1 Department of Veterinary Medicine, University of Perugia, Perugia, Italy; Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
2 Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
3 Istituto Zooprofilattico dell'Umbria e delle Marche, Perugia, Italy.
4 Clinic for Swine, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
5 Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland. Electronic address: vincent.perreten@vetsuisse.unibe.ch.