Welcome to ccrB Typing Tool Homepage!
What is ccrB typing?
Methicillin-resistant Staphylococcus aureus (MRSA) are characterized by a large heterologous mobile genetic element - staphylococcal chromosomal cassette or SCCmec [1] - carrying the mecA gene, the central element of methicillin resistance, and the ccr locus, which encode for recombinases (ccrAB or ccrC) involved in SCCmec mobility. SCCmec types are defined by combining the information on the genetic organization of the mec complex with the ccr type [2], and so far six major types have been identified [1-5] .Concerning the ccr locus, four ccrAB allotypes have been described which can be detected by conventional PCR assays and are specifically associated with SCCmec types [2,4,5]: ccrAB allotype 1 is specific for SCCmec type I, ccrAB 2 is characteristic of types II and IV, ccrAB 3 is specific for type III, and ccrAB 4 is specific for type VI. SCCmec type V is characterized by a single-gene ccr complex (ccrC) which is not closely related to ccrA or ccrB genes [3].
Recently, we have shown that the DNA sequencing of an internal fragment of ccrB enables the characterization of the ccrAB allotype present in MRSA strains and, after cluster analyses, the prediction of SCCmec types I-IV and VI [6]. This strategy has the advantage to be easily integrated into other DNA-sequence based methods, such as spa typing and MLST protocols, and, therefore it maybe useful as a first line SCCmec typing strategy. Moreover, the sequence data generated can be used for tracing the dissemination of SCCmec elements between the MRSA population or even between S. aureus and coagulase-negative staphylococci. This strategy can also replace the ccrAB allotyping by conventional PCR detection.
The database ccrB typing nomenclature is available here.
The experimental procedure details are available here.
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