Mycobacterium tuberculosis causes tuberculosis, the principal chronic bacterial disease in humans and causes more deaths than any other infectious agent worldwide. Over one third of the world's population is thought to be affected by tuberculosis, causing approximately eight million new cases and two million deaths each year.
The nonmotile, aerobic bacilli of M.tuberculosis multiply in the pulmonary epithelium or in macrophages within the alveoli following inhalation. Bacilli that are not killed by the host immune system can be spread by the blood stream to other parts of the body, but in the majority of cases the infection becomes arrested and the patient is unaware they were even infected. However, approximately ten percent of the arrested infections further develop to clinical disease in later life.
Treatment. Several drugs are currently available to treat tuberculosis, however due to the possibility of of drug resistance emerging during treatment, multiple drug therapy is employed. The first choice drugs in current use are isoniazid, rifampin, ethambutol, streptomycin, and pyrazinamide.
Vaccines. An effective vaccine against tuberculosis has been available since the early twentieth century. The vaccine is produced from an attenuated strain of Mycobacterium bovis, called Bacille Calmette-Guerin (BCG). The vaccine is about eighty percent effective against serious forms of tuberculosis and has been used en mass by the World Health Organisation and several European countries.