Impact of bacterial co-isolation on treatment initiation and long-term prognosis of patients with nontuberculous mycobacterial pulmonary disease: analysis of a prospective cohort study.

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Nontuberculous mycobacterial pulmonary disease (NTM-PD), a chronic respiratory condition, presents a growing challenge globally. Uncertainties exist regarding the impact of concurrent bacterial co-isolation on treatment initiation and long-term prognosis. This study analysed data from participants enrolled in an ongoing prospective observational cohort study on NTM-PD (NCT01616745) between 1 July 2011, and 31 December 2022, who provided sputum samples for bacterial culture at enrolment. Identification of potential pathogenic microorganisms (PPMs) was defined as a positive bacterial culture. Clinical characteristics were compared between NTM-PD patients with Pseudomonas, non-pseudomonal PPMs, and those without PPM co-isolation. Cox proportional hazard regression models were employed to assess the association of bacterial co-isolation with rates of NTM-PD treatment initiation and all-cause mortality. Overall, 453 patients (median age, 62 years; 30% male) were included in the analysis. PPMs were co-isolated in 77 patients (17%), including 13 with Pseudomonas species. Co-isolation of Pseudomonas was associated with a significantly higher erythrocyte sedimentation rate (P = 0.02) and St. George's Respiratory Questionnaire score (P = 0.01). Non-pseudomonal PPM co-isolation was significantly associated with a higher likelihood of NTM-PD treatment initiation (adjusted hazards ratio [aHR], 1.56, 95% confidence interval [CI], 1.03-2.36, P = 0.036), whereas co-isolation of Pseudomonas was independently correlated with increased all-cause mortality (aHR, 3.25, 95% CI, 1.08-9.84, P = 0.037). Our findings emphasize the importance of microbial surveillance, as bacterial co-isolation affects treatment initiation and prognosis in patients with NTM-PD.