Chronic pulmonary disease due to atypical mycobacterial infections.

The recognition of tuberculosis or tuberculosis1ike disease in a wide variety of animals preceded the discovery of the tubercle bacillus by many years. Soon after the discovery of the tubercle bacillus it became evident that tuberculosis in various species was caused by organisms closely related to human tubercle bacilli but differing from them in specific and consistent ways. The existence of acid-fast bacilli producing pulmonary disease in humans, but differing from 111ycobacterium tuberculosis in cultural characteristics and in failure to produce progressive' disease in the guinea pig, has been reported sporadically for many years, but with increasing frequency recently (1-13). These bacilli differ from certain other acid-fast organisms such as 111. ulcerans and M, balnei (which have been reported to produce cutaneous lesions in humans occasionally), and also from 111. tuberculosis, in their ability to grow at room temperature (13). They differ from M, fortuitum, another lesionproducing Mycobacterium which also grows at room temperature, as they differ from nonpathogenic saprophytic acid-fact bacilli in that they require at least six to twenty-one days to grow out on culture while the latter two grow in three days or less (13, 14). Three different types of atypical mycobacteria have been described and have been classified according to pigment production when exposed to light (15).