1. Institut de Veille Sanitaire, Saint-Maurice, France
2. Institut Pasteur, National Reference Centre and World Health Organisation Collaborating Centre for Listeria, Paris, France
3. Institut Pasteur, Biology of Infection Unit, Paris, France
4. Paris Descartes University, Necker-Enfants malades University Hospital, Division of Infectious Diseases and Tropical Medicine, Paris, France
5. Institut National de la Sante et de la Recherche Medicale, Inserm U1117, Paris, France