Abstract: The present invention refers to a method for the production of live attenuated bacterial strains, suitable as vaccine candidates, comprising the steps of: A. providing a bacterial strain capable of expressing glutamate racemase and possibly D-amino acid transaminase and comprising a peptidoglycan cell wall, and B. inactivating the gene or genes encoding for the glutamate racemase enzyme and, if needed, the gene or genes encoding for the enzyme D-amino acid transaminase in such way that the bacterial strain is no longer capable of expressing a functional glutamate racemase and/or a functional D-amino acid transaminase; wherein the inactivation of said genes causes said bacterial strain to be auxotrophic for D-glutamate.

Abstract: The present invention refers to a method for the production of live attenuated bacterial strains, suitable as vaccine candidates, comprising the steps of: A. providing a bacterial strain capable of expressing glutamate racemase and possibly D-amino acid transaminase and comprising a peptidoglycan cell wail, and B. inactivating the gene or genes encoding for the glutamate racemase enzyme and, if needed, the gene or genes encoding for the enzyme D-amino acid transaminase in such way that the bacterial strain is no longer capable of expressing a functional glutamate racemase and/or a functional D-amino acid transaminase; wherein the inactivation of said genes causes said bacterial strain to be auxotrophic for D-glutamate.