Bacillus anthracis is the bacterium that causes the disease anthrax. It has historically affected herbivores like cattle, sheep or other grazing herds, but has also been a threat to humans who work with these animals and their by-products.
While in the ground or on a surface, anthrax spores are relatively harmless, but once they come into contact with the right environment they begin to germinate. They need an environment that is rich in amino acids, nucleosides and glucose — like those elements found in blood and other tissues in humans or animals. Once there, a series of changes takes place that can make these bacteria deadly to its host.
Anthrax may also spread when carnivorous animals, such as vultures or even insects, feed on affected herbivores. The bacteria are then transferred to other areas by the host and contaminate the ground when that animal dies. As the animal decays, the bacteria are exposed to oxygen and turn back into the spores that contaminate the soil. The anthrax spores have a very tough outer casing and can remain viable in the ground for decades.
Many diagnostic laboratories around the world have anthrax samples for use in research and for the identification of anthrax. Anthrax can be grown in laboratories from these existing spores. In the wrong hands, these spores can be grown, dried and milled for use in biological weapons.
Anthrax spores can enter the body through:
When viewed at the cellular level, an anthrax bacterium looks like a jointed bamboo rod. When it enters the body and finds the environment it needs, it moves to the lymph nodes. From there it begins to multiply and produce a toxin that attacks human cells resulting in hemorrhaging, swelling, a drop in blood pressure and ultimately death.
The way it attacks the cells and exactly what it does was in question for many years. Research that began in the mid 1980s has revealed some interesting facts about the behavior of the anthrax bacterium when it finds a host.
Researchers found that there are three proteins that are created by the anthrax bacteria. These proteins are harmless individually, but together can be deadly. These proteins are referred to as:
When these proteins are released, the protective antigen binds to the cell surface and forms a type of channel in the cell membrane that allows the edema factor and lethal factor to enter the cell. The edema factor, when combined with the protective antigen, forms a toxin known as the edema toxin. The lethal factor, when combined with the protective antigen, forms a toxin known as the lethal toxin. It is the lethal toxin that does the most damage within the cell.
Research in 1998, by George Vande Woude at the National Cancer Institute in Frederick, MD, revealed clues to what the lethal toxin does to the cells. He found that the lethal factor cuts enzymes in two — the enzymes that are responsible for transmitting signals within the cells. He also identified the enzyme in question. He was studying the mitogen-activated protein kinase (MAPK) pathway, which helps control cell growth, embryonic development and the way oocytes (eggs) mature. He was specifically looking for information about what the pathway actually did in the oocyte maturation cycle, so he searched for compounds that blocked the activity of the MAPK. A database search lead him to the lethal factor.
It is still not completely understood why disrupting the signal transmission within the cell results in the symptoms anthrax generates, but research continues. Research is also being done to find ways to alter the protective antigen to disable its ability to allow the entry of the lethal and edema toxins into cells.
Symptoms of Anthrax
According to an article in the Journal of the American Medical Association, a blood sample is taken from the patient and cultured for six to 24 hours. At this point, a “Gram stain” can be done. The Gram stain highlights the bacteria.
The Gram stain takes about 10 to 15 minutes and can identify whether the bacteria come from the anthrax category. At that point, biochemical testing can be done to find the specific anthrax bacteria, which takes another 12 to 24 hours. Usually, the specimens have to be sent to national reference laboratories for comparison with stock anthrax samples.
Treatment of inhaled anthrax has to start very early in the progression of symptoms. If treatment is begun after the symptoms have progressed too far, then the bacteria may be killed but the toxins remain in the body.