What duration of therapy do you use for treatment of Legionella pneumonia in an immunocompetent host without associated empyema or extrapulmonary infection?

We have little experience of legionellosis, especially in immunocompetent patients. Based on the available information and the published recommendations (these follow), I would generally treat patients for 5-7 days, depending on clinical response.

A recent review: Viasus et al., PMID 35505000

IDSA/ATS guideline: No distinction for Legionella vs other organisms.

We recommend that the duration of antibiotic therapy should be guided by a validated measure of clinical stability (resolution of vital sign abnormalities [heart rate, respiratory rate, blood pressure, oxygen saturation, and temperature], ability to eat, and normal mentation), and antibiotic therapy should be continued until the patient achieves stability and for no less than a total of...

Agree, especially regarding azithromycin, given its exceptionally long intracellular half-life. I might extend the duration for a severely ill patient treated with quinolone.