1. Institute of Medical Microbiology and Hygiene, University of Regensburg, D-93053 Regensburg
2. National Escherichia coli-Shigella Reference Laboratory, Centers for Disease Control and Prevention, Atlanta, Georgia 30333
3. Department of Biology, Yarmouk University, Irbid, Jordan
4. State Laboratory for Veterinary Diagnostics, D-59821 Arnsberg
5. Institute for Hygiene, University of Münster, D-48149 Münster, Germany