TYPING OF STAPHYLOCOCCUS-AUREUS AND STAPHYLOCOCCUS-EPIDERMIDIS STRAINS BY PCR ANALYSIS OF INTER-IS256 SPACER LENGTH POLYMORPHISMS

IS256 elements are present in multiple copies in the staphylococcal ge nome, either flanking the transposon Tn4001 or independent of it, PCR- based analysis of inter-IS256 spaces polymorphisms was developed for t yping of methicillin-resistant Staphylococcus aureus (MRSA) and Staphy lococcus epidermidis strains, Using SmaI macrorestriction analysis res olved by pulsed-field gel electrophoresis (PFGE) as the reference meth od for MRSA typing, excellent reproducibility (100%), discriminatory p ower (97%), and in vivo stability were observed, Good concordance of t he results with those of other molecular typing methods rues found for two MRSA collections, Inter-IS256 PCR analysis of a U.S. collection o f MRSA strains (n = 36), previously characterized by 15 typing methods , showed more limited discrimination, Agreement was 78% with PFGE anal ysis and 83% with ribotyping (HindIII), Analysis of a second set of Be lgian MRSA strains (n = 17), categorized into two widespread epidemic clones by PFGE analysis, showed 65% agreement, Far typing of S. epider midis strains (n = 26), inter-IS256 PCR showed complete typeability (1 00%) and good discriminately power (85%), Inter-IS256 PCR analysis is proposed as an efficient molecular typing assay for epidemiological st udies of MRSA or S. epidermidis isolates.