Tuberculosis (TB) is caused by bacteria (Mycobacterium tuberculosis) that most often affect the lungs. Tuberculosis is curable and preventable. Globally, TB incidence is falling at about 2% per year and between 2015 and 2020 the cumulative reduction was 11%. This was over half way to the End TB Strategy milestone of 20% reduction between 2015 and 2020. By 2022, US$ 13 billion is needed annually for TB prevention, diagnosis, treatment and care to achieve the global target agreed at the UN high level-meeting on TB in 2018. Ending the TB epidemic by 2030 is among the health targets of the United Nations Sustainable Development Goals (SDGs).

Definition

TB, short for tuberculosis, is an infectious disease caused by the bacterium Mycobacterium tuberculosis. TB primarily affects the lungs, but it can also affect other parts of the body such as the brain, kidneys, and spine.

Pathophysiology

TB is transmitted through the inhalation of droplets containing the bacteria. Once inhaled, the bacteria reach the lungs and are phagocytosed by alveolar macrophages, which attempt to destroy the bacteria through a process called phagocytosis. However, M. tuberculosis has developed mechanisms to survive and multiply within the macrophages, which can lead to the formation of granulomas, or small clusters of immune cells, in the lungs.

Within the granulomas, infected macrophages and other immune cells release cytokines, which attract more immune cells to the site of infection. This results in the formation of a tuberculous lesion, or tubercle, which contains the bacteria and immune cells. The tubercle can become calcified, forming a Ghon focus, which can be seen on X-rays.

In some cases, the immune response is unable to contain the bacteria, and they can spread from the lungs to other parts of the body through the bloodstream or lymphatic system. This can lead to extrapulmonary TB, affecting organs such as the brain, kidneys, or bones.

Etiology

Tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis. This bacterium is spread from person to person through the air when an infected person coughs, sneezes, speaks, or even sings.

Risk Factors

Some of the most common risk factors associated with TB may include:

  1. Immune System: Weakened immune system such as those with HIV/AIDS or those taking immunosuppressive medications
  2. Close Contact with Someone with TB: Spending time in close proximity with someone who has active TB increases the risk of infection.
  3. Living Circumstancies: Living conditions such as in prisons or homeless shelters.
  4. Age : People over the age of 65 are more likely to develop TB.
  5. Travel: Traveling to areas with a high prevalence of TB increases the risk of infection.
  6. History: Co-existing medical conditions such as diabetes or kidney disease.
  7. Abuse of Substaces: Substance abuse, particularly injection drug use.
  8. Occupation: Some occupations, such as healthcare workers, laboratory personnel, and those working in the correctional system.
  9. Malnutrition.
  10. Genetics.

Signs & Symptoms

  1. Cough.
  2. Fever.
  3. Excessive sweating, particularly at night.
  4. Fatigue.
  5. Loss of appetite.
  6. Chest pain.
  7. Shortness of breath.
  8. Swelling of the lymph nodes, particularly in the neck, armpits, or groin.
  9. Other Symptoms: In cases of extra-pulmonary TB, symptoms can vary depending on the site of the infection. For example, bone TB can cause joint pain and stiffness, while TB of the kidneys can cause blood in the urine.

Types

The main types of TB include:

  1. Pulmonary TB: This is the most common type of TB and affects the lungs. It is spread through the air when an infected person coughs, sneezes, or talks. Symptoms of pulmonary TB include cough, fever, night sweats, and weight loss.
  2. Extra-Pulmonary TB: This type of TB affects parts of the body other than the lungs, such as the lymph nodes, bones, joints, kidneys, or brain. Extra-pulmonary TB accounts for about 15-20% of all TB cases.
  3. Miliary TB: This is a rare and severe form of TB that occurs when the bacteria spread throughout the body via the bloodstream. Miliary TB can affect multiple organs and cause symptoms such as fever, weight loss, and fatigue.
  4. Latent TB Infection: In some cases, the immune system can contain the TB bacteria and prevent them from causing active disease. This is called latent TB infection, and it can remain in the body for years without causing symptoms. However, people with latent TB infection are at risk of developing active TB disease later in life.
  5. Drug-resistant TB: TB bacteria can become resistant to one or more of the antibiotics commonly used to treat TB. This is known as drug-resistant TB and it is a growing concern worldwide, as it can be more difficult to treat and can require longer and more expensive treatment regimens.
  6. HIV-associated TB: People with HIV/AIDS are at increased risk of developing TB, as their weakened immune systems make them more susceptible to infection. HIV-associated TB can be more difficult to diagnose and treat than TB in people without HIV.

