1. Institute for Food Safety and Hygiene, University of Zurich; Winterthurerstrasse 272 CH-8057 Zurich Switzerland
2. Laboratory for Study and Research on Food Quality and Processes (LERQAP), AFSSA (French Food Safety Agency); 23 Av. du Général De Gaulle Fr-94706 Maisons-Alfort France
3. Food-Borne Zoonoses Unit, Department of Food Safety and Veterinary Public Health; Istituto Superiore di Sanità; 00161 Rome Italy
4. National Reference Laboratory for Escherichia coli (NRL-E.coli), Federal Institute for Risk Assessment (BfR); Diedersdorfer Weg 1 D-12277 Berlin Germany