Schematic diagram of the CMY regions of Newport and Typhimurium. Panel A shows a schematic diagram of the CMY region of plasmid pSN254 present in Newport , which is composed of an inverted repeat CMY element between the traA and traC genes (unfilled arrows indicate the open reading frames, and the blaCMY-2 gene is in red). Panel B shows the CMY region of the Typhimurium ST213 strain YUHS 07-18 containing a single CMY element. Truncated genes are indicated by a line crossing the open reading frame arrows. The PCR amplifications designed to map the CMY region are indicated by double arrowheads under the diagrams (see Additional file 1, Table S1 and Results). The PCRs used to screen the CMY junctions are indicated by black double arrowheads.