Post-bronchoscopy sputum culture improves detection of nontuberculous mycobacterial pulmonary disease: A...

In the diagnosis of Mycobacterium tuberculosis, collecting post-bronchoscopy sputum (PBS), as recommended by major guidelines, enhances the microbiological yield; however, evidence for PBS in nontuberculous mycobacterial pulmonary disease (NTM-PD) remains limited. Therefore, we aimed to investigate whether adding PBS increases the yield in suspected NTM-PD.

This single-center retrospective study included adults who underwent bronchoscopy for suspected NTM-PD between January 2017 and December 2023. After excluding 41 patients due to a lack of PBS submission and 14 with M. tuberculosis, 220 patients were analyzed. All patients underwent bronchial washing or bronchoalveolar lavage, and PBS was collected within 24 h. We compared culture positivity between bronchoscopic specimens and PBS and assessed the incremental yield obtained by adding PBS.

NTM was successfully cultured from bronchoscopic specimens in 71/220 (32.3 %). Before bronchoscopy, sputum cultures were positive in 38/220 (17.3 %), whereas PBS cultures were positive in 72/220 (32.7 %; p < 0.01). PBS was the only positive specimen in 18/220 (8.2 %). Combining bronchoscopic specimens with PBS increased overall culture positivity to 89/220 (40.5 %). The most frequent species were Mycobacterium avium (52/220, 23.6 %) and Mycobacterium intracellulare (32/220, 14.5 %).

Adding PBS following bronchoscopy provided a modest yet clinically meaningful incremental yield in NTM-PD and resembled diagnostic outcomes reported in tuberculosis. PBS collection is a simple and low-burden strategy that enhances the diagnostic information from a single procedure, requiring minimal resources and no additional invasive procedures.