Genomic analyses of 18 strains obtained from different patients in three countries (United States, United Kingdom, and France) were performed; the methods used in this study were restriction fragment length polymorphism (RFLP) analysis, pulsed-field gel electrophoresis (PFGE) analysis, and PCR restriction analysis (PRA) of the gene. A new insertion sequence, IS(GenBank accession no. X97307), belonging to the IS family, was identified in type 1 strains and was characterized by sequencing. When a probe for IS-like sequences was used, the RFLP analysis of type 1 strains revealed that they contained three or four copies of IS in identical genomic positions, while this element was absent in all type 2 strains. PFGE performed with three different endonucleases revealed a unique large restriction fragment (LRF) pattern for type 1 strains, whereas the LRF patterns obtained for type 2 strains were polymorphic. Moreover, PFGE of nondigested genomic DNA revealed extrachromosomal elements in type 2. The type strain of type 3 could not be differentiated from type 1 strains on the basis of the results of the RFLP analysis, the PFGE analysis, and the PRA of IS. In this study we confirmed that types 1 and 2 represent distinct genomic clusters and that the molecular markers in type 2 exhibit greater polymorphism than the molecular markers in type 1.


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