1. Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Princesa (IIS-IP), and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd); Gastroenterology Unit; Madrid Madrid Spain 28006
2. Hôpital Pellegrin; Bactériologie-Enfants; Centre Hospitalier Universitaire de Bordeaux Place Amelia-Raba-Leon Bordeaux Cedex France 33076
3. Universita di Genova; Dipartimento di Medicina Interna e Specialita Mediche; Viale Benedetto xv m6 Genova Italy 16132
4. Universita del Piemonte Orientale; Paediatric Endoscopy Units; Via Solaroli 17 Novara Italy 28100
5. McGill University Health Centre; Faculty of Medicine; Royal Victoria Hospital 687 Pine Avenue West, Room R228 Montreal QC Canada H3A 1A1
6. University of Arkansas for Medical Sciences; Department of Epidemiology; 4301 West Markham, # 820 Little Rock AR USA
7. Università degli Studi di Bologna; Dipartimento di Scienze Mediche e Chirurgiche; Policlinico S.Orsola Via Massarenti 9, Via Borgo San Pietro 137 Bologna Italy I-40138