The Bacillus Anthracis bacterium is commonly found in soil and infects
grazing animals such as cattle. The bacterium has the potential to cause
disease through the spores producing toxins. The zoonotic disease is called
Anthrax and is a virulent disease with the potential to be used in aerosol form
as a biological warfare.
Bacillus anthracis is a gram-positive, rod-shaped bacterium1. It is a
non-motile, spore forming bacteria that is non-hemolytic on blood agar4.
It can be grown in aerobic and anaerobic conditions, making it a facultative
anaerobe. The bacterium is 1-1.2mm in width and 3-5mm in length4.There are two forms of cells
that Bacillus Anthracis exists in. The
vegetative cells which are inside of the host, and dormant, endospore form
cells4. The hard coating of the bacteria helps these spores survive
for long periods of time in harsh and extreme conditions. These spores are
extremely resistant to different outside factors such as UV radiation, nutrient
depletion, and extreme heat4. The ability of the spores to be protected
increases the survival of the spores for decades4.The more
infectious form of the bacteria is the spore form which can release toxins into
the body after germination2. Germination requires an abundance of
nutrients that is found in the tissue and blood of the host1.
Bacillus Anthracis bacterium has two
main virulence features, the poly-g-D-glutaminc acid capsule and tripartite toxin4.
The capsule is produced by the bacteria in order to mask itself from the
macrophages in order to invade the immune system4. The bacterium
produces three proteins that form the combination of toxins that causes the
dangerous effects of the disease1. Bacillus Anthracis has an A-B toxin in which the B, binding,
subunit binds to gain entrance for the A, active, subunit into the host cell6.
The protective antigen, also known as PA is the B subunit for the two different
types of active subunits. In the exotoxins, there is the Edema Factor(EF) and
the Lethal Factor(LF)6. The EF has adenylate cyclase activity which
causes the cells to secrete a large amount of fluid6. The LF has
protease activity that interferes with the immune system’s inflammatory system6.
The etiologic agent of the zoonotic disease anthrax, is a genetically monomorphic
species7. The first plasmid on the different strains is pX01 which
encodes the different toxins while the pX02 encodes the genes needed for capsule
Three of the most well known strains are the
Ames, Sterne, and Vollum4. The
Ames strain carries both of the plasmids which makes it the most virulent
strain that’s known from the species4. The Sterne strain is less
virulent and lacks the plasmid pX02 which codes for the capsule for protection;
this strain is used for vaccine research and is Canada4. The Vollum
strain is also used for research and lacks the pX01 which codes for the toxins4.
Anthracis is the agent responsible
for Anthrax which is a zoonotic disease that has been around for centuries4.
The typical symptoms of the Bacillus
anthracis usually appear between 1 day after infection to more than 2
months after. The severity of the symptoms depends on the ability to seek
treatment in a timely manner with the possibility of serious illness or death2.
The most common form of the disease is cutaneous anthrax and is also the least
dangerous. Cutaneous anthrax occurs when the spores enter the body through
broken skin and reproduce vegetative cells that release exotoxin6. Cutaneous
anthrax begins showing symptoms 2-5 days after the initial exposure10.
These symptoms typically include small itchy blisters or bumps, swelling around
the sore, and painless skin sores like an ulcer with a black center called a Eschar5.
The sores are found mostly on the hands, face, neck, or arms of the infected
individual2. These lesions tend to heal after weeks and end up
The different modes of transmission also affect the
type of symptoms that an infected patient will encounter. Another form of the
disease is inhalation anthrax. The most dangerous form and most fatal even if
treatment is provided in a timely manner8. The case-fatality is
67%-88% even when antibiotic treatment and infection typically develops in 1-7
days but can take up to 2 months after the exposure to appear2. This
form of anthrax is at risk of becoming a biological weapon because it causes
the most harm and would be easier to infect a larger group of people if made into
an aerosol. Inhalation anthrax, also known as woolsorters’ disease, occurs when
the Bacillus Anthracis produces
endospores and these spores are inhaled; attaching to the lung tissue and begin
germination8. The germination process destroys the lung tissue,
eventually entering the blood system and traveling to other vital organs8.
One complication that can arise from all forms but especially inhalation is the
development of anthrax meningitis; this factor also affects the type of antibiotics
and antitoxin prescribed2. For inhalation anthrax, some symptoms
include common flu-like symptoms such as fever, shortness of breath, headache,
confusion/ dizziness, and vomiting2. As the disease progresses, life
threatening symptoms include septic shock, breathing difficulties, and
meningitis- inflammation of the brain and spinal cords8.