Tuberculosis or TB is caused by acid fast bacteria (AFB) belonging to the genus Mycobacterium. In human TB is caused by Mycobacterium tuberculosis species and in cattles by Mycobacterium bovis. Both these species differ in only one aminoacid at position 57 (His in Mycobacterium bovis) which elicits difference in the response to the drug administered. This disease is treated using anti-tuberculosis drugs - rifampicin, isoniasid, ethambutol and pyrazinamide. In these drugs, pyrazinamide is a special drug in that it is the only available drug in the market with proven efficiency which acts on semi dormant bacteria. Other Mycobacterium species Mycobacterium leprae causes leprosy.