Mycobacterium avium complex is a group of mycobacteria comprising Mycobacterium intracellulare and Mycobacterium avium (No mention of M. chimera in ref) that are commonly grouped together because they infect humans together; this group, in turn, is part of the group of nontuberculous mycobacteria. These bacteria cause disease in humans called Mycobacterium avium-intracellulare infection or Mycobacterium avium complex infection. In the Runyon classification, all three are nonchromogens. They can be differentiated from M. tuberculosis and each other by commercially available DNA probes.:245 They are characterized as Gram-positive, nonmotile, acid-fast, short to long rods. Colony characteristics Physiology Differential characteristics M. intracellulare type strains include ATCC 13950, CCUG 28005, CIP 104243, DSM 43223, JCM 6384, and NCTC 13025. M. avium type strains include ATCC 25291, DSM 44156, and TMC 724.