Makindo Medical Notes

Related Subjects:Pneumonia |Pontiac fever (Legionella Pneumophila) |Legionella Pneumophila pneumonia |Asthma |Acute Severe Asthma |Exacerbation of COPD |Pulmonary Embolism |Cardiogenic Pulmonary Oedema |Pneumothorax |Tension Pneumothorax |Respiratory (Chest) infections Pneumonia |Fat embolism |Hyperventilation Syndrome |ARDS |Respiratory Failure |Diabetic Ketoacidosis

Aquatic organisms found in air conditioning, hot water heaters. Because Legionella is an intracellular pathogen, antibiotics that reach intracellular MICs are most likely to be effective. Large numbers of bacteria can be aerosolized from contaminated water, resulting in epidemic infections, usually in urban settings.

Liquid pools in place
Poorly cleaned, drops sprayed at face
Fountains, old AC
Fever, cough, upset GI
Awful CAP, all gone awry
@DrCindyCooper

About

• First identified in an outbreak at an American Legion members convention in Philadelphia in 1976.
• The attendees acquired pneumonia from an infected air conditioning system.
• It causes community-acquired pneumonia and nosocomial-acquired pneumonia.
• Also causes Pontiac fever, a related self-limited upper respiratory infection.
• Penicillin and Cephalosporins are not effective treatments.

Characteristics

• Gram-negative, rod-shaped bacilli, intracellular pathogen.
• Obligate aerobes, slow-growing, and fastidious.
• Non-motile, non-capsulated, facultative intracellular organism.
• Infects and replicates within eukaryotic host cells, such as macrophages.
• Adheres to epithelium via fimbriae.
• Can survive and grow within phagocytic cells.
• L. pneumophila serogroup 1 (Lp1) is the most common cause of human infections.

Vulnerable Patients

• Individuals with cardiac, renal, immunologic, or haematologic diseases.
• Patients with chronic obstructive pulmonary disease (COPD) or congestive heart failure (CHF).
• Organ transplant recipients and immunosuppressed patients, with fatality rates as high as 50% in severe cases.

Source

• Found in water cooling systems, growing in water at 20-45°C.
• Common in environments like hotels, hospitals, showers, and hot water systems.
• Can grow within coexisting amoebae, and there is no human-to-human transmission.
• Made worse by factors in air conditioning systems such as:
• Lukewarm water temperature.
• Obstruction and stagnation of water flow.
• Plumbing materials conducive to biofilm formation.
• Presence of amoebae, which support the growth of Legionella species.

Clinical: GI Symptoms Are a Clue

• Muscle aches, tiredness, headaches, dry cough, and fever.
• Sometimes diarrhoea occurs, and confusion may develop.
• Can lead to atypical pneumonia, which may be severe and necrotising.
• Non-productive cough and flu-like symptoms are common in Pontiac fever.
• Often seen in diabetics, immunosuppressed patients, smokers, and those with alcoholism.

Investigations

• Blood tests: FBC, U&E, LFTs, CRP, ECG.
• Chest X-ray (CXR) for pneumonia.
• Culture on Buffered Charcoal Yeast Extract (BCYE) agar with antibiotics, but it takes 3-5 days to grow.
• Legionella serology and/or urine antigen testing.
• Legionella pneumophila PCR for rapid detection.

Management

• ABC (Airway, Breathing, Circulation), oxygen, HDU/ITU support as needed, IV fluids.
• Antibiotics for 10-21 days: Erythromycin, Azithromycin, Clarithromycin, Levofloxacin, Ciprofloxacin, and Doxycycline are recommended.
• Tetracycline, ciprofloxacin, and fluoroquinolones or macrolides are also effective.
• If the patient has Pontiac fever, do not prescribe antibiotics. It is a self-limited illness with recovery typically within a week.
• Prevention: Hyperchlorination of water systems, maintain water temperature above 70°C.

References

• Review article
• Legionella (Legionnaires' Disease and Pontiac Fever)