Project description:CF patients suffer from chronic and recurrent respiratory tract infections which eventually lead to lung failure followed by death. Pseudomonas aeruginosa is one of the major pathogens for CF patients and is the principal cause of mortality and morbidity in CF patients. Once it gets adapted, P. aeruginosa can persist for several decades in the respiratory tracts of CF patients, overcoming host defense mechanisms as well as intensive antibiotic therapies. P. aeruginosa CF strains isolated from different infection stage were selected for RNA extraction and hybridization on Affymetrix microarrays. Two batch of P. aeruginosa CF isolates are chosen : 1) isolates from a group of patients since 1973-2008 as described in ref (PMID: 21518885); 2) isolates from a group of newly infected children as described in ref (PMID: 20406284).