Effects of the Movement of Insertion Sequences on the Structure of VanA Glycopeptide Resistance Elements in Enterococcus faecium

A Tn1546-related element with IS1216V at position 8839 underwent a structural change after storage of the host strain of Enterococcus faecium at 4°C. The element acquired IS1542 at position 3932, nucleotides 8732 to 8831 were deleted, and the first 3417 nucleotides were lost and replaced by an inverted copy of the IS1216V–vanY–vanZ-inverted-repeat block from the 3′ end. Insertion sequence movement is likely to play a key role in the evolution of VanA resistance elements.