Some bacteria are harmless, but some can be deadly.
In fact, TB was one of the leading causes of death in the United States until the development in the 1940s of antibiotics that could be used to effectively treat it. Since then the disease declined consistently in the United States until the mid-1980s. The latest concern worldwide is that new strains of TB have developed that are resistant to the antibiotics used so successfully in the past. These resistant strains pose a public health hazard for many countries around the globe. TB is a disease caused by the body's attempt to control the multiplying and spreading of the bacterium Mycobacterium tuberculosis.