- Volume 62, Issue 12, 2013

We present a case of bacteraemia due to meticillin-resistant Staphylococcus aureus (MRSA) carrying the mecC gene. The susceptibility to meticillin of Staphylococcus aureus was investigated directly from one blood culture bottle using GenomEra MRSA/SA (Abacus Diagnostica Oy) test. This test identified S. aureus but the presence of the mecA gene result was negative, and the isolate was reported as meticillin-sensitive Staphylococcus aureus (MSSA). Susceptibility studies were done using VITEK 2 AST-P588 susceptibility cards (bioMérieux). The strain was identified as MRSA by the VITEK 2 system, although oxacillin MIC was low (0.5 µg ml−1). In view of these results, the isolate was tested for the presence of the mecC gene by a specific PCR and was verified as MRSA carrying mecC. The emergence of this new mecA homologue could have important consequences for the detection of MRSA when routine PCR methods are used as an identification method or provisional detection of MRSA, as in the case reported in this article, because S. aureus carrying the mecC gene will be wrongly diagnosed as meticillin susceptible. Negative results must be interpreted with caution and should be followed by conventional culture, and antimicrobial susceptibility testing or detection of mecC gene by a specific PCR.