Humans are exposed to a variety of environmental mycobacteria (EM), and most children
are inoculated with live Bacille Calmette-Guérin (BCG) vaccine. In addition, most of the
world's population is occasionally exposed to human-borne mycobacterial species, which
are less abundant but more virulent. Although rarely pathogenic, mildly virulent
mycobacteria, including BCG and most EM, may cause a variety of clinical diseases.
Mycobacterium tuberculosis, M. leprae, and EM M. ulcerans are more virulent, causing …