Legionnaires disease - Clinicals, Diagnosis, and Management

Infectious diseases

Clinicals - 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. 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.
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. 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. This can be a nonproductive cough or a purulent one. Cough
This occurs after the onset of fever.This can be a pronounced cough. This can be a nonproductive cough or a purulent one.
Rigors Along with high fever, this occurs as a mechanism to increase the body temperature. 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. 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.
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. 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.
Pleuritic Chest pain. This can occur either due to the inflammation of the pleura or following intense coughing. 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.
Extrapulmonary: gastro-intestinal symptoms
This is prominent in Legionnaires disease.
Common complaints are : watery diarrhea, nausea, vomiting and abdominal pain.
Extrapulmonary: neurological symptoms These can be variable according to individual patients.
The symptoms are: headache, confusion, obtundation, seizures, hallucinations.
They are due to encephalitis. Confusion and agitation can be a cause of rhabdomyolysis.
Extrapulmonary: neurological symptoms
These can be variable according to individual patients.
The symptoms are: headache, confusion, obtundation, seizures, hallucinations.
They are due to encephalitis. Confusion and agitation can be a cause of rhabdomyolysis.
Extrapulmonary: anuria This is mostly due to rhabdomyolysis. Extrapulmonary: anuria
This is mostly due to rhabdomyolysis.
Hospitalization Pneumonia that develops after 48 hours of hospitalization can occur due to Legionella infections. 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.
The person to person transmission doesn't occur. Optimal water temperatures for growth is in the range of 20°C to 45°C.
Risk factors: environment
Aerosol-generating devices( nebulizers, cooling towers, showers, respiratory therapy equipment,air conditioners) can act as modes of spread of the disease.
The person to person transmission doesn't occur. Optimal water temperatures for growth is in the range of 20°C to 45°C.
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. 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.

Clinicals - Examination

Fact Explanation
Fever This one of the commonest symptoms.In one third of patients its a high fever. Fever
This one of the commonest symptoms.In one third of patients its a high fever.
Tachycardia This is a prominent symptom. Hypoxia, Fever, release of catecholamines can induce tachycardia. Tachycardia
This is a prominent symptom. Hypoxia, Fever, release of catecholamines can induce tachycardia.
Tachypnoea This can be a prominent symptom. Hypoxia and hypercarbia stimulate the respiratory center and induce tachycardia. Tachypnoea
This can be a prominent symptom. 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. Dull percussion note
This can be due to either the consolidation or the pleural effusion.
Coarse crackles This is due to the consolidation. The sound is generated by opening of the collapsed airways. Coarse crackles
This is due to the consolidation. 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. 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. Pleural friction rubs
This sign can indicate small pleural effusions.
Hepatomegaly There can be hepatitis in some of the patients. Hepatomegaly
There can be hepatitis in some of the patients.
Splenomegaly This can be present in some patientsThis is due to the congestion of the Splenic vasculature Splenomegaly
This can be present in some patientsThis 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. 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 Alteration of GCS
This can be due to the encephalitis
Muscle tenderness, swelling This can be a feature of rhabdomyolysis Muscle tenderness, swelling
This can be a feature of rhabdomyolysis

Investigations - Diagnosis

Fact Explanation
FBC with differential count Leucocytosis is prominent feature.But
Leucopenia, thrombocytopenia can be present.
FBC with differential count
Leucocytosis is prominent feature.But
Leucopenia, thrombocytopenia can be present.
CRP As this is an acute phase protein,the levels are elevated. CRP
As this is an acute phase protein,the levels are elevated.
CXR There can be unilateral or bilateral involvement Alveolar pattern and lobar,nodular involvement.

There can be rarely pleural effusions or
cavitations present.
CXR
There can be unilateral or bilateral involvement Alveolar pattern and lobar,nodular involvement.

There can be rarely pleural effusions 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.
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 is by Enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay. Detection of urinary antigen for Legionella pneumophila
Urinary antigen detection 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.
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.
Serologic tests To diagnose the disease, acute and convalescent phase sera ( 2 – 4
weeks apart) are needed
Serologic tests
To diagnose the disease, acute and convalescent phase sera ( 2 – 4
weeks apart) are needed
Polymerase chain reaction (PCR) on sputum PCR will identify both non-viable as well as
viable organisms
Polymerase chain reaction (PCR) on sputum
PCR 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. Direct fluorescent antibody (DFA) staining on sputum
This is another method of identifying the pathogen but it needs expertise.

Investigations - Management

Fact Explanation
Chest X ray after 6 weeks. This is to assess the level of resolution of pneumonia. Chest X ray after 6 weeks.
This is to assess the level of resolution of pneumonia.
Electrolytes Hyponatremia and
Hypophosphatemia can be identifed
Electrolytes
Hyponatremia and
Hypophosphatemia can be identifed
serum creatinine This can be elevated as there is the risk of rhabdomyolysis. serum creatinine
This can be elevated as there is the risk of rhabdomyolysis.
UFR and urinary myoglobin This can indicate rhabdomyolysis UFR and urinary myoglobin
This can indicate rhabdomyolysis
Liver transferases Due to hepatitis, these enzymes can be elevated Liver transferases
Due to hepatitis, these enzymes can be elevated
ECG ECG showed QT prolongation widespread flat T waves and arrhythmias. ECG
ECG showed QT prolongation widespread flat T waves and arrhythmias.
Echocardigraphy Wall hypokinasia and reduced ejection fraction indicates myocarditis and heart failure. Echocardigraphy
Wall hypokinasia and reduced ejection fraction indicates myocarditis and heart failure.
Oxygen saturation by pulse oxymetry. It should be kept above 94%.If it drops below 90% ventilation is needed. Oxygen saturation by pulse oxymetry.
It should be kept above 94%.If it drops below 90% ventilation is needed.
Arterial blood gas level This is done with the additional advantage of knowing the blood pH. Arterial blood gas level
This is done with the additional advantage of knowing the blood pH.

Management - Supportive

Fact Explanation
Oxygen Supplemental oxygen should be given
to maintain saturations in the range of 94% and 98%.
Oxygen
Supplemental oxygen should be given
to maintain saturations in the range of 94% and 98%.
Intravenous fluids This is used to manage hypotensive patients. Intravenous fluids
This is used to manage hypotensive patients.
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. 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 and a dietitian should be consulted. Nutritional support
This is considered in long durations of hospitalisation and a dietitian should be consulted.

Management - Specific

Fact Explanation
Azithromycin This is a well recommended drug.This is a bacteriostatic in action and it has better gram negative cover. Azithromycin
This is a well recommended drug.This is a bacteriostatic in action and it has better gram negative cover.
Fluoroquinolones This is the drug that is considered most situations.,These drugs have a bactericidal effect and has better activity against gram negative organisms Fluoroquinolones
This is the drug that is considered most situations.,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 have bacteriostatic activity and has a good activity against atypical microbes. Rifampin has a bactericidal action and has a broad spectrum activity. Erythromycin or Clarythromycin with Rifampin as an adjunct.
Erythromycin and Clarythromycin have bacteriostatic activity and has a good activity against atypical microbes. Rifampin 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. Co-amoxiclav is a bactericidal agent with better gram positive activity 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. Co-amoxiclav is a bactericidal agent with better gram positive activity and has a broad spectrum activity.

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