Genotypic characterization of Pseudomonas aeruginosa strains recovered from patients with cystic fibrosis after initial and subsequent colonization

Chronic infection by Pseudomonas aeruginosa (PA) in patients with cystic fi brosis (CF) is preceded by a period of colonization and acute infection. Ea rly aggressive antibiotic treatment of initial colonisation may prevent or at least delay chronic pulmonary infection. We initiated treatment with a c ombination of IV beta -lactam tobramycin, followed by nebulized colistin wh en PA was first isolated from patients with CF. Subsequent serial PA isolat es obtained from these colonized CF patients were characterized by means of molecular methods to determine whether they were genetically related to th e initial strain. Initial colonization was eradicated in all 19 patients. All patients reacqu ired PA within 3-25 months during the 3 years of follow-up. Fourteen patien ts acquired a new PA strain with a distinct genotypic profile, suggesting a new source of contamination. Five patients had two PA isolates with identi cal genotypes, suggesting either previous undetected respiratory tract colo nization or a persistent environmental source of contamination. (C) 2001 Wi ley-Liss, Inc.