Heterogeneity of Pseudomonas aeruginosa in Brazilian cystic fibrosis patients.

The aim of this study was to assess the diversity and genomic variability of Pseudomonas aeruginosa isolates from cystic fibrosis (CF) patients being treated at a university hospital in Brazil. Ninety-seven isolates of P. aeruginosa from 43 CF patients were characterized by macrorestriction analysis of chromosomal DNA by pulsed-field gel electrophoresis (PFGE) and tested for susceptibility to 20 antimicrobial agents by broth microdilution. It was possible to evaluate single isolates from 20 patients and multiple isolates (two to seven) from 23 patients collected during a 22-month period. Among all of the unrelated patients, we detected only one pair of patients sharing a common strain. Among the 77 isolates from 23 patients who had multiple isolates analyzed, we identified 37 major types by PFGE, and five different colonization patterns were recognized. The isolates were susceptible to several antimicrobial agents, although consecutive isolates from the same patient may display differences in their susceptibilities. Mucoid isolates were more resistant (P < 0.001) than nonmucoid isolates to five antibiotics. Our results indicate that CF patients remain colonized by more than one strain of P. aeruginosa for long periods of time. In addition, the finding of several different genotypes in the same patient suggests that the colonizing strain may occasionally be replaced.