1. Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, B-9820 Merelbeke,1 and
2. Delft Diagnostic Laboratory, 2600 GA Delft, The Netherlands2
3. Laboratory of Microbiology, Faculty of Pharmaceutical Sciences, Ghent University, B-9000 Ghent,3 Belgium, and