The present invention is directed to a method of selection of purified nucleotidic sequences or polynucleotides encoding proteins or part of proteins carrying at least an essential function for the survival or the virulence of mycobacterium species by a comparative genomic analysis of the sequence of the genome of M. tuberculosis aligned on the genome sequence of M. leprae and M. tuberculosis and M. leprae marker polypeptides of nucleotides encoding the polypeptides, and methods for using the nucleotides and the encoded polypeptides are disclosed.