GENOME MACRORESTRICTION ANALYSIS OF DIVERSITY AND VARIABILITY OF PSEUDOMONAS-AERUGINOSA STRAINS INFECTING CYSTIC-FIBROSIS PATIENTS

Genome macrorestriction fingerprinting with XbaI and DraI was used to analyze the relatedness of 166 Pseudomonas aeruginosa isolates collect ed from 31 cystic fibrosis patients over a 1- to 20-month period and t o correlate their genotype with patterns of resistance to 14 antimicro bial agents. Quantitative comparison of intra- and interpatient simila rities of P. aeruginosa macrorestriction patterns disclosed two discre te ranges that clearly discriminated subclonal variation (>80% related ness) and clonal diversity (10 to 70% relatedness). Cloning-derived mu tants exhibited up to 20% divergence of genomic macrorestriction patte rns during the course of chronic colonization of individual patients. Change of susceptibility to multiple antimicrobial agents developed in 50% of sequential pairs of isolates from individual patients. Only 19 % of these susceptibility changes were attributable to strain substitu tion, while the majority (56%) of resistance changes were associated w ith minor genomic variations of a persistent strain. Sixty-six percent of patients harbored one strain, and 33% carried two strains. Three c ommon strains colonized 5 (28%) of 18 patients attending a cystic fibr osis clinic, and another two strains colonized two patient pairs (31%) of 13 patients staying at a rehabilitation center, suggesting potenti al cross-infection in these settings. By indexing regional polymorphis ms throughout the chromosome structure, macrorestriction analysis can monitor subclonal evolution of P. aeruginosa and identify isogenic res istance mutants. Quantitative macrorestriction fingerprinting enables discrimination between clonal variants and clones of distinct origins and should therefore provide a reliable tool for investigating the mod e of acquisition of P. aeruginosa in cystic fibrosis patients.