Mobile genetic elements related to the diffusion of plasmid-mediated AmpC β-lactamases or carbapenemases from Enterobacteriaceae: findings from a multicenter study in Spain

Abstract

We examined the genetic context of 74 acquired ampC genes and 17 carbapenemase genes from 85 out of 640 Enterobacteriaceae isolates collected in 2009. Using S1-PFGE and Southern hybridization, 37 out of 74 blaAmpC genes were located on large plasmids of different sizes belonging to six Inc groups. We used sequencing and PCR mapping to investigate the regions flanking the acquired ampC genes. The blaCMY-2like genes were associated with ISEcp1, the surrounding blaDHA genes were similar to Klebsiella pneumoniae plasmid pTN60013 associated with IS26 and the psp and sap operons, and blaACC-1 genes were associated with IS26 elements inserted into ISEcp1. All the carbapenemase genes (blaVIM-1, two blaIMP-22 and blaIMP-28) were located in class 1 integrons. Therefore, although plasmids are the main cause of the rapid dissemination of ampC genes among Enterobacteriaceae, we need to be aware that other mobile genetic elements, such as insertion sequences, transposons or integrons, can be involved in the mobilization of these genes of chromosomal origin. Additionally, three new integrons are described in this study (In846 to In848).