Background: Clinical data for bacterial co-infection in patients with non-tuberculous mycobacterial pulmonary disease (NTM-PD) is scarce.

Objective: This study aimed to assess prevalence of bacterial co-infection in NTM-PD patients and clinical features of NTM-PD patients according to bacterial isolates.

Methods: The patients initially diagnosed with NTM-PD through bronchial washing samples were evaluated in a retrospective observational nature of the study between July 2020 to July 2022. Bacterial cultures were also performed on bronchial washing samples at the time of NTM-PD diagnosis.

Results: A total of 180 patients were included in this study. The median age was 65 years, and 122 (68%) patients were female. Mycobacterium avium complex (85%) is the most frequently isolated. Bacteria were detected in 80 (44%) patients. The most common bacterial species was Klebsiella species (n=29, 16%), followed by Pseudomonas species (n=22, 12%) and Staphylococcus aureus (n=20, 11%). Compared to the NTM-PD patients without bacterial co-infection, more patients with bacterial-NTM co-infection showed ? 3 lobes involvement radiologically (33% vs. 1%, p < 0.001). Furthermore, compared to the NTM-PD patients without Pseudomonas infection, NTM-PD patients with Pseudomonas infection were older (p=0.002) and had more respiratory symptoms (70% vs. 37%, p=0.012), and more frequently had ? 3 lobes involvement (60% vs. 1%, p < 0.001).

Conclusions: Newly diagnosed NTM-PD patients with bacterial co-infection have more extensive lung involvement. Moreover, the patients with NTM-Pseudomonas co-infection had significantly more respiratory symptoms and extensive lung involvement.