C68-25 Analysis Of Nontuberculous Mycobacteria Culture Positivity Trends In Patients With Pulmonary Alveolar Proteinosis

Abstract Introduction Nontuberculous Mycobacteria (NTM) are ubiquitous environmental microbes that are increasingly causing pulmonary colonization and infection in patients with underlying risk factors1. One such risk factor is pulmonary alveolar proteinosis (PAP), a rare disease characterized by the accumulation of lipoproteinaceous material in the alveoli, leading to macrophage dysfunction2. Distinguishing between NTM pulmonary colonization and infection in these patients remains challenging, which complicates management decisions. Standard treatment for PAP includes whole-lung lavage (WLL) and inhaled GM-CSF, both of which have been shown to improve macrophage function via several mechanisms3,4. Recently, inhaled GM-CSF has gained increased recognition as a possible therapy for NTM pulmonary disease5. This study aims to characterize the trends and time to culture conversion in a cohort of NTM-positive PAP patients with respect to the number and timing of whole-lung lavages and inhaled GM-CSF therapy. Additionally, this study will highlight patient-specific features that may be associated with the rate of NTM colonization and treatment success. Investigating the relationship between PAP therapy and NTM culture positivity may advance understanding and elucidate trends within this currently underexplored area. Methods Electronic medical records data from patients with a diagnosis of PAP seen at the University of Colorado Hospital from 1/1/2015 to 10/10/2025 were retrospectively analyzed. We used qualitative, descriptive analysis to identify trends in NTM culture positivity, timing of WLL, and duration of inhaled GM-CSF therapy among patients with PAP. Results Of the 29 patients with PAP, 11 had lavage cultures that grew NTM at any point. The vast majority (90.9%) of patients grew species within the classification of Mycobacterium Chimaera/Intracellulare, which are too phenotypically similar to be distinguished on culture. Interestingly, none of these patients were considered to have NTM pulmonary disease, and none received antimicrobial treatment. Yet, all but one patient (90.9%) eventually converted to culture negativity after treatment of their underlying PAP with WLL and inhaled GM-CSF. The patients who successfully converted to culture negativity received an average of 4.2 whole lung lavages and 22.4 months of inhaled GM-CSF therapy prior to culture conversion (Figure 1). The one patient that did not convert to culture negativity was non-compliant with inhaled GM-CSF therapy. Conclusion We postulate that treatment of underlying PAP with WLL and inhaled GM-CSF, even in the absence of antimicrobial therapy, is associated with conversion of NTM-positive cultures to negative. This abstract is funded by: None