Applied Microbiology: Open Access
Open Access

The Classification and Significance of Bacillus anthracis

Neelam Lopaking^{* *}Correspondence: Neelam Lopaking, Department of Microbiology, University of Milan, Milan, Italy, Email:

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Description

Bacillus anthracis is a bacterial pathogen that has plagued humanity for centuries. This microorganism is responsible for anthrax, a potentially dangerous disease that affects humans and animals. Anthrax has been a subject of great concern due to its historical significance, its potential for use as a bioweapon, and its ability to cause severe illness. In this comprehensive exploration, we will delve into the field of Bacillus anthracis, examining its biology, history, clinical manifestations, and the measures taken to combat its threat.

Microbial biology

Taxonomy and classification: Bacillus anthracis is a Grampositive, spore-forming bacterium belonging to the Bacillaceae family. Within the genus Bacillus, it is classified as a member of the Bacillus cereus group, which also includes other species like Bacillus cereus and Bacillus thuringiensis. These bacteria share genetic and phenotypic similarities but vary in their pathogenicity.

Morphology and spore formation: Bacillus anthracis exhibits distinct morphological features. Under a microscope, it appears as large, rod-shaped cells with square ends, typically arranged in chains or pairs. These bacteria produce spores-highly resilient, dormant structures that enable survival in adverse conditions. The spores of Bacillus anthracis are central to its ability to persist in the environment and cause infection.

Virulence factors: Bacillus anthracis possesses several virulence factors that enable it to infect and harm its host:

Capsule: The bacterium is encapsulated with a unique polypeptide capsule composed of D-glutamic acid. This capsule helps it evade the host's immune system by preventing phagocytosis.

Toxins: Bacillus anthracis produces three toxins: Protective Antigen (PA), Edema Factor (EF), and Lethal Factor  (LF). These toxins play a crucial role in the disease's pathogenesis. PA forms a complex with EF or LF, facilitating their entry into host cells. EF and LF disrupt cellular processes, leading to tissue damage and systemic effects.

Plasmids: The bacterium harbors plasmids that encode the production of toxins and other virulence factors. These plasmids are essential for its pathogenicity.

Historical significance

Ancient records: Anthrax is one of the oldest known infectious diseases, with historical records dating back thousands of years. Ancient texts from various civilizations, including the Greeks and Romans, describe outbreaks of a disease resembling anthrax among livestock and humans.

Industrial revolution and wool sorters' disease: During the 18^th and 19^th centuries, the Industrial Revolution brought about significant changes in the textile industry. This period saw a surge in anthrax cases among workers, especially wool sorters. The  disease, known as "wool sorters' disease," resulted from contact with contaminated wool. It played a pivotal role in the understanding of anthrax transmission and led to the development of preventive measures.

Biowarfare and biodefense: Anthrax gained importance in the 20^th century due to its potential as a biological weapon. Nations, including the United States and the Soviet Union, explored the use of Bacillus anthracis spores as bioweapons. The 2001 anthrax attacks in the United States, which involved the deliberate release of anthrax spores through the mail, highlighted the need for enhanced biodefense measures.

Clinical manifestations

Modes of infection: Anthrax can infect humans and animals through various routes:

Cutaneous anthrax: This is the most common form of anthrax infection. It occurs when Bacillus anthracis spores come into contact with a break in the skin. Symptoms include a sore that turns into an ulcer with a black center.

Inhalation anthrax: Inhalation of aerosolized spores is the most lethal form of anthrax. Initial symptoms resemble a common cold but progress rapidly to severe respiratory
distress and systemic infection.

Gastrointestinal anthrax: Ingestion of contaminated, undercooked meat can lead to gastrointestinal anthrax. Symptoms include nausea, vomiting, abdominal pain, and  diarrhea.

Injection anthrax: This rare form of anthrax occurs among drug users who inject contaminated drugs. It can lead to severe soft tissue and systemic infections.

Pathogenesis: Once inside the body, Bacillus anthracis spores germinate into active bacteria. The capsule and toxins aid in evading the immune system. In inhalation anthrax, the bacteria spread through the bloodstream, causing systemic infection and sepsis. In cutaneous and gastrointestinal anthrax, local tissue damage and ulceration are prominent.

Diagnosis and treatment: Diagnosing anthrax involves isolating the bacterium from clinical specimens and identifying it through various laboratory techniques. Early diagnosis is crucial for successful treatment. Treatment typically involves antibiotics, such as ciprofloxacin, doxycycline, or penicillin. Antitoxins may also be administered to neutralize the effects of toxins. Vaccination is available for individuals at risk of occupational exposure.

Prevention and control

Vaccination: Anthrax vaccination has been developed and used primarily for individuals at high risk, such as military personnel and laboratory workers. The vaccine contains a non-virulent strain of Bacillus anthracis that stimulates an immune response without causing disease.

Occupational safety: Occupational safety measures are critical in preventing anthrax among individuals working with animals, animal products, or contaminated materials. These include wearing protective clothing, practicing good hygiene, and decontaminating work areas.

Biodefense: The threat of anthrax as a bioweapon has prompted governments to establish biodefense programs. These programs focus on surveillance, early detection, response planning, and stockpiling vaccines and antibiotics to mitigate the consequences of an anthrax attack.

Public health measures: In the event of an anthrax outbreak or bioterrorism incident, public health authorities play a crucial role in coordinating response efforts, including contact tracing, prophylactic treatment, and communication with the public to prevent panic.

Bacillus anthracis, the bacterium behind anthrax, is a formidable pathogen with a rich historical legacy. Its biology, virulence factors, and modes of infection make it a significant public health concern. Through the lessons of history and advances in microbiology, we have gained valuable insights into anthrax prevention, diagnosis, and treatment. Vigilance and preparedness remain key in our ongoing battle against this microbial menace.