title: Comparative genomics of epidemic versus sporadic Staphylococcus aureus strains does not reveal molecular markers for epidemicity.
abstract: Staphylococcus aureus, especially when it is methicillin resistant, has been recognised as a major cause of nosocomial and community-acquired infections. It has also been shown that certain strains were able to cause clonal epidemics whereas others showed a more incidental occurrence. On the basis of this behavioural distinction, a genetic feature underlying this difference in epidemicity can be assumed. Understanding the difference will not only contribute to the development of markers for the identification of epidemic strains but will also shed light on the evolution of clones. Genomes of strains from two independent collections (n=18 and n=10 strains) were analysed. Both collections were composed of carefully selected, genetically diverse strains with clinically well-defined epidemic and sporadic behaviour. Comparative genome hybridisation (CGH) was performed using an Agilent array for one collection (up to 11 probes per open reading frame - ORF), and an Affymetrix array for the other (up to 30 probes per ORF). Presence and absence information of probe homologues and ORFs was taken for analysis of molecular variance (AMOVA) at the strain and behaviour levels. Not a single probe showed 100% concordant differences between epidemic and sporadic strains. Moreover, probe differences between groups were always smaller than those within groups. This was also true, when the analysis was focussed on presence versus absence of ORF's or when probe information was transformed into allelic profiles. These findings present strong evidence against the presence or absence of a single common specific genetic factor differentiating epidemic from sporadic S. aureus clones.
authors.affiliation: Hospital Preventive Medicine, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Switzerland.
authors.forename: Gerrit
authors.initials: G
authors.lastname: Kuhn
authors.forename: Thibaud
authors.initials: T
authors.lastname: Koessler
authors.forename: Damian C
authors.initials: DC
authors.lastname: Melles
authors.forename: Patrice
authors.initials: P
authors.lastname: Francois
authors.forename: Antoine
authors.initials: A
authors.lastname: Huyghe
authors.forename: Paul
authors.initials: P
authors.lastname: Dunman
authors.forename: Margreet C
authors.initials: MC
authors.lastname: Vos
authors.forename: Giorgio
authors.initials: G
authors.lastname: Zanetti
authors.forename: Jacques
authors.initials: J
authors.lastname: Schrenzel
authors.forename: Alex
authors.initials: A
authors.lastname: van Belkum
authors.forename: Dominique S
authors.initials: DS
authors.lastname: Blanc
mesh_terms: D055028:Comparative Genomic Hybridization; D003428:Cross Infection / Q000453:epidemiology; D004196:Disease Outbreaks; D016680:Genome, Bacterial / Q000187:drug effects; D023281:Genomics; D006801:Humans; D016106:Methicillin Resistance / Q000235:genetics; D017720:Molecular Epidemiology; D020411:Oligonucleotide Array Sequence Analysis; D013203:Staphylococcal Infections / Q000453:epidemiology*; D013211:Staphylococcus aureus / Q000145:classification* / Q000187:drug effects / Q000235:genetics*