A mutated Bordetella strain comprising at least: (a) a mutated pertussis toxin (ptx) gene, in which the S1 portion of said mutated ptx gene encodes a toxin, which is enzymatically inactive but not immunologically affected, (b ) a deleted dermonecrotic gene (dnt) or a mutated dnt gene, where said mutated dnt gene is mutated by point mutation or by insertion of a genetic sequence or a plasmid that disrupts the open reading frame of the dnt gene, and wherein said gene The mutated dnt encodes an enzymatically inhibited DNT protein, and (c) an E. coli ampG gene that replaces the Bordetella ampG gene, where said strain expresses less than 5% residual TCT activity.Una cepa de Bordetella mutada que comprende al menos: (a) un gen de toxina pertussis (ptx) mutado, en el cual la porción S1 de dicho gen ptx mutado codifica una toxina, que es enzimáticamente inactiva pero no está afectada inmunológicamente, (b) un gen dermonecrótico (dnt) eliminado o un gen dnt mutado, donde dicho gen dnt mutado está mutado por mutación puntual o por inserción de una secuencia genética o un plásmido que interrumpe el marco de lectura abierto del gen dnt, y en donde dicho gen dnt mutado codifica una proteína DNT enzimáticamente inhibida, y (c) un gen ampG de E. coli que sustituye el gen ampG de Bordetella, donde dicha cepa expresa menos de 5% de actividad de TCT residual.
