Bacillus anthracis is a pathogenic bacterium with the ability to produce spores that can enter the body of someliving beings. This bacterium has a place of honor in the world of microbiology, since it holds several recognitions: First bacteria seen under the microscope by Aloys Pollender in 1849, and First bacterium recognized as a pathogen, thanks to Robert Koch in 1877.
It is one of the bacteria that has been most studied, since due to its morphological and physiological characteristics, in addition to its virulence, it has even been used as a biological weapon.
The taxonomic classification of Bacillus anthracis is as follows:
Species: Bacillus anthracis.
Because they belong to the genus bacillus, bacterial cells are rod-shaped, with straight ends. In addition, within the standard parameters regarding the size of bacteria, they are considered large. They measure approximately 1 x 3-8 microns.
On the other hand, they do not present any type of extensions or flagella.
By studying infected tissue under the electron microscope, individual cells have been observed, as well as a few forming short chains of 3 to 4 cells. However, in vitro cultures the formation of long chains is observed.
In the central part of each bacterial cell it is possible to notice a round structure, the sporangium, which is where the spores develop.
In the observed cultures, the formation of colonies measuring between 2 and 5 mm, white in color, with an appearance similar to that of ground glass is evidenced.
Similarly, the bacteria is protected by a very resistant capsule. This capsule is peptide, made up of a homopolymer known as poly-gD-glutamate. This compound plays an important role in the survival of the bacteria to the defense mechanisms of the host. This is due to its low immunogenicity.
It is gram positive
This means that it has a thick cell wall made up of peptidoglycan, which makes it turn purple-violet when subjected to Gram staining.
It is catalase positive
They contain the enzyme catalase through which they have the ability to break down the hydrogen peroxide compound into oxygen and water. This is a characteristic that contributes to the correct identification of the bacteria in the laboratory.
The ideal temperature for its growth is at 37 ° C. Above 43 ° C growth is totally inhibited.
It is gamma hemolytic
The Bacillus anthracis is not able to generate the destruction of erythrocytes present in blood. This has been fully demonstrated in blood agar cultures.
Spores are cells that are in a dormant state. In the case of Bacillus anthracis , they are endospores and their function is to guarantee the survival of the bacteria when the environmental characteristics are unfavorable.
Endospores are produced when bacteria are in contact with oxygen. They are highly resistant to hostile environmental conditions such as high temperatures (over 100 ° C) and lack of nutrients.
Likewise, they can remain dormant for many years in different places. For example, they can be kept for 2 years in water and 70 years in silk threads.
It is facultative anaerobic
The bacteria can survive both in environments with oxygen, and in the absence of it. However, to develop spores it must be in a habitat where oxygen is available.
When found in EYA agar (Egg Yolk Agar, “Egg Yolk Agar”), it has been shown to be capable of hydrolyzing casein, starch and gelatin.
Similarly, it has been proven that you can metabolize some carbohydrates such as trehalose and glycogen to produce acid.
Bacillus anthracis spores are highly pathogenic, so when they enter the body of humans, as well as other animals, they generate health problems that in a large percentage of cases lead to death.
Likewise, those who are most at risk are people who have jobs related to agriculture, forestry, contact activities with animals or their products, laboratories, among others.
Mechanism of infection
The spores enter the body and are immediately recognized by cells of the immune system known as macrophages, which engulf them.
Once inside these cells, the spores germinate and the bacterial cells begin to reproduce with their respective capsule and the consequent toxins that are the ones that will generate the damage in the various tissues.
Types of infection
Now, the word “Anthrax” refers to the infection by this bacterium, also specifying the area of the body affected.
In such a way that several pathologies can be studied:
It constitutes 95% of the cases. It occurs when the spores of the bacteria enter the body through a wound or injury to the skin. It has an incubation period of 1 to 12 days.
Generally the injury evolves favorably, after which only the scar remains. If it is not treated promptly, it can have a mortality rate of 20%.
It corresponds to 55% of the cases. It occurs when spores are inhaled and enter the body through the respiratory tract, to the lungs. The incubation period is approximately 1-7 days.
It has a mortality rate close to 100%.
It represents a tiny percentage of the reported cases. It is very unusual. It originates when there is the ingestion of raw meat contaminated with spores. Symptoms appear after 1 to 7 days.
The clinical picture that manifests in a Bacillus anthracis infection depends on the route of entry into the body and the affected tissues.
- A bulging lesion, similar to a mosquito bite, which subsequently evolves into a painless, festering ulcer, eventually becoming a necrotic eschar.
- Fever (37 ° C – 38 ° C)
- Increase in nearby lymph nodes.
- General discomfort.
- Fever (38 ° C)
- Non-productive cough
- General discomfort
- Chills and tiredness
Later these symptoms evolve until the critical phase of the infection, in which the following symptoms appear:
- High fever (39 ° C – 40 ° C)
- Difficulty breathing
Eventually, shock and septicemia occur, which in most cases lead to the death of the patient.
It presents quite nonspecific symptoms:
- Abdominal pain
- Bloody diarrhea
These symptoms progress to severe bacteremia and, if not treated in time, can cause death.
The main element to consider when treating a bacterial infection is the antibiotic. There are a wide variety of antibiotics today, which have proven their effectiveness as bactericidal agents.
In the case of Bacillus anthracis , it has been shown to be susceptible to penicillin, tetracycline, gentamicin, chloramphenicol, and erythromycin.
Of course, the most indicated is the doctor to determine the treatment guidelines to follow, taking into account the specific characteristics of each clinical case.
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