IS26-associated In4-type integrons forming multiresistance loci in enterobacterial plasmids

Abstract

Three distinct multiresistant loci from enterobacterial plasmids each comprised an integron and an IS26-associated sequence. Sequence comparison suggested a common ancestral structure that derived from an IS26 insertion into the 5' conserved segment of an In4-type integron and evolved through acquisition of gene cassettes and IS26-mediated recruitment of additional resistance genes of diverse origin.

FIG. 1.

Graphic presentation of the multiresistant loci found in the enterobacterial plasmids pSEM, pAK33, and p541. Inverted terminal repeats (IRt) at the 3′CS boundaries of the In4-like integrons and target site duplications (TSD) are indicated. The shaded parts represent the common IS26/Δ5′CS sequences.