title: Comparative Genomics of Community-Associated Methicillin-Resistant Staphylococcus aureus Shows the Emergence of Clone ST8-USA300 in Geneva, Switzerland.
abstract: BACKGROUND
  Previous investigations of community-associated methicillin-resistant Staphylococcus aureus(CA-MRSA) isolates have revealed a wide diversity of genetic backgrounds, with only sporadic occurrence of ST8-USA300, in Geneva, Switzerland. We conducted a molecular epidemiologic analysis to identify the origin of a sudden increase of ST8 PVL-positive isolates in Geneva during 2013.
  
  
  METHODS
  On the basis of prospective CA-MRSA surveillance, we collected colonizing and infecting ST8-USA300 isolates and compared them to non-ST8 CA-MRSA isolates. Whole-genome sequencing (WGS) was performed for each isolate of this collection, and discriminating molecular features were linked to patient data.
  
  
  RESULTS
  In 2013, 22 isolates with the ST8-USA300 profile were identified among 46 cases of CA-MRSA. WGS revealed 2 groups of strains that differed by the type of the SCCmec IV element encoded and whether they harbored an arginine catabolism mobile element (ACME) locus. ACME-negative strains were mainly isolated from patients traveling in or originating from South America. Single-nucleotide polymorphism positions in isolate groups were used to infer their common ancestor, determine their geographical origin, and trace their relatedness.
  
  
  CONCLUSIONS
  WGS allowed the identification of transmission events and revealed that the increased prevalence of USA300 CA-MRSA isolates resulted from multiple importation events from the Americas but not from local clonal expansion of a successful clone.
authors.affiliation: Infection Control Program, Geneva University Hospitals Faculty of Medicine, University of Geneva, Switzerland.
authors.forename: Elodie
authors.initials: E
authors.lastname: Von Dach
authors.affiliation: Genomic Research Laboratory, Service of Infectious Diseases, Geneva University Hospitals Faculty of Medicine, University of Geneva, Switzerland.
authors.forename: Seydina M
authors.initials: SM
authors.lastname: Diene
authors.affiliation: Infection Control Program, Geneva University Hospitals Faculty of Medicine, University of Geneva, Switzerland.
authors.forename: Carolina
authors.initials: C
authors.lastname: Fankhauser
authors.affiliation: Genomic Research Laboratory, Service of Infectious Diseases, Geneva University Hospitals Faculty of Medicine, University of Geneva, Switzerland.
authors.forename: Jacques
authors.initials: J
authors.lastname: Schrenzel
authors.affiliation: Infection Control Program, Geneva University Hospitals Faculty of Medicine, University of Geneva, Switzerland.
authors.forename: Stephan
authors.initials: S
authors.lastname: Harbarth
authors.affiliation: Genomic Research Laboratory, Service of Infectious Diseases, Geneva University Hospitals Faculty of Medicine, University of Geneva, Switzerland.
authors.forename: Patrice
authors.initials: P
authors.lastname: François
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000382:microbiology*; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D005260:Female; D023281:Genomics; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000235:genetics*; D008875:Middle Aged; D017720:Molecular Epidemiology; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013557:Switzerland / Q000453:epidemiology; D055815:Young Adult
chemical_list: D004269:DNA, Bacterial
keywords: USA300; comparative genomics; epidemiological survey; genome evolution; high throughput sequencing; importation event; methicillin-resistant Staphylococcus aureus