Yixin Chen,1,* Chenglin Yu,2,* Jiannan Chai,3 Min Chai,1 Yuqi Xiao,1 Hongwei Loong,4 Dahai Xu,1 Lijun Wang5 

1Department of Emergency Medicine, The First Hospital of Jilin University, Changchun, Jilin, 130000, People’s Republic of China; 2Department of Emergency Medicine, Yanbian University Hospital, Yanji, Jilin, 133000, People’s Republic of China; 3Department of Laboratory, The First Hospital of Jilin University, Changchun, Jilin, 130000, People’s Republic of China; 4Department of Neurosurgery, Meihekou Central Hospital, Changchun, Jilin, 130000, People’s Republic of China; 5Department of Pediatric Respiratory, Children’s Medical Center, The First Hospital of Jilin University, Changchun, Jilin, 130000, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Dahai Xu, Department of Emergency Medicine, The First Hospital of Jilin University, No. 1 Xinmin Street, Chaoyang District, Changchun, Jilin, 130000, People’s Republic of China, Tel +8615043032548, Email xudahai0319@jlu.edu.cn Lijun Wang, Department of Pediatric Respiratory, Children’s Medical Center, The First Hospital of Jilin University, No. 1 Xinmin Street, Chaoyang District, Changchun, Jilin, 130000, People’s Republic of China, Tel +8613504404994, Email wlj_612006@jlu.edu.cn

Abstract: Fusobacterium nucleatum (F. nucleatum) is a Gram-negative, anaerobic bacterium predominantly found in the oral cavity, gastrointestinal tract, and urogenital system. It accounts for less than 1% of anaerobic bacterial infections in clinical settings and can lead to a spectrum of severe infections. This report details the case of a 55-year-old male who presented with a one-month history of productive cough, acute right-sided chest pain, dyspnea, and fever. Initial examinations showed elevated inflammatory markers and a right-sided pleural effusion on chest CT. Despite empirical therapy, the patient’s condition worsened, culminating in a diagnosis of right-sided encapsulated hydropneumothorax. F. nucleatum was isolated from the pleural fluid culture. Treatment with meropenem and linezolid led to gradual clinical improvement, and the patient recovered without complications during follow-up. Although rare, F. nucleatum pleural infections can progress swiftly and are frequently misdiagnosed, posing significant diagnostic challenges. Given their potential severity, such as in cases of pyopneumothorax, immediate drainage and targeted antibiotic treatment are imperative. Clinicians should exercise heightened vigilance in diagnosing and managing this severe and often overlooked infection.

Keywords: Fusobacterium nucleatum, pyopneumothorax, pleural effusion, case report