Several studies investigated the type of the bacterial pathogens isolated in the sputum of patients admitted to hospital for acute exacerbations and analysed the possible relation between the lung function and the type of isolated bacteria (23, 24). The usual three bacterial species (H. influenzae, Streptococcus pneumoniae and Moraxella catarrhalis) were leading in GOLD severity stages I and II. In GOLD severity stage III and especially in GOLD stage IV, Gram-negative pathogens like Enterobacteriaceae and Pseudomonas aeruginosa dominated in the respective sputum cultures. This data was recently confirmed in a large prospective study in our hospital and the data has been submitted for publication (25).