A case of severe Legionella pneumonia treated with omadacycline and nemonoxacin.

Severe Legionella pneumophila pneumonia carries high mortality, and treatment is challenged by emerging resistance to conventional fluoroquinolones/macrolides and diagnostic delays. Novel agents such as omadacycline and nemonoxacin show theoretical promise, yet robust clinical evidence in legionellosis is lacking. We report a 59-year-old man with severe community-acquired pneumonia(sCAP) who initially received empiric ceftazidime-avibactam plus nemonoxacin. Respiratory failure did not improve, and the inflammatory markers did not decline. Subsequent bronchoalveolar lavage fluid metagenomic next-generation sequencing(BALF-mNGS) and urinary Legionella antigen confirmed Legionella pneumonia. We then switched to dual therapy with omadacycline and nemonoxacin. The combination led to rapid improvements in inflammatory markers, hypoxemia, and creatine kinase levels. This case provides a clinical rationale for using omadacycline plus nemonoxacin as salvage therapy in severe Legionella pneumonia when conventional regimens fail.