M tuberculosis is transmitted from person to person by the airborne route.
M tuberculosis tends to invade the host and cause disease, whereas NTM colonize with infrequent tissue invasion. Many drugs effective against M tuberculosis are ineffective for NTM infections. At first glance, it seems paradoxical that M tuberculosis, infecting more than a billion people worldwide, rarely causes infection in the severely immunocompromised host undergoing bone marrow transplantation. In developed countries, where bone marrow transplantation is done often, the incidence of tuberculosis is low. In comparison, Ip et al.