1. Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA1
2. Biocentrum, Bldg 301, Technical University of Denmark, DK-2800 Lyngby, Denmark2
3. Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA3
4. Department of Gastrointestinal Infections, Statens Serum Institut, DK 2300 Copenhagen, Denmark4
5. Department of Microbiology, University of Virginia, Health Sciences Center, Charlottesville, VA 22908, USA5