Bacterial infection and risk factors in outpatients with acute exacerbation of chronic obstructive pulmonary disease: A 2-year prospective study

Background and objectives:  Acute exacerbations of COPD (AECOPD) are commonly observed in community-based patients worldwide. The factors causing exacerbation are largely unknown. This study was undertaken to determine the predominant bacterial pathogens cultured from sputum in community-based patients with AECOPD, to assess the risk factors associated with exacerbations and to compare these findings with published studies.

Methods:  Forty-five patients with stable COPD were prospectively followed in the outpatients’ clinic of King Abdulaziz University Hospital. At the first visit, personal data, CXR and measurement of baseline PEF were obtained from each patient. In the subsequent visits, sputum culture and CXR were carried out during exacerbations.

Results:  Over a period of 24 months, patients made a total of 139 visits for exacerbations, and 69.8% had a positive sputum culture for a single pathogen. Moraxella catarrhalis (25.2%), Pseudomonas aeruginosa (12.2%) and Haemophilus influenzae (11.5%) were the most common isolated organisms. Patients with a lower level of baseline PEF had a significantly increased frequency of exacerbations (r = 0.337, P = 0.024). However, there was a weak correlation between exacerbation frequency and duration of COPD and exposure to cigarette smoking.

Conclusion  There was a higher incidence of Moraxella catarrhalis and Pseudomonas aeruginosa than reported in previous studies. These findings should influence antibiotic selection for exacerbations. COPD patients with a low baseline PEF are at a higher risk of having repeated exacerbations and gram-negative pathogens.