The population structure of Staphylococcus aureus isolates of ICU patients in the Netherlands between 1996 and 2006

Abstract number: R2346

Rijnders M.I.A., Deurenberg R.H., Boumans M.L., Hoogkamp-Korstanje M.A.A., Stobberingh E.E.

Objectives: In The Netherlands, the meticillin-resistant Staphylococcus aureus (MRSA) prevalence is increasing. This increase could be due to a genetic macro-evolution of the meticillin-susceptible S. aureus (MSSA) isolates in The Netherlands. MRSA originated through the transfer of the mobile resistant element staphylococcal cassette chromosome mec (SCCmec) into MSSA. In order to investigate the changes in the population structure of S. aureus and the macro-evolutions of MSSA in The Netherlands, MSSA isolates from ICU patients were analysed.

Methods:S. aureus isolates (n = 856) from ICU patients were collected in The Netherlands between 1996 and 2006. They were yearly collected from January until July in two university hospitals and twelve general hospitals. The minimal inhibitory concentration (MIC) of oxacillin was determined by a micro-dilution method according to CLSI guidelines. The genetic background of the isolates was determined with spa typing and the algorithm based upon repeat pattern (BURP).

Results: Twenty-one isolates (2.5%) were resistant to oxacillin. Of the 287 spa types observed, 58 new spa types were identified and three new spa repeats were found among the new spa types. Among the S. aureus isolates, fourteen spa-clonal complexes were found. Ten isolates could not be clustered, and were singletons. Three of the singletons were classified as ST109. Seventy isolates were excluded from the analyses. A genetic background common to MRSA clones, e.g. CC1, CC5, CC8, CC22, CC30 and CC45 was observed among 46% of the isolates (n = 393). The remaining isolates were associated with CC7, CC15, CC25, CC26, CC51, CC97 and CC101.


1Half of the MSSA isolates (46%) had a genetic background common to MRSA clones.

2The prevalence of oxacillin resistance was higher in this study than the prevalence found in The Netherlands. These isolates will be further analysed using SCCmec typing.

3Several clonal complexes not related to MRSA clones were prevalent in the hospitals.

4Further investigations to the changes over time and the virulence factor Panton Valentine leukocidin (PVL) are necessary.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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