Pseudomonas aeruginosainfection and exacerbations in bronchiectasis: more questions than answers

Apart from the presence of comorbidities [1], there are two other circumstances that have demonstrated a negative impact on the natural history of bronchiectasis: chronic bronchial infection (CBI) by Pseudomonas aeruginosa and exacerbations. Many studies have shown an association between CBI by P. aeruginosa and reduced quality of life [2], a steep decline in lung function [3], increased inflammation (both bronchial and systemic) [4], higher healthcare costs [5], and even a higher mortality rate [6]. One recent meta-analysis concluded that this association is more evident with CBI by P. aeruginosa rather than by other pathogenic microorganisms [7]. Similarly, exacerbations (particularly multiple and/or severe exacerbations) have been associated with various parameters of severity in bronchiectasis [3], including a higher mortality rate [8, 9]. It is hardly surprising, therefore, that the three validated multidimensional scores published to date to evaluate the severity or prognosis of bronchiectasis [8–10] include the presence of a CBI by P. aeruginosa as one of their variables, and that two of the three [8, 9] also include the frequency and/or severity of exacerbations. Accordingly, some authors have even suggested that those bronchiectasis patients with CBI by P. aeruginosa and those who present multiple exacerbations could represent two distinct clinical phenotypes of bronchiectasis patients, each with their own clinical characteristics and prognoses [11, 12]. Finally, it should be stressed that both these circumstances are extremely important from a therapeutic standpoint. In fact, the vast majority of the treatments on the market or in development are primarily aimed at infection by P. aeruginosa , with a drop in the number of exacerbations as the main objective [13]. Both chronic infection by P. aeruginosa and exacerbations have a negative impact in bronchiectasis prognosis