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10. Kongress für Infektionskrankheiten und Tropenmedizin (KIT 2010)

Deutsche Gesellschaft für Infektiologie,
Deutsche AIDS-Gesellschaft,
Deutsche Gesellschaft für Tropenmedizin und Internationale Gesundheit,
Paul-Ehrlich-Gesellschaft für Chemotherapie

23.06. - 26.06.2010, Köln

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MRSA (methicillin-resistant S. aureus) isolates have a similar cellular invasion capacity between colonization and infection, but differ with regard to spa type distribution from nasal MSSA (methicillin-susceptible S. aureus) isolates

MRSA (Methicillin-resistente S. aureus)-Isolate von Kolonisation und Infektion haben eine vergleichbare Invasionskapazität, aber unterscheiden sich in ihrer spa-Typ-Verteilung von MSSA (Methicillin-sensible S. aureus)-Isolaten

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  • B. Sinha - University of Würzburg, Institute for Hygiene and Microbiology, Würzburg, Germany
  • M. Raspe - University of Würzburg, Institute for Hygiene and Microbiology, Würzburg, Germany
  • J. Priller - University of Würzburg, Institute for Hygiene and Microbiology, Würzburg, Germany

10. Kongress für Infektionskrankheiten und Tropenmedizin (KIT 2010). Köln, 23.-26.06.2010. Düsseldorf: German Medical Science GMS Publishing House; 2010. DocP79

doi: 10.3205/10kit134, urn:nbn:de:0183-10kit1349

Published: June 2, 2010

© 2010 Sinha et al.
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Background: Data on spa type distribution of MSSA vs. MRSA isolates are limited. Fibronectin binding has been reported to correlate with the propensity to cause invasive disease. Here we compared spa type distribution of MSSA and MRSA, and tested the hypothesis whether cellular invasiveness predicts the propensity to cause infections of MRSA in a prospective patient cohort.

Methods: MRSA isolates from the nose and infection site (n=109), as well as nasal MSSA isolates from a single center prevalence study (J. Elias et al., in preparation) were prospectively collected and identified by standard biochemical and molecular methods. The collection period for MSSA was roughly 1/3 of the total study. Additional 13 infection isolates were used as a comparator group. SCCmec typing was performed by multiplex PCR (Boye K et al. Clin Microbiol Infect. 2007). Respective spa types were assigned using the spa server (Harmsen D et al. J Clin Microbiol. 2003). Cellular invasiveness was determined by a flow cytometric invasion assay for 293 cells (relative to reference strain Cowan I).

Results: Parallel control cultivation of MSSA isolates during part of the study yielded an overall S. aureus nasal colonization rate of 20.5%. MRSA isolates with spa type t003 were most frequent, thus 1/3 were assayed further, whereas MSSA spa type distribution was much more diverse. Most frequent MSSA spa types were t084, t091, and t012. Cellular invasiveness of MRSA clustered according to molecular markers (spa, SCCmec, pls). Cellular invasiveness of 59 colonizing and 16 infecting isolates was 100±37 % and 89±42 % (means ± SD) of Cowan I (p=0.48), respectively, whereas 13 comparator isolates derived from infection had a mean invasiveness of 109±34 % (p=0.35; p=0.24 between both infection groups).

Conclusion: MRSA and MSSA isolates show a different spa type distribution. Cellular invasiveness of MRSA isolates appears to be reproducible with regard to molecular markers. However, cellular invasiveness did not differ statistically significantly for colonizing versus infecting MRSA isolates in this study. This suggests that cellular invasiveness (and thus fibronectin binding capacity) may not be used as a global surrogate parameter for the virulence potential of a given isolate.