医院相关性MRSA散发和流行株的进化关系

David

Clinical Microbiology and Infection
Volume 14 Issue 7, Pages 659 - 669
Published Online: 9 Jun 2008

ORIGINAL ARTICLE
Evolutionary relationships between sporadic and epidemic strains of healthcare-associated methicillin-resistant Staphylococcus aureus
医院相关性MRSA散发和流行株的进化关系

M. Hallin, O. Denis, A. Deplano, R. De Ryck, S. Crèvecoeur, S. Rottiers, R. de Mendonça and M. J. Struelens
Laboratoire de Référence MRSA-Staphylocoques, Department of Microbiology, Hôpital Erasme, Université Libre de Bruxelles, Brussels, Belgium
Corresponding author and reprint requests: M. Hallin, Service de Microbiologie, Hôpital Erasme, 808, route de Lennik, 1070 Brussels, Belgium
E-mail: mahallin@ulb.ac.be
Copyright © 2008 European Society of Clinical Microbiology and Infectious Diseases
KEYWORDS
Epidemiology • evolution • genetic background • MRSA • PFGE • typing
ABSTRACT
National surveillance of healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) isolates by pulsed-field gel electrophoresis (PFGE) typing allowed identification of rarely occurring 'sporadic' isolates with patterns significantly distinct from those of major epidemic clones of methicillin-resistant S. aureus (MRSA) circulating in Belgian hospitals. The aim of the present study was to compare the genetic background, antibiotic susceptibility profile and in vitro growth rates of 36 MRSA isolates with either 'epidemic' or 'sporadic' PFGE profiles to identify factors that could be involved in the epidemic behaviour of S. aureus. Sequence analysis of seven housekeeping genes (multilocus sequence typing) and seven surface-associated genes, combined with staphylococcal cassette chromosome mec (SCCmec) typing and spa typing results, segregated sporadic isolates into four groups: (1) isolates phylogenetically distant from epidemic HA-MRSA clones that possessed several properties of community-acquired MRSA strains; (2) isolates derived from the same methicillin-susceptible S. aureus ancestor as epidemic isolates but possessing a distinct type of SCCmec; and (3) and (4) isolates that were closely related to epidemic strains, either as recent descendants of these or as intermediate evolutionary steps between epidemic HA-MRSA strains and their putative ancestors. Sporadic isolates did not show slower growth in vitro than epidemic isolates. These findings suggest that the SCCmec type and insertion/deletion of other mobile genetic elements may be involved in modulating the epidemic behaviour of MRSA strains of similar genetic background, independently of fitness cost.


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Original Submission: 3 December 2007;  Revised Submission: 5 February 2008;  Accepted: 29 February 2008