1. 1Labocor, S. L. Poligono Industrial La Mina Nave, 38 Colmenar Viejo, Madrid, Spain
2. 2Faculty of Veterinary Medicine, Utrecht University, Yalelaan 8, 3584 CM Utrecht, The Netherlands
3. 3Department of Microbiology, Free University, Amsterdam, De Boelelaan 1117, 1007 MB Amsterdam, The Netherlands
4. 4RIKILT, Institute of Food Safety, P.O. Box 230, 6700 AE Wageningen, The Netherlands