Mycobacteria are abundant in soil and water but are more infamous for the diseases that they can cause. Mycobacterium tuberculosis is perhaps the most well known member of the group and is the bacterium that causes tuberculosis. However, there are other species of mycobacteria, for example Mycobacterium leprae causes leprosy, Mycobacterium bovis causes tuberculosis in cattle, Mycobacterium avium causes disease in immunocompromised people, Mycobacterium bovis Bacille Calmette-Guérin (BCG) is a strain of Mycobacterium bovis used as a vaccine and Mycobacterium smegmatis is a non-pathogenic species used in laboratory research. (Reference: Mycobacterium: Genomics and Molecular Biology ISBN: 978-1-904455-40-0)
About one-third of the world's population is infected with tuberculosis, although the infection is latent because the immune system is usually able to control the Mycobacterium tuberculosis infection. About 10% of infected people become ill with an active form of tuberculosis.
Latent tuberculosis infection is when a person is infected with Mycobacterium tuberculosis but does not have symptoms of disease. They are said to be asymptomatic. Active tuberculosis disease is the full-blown disease which, if not treated, will kill half of the patients. One in ten latent infections will progress to active tuberculosis disease. Typical symptoms of an active tuberculosis patient include weakness, fever, chest pain, respiratory insufficiency, fever and cough. Strains of Mycobacterium tuberculosis have become multidrug-resistant making the disease particularly problematic to treat. Treatment includes chemotherapy and a combination of different types of drug. Tuberculosis is spread by infectious organisms produced through coughing by patients with active tuberculosis. The air-borne particles carrying the bacteria can be inhaled by other people.
Leprosy is a disease caused by Mycobacterium leprae , a bacterium related to the species that causes tuberculosis. In medical terms, leprosy is described as a granulomatous disease of the peripheral nerves and mucosa of the upper respiratory tract. Skin lesions are the main visible symptoms. According to the World Health Organization as many as three million people have been disabled due to leprosy. In recent years, leprosy has become a problem in HIV patients using anti-retroviral drugs.
Different species of Mycobacterium cause tuberculosis, leprosy and other illneses. Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. Much scientific research is being conducted on these microorganisms. In particular much effort is being directed to the understanding of the genome of Mycobacterium with a view to developing and improving strategies for treatment. (Reference: Mycobacterium: Genomics and Molecular Biology ISBN: 978-1-904455-40-0)