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Open Access Highly Accessed Research article

Pseudomonas aeruginosa isolates in severe chronic obstructive pulmonary disease: characterization and risk factors

Miguel Gallego123*, Xavier Pomares1, Mateu Espasa4, Eva Castañer5, Mar Solé6, David Suárez7, Eduard Monsó123 and Concepción Montón1

Author Affiliations

1 Department of Respiratory Medicine, Hospital de Sabadell, Institut Universitari Parc Taulí-UAB, Sabadell, Spain

2 Universitat Autonoma de Barcelona, Esfera UAB, Barcelona, Spain

3 CIBER de Enfermedades Respiratorias, CIBERES, Bunyola, Spain

4 Department of Microbiology, SDI UDIAT, Institut Universitari Parc Taulí-UAB, Sabadell, Spain

5 Department of Radiology, SDI UDIAT, Institut Universitari Parc Taulí-UAB

6 Barcelona Centre for International Health Research (CRESIB), Department of Clinical Microbiology, Hospital Clínic-Fundació Clínic per la Recerca Biomèdica, University of Barcelona, Barcelona, Spain

7 Epidemiology and Assessment Unit, Fundació Parc Taulí, Universitat Autònoma de Barcelona, Sabadell, Spain

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BMC Pulmonary Medicine 2014, 14:103  doi:10.1186/1471-2466-14-103

Published: 26 June 2014



Patients with severe chronic obstructive pulmonary disease (COPD) are at increased risk of infection by P. aeruginosa. The specific role of bronchiectasis in both infection and chronic colonization by this microorganism in COPD, however, remains ill defined.

To evaluate the prevalence and risk factors for P. aeruginosa recovery from sputum in outpatients with severe COPD, characterizing P. aeruginosa isolates by pulsed-field gel electrophoresis (PFGE) and focusing on the influence of bronchiectasis on chronic colonization in these patients.


A case-cohort study of 118 patients with severe COPD attended at a Respiratory Day Unit for an acute infectious exacerbation and followed up over one year. High-resolution CT scans were performed during stability for bronchiectasis assessment and sputum cultures were obtained during exacerbation and stability in all patients. P. aeruginosa isolates were genotyped by PFGE. Determinants of the recovery of P. aeruginosa in sputum and chronic colonization by this microorganism were assessed by multivariate analysis.


P. aeruginosa was isolated from 41 of the 118 patients studied (34.7%). Five of these 41 patients (12.2%) with P. aeruginosa recovery fulfilled criteria for chronic colonization. In the multivariate analysis, the extent of bronchiectasis (OR 9.8, 95% CI: 1.7 to 54.8) and the number of antibiotic courses (OR 1.7, 95% CI: 1.1 to 2.5) were independently associated with an increased risk of P. aeruginosa isolation. Chronic colonization was unrelated to the presence of bronchiectasis (p=0.75). In patients with chronic colonization the isolates of P. aeruginosa retrieved corresponded to the same clones during the follow-up, and most of the multidrug resistant isolates (19/21) were harbored by these patients.


The main risk factors for P. aeruginosa isolation in severe COPD were the extent of bronchiectasis and exposure to antibiotics. Over 10% of these patients fulfilled criteria for chronic colonization by P. aeruginosa and showed clonal persistence, independently of the presence of bronchiectasis.

Chronic obstructive pulmonary disease; Bronchiectasis; Chronic colonization; Pseudomonas aeruginosa