Abstract
Atypical pneumonia caused by Chlamydia pneumoniae often presents diagnostic challenges due to its nonspecific symptoms and slow progression. While most cases are mild and self-limiting, severe infections in immunocompetent adults are rare. This report describes a 32-year-old Chinese female with progressive pneumonia unresponsive to empirical quinolone therapy. Bronchoalveolar lavage (BAL) and next-generation sequencing (NGS) identified C. pneumoniae as the causative pathogen. The patient showed significant clinical improvement following treatment with omadacycline, a novel tetracycline-class antibiotic. This case highlights the importance of bronchoscopic evaluation, BAL cytology, and NGS in diagnosing atypical pneumonia. It also underscores omadacycline's potential in treating quinolone-refractory C. pneumoniae pneumonia.