The clinical outcomes, CF Transmembrane conductance Regulator (CFTR) genotypes, and microbiological data of patients reported positive at least once for P. aeruginosa (“Pyo” group, n = 1,827) were compared to those of patients with no history of P. aeruginosa isolation (“Never” group, n = 303). The gene discussed is CFTR; the disease is cystic fibrosis.