Rapid-growing Mycobacteria comprise approximately half of the currently known mycobacterial species and are divided into five major groups: Mycobacterium fortuitum, M. chelonae/M. abscessus complex, M. smegmatis, M. mucogenicum, and the pigmented rapidly-growing Mycobacteria. In clinical practice, the most commonly encountered species are M. fortuitum and M. chelonae/abscessus.