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J Infect Dis. 2016 May 1;213(9):1370-9. doi: 10.1093/infdis/jiv489. Epub 2015 Oct 13.

Comparative Genomics of Community-Associated Methicillin-Resistant Staphylococcus aureus Shows the Emergence of Clone ST8-USA300 in Geneva, Switzerland.

Author information

1
Infection Control Program, Geneva University Hospitals Faculty of Medicine, University of Geneva, Switzerland.
2
Genomic Research Laboratory, Service of Infectious Diseases, Geneva University Hospitals Faculty of Medicine, University of 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.

KEYWORDS:

USA300; comparative genomics; epidemiological survey; genome evolution; high throughput sequencing; importation event; methicillin-resistant Staphylococcus aureus

PMID:
26464204
DOI:
10.1093/infdis/jiv489
[Indexed for MEDLINE]

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