Genetic nature and virulence of communityassociated methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) emerged in 1961, just after the introduction of methicillin as a countermeasure against penicillinase-producing "multidrugresistant" S. aureus, a threat at that time. Since then, MRSA has posed a continuous threat to medical care as a major multidrug-resistant pathogen in hospitals. In 1997e1999, severe invasive infection with MRSA occurred in the community, and this attracted attention as community-associated MRSA (CA-MRSA). The evolutionary steps include species-tospecies transfer and salvage of key genetic structures, responsible for community spread, virulence, and resistance. The MRSA epidemic, including invasive diseases, in the community is dynamic. Copyright (C) 2012, China Medical University. Published by Elsevier Taiwan LLC. All rights reserved.