Molecular Epidemiology and Phylogenomics of Staphylococcus aureus Bacteremia in Latin-America: A Prospective Cohort Multicenter Study in Nine Countries [PublishAheadOfPrint]

Staphylococcus aureus are important pathogens causing a spectrum of diseases ranging from mild skin and soft tissue infections to life-threatening conditions. Bloodstream infections are particularly important and the treatment approach is complicated by the presence of methicillin resistance among S. aureus isolates (MRSA). Emergence of new genetic lineages of MRSA has occurred in Latin America (LA) with the rise and dissemination of the community-associated USA300 Latin American Variant (USA300-LV). Here, we prospectively characterized bloodstream MRSA recovered from selected hospitals in 9 Latin American countries. All isolates were typed by pulsed field gel electrophoresis (PFGE) and subjected to antibiotic susceptibility testing. Whole genome sequencing was performed in 96 MRSA representatives. MRSA represented 45% of all isolates (out of 1,185 S. aureus). The majority of MRSA isolates belonged to clonal cluster (CC) 5. In Colombia and Ecuador, most isolates (≥ 72%) belonged to the USA300-LV lineage (CC8). Phylogenetic reconstructions indicated that MRSA isolates from participating hospitals belonged to three major clades. Clade A grouped isolates with ST5, ST105, and ST1011 (mostly SCCmec I and II). Clade B included ST8, ST88, ST97, and ST72 strains (SCCmec IV, subtypes a, b, and c/E) and clade C grouped mostly Argentinian MRSA belonging to ST30. In summary, CC5 MRSA was prevalent in bloodstream infections in LA with the exception of Colombia and Ecuador where USA300-LV is now the dominant lineage. Clonal replacement appears to be a common phenomenon and continuous surveillance is crucial to identify changes in the molecular epidemiology of MRSA.

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