Clinically, Mycobacterium szulgai infection is indistinguishable from classic infection with M. tuberculosis . Clinical distinction between infection with M. szulgai and tuberculosis and other nontuber-culous mycobacterial infections is not possible.
Definitive diagnosis requires isolation and identification of the causative agent.
On acid-fast stain of the organism, M. szulgai may exhibit some banding, such as that seen with M. kansasii . A unique feature of pigment production in M. szulgai is the temperature-dependent nature of this phenomenon. This places the organism in the Runyon group II classification of mycobacteria. Another characteristic of M. szulgai is relatively rapid growth in culture, with production of smooth or rough colonies on solid media within 2 weeks. Biochemical tests will help further differentiate the organism.