10.1136/thorax.56.suppl_4.iv1

Investigations - Followup

Fact Explanation
Chest X ray after 6 weeks. This is to assess the level of resolution of pneumonia.[1]
References
  1. BTS Guidelines for the Management of Community Acquired Pneumonia in Adults Thorax [online] 2001 Dec, 56(Suppl 4):iv1-iv64 [viewed 19 June 2014] Available from: doi:10.1136/thorax.56.suppl_4.iv1

Management - General Measures

Fact Explanation
Oxygen Supplemental oxygen should be given to maintain saturations in the range of 94% and 98%. [1]
Intravenous fluids This is used to manage hypotensive patients.[1]
Simple analgesia (paracetamol or non-steroidal anti-inflammatory drugs) It relieves pleuritic pain to improve respiration and reduces complications such as atelectasis or secondary infection.
Nutritional support This is considered in long durations of hospitalisation[1] and a dietitian should be consulted.
References
  1. BTS Guidelines for the Management of Community Acquired Pneumonia in Adults Thorax [online] 2001 Dec, 56(Suppl 4):iv1-iv64 [viewed 19 June 2014] Available from: doi:10.1136/thorax.56.suppl_4.iv1

Management - Specific Treatments

Fact Explanation
Azithromycin This is a well recommended drug.[1][2]This is a bacteriostatic in action and it has better gram negative cover.
Fluoroquinolones This is the drug that is considered most situations.[1],[2]These drugs have a bactericidal effect and has better activity against gram negative organisms
Erythromycin or Clarythromycin with Rifampin as an adjunct. Erythromycin and Clarythromycin[4][5] have bacteriostatic activity and has a good activity against atypical microbes. Rifampin[1][2] has a bactericidal action and has a broad spectrum activity.
For severe patients Hospitalized/ ICU patients(CURB 65 score 3<) An Empirical regime should be used Co-amoxiclav intravenously in combination with clarithromycin intravenously or fluoroquinolone. [3] Co-amoxiclav is a bactericidal agent with better gram positive activity and has a broad spectrum activity.
References
  1. DEDICOAT M.. The treatment of Legionnaires' disease. [online] 1999 June, 43(6):747-752 [viewed 19 June 2014] Available from: doi:10.1093/jac/43.6.747
  2. ROIG J.. Legionnaires' disease: a rational approach to therapy. [online] December, 51(5):1119-1129 [viewed 20 June 2014] Available from: doi:10.1093/jac/dkg191
  3. BTS Guidelines for the Management of Community Acquired Pneumonia in Adults Thorax [online] 2001 Dec, 56(Suppl 4):iv1-iv64 [viewed 19 June 2014] Available from: doi:10.1136/thorax.56.suppl_4.iv1