Mycobacterium tuberculosis
Mycobacterium tuberculosis is the bacterium that is known to cause tuberculosis (usually denoted as TB). The bacterium attacks various parts of the body which will be disucussed later in the following study paper. It is imperative to note that even though one might be infected with TB, not everyone will get sick. The following is a detailed discussion about the bacteria mycobacterium tuberculosis, providing a brief history, scientific classification, life cycle, how it is tested and how it is treated.
History of Mycobacterium tuberculosis
The bacterium Mycobacterium tuberculosis has claimed human lives all through human history. The bacterium was first discovered by Dr. Robert Koch on 24th March, 1882 (Merker et al., 2015). Before this, the bacterium had killed every seven individuals who were living in the United States. At one time in history, the bacteria is known to have reached epidemic proportions in Europe and North America. It was during this time that it earned the sobriquet “Captain Among these Men of Death.” Previously, TB was suggested to have originated from animals. However, recent studies that use molecular genetics suggest that TB predated in other animals such as cattle. In animals, it is known as bovine TB. Among the ealiers historical references of TB are found in Egypt. This was during the medial papyrus dating back as far as the 1550 BC. One particular type of TB identified as Pott’s disease has been detected among some Egyptian mammies. Also, during this time, it was also identified in India in a Sanskirit hymn (Rig Veda) and in the 2700 BC, it was identified in a medical text from China. The discovery by Dr. Koch was an important step towards the control and elimination of the bacterium that caused the deadly disease, tuberculosis. After a century of the bacterium discovery by Dr. Koch, March 24th was designated as the World TB Day. The day was meant to educate the public on the impact of TB around the world. Until the disease is eliminated, the day will not be a celebration. However, it provides a valuable opportunity to educate the public on the devastation of TB, how it is spread and how it can be stopped.
Scientific Classification
Below is a brief summary of the scientific classification of Mycobacterium tuberculosis, depicting its taxonomy and nomenclature, and taxonomic hierarchy (Shitikov et al., 2017).
Taxonomic Hierarchy
Kingdom
Bacteria
Subkingdom
Posi bacteria
Phylum
Actinobacteria
Subclass
Antinobacteridae
Order
Actinomycetales
Suborder
Corynebacterineae
Family
Mycobacteriaceae
Genus
Mycobacterium
Species
Mycobacterium tuberculosis
Lineage
Cellular organisms
Bacteria
Terrabacteria group
Actinobacteria
Actinobacteria
Corynebacteriales
Mycobacteriaceae
Mycobacterium
Mycobacterium tuberculosis complex
Life Cycle
The lifecycle of of Mycobacterium tuberculosis from the time it enters the body of a human being occurs in five stages: initial macrophage response, growth stage, immune control stage and lung cultivation (Eoh et al., 2017).
Stage one
The first stage of infection of tuberculosis begins when the bacteria strain TB bacillus is inhaled through the air by a human being. This first stage is called the onset. There have been known cases during this stage when the bacteria is able to reproduce and induce infection. The infection of TB therefore begins when the bacteria is inhaled and reaches the alveolar macrophages of the lungs.
Stage two
The second stage of infection is known as symbiosis. Symbiosis can take up to 21 days. At this stage, the bacteria will begin to reproduce if it has not been detected by white blood cells and killed. Reproduction occurs when the initial bacillus sprouts out two new ones. The two new then produces two each and the process continues that leads up to the rapid expansion of the TB bacillus. The macrophages in the lungs are usually not able to contain their spread during this stage.
Stage three
At the third stage, the reproduction of bacilli is reduced. At this stage its growth and destruction is usally balanced by macrophages. The reason behind this is because the body responds to the exponential growth of the bacilli by bringing in more immune cells in order to stablilize them. Most patients infected with M. tuberculosis do not show any symptoms or signs at this stage. However, in the patient’s lungs, the TB bacilli that have been swallowed by macrophages from a round complex with the TB bacilli and the infected macrophages right in the middle of the healthy macrophages. This process is usually called Ghon focus and it also affects the surrounding lymph nodes.
Stage four
At this stage, the TB bacilli become reactivated. This happens after 12 to 24 months after the initial infection. This reactivation involves rapid reproduction of the TB bacilli, forming a cavity tiessiue where the immune system of the body cannot reach. This cavity enables the TB bacilli to spread thtough the tissue of the infected persons. At this stage, the person exhibits symptoms of TB including coughing. The immune system of the individual is usually weakened at this stage. The person is also highly infectious at this stage. This is because their sputum contains the active bacteria.
Testing and Treatment of Tuberculosis
The testing of TB bacteria in the body is of two kinds: TB Skin Test (TST) and TB blood tests. The skin tests involve injecting the patient with PPD tuberculin. This injection is done just below the skin inside the forearm of the patient. After 48 to 72 hours, the health professional will check the injection site of the patient for swelling. Having a hard-red bump indicates infection of TB with the size of bump determining how significant the test was (Schön et al., 2017). The skin test is usually not perfect. Blood tests are used to confirm the presence of active or latent tuberculosis. The tests occur through the use of technology that can measure the body’s immune system reaction to the presence of Mycobacterium tuberculosis bacteria. Other test includes imaging tests that involve an X-ray on the patient’s chest of a CT scan to identify white spots in the lungs of the patient where the process of Ghon focus has occurred. Sputum tests are also used where samples of the sputum are taken and analysed for the presence of TB bacteria.
The treatment of TB takes a lot longer than other bacterial infections. Treatment involves the active take of antibiotics by patients for at least six months. The patient is required to finish their dose even after they start feeling better. Treatment also requires the intake of several drugs depending on the length of infection and the age of the person. According to Horsburgh et al. (2015), The drugs used to treat tuberculosis include Isoniazid, Rifampin, Ethambutol and Pyrazinamide. Completing the treatment is essential for full recovery.
Conclusion
Mycobacterium tuberculosis is the bacterium that is known to cause tuberculosis. The bacterium enters the human body through initial inhalation of the bacteria. The bacteria target the lungs in order to cause an infection. During its initial stages, the patient might not know they have TB due to the inactive nature of the bacteria. However, later on, after around a year, the bacteria might be active and the symptoms of TB will start to show. Treatment however is possible through proper medication of antibiotics.