Molecular epidemiology of chronic pulmonary colonisation by Pseudomonas aeruginosa in cystic fibrosis.

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.