1. Department of Surgery, VU University Medical Centre, Amsterdam, the Netherlands
2. Department of Surgery, Spaarne Gasthuis, Haarlem/Hoofddorp, the Netherlands
3. Department of Medical Microbiology and Infection Control, VU University Medical Centre, Amsterdam, the Netherlands
4. Department of Epidemiology and Biostatistics, VU University Medical Centre, Amsterdam, the Netherlands
5. VU University Medical Centre Amsterdam
6. Spaarne Gasthuis, Haarlem/Hoofddorp
7. MC Slotervaart, Amsterdam
8. Zaans Medisch Centrum, Zaandam
9. Westfries Gasthuis, Hoorn
10. IS-Diagnostics, Amsterdam