Presence of pldA and exoU in mucoid Pseudomonas aeruginosa is associated with high risk of exacerbations in non-cystic fibrosis bronchiectasis patients.

OBJECTIVES: To explore the association between the virulence genes exoU and pldA in isolated mucoid Pseudomonas aeruginosa and the clinical outcomes of patients with non-cystic fibrosis (CF) bronchiectasis.

METHODS: A prospective observational cohort study was performed in the Shanghai Pulmonary Hospital from October 2012 to January 2015. We consecutively enrolled all non-CF bronchiectasis patients with mucoid P. aeruginosa isolates obtained from bronchoalveolar lavage fluid or sputum. The exposure variable was the presence of virulence gene, exoU or pldA, in the strains. The primary outcome was exacerbation of bronchiectasis. Logistic regression analysis was performed to evaluate the association between virulence genes and exacerbation.

RESULTS: The final analysis included 147 patients (mean (SD) age, 57.86 (11.43) years, 101 female subjects) with median (interquartile range) follow-up of 18 (13-26) months. The following factors were relative to exacerbations: body mass index ≤18.5 kg/m2 (odds ratio (OR) = 5.05; 95% confidence interval (CI), 1.37-18.57), length of stay ≥8 days (OR = 2.65; 95% CI, 1.14-6.19) and positive for either virulence gene (OR = 6.80; 95% CI, 1.47-31.37). The gene-positive group had more exacerbations per year (mean 2.37, SD 2.10, n = 33 vs. mean 0.79, SD 0.83, n = 114) and a higher proportion of patients with exacerbation (31/33, 93.94% vs. 74/114, 64.91%). The proportion of patients being exoU or pldA positive increased as the exacerbation frequency of bronchiectasis increased.

CONCLUSIONS: The virulence genes exoU and pldA in mucoid P. aeruginosa are significant risk factors for exacerbations in patients with non-CF bronchiectasis.