The most frequently isolated microorganisms was Pseudomonas aeruginosa (59.2%), followed by Staphylococcus aureus (19%) and Haemophilus influenzae (18.4%). In patients younger than 1 year of age other different microorganisms were identified in 61.1% of cases, but S. aureus (11.1%) and Pseudomonas aeruginosa (5.5%) were also isolated. The incidence of Pseudomonas cepacia (0.6%) is low in our environment. We did not isolate any Legionella sp. strain.