This lesson will discuss the disease known as tuberculosis. We will talk about mycobacterium tuberculosis, latent TB, TB disease, mycolic acid, and the symptoms, signs, and treatments used for this terrible disease.
In 1986, the worst nuclear disaster in world history occurred at the Chernobyl nuclear power plant, in what is now the Ukraine. Dozens of people died as a direct result of this accident, and certainly thousands more were negatively affected for many years to come. In order to try and stem the flow of poisonous and radioactive material coming from the plant, a giant sarcophagus was built over the nuclear reactor.
In a similar way, your body also builds sarcophagi-like structures to entomb dangerous things such as bacteria. One type of bacterium your body tries to entomb is called Mycobacterium tuberculosis, and this is an acid-fast, aerobic bacterium responsible for causing a disease known as tuberculosis.The reason this bacterium is called acid-fast is because a fatty acid in the cell wall of acid-fast bacteria, known as mycolic acid, gives these cells the ability to resist decolorization with acid alcohol in certain staining procedures that are used to identify this bacterium. In addition, this mycolic acid also makes these bacteria impermeable to a lot of stains, such as those used in the Gram stain.You can basically think of the mycolic acid as a type of wax coating applied to the cell wall of Mycobacterium tuberculosis. If you were to take a little drop of olive oil and put it on a wax cookie sheet, the oil would slide right off. It wouldn’t be absorbed.
Likewise, many stains would slide right off of this bacterium in a very similar fashion.
As I mentioned, this bacterium causes a condition known as tuberculosis, or TB for short. This is a respiratory disease that may cause everything from a bloody cough to death. The fact that this is a respiratory disease, meaning it is associated with air, should make perfect sense.I mentioned the fact that Mycobacterium tuberculosis is an aerobic bacterium, meaning it needs air to survive.
Therefore, it follows that, as a general rule, this bacterium will probably be associated with something like the lungs, which obviously help you breathe in air.If a person has an infection of tuberculosis and they cough or sneeze or even talk around you, they may spread this bacterium around. Once you inhale it, it will enter your lungs and, in 90% of cases, will thankfully not cause an active infection.
Latent and Active Tuberculosis
This means that it will cause a latent TB infection, or an infection by Mycobacterium tuberculosis that does not cause an individual to fall ill. The reason this occurs goes back to our introductory scenario.
If tuberculosis-causing bacteria enter your lungs, they will be immediately attacked by cells called white blood cells.These cells are important in something known as your immune system. This is basically the force that protects your body from infection and disease. As soon as these white blood cells, such as macrophages, see these bacteria in your lungs, they will surround these bacteria on all sides.By doing so, your white blood cells will wall off, or entomb these bacteria within the immune system’s equivalent of a sarcophagus. This sarcophagus is more technically called a granuloma and causes these bacteria to go latent. The nodule that forms in the lungs as a result of a granuloma is called a tubercle, and is obviously what gives this disease its name.
However, if a person’s immune system is compromised due to something like an HIV infection, then these granulomas will be unable to form. This is equivalent to that sarcophagus never being built around the Chernobyl nuclear power plant. That means the radiation would be able to continue to leak out of it, causing serious disease.Likewise, with no granuloma formation, the tuberculosis-causing bacteria will be able to multiply and spread about, causing the active form of tuberculosis to occur. We term this active form more technically and unsurprisingly as TB disease.
The disease-causing form of tuberculosis can cause signs, or objective identifiable things, such as:
- A bloody cough
- Fever and
- Scarring of the lungs
And symptoms, or subjective experiences that aren’t readily measured by objective standards, such as:
- Fatigue or
- Chest pain
Diagnosis and Treatment
While a vaccine is available for tuberculosis, it is not commonly used in the United States since its effectiveness is questionable. Therefore, if a person is suspected to have tuberculosis, it can be tested for in numerous ways.One commonly known test is the tuberculin skin test. In this test, harmless little pieces of tuberculosis-causing bacteria are injected into the skin. If a small, red swelling appears in the area within three days, it is considered a sign that the person either has a latent TB infection, active TB disease, or received a vaccine for tuberculosis that caused this reaction.If there is no reaction, that means that none of those things have occurred, or the person’s immune system is really weak and cannot form a reaction to the test.
Other ways by which TB is diagnosed is through blood tests, analyzing samples of coughed up sputum and chest x-rays.If a person is diagnosed with this disease, they are treated with a combination of antibiotics, such as rifampin and isoniazid, for an average of 6-9 months. Usually, this process is monitored by healthcare professionals to ensure that people taking these antibiotics actually do so.
That’s because if they don’t take the medication as prescribed, they may cause antibiotic resistance to these drugs to develop, leading to the development of far more dangerous strains of this bacteria.
We certainly wouldn’t want these dangerous strains to develop as some already have since it will be much more difficult to kill off the Mycobacterium tuberculosis, which is the acid-fast, aerobic bacterium responsible for causing a disease known as tuberculosis. Tuberculosis, or TB for short, is a respiratory disease that may cause everything from a bloody cough to death.One form of tuberculosis is known as a latent TB infection, or an infection by Mycobacterium tuberculosis, that does not cause an individual to fall ill, whereas the active form of tuberculosis is known as TB disease. In any case, the reason the bacteria that cause tuberculosis are called acid-fast is because a fatty acid in the cell wall of acid-fast bacteria, known as mycolic acid, gives these cells the ability to resist decolorization with acid alcohol in certain staining procedures that are used to identify this bacterium. In addition, this mycolic acid also makes these bacteria impermeable to a lot of stains, such as those used in the Gram stain.
Upon completion of this lesson, a student should be able to:
- Define and describe tuberculosis
- Discuss the differences between latent TB infection and TB disease
- Recall the various treatments available for the disease