Tuberculosis (TB) is at least as old as mankind and the history of this disease is intertwined with the history of civilization. Like no other illness, TB has taken its toll of human life over the millennia and has spread worldwide. Due to its worldwide incidence and prevalence, it has been referred to as "White Plague".

Robert Koch first described the tubercle bacillus in 1882.They are slender, rod-shaped, aerobic, non-spore forming and non-motile bacteria. One of the most striking feature of these bacilli is the acid-fastness i.e: difficult to stain. But once stained, they strongly retain the dye, which is not removed even by acid alcohol. These can also be stained with fluorescent dyes. These are 2 - 4 micrometer long and 0.2 -0.5 micrometer wide in size.

TB is an infection, often of long term duration caused by 2 species of family Mycobacteriaceae, Order Actinomycetales-- M. tuberculosis and M. bovis which is the main cause of TB in humans, transmitted through unpasteurized milk. These mycobacteria can cause disease in virtually every organ system in the body predominantly in the lungs. The disease is characterized histologically by granuloma formation.