Mycobacterium

            Mycobacteria are slender rods, sometimes show branching filamentous forms. In liquid cultures they form a mold-like pellicle, hence the name mycobacteria, meaning fungus-like bacteria. They do not stain readily, but once stained resist decolurisation with dilute mineral acids, therfore they are called “Acid Fast Bacilli” or AFB. They are aerobic, nonmotile, noncapsulated, nonsporing. Generally slow growth, obligate parasites, opportunistic pathogens and saprophytes.