What is "bacillus anthracis"

malignant \ma*lig"nant\, a. [L. malignans, -antis, p. pr. of malignare, malignari, to do or make maliciously. See Malign, and cf. Benignant.]

1. Disposed to do harm, inflict suffering, or cause distress; actuated by extreme malevolence or enmity; virulently inimical; bent on evil; malicious.

   A malignant and a turbaned Turk.
   --Shak.

2. Characterized or caused by evil intentions; pernicious. ``Malignant care.''
   --Macaulay.

   Some malignant power upon my life.
   --Shak.

   Something deleterious and malignant as his touch.
   --Hawthorne.

3. (Med.) Tending to produce death; threatening a fatal issue; virulent; as, malignant diphtheria.

   Malignant pustule (Med.), a very contagious disease produced by infection of subcutaneous tissues with the bacterium Bacillus anthracis. It is transmitted to man from animals and is characterized by the formation, at the point of reception of the infection, of a vesicle or pustule which first enlarges and then breaks down into an unhealthy ulcer. It is marked by profound exhaustion and often fatal. The disease in animals is called charbon; in man it is called cutaneous anthrax, and formerly was sometimes called simply anthrax.

Anthrax \An"thrax\, n. [L., fr. Gr. ? coal, carbuncle.]

1. (Med.)

   1. A carbuncle.

   2. A malignant pustule.

2. (Biol.) A microscopic, bacterial organism ( Bacillus anthracis), resembling transparent rods. [See Illust. under Bacillus.]

3. An infectious disease of cattle and sheep. It is ascribed to the presence of a rod-shaped gram-positive bacterium ( Bacillus anthracis), the spores of which constitute the contagious matter. It may be transmitted to man by inoculation. The spleen becomes greatly enlarged and filled with bacteria. Called also splenic fever.

Anthrax vaccine \An"thrax vac"cine\ (Veter.) A fluid vaccine obtained by growing a bacterium ( Bacillus anthracis, formerly Bacterium anthracis) in beef broth. It is used to immunize animals, esp. cattle. [Webster 1913 Suppl.] ||

Bacillus anthracis is the etiologic agent of anthrax—a common disease of livestock and, occasionally, of humans—and the only obligate pathogen within the genus Bacillus. B. anthracis is a Gram-positive, endospore-forming, rod-shaped bacterium, with a width of 1.0–1.2 µm and a length of 3–5 µm. It can be grown in an ordinary nutrient medium under aerobic or anaerobic conditions. It is one of few bacteria known to synthesize a protein capsule (poly-D-gamma-glutamic acid). Like Bordetella pertussis, it forms a calmodulin-dependent adenylate cyclase exotoxin known as Anthrax edema factor, along with anthrax lethal factor. It bears close genotypical and phenotypical resemblance to Bacillus cereus and Bacillus thuringiensis. All three species share cellular dimensions and morphology. All form oval spores located centrally in an unswollen sporangium. B. anthracis spores, in particular, are highly resilient, surviving extremes of temperature, low-nutrient environments, and harsh chemical treatment over decades or centuries.

The spore is a dehydrated cell with thick walls and additional layers that form inside the cell membrane. It can remain inactive for many years, but if it comes into a favorable environment, it begins to grow again. It is sometimes called an endospore because it initially develops inside the rod-shaped form. Features such as the location within the rod, the size and shape of the endospore, and whether or not it causes the wall of the rod to bulge out are characteristic of particular species of Bacillus. Depending upon the species, the endospores are round, oval, or occasionally cylindrical. They are highly refractile and contain dipicolinic acid. Electron micrograph sections show they have a thin outer spore coat, a thick spore cortex, and an inner spore membrane surrounding the spore contents. The spores resist heat, drying, and many disinfectants (including 95% ethanol). Because of these attributes, B. anthracis spores are extraordinarily well-suited to use (in powdered and aerosol form) as biological weapons. Such weaponization has been accomplished in the past by at least five state bioweapons programs—those of the United Kingdom, Japan, the United States, Russia, and Iraq—and has been attempted by several others.