Localized soft-tissue death (necrosis) from prolonged blood-supply blockage. It can occur in atherosclerosis, diabetes mellitus, or decubitus ulcer, and after severe burns or frostbite. In dry gangrene, gradual blood-supply decrease turns the part discoloured and cold, then dark and dry. Treatment requires improving blood flow. Moist gangrene comes from a sudden blood-supply cutoff. Bacterial infection causes swelling, discoloration, and then a foul smell. Along with antibiotics, tissue removal may be needed to prevent spread, which can be fatal. A more virulent form, gas gangrene, is named for gas bubbles under the skin produced by a highly lethal toxin from clostridium bacteria. The wound oozes brownish, smelly pus. Infection spreads rapidly, causing death. All dead and diseased tissue must be removed and antibiotics given; an antitoxin can also be used.