Diagnosis

  1. Tuberculin Skin Test: This is a simple skin test that involves injecting a small amount of purified protein derivative (PPD) under the skin of the forearm. If a person has been infected with TB bacteria, their immune system will react to the PPD and cause a small bump or swelling at the site of injection. This test can indicate whether a person has been infected with TB bacteria, but it cannot distinguish between active TB disease and latent TB infection.
  2. Blood Tests: Blood tests can be used to detect TB antibodies or to measure levels of interferon-gamma release in response to TB antigens. These tests can help diagnose TB infection, but they cannot distinguish between active TB disease and latent TB infection.
  3. Sputum Tests: Sputum tests involve examining samples of sputum or phlegm under a microscope or culturing the samples to grow the bacteria. This can help diagnose active TB disease and determine the strain of TB bacteria, which can guide treatment decisions.
  4. Imaging Studies: Chest X-rays or CT scans can help detect signs of TB disease in the lungs, such as lung lesions or cavities. Imaging studies can also help detect TB in other parts of the body, such as the bones or lymph nodes.
  5. Biopsy: In some cases, a biopsy may be needed to confirm a diagnosis of TB in extra-pulmonary sites. This involves removing a small sample of tissue or fluid from the affected area and examining it under a microscope or culturing it to grow the bacteria.

Treatment

The treatment of TB requires a combination of medications, supportive care, and close monitoring to ensure that the disease is effectively treated and complications are managed.

  • Medications: The treatment of TB requires a combination of medications and these medications are usually taken for a minimum of six months, and sometimes up to 12 months or longer for drug-resistant TB. Treatment is usually started with a “first-line” regimen of INH, RIF, EMB, and PZA. If drug resistance is suspected, additional medications may be added to the regimen.
    1. Isoniazid (INH).
    2. Rifampin (RIF).
    3. Ethambutol (EMB).
    4. Pyrazinamide (PZA).
  • Supportive Care: This may include rest, fluids, and pain relief medications. People with TB are also typically advised to stay home from work or school until they are no longer contagious, which usually takes several weeks of treatment.
  • Follow Up: Regular follow-up care and monitoring are also important for people with TB to ensure that the medications are working and to detect any side effects or complications. In some cases, surgery may be needed to remove infected tissue or fluid from the lungs or other affected areas.

Complications

  1. Respiratory Failure: TB can damage the lungs and interfere with breathing, leading to respiratory failure.
  2. Pleural Effusion: TB can cause fluid to accumulate in the space between the lungs and chest wall, a condition known as pleural effusion.
  3. Miliary TB: This is a rare but serious form of TB in which the bacteria spread throughout the body and infect multiple organs, including the liver, spleen, and bone marrow.
  4. Spinal TB: TB can also infect the bones and joints, including the spine. This can cause back pain, stiffness, and other symptoms, and may lead to spinal deformity or paralysis if not treated promptly.
  5. Drug-Resistant TB: If TB is not treated properly, the bacteria can become resistant to the medications used to treat it.
  6. HIV/AIDS: TB is a common opportunistic infection in people with HIV/AIDS, as the weakened immune system makes them more vulnerable to TB infection and complications.

Prevention

  1. Vaccination: The Bacillus Calmette-Guérin (BCG) vaccine is a vaccine that can help prevent TB in children.
  2. Infection Control Measures: To prevent the spread of TB, it is important to maintain good ventilation in closed spaces, such as homes and workplaces, and to use masks or other protective equipment if you are in close contact with someone who has TB.
  3. Screening and Testing: People who are at high risk of TB, such as those who have been in close contact with someone who has TB or those with weakened immune systems, should be screened and tested for TB. This can help identify and treat TB early, before it has a chance to spread.
  4. Treatment of Latent TB Infection: People who have been exposed to TB but do not have active TB may have a latent TB infection, which means that the bacteria are in their body but are not causing symptoms. Treatment with antibiotics can help prevent latent TB from becoming active TB.
  5. Treatment of Active TB: Prompt diagnosis and treatment of active TB is crucial to prevent the spread of the disease to others. People with active TB should be treated with a combination of medications for several months to ensure that the bacteria are completely eliminated.
  6. Education and Awareness: Educating people about the signs and symptoms of TB, how it is spread, and how to prevent it can help raise awareness and reduce the spread of the disease.
2 thoughts on “Pulmonary Tuberculosis (TB)”
    1. Thank u for your question. The answer is in the article under the title of “Prevention”.

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