1 Department of Internal Medicine and Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, the Netherlands.
2 Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
3 Center for Computational and Integrative Biology and Gastrointestinal Unit, Massachusetts General Hospital, Harvard School of Medicine, Boston, Massachusetts, USA.
4 Broad Institute of MIT and Harvard University, Cambridge, Massachusetts, USA.