PERSISTENCE OF STAPHYLOCOCCUS-AUREUS STRAINS AMONG CYSTIC-FIBROSIS PATIENTS OVER EXTENDED PERIODS OF TIME

Pulsed-field gel electrophoresis (PFGE) of SmaI macrorestriction fragm ents of chromosomal DNA tvas used to confirm the persistence of methic illin-sensitive Staphylococcus aureus isolates in the sputum of 25 cys tic fibrosis patients in five French hospitals. Three-to-eight consecu tive isolates, with the same esterase electrophoretic type isolated fr om each patient over a period of 12-28 months, were analysed, Consecut ive isolates with indistinguishable PFGE profiles were found in 12 pat ients (48%) and consecutive isolates with similar PFGE profiles showin g minor differences of one-to-four fragments (similarity coefficient g reater than or equal to 84%) were found in ii patients, Consecutive is olates with different PFGE profiles mere obtained from only two patien ts, but the profiles found in each patient were more closely related t o each other than to other profiles. The results were in agreement wit h esterase electrophoretic typing for 23 patients, and we considered t hat those patients were infected with a single persistent strain. For any given patient, variations in antibiotypes and phage types of conse cutive isolates were not associated with major genotypic variations. P FGE is useful in confirming the persistence of S. aureus strains in cy stic fibrosis patients over long periods.