Study of pyoverdine type and production by Pseudomonas aeruginosa isolatedfrom cystic fibrosis patients: prevalence of type II pyoverdine isolates and accumulation of pyoverdine-negative mutations

The lungs of cystic fibrosis patients are frequently colonized by Pseudomon as aeruginosa, which produces high-affinity fluorescent peptidic siderophor es, pyoverdines. Three pyoverdines which differ in their peptide chain and are easily differentiated by isoelectric focusing exist, only one being pro duced by a given strain. P. aeruginosa isolates from cystic fibrosis patien ts of a German hospital were analyzed by sequential, pulse-field gel electr ophoresis (PFGE) and for pyoverdine production and type. Only producers of type I and type LI pyoverdine were found. There was a perfect correlation b etween the type of pyoverdine produced and the clonality determined by PFGE . PFGE clone C, the most prevalent among cystic fibrosis patients, and foun d in an aquatic environment, produced type II pyoverdine. Pyoverdine-negati ve mutants seemed to increase as a function of the lung colonization time, but retained the capacity to take up pyoverdines. Most isolates that took u p type Il pyoverdine were also able to utilize type I pyoverdine as judged by growth stimulation experiments. No correlation was observed between the loss of pyoverdine production and mucoidy.