Na Guo,1,* Guannan Ma,2,* Huimin Liu,1 Jingxuan Qiu,1 Yan Yu,1 Yunlei Gao,1 Zhong Yi,1 Zhirong Wan,1 Lei Zhang,2,3 Xiaorui Wu4 

1Department of Geriatrics, Aerospace Center Hospital, Beijing, People’s Republic of China; 2Medical Research Center, Key Laboratory of Digital Technology in Medical Diagnostics of Zhejiang Province, Hangzhou, People’s Republic of China; 3The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, People’s Republic of China; 4Department of Respiratory and Critical Care Medicine, Aerospace Center Hospital, Beijing, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Xiaorui Wu; Lei Zhang, Email wuxr1124@163.com; zhanglei3@dazd.cn

Background: Severe pneumonia with empyema in elderly patients presents diagnostic and therapeutic challenges. Traditional culture methods often fail to identify the causative pathogen, leading to delays in targeted treatment. Metagenomic next-generation sequencing (mNGS) has emerged as a powerful tool for detecting rare and fastidious pathogens.
Case Presentation: We report a 77-year-old male with a history of chronic smoking and alcohol consumption who presented with a two-month history of cough, sputum production, and progressive dyspnea. His condition rapidly deteriorated with high fever and respiratory failure. Initial antibiotic therapy was ineffective, and multiple cultures of blood, sputum, and pleural fluid were negative. However, mNGS of blood and pleural fluid identified Porphyromonas gingivalis, a well-known periodontal pathogen rarely associated with pulmonary infections. The patient’s treatment was adjusted to include targeted anaerobic coverage (imipenem plus vancomycin) alongside chest tube drainage, leading to significant clinical improvement.
Conclusion: This case highlights the clinical utility of mNGS in diagnosing culture-negative pulmonary infections. Porphyromonas gingivalis should be considered a potential pathogen in patients with severe pneumonia and empyema, particularly in those with poor oral hygiene or periodontal disease.

Keywords: Porphyromonas gingivalis, metagenomic next-generation sequencing, severe pneumonia, empyema, case report