1. Department of Food Science and Technology, University of Reading, Reading RG6 6AP,1
2. Culture Collection, Department of Clinical Bacteriology, University of Göteborg, Göteborg, Sweden2
3. Department of Animal and Microbial Sciences, University of Reading, Reading RG6 6AJ,3 and
4. SAC Veterinary Science Division, Inverness, IV2 4JZ,4 United Kingdom, and