Bacillus anthracis causes the well-known animal disease anthrax and was discovered by Aloys Pollender in 1849. In 1876, it was first propagated in the laboratory and identified as the anthrax agent by Robert Koch. The first vaccine against the contagious fatal animal disease was developed by Louis Pasteur in 1881 and successfully tested on a large flock of sheep.
What is Bacillus anthracis?
Bacillus anthracis is the medical name of a bacterium that causes dangerous anthrax in animals and humans. The pathogen, which otherwise infects only people who deal with animals professionally (farmers, veterinarians, etc.), became known internationally in the late 1990s. During this time, a series of terrorist attacks with anthrax spores occurred. They were used as biological weapons by the perpetrators and sometimes even caused deaths because the infected people could not be treated in time. In 2001, several employees of a U.S. postal branch died when they came into contact with letters contaminated with Bacillus anthracis spores. The name anthrax is derived from the markedly enlarged spleen in infected individuals, which turns black after a period of time. Anthrax is actually an animal disease. It is extremely rare in humans. It affects people who have frequent contact with animals and their products. The severe and always fatal disease if left untreated can affect the skin, respiratory tract and gastrointestinal tract.
Occurrence, distribution, and characteristics
Bacillus anthracis is found in the soil in the form of endospores. In addition, the pathogen is found on the skin, fur, and in the bodies of infected animals and humans. It is widespread all over the world. Its permanent survival in the soil is favored by extreme drought and long periods of fallow land. In industrialized countries, anthrax cases are rare. The disease occurs more frequently in areas with a warm climate and intensive livestock farming. If humans are affected by infection with the bacterium, it is predominantly cutaneous anthrax. Bacillus anthracis transmission occurs through endospores formed by the pathogen itself. They emerge from the narrower central zone of the bacterium when it is exposed to intense heat or extreme food shortages. It then immediately reduces its metabolic activity and forms a thicker cell membrane. This enables it to ensure its long-term survival. If the endospores enter the bloodstream, they develop into dangerous bacteria that multiply extremely rapidly. Bacillus anthracis is highly infectious, as its spores survive for decades in the soil and from there enter the animal organism via food. After the death of the grazing animal, they continue to spread through its carcass. Animals that die of anthrax must be incinerated immediately. Otherwise, the anthrax bacteria enter their spore state and remain in the soil. Transmission with the often fatal pathogen usually occurs from animal to human. Human-to-human spread is exceedingly rare. The gram-positive bacteria consist of approximately 83 percent branched-chain fatty acids and belong to the Bacillaceae family. They can grow up to 6 micrometers long, are immobile and have a rod shape. Bacillus anthracis can combine with other bacteria of its kind to form filaments and chains. If it gets into a living organism, it immediately surrounds itself with a polyglutamate capsule. This protects the bacterium from destruction by animal or human immune cells. In in vitro experiments, the capsule formation is omitted. Today, the dangerous anthrax pathogen can be successfully treated with antibiotics such as doxycycline and ciprofloxacin. Special monoclonal antibodies are available as antitoxins. Prophylactic treatment is given with special anthrax vaccines. It is also required in persons who are only potentially exposed to the bacterium.
Diseases and medical conditions
Bacillus anthracis, with the help of its plasmid pXO1, forms toxin molecules that are released when the bacterium destroys the walls of blood vessels. This leads to inflammation and bleeding. A part of the toxin molecule, the antigen PA, docks onto the receptor of the respective cell and opens it. With the help of a specific enzyme, the toxin blocks the activity of the leukocytes. The enzyme LT, which is also present in the bacterium, renders the remaining immune system non-functional.Another plasmid called pXO2 forms the protective bacterial capsule. The anthrax pathogen causes skin, lung and intestinal anthrax. If it also spreads through the bloodstream, fatal blood poisoning occurs. In cutaneous anthrax, the bacterium enters the skin through a wound and forms a crater-like depression with a purulent carbuncle. It is surrounded by a raised infectious ring. Hemorrhagic edema then develops at this site. The carbuncle itself becomes covered with black eschar as the disease progresses. If left untreated, the lethality of cutaneous anthrax is 5 to 20%. If the anthrax spores are deeply inhaled, bronchopneumonia occurs, a special form of pneumonia in which the bronchi are also affected. The patient coughs up bacteria-contaminated blood, has chills and a high fever, and dies from suffocation (hypoxia) within 3 days without antibiotics. The very rare intestinal infection with anthrax pathogens is caused by raw consumption of infected meat, offal, and uncooked milk. The sufferer excretes bloody stools and vomits blood due to hemorrhagic bowel inflammation. This form of anthrax is also fatal without medication.
