Primers RH929 and RH930 (PCR A1) detect the backbone position occupied by the ARI-A resistance island, which is only found in type 1 IncC plasmids. They yield an amplicon of 1207 bp when the backbone is uninterrupted as in the type 2 plasmid pSCR119-A/C, which lacks ARI-A (Table 4). An amplicon was not produced from pRMH760 or pDGO100, due to the large ARI-A occupying this location.