Tuberculosis is a highly contagious airborne disease caused by the bacteria ‘’Mycobacterium tuberculosis”. Mycobacterium is an obligate pathogenic bacteria and the causative agent of tuberculosis. M. tuberculosis is highly aerobic and requires high levels of oxygen. Mycobacteria are non-motile, non-capsulated and non-sporing. It was first discovered by Robert Koch, in 1882.M. tuberculosis has an unusual, waxy coating on its cell surface, due to the presence of mycolic acid, which makes the cells unaffected to Gram staining. M. tuberculosis can appear Gram- positive and Gram- negative in clinical settings. The acid-fast stain, Ziehl-Nelsen stain or by fluorescent dyes is used preferably. In liquid cultures they form a mold -like pellicle, hence the name “Mycobacteria”, meaning fungus like bacteria. The most frequently used diagnostic methods for tuberculosis are the tuberculin skin test, acid-fast stain, and chest radiographs.