MYCOBACTERIUM TUBERCULOSIS
“Captain of all these men of death.”
Mycobacterium Tuberculosis causes the bacterial infection TUBERCULOSIS spread through inhaling tiny droplets from the coughs or sneezes of an infected person.
HISTORY
- On March 24, 1882, Dr. Robert Koch announced the discovery of Mycobacterium tuberculosis, the bacteria that causes tuberculosis (TB).
- In 1905, he won the Nobel Prize for Medicine and Physiology.
- Johann Schonlein coined the term “tuberculosis” in the 1834.World TB day is celebrated on MARCH 24 every year.
- Tuberculosis (TB) was called as “phthisis” in ancient Greece, “tabes” in ancient Rome, and “schachepheth” in ancient Hebrew. In the 1700s, TB was called “the white plague” due to the paleness of the patients.
- It was also called the “Captain of all these men of death.”
- The WHO estimates that in 2020, nearly 10 million people worldwide developed TB and 1.5 million people died from the disease, including 214,000 people who also had HIV.
SANATORIUMS
Tuberculosis sanatoriums were places that provided treatment for TB patients and took the patients out of their home, which reduced the chance to spread TB to their families.In 1875, Joseph Gleitsmann opened the first sanatorium in the United States in Asheville, North Carolina. Edward Livingston Trudeau (who had TB disease himself) opened the second, Adirondack Cottage Sanatorium, in Saranac, New York in 1884.
HOW IT IS TRANSMITTED..?
- Tuberculosis is spread from person to person through the air by droplet nuclei, particles 1 to 5 μm in diameter that contain M. tuberculosis complex .
- Droplet nuclei are small enough to reach the alveoli within the lungs, where the organisms replicate
- There are five closely related mycobacteria grouped in the M. tuberculosis complex: M. tuberculosis, M. bovis, M. africanum, M. microti, and M. canetti
- Mycobacterium bovis may penetrate the gastrointestinal mucosa or invade the lymphatic tissue of the oropharynx when ingested in milk containing large numbers of organisms.
Four factors determine the likelihood of transmission of M. tuberculosis:
(1) the number of organisms being expelled into the air
(2) the concentration of organisms in the air determined by the volume of the space and its ventilation
(3) the length of time an exposed person breathes the contaminated air, and
(4) presumably the immune status of the exposed individual
PATHWAY OF ORGANISM
After inhalation, the droplet nucleus is carried down the bronchial tree and implants in a respiratory bronchiole or alveolus. Whether or not an inhaled tubercle bacillus establishes an infection in the lung depends on both the bacterial virulence and the inherent microbicidal ability of the alveolar macrophage that ingests it . If the bacillus is able to survive initial defenses, it can multiply within the alveolar macrophage. The tubercle bacillus grows slowly, dividing approximately every 25 to 32 h within the macrophage. Mycobacterium tuberculosis has no known endotoxins or exotoxins; therefore, there is no immediate host response to infection. The organisms grow for 2 to 12 wk, until they reach 103 to 104 in number, which is sufficient to elicit a cellular immune response .
Before the development of cellular immunity, tubercle bacilli spread via the lymphatics to the hilar lymph nodes and thence through the bloodstream to more distant sites. Certain organs and tissues are notably resistant to subsequent multiplication of these bacilli. The bone marrow, liver, and spleen are almost always seeded with mycobacteria. Organisms deposited in the upper lung zones, kidneys, bones, and brain may find environments that favor their growth, and numerous bacterial divisions may occur before specific cellular immunity develops and limits multiplication.
LATENT TUBERCULOSIS
An individual can have TB bacteria in their body and never develop symptoms. In most people, the immune system can contain the bacteria so that they do not replicate and cause disease. In this case, a person will have TB infection but not active disease.
This refer to as latent TB. An individual may never experience symptoms and be unaware that they have the infection. There is also no risk of passing on a latent infection to someone else. However, a person with latent TB still requires treatment.The CDC estimates that as many as 13 million people in the U.S. have latent TB.
ACTIVE TUBERCULOSIS
- The body may be unable to contain TB bacteria. This is more common when the immune system is weakened due to illness or the use of certain medications.
- When this happens, the bacteria can replicate and cause symptoms, resulting in active TB. People with active TB can spread the infection.
- Without medical intervention, TB becomes active in 5–10% of people with the infection. According to the CDC, progression occurs within 2–5 years in about 50% of these people.
DRUGS
The most common medications used to treat tuberculosis include:
- Isoniazid
- Rifampin (Rifadin, Rimactane)
- Ethambutol (Myambutol)
- Pyrazinamide
If you have drug-resistant TB, a combination of antibiotics called fluoroquinolones and injectable medications, such as amikacin or capreomycin (Capastat), are generally used for 20 to 30 months. Some types of TB are developing resistance to these medications as well.
Some drugs might be added to therapy to counter drug resistance, including:
- Bedaquiline (Sirturo)
- Linezolid (Zyvox)
HOW DO YOU GET TESTED FOR TB?
There are two tests that can be used to help detect TB infection: a skin test or TB blood test.The Mantoux tuberculin skin test is performed by injecting a small amount of fluid (called tuberculin) into the skin in the lower part of the arm. A person given the tuberculin skin test must return within 48 to 72 hours to have a trained health care worker look for a reaction on the arm. The TB blood tests measure how the patient’s immune system reacts to the germs that cause TB.
WHAT DOES A POSITIVE TEST FOR TB INFECTION MEAN?
A positive test for TB infection only tells that a person has been infected with TB germs. It does not tell whether or not the person has progressed to TB disease. Other tests, such as a chest x-ray and a sample of sputum, are needed to see whether the person has TB disease.
WHAT IS Bacille Calmette–Guèrin (BCG)?
BCG is a vaccine for TB disease. BCG is used in many countries, but it is not generally recommended in the United States. BCG vaccination does not completely prevent people from getting TB. It may also cause a false positive tuberculin skin test. However, persons who have been vaccinated with BCG can be given a tuberculin skin test or TB blood test..
PUBLIC HEALTH
The World Health Organization (WHO) declared TB a “global health emergency” in 1993,and in 2006, the Stop TB Partnership developed a Global Plan to Stop Tuberculosis that aimed to save 14 million lives between its launch and 2015.A number of targets they set were not achieved by 2015, mostly due to the increase in HIV-associated tuberculosis and the emergence of multiple drug-resistant tuberculosis.A tuberculosis classification system developed by the American Thoracic Society is used primarily in public health programs.In 2015,it launched the End TB Strategy to reduce deaths by 95% and incidence by 90% before 2035. The goal of tuberculosis elimination is hampered by the lack of rapid testing, of short and effective treatment courses, and of completely effective vaccines.
The benefits and risks of giving anti-tubercular drugs in those exposed to MDR-TB is unclear. Making HAART therapy available to HIV-positive individuals significantly reduces the risk of progression to an active TB infection by up to 90% and can mitigate the spread through this population.
“SAY BYE TO TB”
KAVIN.G
Third year BVSc & AH
GUIDED BY
D R. V. RAMAKRISHNAN, ASSISTANT PROFESSOR
VETERINARY COLLEGE AND RESEARCH INSTITUTE – TIRUNELVELI
TANUVAS – CHENNAI
https://www.pashudhanpraharee.com/bovine-tuberculosis/
https://www.sciencedirect.com/topics/medicine-and-dentistry/mycobacterium-tuberculosis
