Characteristics of different pathogenic bacterial infections and their effects on prognosis in adult patients with bronchiectasis

The present study aimed to analyse the types of pathogens infecting adults with bronchiectasis and the effects of different pathogens on the number of acute exacerbations and the length of hospitalization for 1 year in patients with severe bronchiectasis. A total of 522 patients with bronchiectasis admitted to the Department of Respiratory and Critical Care Medicine at the Second Hospital of Jiaxing (Zhejiang, China) between January 2019 and December 2022 were retrospectively analysed. The patients were divided into a mild to moderate group and a severe group according to the bronchiectasis severity index criteria. The basic and clinical information of all the patients was collected. The patients were followed up for 1 year after the day when the sputum or alveolar lavage fluid samples tested positive for pathogens. The follow-up information included the exacerbation of cough symptoms, the number of hospitalizations and the number of days of antibiotic use in patients with bronchiectasis. A total of 522 patients with bronchiectasis were positive for pathogens, including 192 patients with <i>Pseudomonas aeruginosa</i> (<i>P. aeruginosa</i>; 36.8%), 60 patients with <i>Klebsiella pneumoniae</i> (<i>K. pneumoniae</i>; 11.5%), 48 patients with mixed pathogens (≥2 pathogens at the same time; 9.2%), 36 patients with <i>Staphylococcus aureus</i> (6.9%), 33 patients with <i>Aspergillus fumigatus</i> (6.3%), 30 patients with <i>Haemophilus influenzae</i> (5.7%), 15 patients with <i>Acinetobacter baumannii</i> (<i>A. baumannii</i>; 2.9%) and 108 patients with other pathogens (20.7%). Compared with patients with mild to moderate bronchiectasis, patients with severe bronchiectasis were more likely to have <i>P. aeruginosa</i> but less likely to have <i>K. pneumoniae</i> and other pathogens. The length of hospitalization and duration of antibiotic use in the severe group of patients with bronchiectasis caused by <i>P. aeruginosa</i>, <i>A. fumigatus</i>, or <i>A. baumannii</i> were significantly longer than those in the mild to moderate group. During the 1-year follow-up, the number of acute exacerbations and hospitalizations of patients with severe bronchiectasis caused by <i>A. baumannii</i> and <i>P. aeruginosa</i> were significantly greater than those of patients with severe bronchiectasis caused by other pathogens. According to logistic regression analysis, <i>A. baumannii</i> and <i>P. aeruginosa</i> were independent risk factors for acute exacerbation of severe bronchiectasis in the following year. In patients with severe bronchiectasis, the pathogens <i>A. baumannii</i>, <i>P. aeruginosa</i> and <i>A. fumigatus</i> were independent risk factors for future acute exacerbations and increased risk of hospitalization.