Mycobacterium bovis skin infection

The bovine tubercle bacillus must firstly be placed in context among the other agents of tuberculosis. In the early decades of the twentieth century, bacteriologists recognized four varieties of tubercle bacilli (human, bovine, avian and cold-blooded), depending on the life forms from which they were isolated. By the middle of the century, only two varieties were still recognized as agents of human and bovine tuberculosis (TB), namely Mycobacterium tuberculosis and M. bovis, respectively. In the 1960s, another TB agent was isolated in Africa, and named M. africanum, but this was later seen to include two varieties. Finally, in the 1980s it was found that two varieties of M. tuberculosis itself could also be distinguished: classical and Asian. This group of organisms, to which M. microti, M. pinnipedii, M. canettii, and M. caprae were later added, is denominated the M. tuberculosis complex . The bacillus Calmette-Guérin (BCG) was classed with M. bovis. The avian and cold-blooded tubercle bacilli were then classified separately: the first, that includes M. avium and M. intracellulare, is included in the M. avium complex (together with M. lepraemurium and M. paratuberculosis), while the second includes M. chelonae and M. fortuitum.