Escalante, P

Abstract Rationale Blood eosinophil count (BEC) has emerged as a marker of inflammatory endotypes in bronchiectasis. We examined whether bacterial and mold respiratory culture profiles differ by BEC, comparing patients with BEC ≥300 cells/μL to those with lower BEC. Methods We analyzed patients with bronchiectasis evaluated at a specialized clinic (2019-2025) who had contemporaneous respiratory bacterial and fungal cultures and BEC. Patients were stratified by BEC <300 vs ≥ 300 cells/μL; those with BEC <300 were further subclassified (<100 and 100-299 cells/μL) for figure presentation only. Cultures were evaluated for overall growth and organism-specific prevalence across eosinophil strata, focusing on the most frequently isolated organisms. Group comparisons were performed using Fisher’s exact test. Results A total of 608 patients met inclusion criteria (median age 69 years [IQR 61-77], 72% female); 138 (22.7%) had BEC ≥300 cells/μL. Bacterial growth occurred in 277 patients (45.6%) and mold growth in 366 (60.2%). The odds of bacterial growth were similar between BEC ≥300 and <300 groups (47.1% vs 45.2%). In contrast, BEC ≥300 was associated with higher odds of mold growth (68.1% vs 58.0%; OR 1.54, p = 0.038). Pseudomonas species (18.9%) were the most common bacterial isolates and comprised a greater proportion of all bacterial isolates in patients with BEC ≥300 compared with lower BEC (44.7% vs 30.0%; OR 1.89, p = 0.019). Penicillium species (27.5%), followed by Aspergillus (26.9%), were the most frequently isolated molds, with no differences in distribution across BEC strata. Conclusions BEC ≥300 cells/μL was associated with increased odds of respiratory mold growth and enrichment of Pseudomonas species, suggesting that eosinophil-defined endotypes may identify patients with distinct airway microbiologic patterns that could inform future phenotyping and treatment strategies. This abstract is funded by: None

Abstract Background Sputum color is a visual marker of airway inflammation and disease activity in bronchiectasis, ranging from clear or light gray (mucoid) to yellow-green (purulent), the latter largely reflecting neutrophil myeloperoxidase release. This study evaluated associations between sputum color and common clinical markers of disease activity to determine which parameters differed most between color categories. Methods Forty spontaneous sputum samples were analyzed from 80 consecutive adults with non-cystic fibrosis bronchiectasis (median age 70 years [IQR 12]; 74% female) enrolled between January 2024 and April 2025 in an observational study. Sputum color was graded using the Murray Sputum Color Chart and classified as mucoid (color #1) or purulent (colors #2-4). Clinical parameters, including blood cell counts, C-reactive protein (CRP), fractional exhaled nitric oxide (FeNO), and results of bacterial and acid-fast bacillus cultures (induced or bronchoscopic), were obtained from medical records if available within one month of enrollment. Categorical variables were analyzed using chi-square or Fisher’s exact tests and continuous variables with the Mann-Whitney U test. A secondary analysis compared patients who could versus could not produce spontaneous sputum. Results Of 40 samples, 20 (50%) were purulent. Blood neutrophil counts (median 4.5 vs. 3.9 x109/L), neutrophil-to-lymphocyte ratios (2.5 vs. 2.6), and eosinophil counts (1.7 vs. 1.7 x109/L) did not differ significantly between groups (n = 26). FeNO was normal in all 10 patients with available data and was not analyzed further. CRP was higher among patients with purulent sputum (4.6 vs. <3 mg/L; n = 20; p = 0.044). Bacterial growth was more frequent in purulent than mucoid samples (73% vs. 31%; n = 31; p = 0.032). Isolates in the purulent group included Klebsiella, Pseudomonas, Staphylococcus, and Streptococcus (n = 2 each), and single isolates of Acetobacter, Acinetobacter, Chryseobacterium, Delftia, Enterobacter, Escherichia, and Moraxella. In the mucoid group, Pseudomonas, Staphylococcus (n = 2 each), and Stenotrophomonas (n = 1) were identified. Mycobacterial growth did not differ significantly (20% vs. 12.5%; n = 31; p = 0.65). Patients unable to produce spontaneous sputum had a higher rate of mycobacterial isolation on induced/bronchoscopic samples (43% vs. 16%; n = 54; p = 0.027), though other parameters were similar. Over 90% of measurements were obtained within three days of enrollment, and freezing did not appear to alter sputum color. Conclusions Even within a small cohort, purulent sputum was associated with higher CRP and greater bacterial growth, supporting sputum color as a rapid, inexpensive marker of disease activity in bronchiectasis. Further research should clarify whether sputum color primarily reflects bacterial colonization, airway inflammation, or both. This abstract is funded by: None