To address this issue, the presence of the ersA gene and its expression levels were assessed in a panel of 31 P. aeruginosa strains isolated in respiratory samples from CF and COPD patients collected during intermittent or chronic infections at different stages and compared with those in 5 P. aeruginosa isolates from environmental habitats (13, 41, 42), using the PAO1 strain as a reference. This evidence concerns the gene SMOX and chronic obstructive pulmonary disease.