Identification of Diverse Integron and Plasmid Structures Carrying a Novel Carbapenemase Among Species.

A novel carbapenem-hydrolyzing beta-lactamase, called IMP-63, was identified in three clonally distinct strains of and two strains of isolated within a 4 year timeframe in three French hospitals. The gene that encodes this carbapenemase turned out to be located in the variable region of four integrons (In, In, In, and In) and to coexist with novel or rare gene cassettes (, , ) and insertion elements (IS, IS). All these integrons except one (In) were flanked by a copy of insertion sequence IS next to the putative gene, and were carried by non-conjugative plasmids (pNECK1, pROUSS1, pROUSS2, pROUE1). These plasmids exhibit unique modular structures and partial sequence homologies with plasmids previously identified in various non-fermenting environmental Gram-negative species. Lines of evidence suggest that IS promoted the transposition of IMP-63-encoding integrons on these different plasmids. As demonstrated by genotyping experiments, isolates of harboring the 28.9-kb plasmid pNECK1 and belonging to international "high-risk" clone ST308 were responsible for an outbreak in one hospital. Collectively, these data provide an insight into the complex and unpredictable routes of diffusion of some resistance determinants, here , among species.