Abstract
Mycobacterium nonchromogenicum, M. terrae and M. triviale are regarded as nonpathogens belonging belonging to the Group III of Runyon. Several authors have reported that these be differentiable from each other, while it is also true that these resemble each other and form a complex, M. nonchromogenicum complexi. Recently, several papers appeared, informing that these organisms caused infections in human. It is noteworthy that there are papers reporting that all these three have caused arthritisl. It is desired to detect a simple method for identifying and differentiating these organisms from other slowly growing mycobacteria.
Previously, Tsukamura and Tsukamura reported that M. nonchromogenicum and M. terrae could grow on a modified Sauton agar medium containing 0. 1% NaNO2 after incubation for 4 weeks, and Abbott et al. reported that M. terrae and M. triviale grew on oleic acid-albumin agar medium containing nitrite. However, there were a considerable number of strains that did not grow on these media.
In the present study, the present authors have presented a selective medium for the M. nonchromogenicum complex. It is an Ogawa egg medium containing 0.2% NaNO2. The nitrite Ogawa egg medium and the Ogawa egg medium (control) were inoculated with one loopful of test organisms, and growth on these media were observed after incubation at 37°C for 2 weeks. It has been shown that all strains tested belonging to the M. nonchromogenicum complex grew on the nitrite-Ogawa egg medium, while other slowly growing mycobacteria did not grow on it (Table 1).
