Schematic drawing of SCCmec composite elements detected in the present study. “A” structures have prototype SCCmec IVa (11), and “B” structures have SCCmec IVa with the novel J3 region characterized by two unique clusters of ORFs (reg1 and reg2) (2). A1 (SCCmec IVa), A2 (SCCmec IVa with ACME I downstream), B1 (SCCM1, ΨSCCarc, SCCmecIVa [2B]; J1, subtype 1-specific ORFs; J3, subtype 3-specific ORFs for M1), and B2 (SCCmec IVa [2B]; J1, subtype 1-specific ORFs; J3, subtype 3-specific ORFs for M1) have been previously described (2, 5, 11) and fully sequenced (GenBank accession numbers NC_003923, NC_007793, HM030720, and HM030721). B3 and B4 are proposed structures of new SCCmec IVa composite elements based on PCR mapping and partial sequencing. Approximate targets of PCRs 1 to 9 are shown by broken lines.