Epidemiologic characterization of Pseudomonas aeruginosa in patients with cystic fibrosis

Objective To determine persistence and variability of colonization with Pse udomonas aeruginosa in cystic fibrosis patients over long time periods, and to look for possible cross-colonization. Methods In total, 469 Pseudomonas aeruginosa isolates were obtained from 30 patients during the period from April 1994 to April 1996. The sources were mainly sputum and a few deep throat swabs. All grown strains dissimilar in macromorphology were processed separately. Typing with PFGE was carried ou t by contour-clamped homogeneous electric field electrophoresis. Genomic DN A was subjected to the rare-cutting restriction enzyme SpeI. For pyocin typ ing, the procedure described by Fyfe was applied. Results After typing with PFGE, we observed 40 restriction profiles. Eighte en different pyocin types were found. The most frequent pyocin type was typ e 3, followed by types 1 and 5. Twenty-two patients were persistently colon ized by one clone specific and different for each patient, and four were co -colonized by a second clone also different for each of these patients. Cro ss-colonization had apparently been rare in the cystic fibrosis center of L eipzig. Conclusions Typing with PFGE is well suited for detailed investigations of colonization with Pseudomonas aeruginosa in cystic fibrosis patients. Pyoci n typing can provide additional information for epidemiologic purposes.