High frequency and diversity of cassette chromosome recombinases (ccr) in methicillin-susceptible Staphylococcus sciuri

Results: ccrAB were identified in 35% of the isolates (n ¼ 41), represented by 24 PFGE types, but ccrC was not found. None of the isolates carried mecA or its regulators, but all isolates carried mecA1/pbpD. In the majority of isolates, ccr and mecA1 were located near orfX, the SCCmec integration site. Moreover, in 31% (n¼ 13) of the ccrAB-carrying strains, ccrAB, mecA1 and orfX colocalized in the chromosome. The nucleotide sequence of ccrA/ ccrB was highly diverse, including ccr genes closely related (80%–97%) to those found in MRSA. Conclusions: Our results suggest thatS. sciuri was a natural recipient and a rich reservoir ofccr for the assembly of SCCmec. The chromosomal location of mecA1, near orfX, the recognition site of ccr, was probably crucial for its mobilization out of S. sciuri species into SCCmec.