RANDOM AMPLIFIED POLYMORPHIC DNA TYPING OF PSEUDOMONAS-AERUGINOSA ISOLATES RECOVERED FROM PATIENTS WITH CYSTIC-FIBROSIS

Pseudomonas aeruginosa isolates recovered from chronically colonized p atients with cystic fibrosis (CF) are phenotypically different from th ose collected from other patients or from the environment. To assess w hether alterations in motility, mucoidy, and serum susceptibility repr esented an adaptation to chronic infection or replacement by a new str ain, sequential P. aeruginosa isolates of known phenotype collected fr om 20 CF patients were typed by random amplified polymorphic DNA (RAPD ) analysis. A total of 35 RAPD strain types were found among 385 isola tes from 20 patients, and only two patients had P. aeruginosa strains of the same RAPD fingerprint. Eight strain pairs representative of the first eight RAPD types were also analyzed by SpeI macrorestriction fo llowed by pulsed-field gel electrophoresis (PFGE); the strain types fo und by both finger-printing techniques correlated exactly, In 11 of 20 patients, the RAPD types of serial P. aeruginosa isolates remained st able despite alterations in isolate motility, colonial morphology, and lipopolysaccharide phenotype. However, in isolates collected from one CF patient, a single band change in RAPD fingerprint and CeuI PFGE pr ofile correlated with the appearance of an RpoN mutant phenotype, sugg esting that the altered phenotype may have been due to a stable genomi c rearrangement. Secretion of mucoid exopolysaccharide, loss of expres sion of RpoN-dependent surface factors, and acquisition of a serum-sus ceptible phenotype in P. aeruginosa appear to evolve during chronic co lonization in CF patients from specific adaptation to infection rather than from acquisition of new bacterial strains.