Association of nine pathobionts with periodontitis in four South American and European countries oleh Gerard Àlvarez, Alexandre Arredondo, Sergio Isabal, Wim Teughels, Isabelle Laleman, María José Contreras, Lorena Isbej, Enrique Huapaya, Gerardo Mendoza, Carolina Mor, José Nart, Vanessa Blanc, Rubén León