A novel IncQ plasmid type harbouring a class 3 integron from Escherichia coli

To determine the genetic structures at the origin of the mobilization of the extended-spectrum beta-lactamase (ESBL) bla(GES-1) gene in an Escherichia coli clinical isolate.

ESBL-encoding genes and class 1 or class 3 integron-specific motifs were screened. Conjugation experiments were performed to determine whether the plasmid-carrying bla(GES-1) gene was self-transferable. Plasmid sequencing was achieved by a primer-walking approach.

The bla(GES-1) gene was located in a class 3 integron. That unusual genetic structure was itself located on an approximately 9 kb plasmid, pQ7, which was not self-transferable. Sequence analysis revealed that plasmid pQ7 belonged to a novel subtype of the IncQ group.

This study identified for the first time the bla(GES-1) gene in E. coli and in Switzerland. It describes a novel IncQ-type plasmid subgroup that possesses original features, in particular iteron sequences that constitute a hot spot for integration of foreign DNA.