CHIA-LING CHANGSheu, Chau-ChyunChau-ChyunSheuWang, Ping-HuaiPing-HuaiWangHsieh, Meng-HengMeng-HengHsiehHsu, Wu-HueiWu-HueiHsuChen, Ming-TsungMing-TsungChenOu, Wei-FanWei-FanOuWei, Yu-FengYu-FengWeiYang, Tsung-MingTsung-MingYangLan, Chou-ChinChou-ChinLanWang, Cheng-YiCheng-YiWangLin, Chih-BinChih-BinLinLin, Ming-ShianMing-ShianLinWang, Yao-TungYao-TungWangLin, Ching-HsiungChing-HsiungLinLiu, Shih-FengShih-FengLiuCheng, Meng-HsuanMeng-HsuanChengCheng, Wen-ChienWen-ChienChengYEN-FU CHENPeng, Chung-KanChung-KanPengChan, Ming-ChengMing-ChengChanJao, Lun-YuLun-YuJaoWang, Ya-HuiYa-HuiWangChen, Ching-YiChing-YiChenChen, Chi-JuiChi-JuiChenChen, Shih-PinShih-PinChenTsai, Yi-HsuanYi-HsuanTsaiCheng, Shih-LungShih-LungChengLin, Horng-ChyuanHorng-ChyuanLinHAO-CHIEN WANGJUNG-YIEN CHIEN2025-09-062025-09-062025-07https://scholars.lib.ntu.edu.tw/handle/123456789/731879Background The clinical impact of bacterial and mycobacterial isolates on bronchiectasis remains uncertain. Methods Patients with bronchiectasis at 16 hospitals in Taiwan were recruited with a 1-year follow-up. The patients were classified into six groups: Group 1, Pseudomonas aeruginosa; Group 2, Klebsiella pneumoniae; Group 3, other bacteria; Group 4, non-tuberculous mycobacteria (NTM); Group 5, daily sputum without bacterial or NTM colonisation; and Group 6, dry bronchiectasis. Results In total, 1416 patients (mean age 67 years; 43% males) were included. The mean modified Reiff score was 5 (range 1–18). 59% (829 patients) had sputum, whereas the remaining did not. The proportions of bacteria and NTM cultured from sputum within 1 year of observation were 27% (381/1416) and 15% (202/1416), respectively. The most common bacterial isolate was P. aeruginosa (13%), followed by K. pneumoniae (7%). 26% of the patients experienced severe exacerbations at least once within the year. The 1-year all-cause mortality rate was 3%. Patients with sputum exhibited a higher rate of severe exacerbations compared to patients with dry bronchiectasis, regardless of the presence of bacteria or NTM ( p<0.001). Patients with bacterial colonisation had a higher mortality rate ( p<0.001). Further, the highest mortality rate was observed among those with K. pneumoniae colonisation (hazard ratio (HR) 8.39 (95% CI 2.39–29.49)), followed by individuals colonised with other bacteria (HR 8.04 (95% CI 2.36–27.38)) and P. aeruginosa (HR 7.83 (95% CI 2.45–25.03)). Additionally, old age was an independent risk factor (HR 2.72 (95% CI 1.19–6.18)). Conclusion K. pneumoniae was more frequently isolated from patients with bronchiectasis in Taiwan compared to Western countries and was associated with unfavourable clinical outcomes.en[SDGs]SDG3journal article10.1183/23120541.00865-202440661934