The emergence of mecC methicillin-resistant Staphylococcus aureus

• A novel mecA homologue, mecC, confers methicillin resistance to methicillin-resistant Staphylococcus aureus (MRSA).
• mecC MRSA produce negative results with common diagnostic tools.
• Reported from throughout Western Europe. Recent increase in Denmark.
• Found in a range of host species and may pose a zoonotic risk to humans.

The report of methicillin-resistant Staphylococcus aureus (MRSA) encoding a divergent mecA gene in 2011 was highly significant. This homologue, designated mecC, poses diagnostic problems with the potential to be misdiagnosed as methicillin-sensitive S. aureus, with important potential consequences for individual patients and for the surveillance of MRSA. mecC MRSA have now been reported from 13 European countries and have been isolated from 14 different host species, with evidence of a recent increase in Denmark. The emergence of mecC MRSA is a topic of interest to human and veterinary microbiology, and we consider it timely to review here its discovery and subsequent investigation.