World J Gastroenterol 2016 January 7; 22(1): 145-154.Patrizia Caligiuri, Giancarlo Icardi, Department of Health Sciences, University of Genoa, 16132 Genoa, ItalyRita Cerruti, Giancarlo Icardi, Bianca Bruzzone, Hygiene Unit, I.R.C.C.S. A.O.U. San Martino-IST, 16132 Genoa, ItalyAuthor contributions: Caligiuri P, Cerruti R, Icardi G and Bruzzone B analyzed the literature and wrote this review. Conflict-of-interest statement :The authors…