Mycobacterium bovis

Mycobacterium bovis (M. bovis) is a slow-growing (16- to 20-hour generation time) aerobic bacterium and the causative agent of tuberculosis in cattle (known as bovine TB). It is related to Mycobacterium tuberculosis, the bacterium which causes tuberculosis in humans. M. bovis can jump the species barrier and cause tuberculosis-like infection in humans and other mammals. The bacteria are curved or straight rods (Mycobacterium Family). They sometimes form filaments, which fragment into bacilli or cocci once disturbed. In tissues they form slender rods, straight or curved, or club-shaped. Short, relatively plump bacilli (rods) in tissue smears, large slender beaded rods in culture. They have no flagella or fimbria, no capsule. Mycobacterium tuberculosis group bacteria are 1.0 - 4.0 µm long by 0.2 - 0.3 µm wide in tissues. In culture they may appear as cocci, or as bacilli up to 6 - 8 µm long . The bacteria stain Gram-positive, acid-fast. The cell wall contains as high as 60% lipid, giving the mycobacteria their hydrophobic characteristics, slow growth and resistance to desiccation, disinfectants, acids and antibodies. (Mycobacterium Family). They are not easy to stain with analine dyes; although they are Gram positive it may not be easy to confirm this.Ziehl-Neelsen staining results in stain pink with hot carbol fuscin and then resist decolourisation with 3 percent hydrochloric acid in 95% alcohol (i.e. they are acid-alcohol fast); following washing, the slide is counterstained with e.g. methylene blue.