Exploring the Association of Bacterial Coinfections with Clinical Characteristics of Patients with Nontuberculous Mycobacterial Pulmonary Disease

Background: Clinical data for bacterial coinfection of the lower respiratory tract in patients with nontuberculous mycobacterial pulmonary disease (NTM-PD) are scarce. This study aims to assess the prevalence of bacterial coinfection and clinical features in NTM-PD patients.Methods: This retrospective study screened 248 patients with NTM-PD who underwent bronchoscopy between July 2020 and July 2022, from whom newly diagnosed NTM-PD patients were analyzed. Bacterial culture using bronchial washing fluid was performed at the time of NTM-PD diagnosis.Results: In the 180 patients (median age 65 years; 68% female), <i>Mycobacterium avium</i> complex (86%) was the most frequent NTM isolated. Bacterial coinfections were detected in 80 (44%) patients. Among them, the most common bacterium was <i>Klebsiella pneumoniae</i> (n=25/80, 31.3%), followed by <i>Pseudomonas aeruginosa</i> (n=20/80, 25%) and <i>Staphylococcus aureus</i> (n=20/80, 25%). Compared with NTM-PD patients without bacterial coinfections, patients with bacterial coinfections showed more frequent extensive lung involvement (33% vs. 1%, p<0.001). Additionally, compared with NTM-PD patients without <i>P. aeruginosa</i> infection, those with <i>P. aeruginosa</i> infection were older (74 years vs. 64 years, p=0.001), had more frequent respiratory symptoms (cough/excessive mucus production 70% vs. 38%, p=0.008; dyspnea 30% vs. 13%, p=0.047), and had extensive lung involvement (60% vs. 9%, p<0.001).Conclusion: Less than half of patients with newly diagnosed NTM-PD had bacterial coinfections, linked to extensive lung involvement. Specifically, <i>P. aeruginosa</i> coinfection was significantly associated with older age, more frequent respiratory symptoms, and extensive lung involvement.