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The hidden world of anthrax: Do you know how Bacillus anthracis affects human and animal health?
Bacillus anthracis, a Gram-positive bacillus, is responsible for causing anthrax. This deadly contagious disease mainly affects livestock but sometimes spreads to humans as well. Since its discovery by German physician Robert Koch in 1876, B. anthracis has been a major advance in human understanding of pathogens and became the first experimental evidence to support the pathogenic theory. Furthermore, the presence of this bacterium represents a potential public health risk, particularly due to its use in biological weapons.
The spread of anthrax is primarily through animal infection, making the disease an obvious cross-species disease (zoonotic disease).
B. anthracis bacteria are rod-shaped, with a length of about 3 to 5 microns and a width of about 1 to 1.2 microns. Its genome structure is a 5,227,419 base pair circular chromosome and two extrachromosomal DNA plasmids pXO1 and pXO2. These two plasmids are key to the pathogenicity of this bacterium. When environmental conditions are suitable, the bacterium forms a protective layer of endospores that allows it to withstand harsh conditions and remain inactive for many years before adapting and reproducing again.
Due to the toughness of the endospores, B. anthracis is one of the most popular choices for biological weapons.
The bacterium has the ability to evade immune responses, and its protein sheath (poly-D-gamma-glutamate) is one of its key weapons. B. anthracis feeds on the hemoglobin blood matrix via two secreted ferritin transport proteins, which allows it to survive and reproduce in the host. Additionally, untreated B. anthracis infection is often fatal, and indicators of infection include the development of inflamed black necrotic lesions (charcoal scab).
There are four main forms of anthrax that infect humans, and each form takes anywhere from one day to two months to develop. Cutaneous type is the most common, accounting for about 95%. This form of infection usually appears 1 to 7 days after exposure, with lesions occurring on areas such as the face, neck, and extremities. Inhalation infection, although rare but extremely fatal, usually develops within a week and is accompanied by flu-like symptoms.
Symptoms vary depending on the form of infection, and all types of anthrax have the potential to spread without treatment and cause severe illness or even death.
In 1881, French chemist Louis Pasteur developed the first animal vaccine against anthrax. Today, different human and animal vaccines have been developed. Although cases of infection with B. anthracis require early treatment, there are many antibiotics that are effective against this bacteria, such as penicillins, fluoroquinolones, and tetracyclines.
So, with the advancement of science, are humans' weapons against this deadly bacteria still sufficient to deal with possible future epidemic threats?
