1. Robert Koch Institute, Department of Infectious Disease Epidemiology, Berlin, Germany
2. Istituto Superiore di Sanità, Department of Food Safety, Nutrition and Veterinary Public Health, Rome, Italy
3. Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise G. Caporale, National Reference Laboratory for Listeria monocytogenes, Teramo, Italy
4. European Food Safety Authority, Parma, Italy
5. Statens Serum Institut, Infectious Disease Epidemiology and Prevention, Copenhagen, Denmark