Relationship between photochromogenicity and test temperature in mycobacteria.

Although it has been recommended that photochromogenicity of mycobacteria should be tested after incubation at 25 to 30 degrees C for 2 weeks (Wayne et al., Int. J. Syst. Bacteriol. 24:412-419, 1974), our results indicate that photochromogenicity should be determined at 37 degrees C in the dark and under continuous exposure to light for 2 weeks. The test at 37 degrees C gives more stable results for Mycobacterium kansasii, Mycobacterium marinum and Mycobacterium szulgai.