1. Department of Infectious Disease Epidemiology, Robert Koch Institute, Berlin, Germany.
2. National Reference Centre for Salmonella and Other Pathogens, Robert Koch Institute, Wernigerode, Germany.
3. Exomed, Berlin, Germany.
4. Department of Medical Microbiology, Institute for Hygiene and the Environment, Hamburg, Germany.
5. Institute for Hygiene and Public Health, University of Bonn, Bonn, Germany.