CFTR and cystic fibrosis: Impaired mucociliary clearance and dehydrated airway surface fluid is likely to impact overall bacterial clearance in the CF transmembrane conductance regulator (CFTR)-mutant lung [5], but in itself does not explain why P. aeruginosa, but rarely Klebsiellae, Escherichia coli, Proteus or the other common opportunists, is so specific for CF.