Differential Expression of ccrA in Methicillin-Resistant Staphylococcus aureus Strains Carrying Staphylococcal Cassette Chromosome mec Type II and IVa Elements

Abstract
Excision of staphylococcal cassette chromosome mec (SCC mec ) is mediated through the ccrA - and - B -encoded recombinases. We investigated the effects of different antimicrobial agents on ccrA expression by using a ccrA :: lacZ fusion and reverse transcription-PCR with methicillin (meticillin)-resistant Staphylococcus aureus strains MW2 (SCC mec IVa) and N315 (SCC mec II). Upregulation of ccrA was observed upon exposure to β-lactam antibiotics. Vancomycin increased ccrA expression in MW2 but had no effect on N315. Vancomycin may contribute to the transfer of SCC mec IVa but have no effect in SCC mec II.

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