Which of the following Mycobacterium spp. would be most likely to grow on a MacConkey agar plate?

The Mycobacterium chelonae-fortuitum complex is notable for its ability to grow on MacConkey agar, which is a selective medium for Gram-negative bacteria that contains bile salts and crystal violet to inhibit the growth of Gram-positive organisms. While Mycobacterium species are primarily known for being relatively slow-growing and often challenging to culture, the M. chelonae-fortuitum complex is considered more versatile in the laboratory setting.

This complex includes species that are more often associated with environmental sources and can exhibit biofilm formation and rapid growth characteristics under certain laboratory conditions, allowing them to thrive on this type of medium. Other species mentioned, such as M. ulcerans, M. marinum, and the M. avium-intracellulare complex, typically do not grow on MacConkey agar, as they prefer different growth media that provide specific nutrients conducive to their growth and are generally categorized as slower-growing or more fastidious Mycobacterium species.