SCCmec¶
The staphylococcal cassette chromosome (SCC) is a gene cassette widely disseminated in staphylococci. SCCmec is characterized by the carriage of methicillin resistant determinant gene (mecA).
Structural characteristics of SCCmec elements.¶
They carry the class A mec gene complex, consisting of mecA, its regulatory genes, mecI and mecR1, and the insertion sequence IS431.
They carry a ccr gene complex (ccr).
They carry two site-specific recombinase homologues.
They have characteristic direct repeats and inverted repeats at both ends.
They integrate into ISS (integration site sequence for SCC), which is located at 3’ end of orfX. It is located at the 3’ end of orfX.
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SCCmec typing¶
The type of SCCmec is defined by the combination of the type of ccr-gene complex and the class of mec-gene complex [3]. Subtype of the SCCmec is based on the difference in the J regions (standing for junkyard): J1, J2, and J3.
ccr |
mec |
combination ccr and mec |
SCCmec type |
|---|---|---|---|
type 1 |
class B |
1B |
Type I |
type 2 |
class A |
2A |
Type II |
type 3 |
class A |
3A |
Type III |
type 2 |
class B |
2B |
Type IV |
type 5 |
class C |
5C |
Type V |
type 4 |
class B |
4B |
Type VI |
Original source: Hiramatsu et. al. 2013 (PMID: 24265961)¶
(A) Basic structure of SCCmec. SCCmec is bracketed by direct repeats (DRs) that contain integration site sequence (ISS) recognized by cassette chromosome recombinase (CCR). A pair of inverted repeats (IRs) are present at the termini of SCCmec.
(B) Various types of SCCmec. The structures of 11 types of SCCmec are illustrated based on the nucleotide sequences deposited in the DDBJ/EMBL/GenBank. See original source for additional details.
Direct repeats that comprise integration site sequences of SCC are located at both extremities of SCCmec (the red arrowheads). The location of five (A-E) classes of mec-gene complexes is indicated by pink belt. The locations of ccr-gene complexes are indicated by blue belt. Insertion sequences and transposons are indicated in yellow. Representative genes related to heavy metal resistance and integrated plasmids located in the J regions are also indicated. Type XI is a newly identified SCCmec found in the MRSA strains of bovine sources.
SCCmec database¶
We would use SCCmecFinder