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What are Anthrax Bacteria?

written by: •edited by: Paul Arnold•updated: 6/14/2010

Anthrax is the name of the disease caused by anthrax bacteria, though the correct name for the bacterium is Bacillus anthracis. There's more on this and other interesting facts about anthrax in this article.

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    The Shape of Anthrax Bacteria

    B anthracis diagram en Bacillus anthracis is a large rod-shaped spore-forming Gram-positive bacterium. The sizes of the bacteria range from 3-9 micrometres in length and 1-1.2 micrometres in width. They were the first bacterium to be shown to cause disease. In 1877 the German physician Robert Koch isolated Bacillus anthracis and grew it in pure culture, demonstrating its ability to form endospores. He produced anthrax by injecting the microbe into animals.

    Bacillus anthracis are soil-based microbes that usually exist in the endospore state. These spores are particularly robust in that they can survive for years, sometimes decades under extremes of temperature, or harsh chemical environments, and on substrates where there are low levels of nutrients.

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    Bacillus anthracis Pathogenesis

    The potency of anthrax bacteria are due to their virulence factors which are coded for by two plasmids pX01 and pX02.

    The pX01 plasmid codes for three toxins that can cause haemorrhage, necrosis, and oedema. The pX02 plasmid encodes three genes that are involved in the production of the polyglutamyl capsule that inhibits host phagocytosis of the vegetative form of the bacterium. Both plasmids are needed for the bacteria to be able to cause anthrax. If either are inhibited the bacteria are said to be attenuated. Infection with Bacillus anthracis occurs after a spore has either managed to get in via a break or cut in the skin or via mucosa.

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    Anthrax is a serious, sometimes fatal disease of animals and humans. It is not passed directly from one infected person or animal coming into contact with another; it is spread by spores. The illness can be treated by vaccines, and it sometimes responds to antibiotics.

    Cutaneous anthrax

    The most common form of anthrax is cutaneous anthrax, which accounts for about 95% of all cases. The spores can enter skin cuts, and people who work with dead animals, such as those in abattoirs are at most risk. The spores cause the formation of black necrotic lesions, and if left untreated they can cause blood poisoning.

    Inhalation anthrax

    Caused by the inhalation of endospores by humans or animals. It is a disease of the lungs and the spores are usually picked up by macrophages, and transported to the lymph nodes in the chest cavity. But the spores germinate to produce active bacteria which split the macrophages and release the toxins into the bloodstream that cause haemorrhaging and tissue decay.

    Gastrointestinal anthrax

    Caused when endospores enter the gastrointestinal tract, usually from the consumption of infected meat.

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    Deliberate Infection

    Bacillus anthracis has been used by terrorists, various armed forces around the world, and perhaps most famously in the 2001 anthrax attacks in the United States, where letters containing anthrax spores were sent to media outlets and two Democratic senators. Five people were killed, and 17 injured. The FBI's prime suspect was identified in 2008. He was the late Dr Bruce Ivins, who worked at the army biological weapons laboratory in Fort Detrick, Maryland.

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    Image Credit

    Permission granted under GNU Free Documentation License