1. Department of Microbiology, Swedish University of Agricultural Sciences, Box 7025, SE-75007 Uppsala, Sweden1
2. Department of Infectious Diseases and Medical Microbiology, Lund University, Sölvegatan 23, SE-22362 Lund, Sweden2
3. Department of Microbiology, Pathology and Immunology, Huddinge University Hospital, Karolinska Institutet, SE-14186 Huddinge, Sweden3