Infections due to atypical mycobacteria appear to be growing in importance. In part, this may be due to enhanced recognition as tuberculosis recedes and laboratory identification improves. In a larger part, however, it is due to real increase in the incidence of infections and disease and to our appreciation of a wide spectrum of manifestations of common problems as in pulmonary disease due to MAIS, as well as newer diseases in unexpected places such as infected prostheses due to M. fortuitum complex. These organisms generally conform to a role as opportunists. The average case occurs when some type of host compromise is present and the disease course is chronic and indolent. However, otherwise healthy host can be affected and severe and progressive diseases also do occur. These mycobacteria are all more resistant to antituberculosis chemotherapy than is M. tuberculosis. Effective therapy has been found for some, especially M. kansaii. For most others, more predictable, effective, and safe therapy is greatly needed.
