Multilocus sequence typing and the evolution of methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) continue to adapt to the selective pressure of antimicrobial agents and to exploit new niches, as evidenced by the recent isolation of strains with high-level vaneomycin resistance and the emergence of MRSA as a community pathogen. The combined use of the bacterial genotyping technique, multilocus sequence typing (MLST), and characterization of the mobile methicillin-resistance determinant, staphylococcal chromosomal cassette mec (SCCmec), has provided new insights into MRSA strain nomenclature, evolution, and epidcmiology. The first MRSA emerged when SCCmec was acquired by an epidemic methicillin-susceptible strain prevalent in Europe. Acquisition of SCCmec by other successful strains has led to the emergence of at least 11 major epidemic MRSA strains belonging to five distinct lineages with a global geographic distribution. These five lineages have evolved both hospital-acquired and community-acquired MRSA, but some of the newly emerging community strains descend from other lineages.

Robinson DA, Enright MC. Multilocus sequence typing and the evolution of methicillin-resistant Staphylococcus aureus. Clin Microbiol Infect 2004;10:92-7.