Mycobacterium

Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. Over 190 species are recognized in this genus. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis (Mycobacterium tuberculosis) and leprosy (Mycobacterium leprae) in humans. Mycobacteria can colonize their hosts without the hosts showing any adverse signs. For example, billions of people around the world have asymptomatic infections of M. tuberculosis. Mycobacterial infections are notoriously difficult to treat. The organisms are hardy due to their cell wall, which is neither truly Gram negative nor positive. In addition, they are naturally resistant to a number of antibiotics that disrupt cell-wall biosynthesis, such as penicillin. Due to their unique cell wall, they can survive long exposure to acids, alkalis, detergents, oxidative bursts, lysis by complement , and many antibiotics. Most mycobacteria are susceptible to the antibiotics clarithromycin and rifamycin , but antibiotic-resistant strains have emerged. As with other bacterial pathogens, M. tuberculosis produce a number of surface and secreted proteins that contribute to its virulence. However, the mechanism by which these proteins contributes to virulence remains unknown.