1. The Bateson Centre and Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
2. The Florey Institute for Host-Pathogen Interactions, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
3. Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, Utrecht 3584 CX, The Netherlands