This work was supported by the Spanish Ministry of Science and Innovation (projects FISS PI052489 and FISS PI080656) and by the Federal Institute for Risk Assessment, Germany (projects BfR 45-004, 45-005 and 46-001). M. A. A. was supported by the Ministry of Science and Innovation, Spain (grant FPU AP-2004-3641), co-funded by the European Social Fund, and performed a short stay at the Department of Biological Safety of the Federal Institute for Risk Assessment (BfR), Berlin, Germany, supported by the same grant. We are grateful to F. Carreño (Microbiology Laboratory, MNH) for assistance with the S. aureus strains; Dr. N. Castaño (Documentation Department, MNH) for supplying patient data; Dr. W. Witte (National Reference Center for Staphylococci, Robert Koch Institute, Wernigerode, Germany) and Dr. K. Weist (formerly at the National Reference Center for Surveillance of Nosocomial Infections, Charité University Medicine, Berlin, Germany) for strains used as controls in SCCmec typing; and the Department of Biological Safety of Berlin for its hospitality towards M. A. A. during her short-term visit.