Novel Type XII Staphylococcal Cassette Chromosome mec Harboring a New Cassette Chromosome Recombinase, CcrC2

Excision and integration of staphylococcal cassette chromosomemec (SCCmec ) are mediated by cassette chromosome recombinases (Ccr), which play a crucial role in the worldwide spread of methicillin resistance in staphylococci. We report a novelccr gene,ccrC2 , in the SCCmec of aStaphylococcus aureus isolate, BA01611, which showed 62.6% to 69.4% sequence identities to all publishedccrC1 sequences. A further survey found that theccrC2 gene was mainly located among coagulase-negative staphylococci (CoNS) and could be found in staphylococcal isolates from China, the United States, France, and Germany. Theccr gene complex harboring theccrC2 gene was designated a type 9 complex, and the SCCmec of BA01611 was considered a novel type and was designated type XII (9C2). This novel SCCmec element in BA01611 was flanked by a pseudo-SCC element (ΨSCCBA01611 ) carrying a truncatedccrA1 gene. Both individual SCC elements and a composite SCC were excised from the chromosome based on detection of extrachromosomal circular intermediates. We advocate inclusion of the ccrC2 gene and type 9ccr gene complex during revision of the SCCmec typing method.