Distribution of Insertion Sequences Associated with Tn 1546 -Like Elements among Enterococcus faecium Isolates from Patients in Korea

Abstract

The vanA gene cluster is carried as a part of Tn 1546 -like elements. The genetic diversity in Tn 1546 -like elements has been documented previously. The differences described thus far have included the integration of insertion sequence (IS) elements IS 1216V , IS 1251 , IS 1476 , and IS 1542 . Among these, IS 1216V has been reported to be widespread in VanA enterococci of diverse geographic areas, whereas IS 1542 and IS 1476 have been reported only in the United Kingdom and Canada, respectively. We investigated the distribution of ISs among 20 vanA -containing Enterococcus faecium isolates from human patients in nine different university hospitals in Korea. Pulsed-field gel electrophoresis (PFGE) was performed to identify the clonality of the isolates. Moreover, PCR amplification of the internal regions of Tn 1546 was performed for structural analysis of the van gene, and both DNA strands of the PCR amplicons were directly sequenced by the dideoxy termination method. The PFGE patterns revealed a high degree of clonal diversity. Structural analyses of the van gene detected IS 1542 and IS 1216V in the genomes of all 20 isolates, whereas it did not detect IS 1476 or IS 1251 in the genomes of any of the isolates. In addition, IS 19 was detected in the vanS - vanH intergenic region of one isolate. These data indicate that identification of the IS within a vanA gene cluster could be a useful tool in epidemiological investigations. In addition, the distribution of ISs associated with Tn 1546 -like elements among the Korean isolates is therefore similar to that among European vancomycin-resistant enterococci.