The invention concerns recombinant vectors replicated in mycobacteria, a set of sequences coding for exported polypeptides detected by fusion with alkaline phosphatase, in particular one polypeptide, called DP428, of about 12 kD corresponding to an exported protein found in mycobacteria belonging to the Mycobacterium tuberculosis complex. The invention also concerns methods and kits for detecting in vitro the presence of a mycobacterium and in particular a mycobacterium belonging to the Mycobacterium tuberculosis complex in a biological sample using said polypeptides, their fragments or polynucleotides coding for the latter. The invention also concerns immunogenic or vaccine compositions for preventing and/or treating infections caused by mycobacteria and in particular a mycobacterium belonging to said complex, particularly tuberculosis.