Abstract: The present invention is related to double and triple attenuated mutant strains of a bacterium infecting veterinary species such as Salmonella enterica and/or (a pathogenic) Escherichia coli. The mutants of the invention contain at least one first genetic modification and at least one second genetic modification, said first modification in one or more motility genes, and said second modification in one or more genes involved in the survival or the proliferation of the pathogen in the host. The present invention further relates to live attenuated vaccines based on such mutants for preventing amongst others Salmonellosis and/or an infection by an E. coli pathogen in a veterinary species.

Abstract: The present invention relates to attenuated guaB deletion mutants of a bacterium infecting veterinary species, more in particular Salmonella enterica, to their use and production. The present invention further relates to live attenuated vaccines based on such mutants for preventing bacterial infections, and more in particular Salmonellosis, in a veterinary species, more in particular poultry.