SCCmec

SCC"mec, or staphylococcal cassette chromosome "mec, is a mobile genetic element of "Staphylococcus" bacterial species. This genetic sequence includes the "mecA" gene coding for resistance to the antibiotic methicillin and is the only known way for "Staphylococcus" strains to spread the gene in the wild by horizontal gene transfer.
Classification.
Not all SCC"mec" elements are identical (in fact, SCC elements without the "mecA" gene do exist.) SCC"mec" elements have been classified into twelve types (I through XII) on the basis of two specific regions of their nucleotide sequences. One region is the "mec" complex including the "mecA" gene. The other is the "ccr" gene complex including genes coding for recombinases.
The "mec" complex is divided further into five types (I through V) based on the arrangement of regulatory genetic features such as "mecR1", an inducer.
Distribution.
The SCC"mec" found in methicillin-resistant "Staphylococcus aureus" likely originated in coagulase-negative staphylococcal species and was acquired by "S. aureus".
Staphylococcal strains isolated from pig farms were found to carry several different types of SCC"mec", suggesting that they may serve as a reservoir of these elements.