Sputum bacteriology in hospitalized patients with acute exacerbation of chronic obstructive pulmonary disease in Taiwan with an emphasis on Klebsiella pneumoniae and Pseudomonas aeruginosa

BACKGROUND AND OBJECTIVE: Bacterial infection is one of the major causes of acute exacerbation of COPD (AECOPD). This study was undertaken to investigate the microbiology of AECOPD. METHODS: Medical records from 494 episodes of AECOPD in patients admitted to the National Taiwan University Hospital from January 2000 to June 2004 were reviewed. Severity of COPD was classified according to the 2003 Global Initiative for Chronic Obstructive Lung Disease guideline. RESULTS: Potential pathogenic microorganisms were isolated from patients in 328 (66.4%) episodes of AECOPD. The predominant bacteria were Klebsiella pneumoniae (19.6%), Pseudomonas aeruginosa (16.8%) and Haemophilus influenzae (7.5%), followed by Acinetobacter baumannii (6.9%), Enterobacter species (6.1%) and Staphylococcus aureus (6.1%). The incidence of Streptococcus pneumoniae was 2.4%. Spirometry results obtained within 1 year of the exacerbation were available in 186 cases. K. pneumoniae was more frequently isolated in stage I COPD (39.1%) than stage II (16.6%), III (13.8%) and IV (9.4%). No glucose non-fermentative Gram-negative bacilli were isolated in stage I patients. Multivariate logistic regression analysis revealed that P. aeruginosa (odds ratio (OR) 3.19; 95% confidence interval (CI): 1.21-8.38), intubation (OR 14.81; 95% CI: 5.08-43.12) and age (OR 1.1; 95% CI: 1.03-1.17) were independent risk factors for mortality. CONCLUSIONS: Klebsiella pneumoniae and P. aeruginosa are the most common sputum pathogens in hospitalized patients with AECOPD in Taiwan, with the former being more commonly isolated from mild COPD and the latter associated with poor clinical outcome. These results should be considered when deciding which antibiotics should initially be used to treat patients with AECOPD.