Schaalia cardiffensis: an infrequent etiology of empyema with community-acquired pneumonia.

Schaalia infections are uncommon, with Schaalia cardiffensis infections being exceptionally rare. A 66-year-old, penicillin-allergic female presented with fever, cough and purulent sputum. Chest computed tomography revealed bilateral pneumonia, right loculated empyema and right lower lobe atelectasis. Initial drainage cultures identified only Streptococcus oralis, but subsequent anaerobic enrichment and 16 S rRNA gene sequencing confirmed S. cardiffensis, an obligate anaerobe. Due to absent susceptibility data, we established initial antimicrobial susceptibility profile for S. cardiffensis. Successful management was achieved using alternative antibiotics combined with percutaneous drainagein. This first Chinese case of an empyema co-infected with S. cardiffensis and S. oralis highlights diagnostic challenges and provides crucial susceptibility guidance.