Clinical significance of respiratory bacteria and mycobacteria isolates in adult bronchiectasis in Taiwan

Background 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.