1. Department of Veterinary Sciences, School of Agriculture and Veterinary Medicine, University of Turin, 10095 Grugliasco, Italy
2. Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
3. Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI 53706, USA
4. Division of Epidemiology and Public Health, School of Medicine, University of Nottingham, Nottingham NG7 2UH, UK
5. Department of Agrifood, Environmental and Animal Science, University of Udine, 33100 Udine, Italy