1. 1Department of Poultry, Fish and Fur Animals, Danish Veterinary Institute, Hangoevej 2, DK-8200, Aarhus N, Denmark
2. 2Department of Bacteriology, Mycology and Parasitology, Statens Serum Institut, Artillerivej 5, DK-2300, Copenhagen S, Denmark
3. 3The International Escherichia and Klebsiella Centre (WHO), Statens Serum Institut, Artillerivej 5, DK-2300, Copenhagen S, Denmark