Background : The widespread dissemination of Tn1546 has been attributed to transposition into plasmid or transferable elements. The transposition has been achieved through the activity of insertion sequences. Genetic diversity in Tn1546 includes integration of IS elements such as IS1216V, IS1251, IS1476 and IS1542. We investigated molecular typing and the distribution of insertion sequences in vanA-containing Enterococcus faecium isolated from patients in a teaching hospital.

Methods : Sixteen strains of vanA-containing E. faecium isolated from Ajou university hospital were analyzed. PCR amplification of internal regions of Tn1546 was performed and PCR amplicons were directly sequenced on both DNA strands by the dideoxy termination method.

Results : For all 16 isolates, IS1216V sequences were located within Tn1546. IS1542 sequences were detected in the genome of 9 isolates. One isolate contained IS1216V in the vanS intragenic region. The structural analysis of Tn1546 in VRE isolates produced three different groups by the presence of the insertion sequences. Group I was characterized by deletions of orf1 and orf2 and IS1216V insertion in the vanXY intergenic region. Group II represented IS1542 in the orf2-vanR and IS1216V in the vanXY intergenic region with deletion of orf1 region. Group III represented IS1542 in the orf2-vanR and IS1216V in the vanXY intergenic region without any deletion.

Conclusions : Most of Korean isolates contained IS1216V and IS1542 sequences. Transposon typing of isolates in this study revealed a similarity to the European’s. The identification of insertion sequence within vanA gene cluster can be a useful tool in epidemiological investigations. (Korean J Clin Microbiol 2003;6(2):119-125)