1. Department of Molecular Microbiology and Microbiology; Tufts University, School of Medicine; Boston MA 02111
2. Institute of Veterinary Bacteriology; University of Berne; Laenggassstrasse 122 3012 Berne Switzerland
3. Food Directorate, Health Canada, Sir Frederick Banting Research Centre; Address Locator 2204A1, Tunney's Pasture Ottawa Ontario K1A 0L2 Canada