Legionnaires’ Disease in the Era of Molecular Diagnostics: Impact of Multiplex Respiratory Panels on the Early Detection of Legionella pneumophila Molecular Diagnosis of Legionella Pneumonia

Resumen

Background: Legionnaires’ disease is a severe form of community-acquired pneumonia primarily caused by Legionella pneumophila. Although relatively uncommon, delayed diagnosis is associated with increased morbidity and mortality. Clinical suspicion is supported by extrapulmonary manifestations such as gastrointestinal symptoms, hyponatremia, and failure to respond to beta-lactam therapy. Case presentation: A 65-year-old male with hypertension and dyslipidemia developed fever, progressive dyspnea, and dry cough after environmental exposure to bird droppings. Laboratory tests showed leukocytosis, elevated C-reactive protein, and mild hyponatremia. After lack of response to amoxicillin-clavulanate and negative viral testing, multiplex PCR respiratory panel (FilmArray®) identified Legionella pneumophila. Targeted therapy with azithromycin led to rapid clinical improvement. Discussion: Legionella infection may mimic viral or typical bacterial pneumonia. Molecular multiplex diagnostic tools enable rapid pathogen identification. Early initiation of macrolides or fluoroquinolones significantly improves outcomes. Conclusions: Legionnaires’ disease should be suspected in atypical pneumonia with systemic features and poor response to beta-lactams. Early molecular diagnosis and prompt intracellularly active antibiotic therapy are crucial determinants of prognosis.