Abstract
Department of Poultry, Fish, and Fur Animals, Danish Veterinary Laboratory, Hangøvej 2, DK-8200 Aarhus N, *International Escherichia and Klebsiella Center (WHO), Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen S, †Department of Microbiology, Danish Veterinary Laboratory, Bulowsvej 27, DK-1790 Copenhagen V and ‡Department of Virology, Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen S, Denmark
Corresponding author: Dr D.D. Bang (e-mail: ddb{at}svs.dk ).