1. Division of Digestive Surgery, University Hospitals of Geneva, Genève, Switzerland
2. Department of Global Public Health, Karolinska Institutet, Stockholm, Sweden
3. Division of Clinical Epidemiology, University Hospitals of Geneva, Genève, Switzerland
4. Division of Gastroenterology, University Hospitals of Geneva, Genève, Switzerland
5. Laboratory of Bacteriology, University Hospitals of Geneva, Genève, Switzerland