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We investigated why a clinical meticillin-resistant (MRSA) isolate yielded false-negative results with some commercial PCR tests for MRSA detection. We found that an epidemic European CC1-MRSA-IV clone generally exhibits this behaviour. The failure of the assays was attributable to a large insertion in the /SCC integration site. To ensure the reliability of molecular MRSA tests, it is vital to monitor emergence of new SCC types and junction sites.


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