Mycobacterium bovis BCG Pasteur 1173P2

Mycobacterium bovis (strain BCG / Pasteur 1173P2) is a major cause of tuberculosis in a range of animal species and man. It was also the progenitor of the M.bovis bacillus Calmette-Guerin (BCG) strain used as a vaccine against tuberculosis. BCG was derived by serial passages on slices of potato imbibed with glycerol for 13 years. Once the strain was proven to no longer be virulent it was disseminated and different laboratories continued this passaging. This particular strain, M.bovis BCG 1173P2, has been passaged 1,173 times at the Pasteur Institute Paris, France. Different centers have different stocks of BCG, which have continued to change with time, accumulating insertion, deletion and single nucleotide polymorphisms. M.bovis BCG 1173P2 has two independent tandem duplications, DU1 and DU2; DU1 is found only in this Pasteur strain whereas different forms of DU2 are found in different BCG strains. A genealogy of BCG strains is presented in the paper as well as transcriptomic analysis of several different early and late BCG strains. It is suggested that the strains currently used for vaccine production are not optimal and that an earlier derived strain, such as those still used in Japan, might make a better vaccine, a suggestion that the authors recommend should be tested in clinical trials.