Population structure and antimicrobial susceptibility of both nonpersistent and persistent Pseudomonas aeruginosa isolates recovered from cystic fibrosis patients.

Seventy-six Pseudomonas aeruginosa isolates recovered from chronically (n=18) and nonchronically (n=18) colonized cystic fibrosis (CF) patients (2002 to 2009) were grouped in separate polyclonal populations. International CF epidemic clones were not identified, but the high-risk clone ST274, also found circulating in Spanish hospitals, was present. Persistent isolates were more resistant to antibiotics than nonpersistent isolates.