Documented evolution of the four M. bovis BCG strains currently licensed to produce for use in humans by the World Health Organization. The arrows indicate the chronologic evolution of Japanese and Danish strains from the original BCG Pasteur 1921 and Glaxo strain from Danish 1331. Boxes indicate occurrence of deletions of the genome during derivation of BCG. The year of derivation are indicated by (). The number in the arrows is the in vitro passages documented to have occurred during the evolution of BCG Pasteur and daughter strains since 1921 to the freeze dried of BCG in 60th.
Castañón-Arreola and López-Vidal Annals of Clinical Microbiology and Antimicrobials 2004 3:10 doi:10.1186/1476-0711-3-10