ABSTRACTWe examined the genetic context of 74 acquired ampCgenes and 17 carbapenemase genes from 85 of 640 Enterobacteriaceaeisolates collected in 2009. Using S1 pulsed-field gel electrophoresis and Southern hybridization, 37 of 74 blaAmpCgenes were located on large plasmids of different sizes belonging to six incompatibility groups. We used sequencing and PCR mapping to investigate the regions flanking the acquired ampCgenes. The blaCMY-2-like genes were associated with ISEcp1; the surrounding blaDHAgenes were similar to Klebsiella pneumoniaeplasmid pTN60013 associated with IS26and the pspand sapoperons; and the blaACC-1genes were associated with IS26elements inserted into ISEcp1. All of the carbapenemase genes (blaVIM-1, blaIMP-22, and blaIMP-28) were located in class 1 integrons. Therefore, although plasmids are the main cause of the rapid dissemination of ampCgenes 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 (In846 to In848) are described in this study.