Two variants of staphylococcal cassette chromosome mec type IVA in community-associated meticillin-resistant Staphylococcus aureus strains in South Korea

Meticillin-resistant Staphylococcus aureus (MRSA) strains harbouring staphylococcal cassette chromosome mec (SCCmec) type IVA are known to be more prevalent in South Korea than in other countries. Variations in the SCCmec IVA structure have been identified, including in sequence type (ST) 1 and ST72 strains. This study compared and investigated the genetic characteristics of two subtypes common in South Korea. Type IVA SCCmec of ST1 strains was characterized by type IV features with the linearized pUB110 at the junkyard (J) 3 region. However, that of ST72 strains carried a variant class B mec complex, ccrA2, with an identity of ∼96% and the linearized pUB110 at the J3 region. In SCCmec of ST72 strains, the organization of the class B variant and the J3 region may be more similar to that of type IA than to other types, but the ccr type and other J regions seemed to be derived from type IV. These genetic characteristics showed that type IVA appears to result from the dynamic genetic exchange and recombination of SCC DNA.