SCC (Staphylococcal cassette chromosome) elements are genomic islands, which commonly carry ccr gene complex and demarcated by characteristic nucleotides. They encode genes that are profitable for their survival, and are mostly integrated at the 3’end of orfX at specific site called integration site sequence. Among them, we focus on SCCmec elements carrying mecA, and would like to discuss on the points as follows.
1. SCCmec elements have been classified by the difference of the combination of mec gene complex and ccr gene complex and it was consented to indicate by Roman numeral. How should we give Roman numeral to novel SCCmec elements?
2. Recently, some elements that should be regarded as the composite of a SCC and a SCCmec have been reported. How should we regard the element?
3. When a mec gene complex was identified in a cassette without ccr, how should we regard the element?
4. CA-MRSA strains tend to carry the SCCmec element, which is different from that carried by HA-MRSA. The identification of SCCmec elements (type I, II, IV, and V) carrying different J region (especially J1 region) strongly suggest that SCCmec elements were formed by the acquisition of mec gene complex into SCC element, which disseminated in staphylococci.
5. Some staphylococcal strains carry several SCC or SCC-like elements arranged in tandem. How were they integrated or arranged?