a procedure for obtaining the expression of a membrane antigen of a pathogen against which an live oral vaccine development is desirable on the surface of a negative gram bacteria to which virulence is attenuated , or another bacteria or other gram negative or positive bacteria with probiotic features which are compatible with the proposed expression system and that can be used as a live oral vaccine , wherein a plasmid is constructed and obtained based on the structure of pet family plasmids , with tbpb gene incorporated under the control of t7 promoter or another equivalent one , with the addition of a metabolic marker in the plasmid vector , previously cloned with its own promoter , inactivating , at the same time , the antibiotic resistance . in addition , recombinant microorganism such as an attenuated vaccine strain against group b meningitis with immunizing and protective properties against infection by neisseria meningitidis .