Abstract
The epidemiology of pulmonary colonisation by Pseudomonas aeruginosa was studied in 21 patients with cystic fibrosis (CF) by field inversion gel electrophoresis. DraI-DNA restriction patterns were analysed for 187 P. aeruginosa isolates from these patients. The results revealed that the strains present in individual patients varied during the course of chronic colonisation; the emergence of new strains often was associated with periods of antibiotic therapy. Patients often were colonised by more than one strain (two or three strains were present in 54% of the patients) and the strains obtained from unrelated patients were highly heterogeneous, in contrast to those isolated from a pair of twins. These results demonstrate the heterogeneity and variability of P. aeruginosa isolates in the pulmonary flora of chronically infected CF patients.