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 degrees 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.