ABSTRACT
Nonchrото genic mycobacteria (group III) are the most significant cluster of NTM producing human disease. Two closely related species, M. avium and M. intracellulare, have been lumped together taxonomically as M. avium complex (MAC). These organisms historically were associated with disease mainly in the southeastern United States. How ever, over the past quarter-century, MAC cases have been seen in apparently increasing numbers from all of the continental states, Alaska, and Hawaii. Less frequent pathogens of this group include M. xenopi and M. malmoense.
