Abstract:

The genus Mycobacterium comprises more than 170 characterized species that are nonmotile, nonspore-forming, aerobic, acid-fast bacilli measuring 0.2 to 0.6 × 1 to 10 µm. They are conveniently separated into slow-growing (> 7 d for colony formation) and rapid-growing (< 7 d for colony formation) species. Many species are capable of causing disease in humans.¹ The two most recognized pathogens in this group include Mycobacterium tuberculosis and Mycobacterium leprae, the causative agents of tuberculosis and Hansen’s disease (leprosy), respectively. However, there has been an increase globally in the incidence of disease and death caused by opportunistic mycobacteria (also called nontuberculous mycobacteria or NTM), which are ubiquitous in nature and resistant to many commonly used antibiotics.² In the genus Mycobacterium, the most important environmental opportunistic pathogens include M. avium and M. intracellulare, M. kansasii, M. marinum, M. xenopi, and M. simiae. A number of the rapid-growing mycobacterial species (e.g., M. fortuitum, M. chelonae, and M. abscessus) have been found in cases of nosocomial infections.³ Some of the common hosts and environmental reservoirs of Mycobacteria are shown in Table 9272:1.