Dynamic state of plasmid genomic architectures resulting from XerC/D-mediated site-specific recombination in Rep_3 superfamily resistance plasmids carrying - and Tn-resistance modules.

The acquisition of genes encoding different carbapenem-hydrolyzing class-D β-lactamases (CHDL) represents a main determinant of carbapenem resistance in the nosocomial pathogen . The gene, in particular, is generally embedded in similar resistance modules (RM) carried by plasmids unique to the genus lacking self-transferability. The ample variations in the immediate genomic contexts in which -containing RMs are inserted among these plasmids, and the almost invariable presence at their borders of non-identical 28-bp sequences potentially recognized by the host XerC and XerD tyrosine recombinases (pXerC/D-like sites), suggested an involvement of these sites in the lateral mobilization of the gene structures they encircle.