To trace the origin, evolution, and dissemination pattern of the USA300 CA-MRSA clone in France, we sequenced a collection of strains of this lineage from cases reported in France in the last decade and compared them with 431 ST8 strains from the USA.. Demography and intercontinental spread of the USA300 CA-MRSA lineage

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was recognized worldwide during the 1990s; in less than a decade, several genetically distinct CA-MRSA lineages carrying the Panton-Valentine leukocidin have emerged on every continent. Most notably, in the US, the ST8-IV clone known as USA300, has become highly prevalent, outcompeting MSSA and other MRSA both in the community and hospital settings. CA-MRSA are much less prevalent in Europe where co-exist the European ST80-IV European CA-MRSA clone, the USA300 CA-MRSA as well as other lineages such as the ST22-IV. The question arises if the USA300 CA-MRSA present in Europe was imported once or on very few instances followed by a broad geographic spread, anticipating an increasied prevalence in the future, or if it derived from multiple imports with limited spreading success.