1. 1Public Health England Gastrointestinal Bacteria Reference Unit, 61 Colindale Avenue, London, NW9 5EQ, UK
2. 2National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Gastrointestinal Infections at University of Liverpool, Liverpool, UK
3. 3Statens Serum Institut, 5 Artillerivej, DK-2300, Copenhagen S, Denmark
4. 4Maisons-Alfort Laboratory for Food Safety, Salmonella and Listeria Unit, University of Paris-Est, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), Maisons-Alfort, France
5. 5School of Biological Sciences, The University of Aberdeen, Cruickshank Building. St Machar Drive, Aberdeen, Scotland, AB24 3UU, UK
6. 6Institute of Complex Systems and Mathematical Biology, SUPA, School of Natural and Computing Sciences, University of Aberdeen, Aberdeen, Scotland, UK
7. 7Institut Pasteur, Paris, France
8. 8School of Medicine and Dentistry, The University of Aberdeen, Foresterhill, Aberdeen, Scotland, AB25 2ZD, UK