Legionnaires' disease (Guidelines)

Incubation:

• 2 to 14 days (commonly 5 to 6 days)

Risk factors for infection:

• Can occur in previously well patients, increased risk in immunocompromised patients and smokers.

Clinical presentation:

Primarily pneumonia, important to note the pneumonia can present in atypical ways:

• Diarrhoea and GI symptoms
• Confusion
• Hyponatraemia
• Abnormal LFT’s
• Cough, non productive/ small amount sputum

Actions for clinical assessment:

• Bloods: FBC, U+E, LFT, CRP
• Blood cultures, if indicated
• Viral throat swab
• Send urine (white top container) for Legionella Antigen
• Send sputum and add ?legionella on the request form
• Chest X-ray

Results from the urine antigen test should be available same day or next day.

• A positive result confirms legionella, but a negative result does NOT exclude it.
• If clinical suspicion, then treat with antibiotics empirically.

Antibiotics: 

Legionella is covered by macrolides and quinolones.

Recommended empiric treatment of HAP with cover for legionella:

• Add azithromycin: 500mg daily for 5 days to the standard Hospital acquired pneumonia (Antimicrobial) recommended treatment
  • If azithromycin is contraindicated, please discuss with Duty Consultant Microbiologist.
  • Note azithromycin is a QT prolonging drug.

Ie: empiric treatment of HAP

• For non-severe HAP: patient will be on either co-trimoxazole PLUS azithromycin; or doxycycline PLUS azithromycin.
• For severe HAP: patient will be on vancomycin plus aztreonam PLUS azithromycin

If patient is already on a quinolone (ciprofloxacin or levofloxacin), then azithromycin is NOT required.

Treatment of confirmed Legionella:

• Confirmed cases should be discussed with Duty Microbiologist

Discussion of cases:

• Please discuss with duty microbiologist cases where you have a high index of suspicion for Legionnaires' disease, or where you are unclear of the management.

We as a microbiology team are always happy to discuss if any concerns, and are available 24/7 via Raigmore switchboard