Tuberculosis (TB): A severe Lung Infection

 

Discovery and History of Tuberculosis (TB):

• Tuberculosis has been a known disease for centuries, but it was Robert Koch who discovered the bacterium Mycobacterium tuberculosis in 1882 as the cause of TB.
• At that time, TB was a leading cause of death, especially in Europe, where:
• 1 in 7 deaths was due to TB.
• Among young adults, it caused 1 in 3 deaths.
• This discovery was groundbreaking because it showed that TB was caused by a specific microorganism, paving the way for diagnosis and treatment.
• Mycobacterium tuberculosis

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Current Global Impact:

• Even today, TB remains a major health problem worldwide.
• About 1 billion people (20% of the global population) are infected.
• Every year, millions of new cases of TB are being reported,
• TB is especially serious in regions with poor healthcare systems, where people lack access to proper diagnosis and treatment.

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People more prone to TB:

• TB is more common in certain groups, such as:
• Homeless individuals.
• Elderly people, malnourished individuals, and those with alcohol addiction.
• Minorities, immigrants, and prisoners.
• TB spreads from person to person when an infected individual coughs or sneezes, releasing tiny droplets containing the bacteria into the air.
• Many active TB cases result from the reactivation of dormant infections rather than new transmissions.

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Causes of TB:

• TB is primarily caused by the bacterium Mycobacterium tuberculosis.
• In some cases, other bacteria like:
• Mycobacterium bovis (spread through infected animals or unpasteurized milk).
• Mycobacterium africanum (prevalent in West Africa) a member of the M. tuberculosis complex (MTBC) can also cause TB.
• The AIDS epidemic has made TB worse globally because:
• HIV weakens the immune system, increasing the risk of TB in HIV-infected individuals.
• People with both infections are at higher risk of developing severe TB.

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How TB Affects the Body:

• When TB bacteria enter the lungs, they are engulfed by immune cells called macrophages.
• The body tries to contain the bacteria by forming small, hard nodules in the lungs called tubercles.
• Over time:
• Tubercles may harden and turn into Ghon complexes, visible on chest X-rays.
• In some cases, the bacteria survive inside the macrophages and form caseous lesions (cheese-like structures).
• If these lesions liquefy, they can form cavities, allowing the bacteria to spread to other parts of the body. This spread is called miliary TB, which creates tiny lesions like millet seeds in tissues.
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  Infected Lungs with caseous lesions

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Symptoms of TB:

• TB develops slowly, and its symptoms include:
• Fever, fatigue, weight loss.
• Persistent cough, which may produce bloody sputum if the lungs are severely affected.
• These symptoms can worsen if the disease is not treated in time, leading to serious complications.

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Diagnosis of TB:

• TB is diagnosed using various methods:
1. Skin tests:
• The Mantoux test involves injecting a TB protein (PPD) under the skin.
• A positive test shows a reaction (redness and swelling) if the person has been exposed to TB.
• Mantoux test shows a reaction (redness and swelling)
  
  
• However, a positive test could mean:
• Active infection.
• Past infection or vaccination.
2. X-rays: To check for tubercles or Ghon complexes in the lungs.
3. Laboratory tests: TB blood test (Interferon Gamma Release Assay [IGRA]), test measures interferon-gamma (IFN-γ), which produces T cells in response to TB antigens
4. DNA tests: To quickly identify the presence of TB bacteria. The polymerase chain reaction (PCR) was used to identify mycobacterial DNA sequences in uncultured clinical specimens.

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Treatment of TB:

• TB treatment involves a combination of antibiotics, including:
• Isoniazid (INH), Rifampin, Ethambutol, and Pyrazinamide.
• These drugs are taken together for 12 to 24 months to ensure all bacteria are killed and to prevent drug resistance.
• Stopping treatment early or taking medications irregularly can lead to incomplete cure and drug-resistant TB.

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Drug-Resistant TB:

• Multi-drug-resistant TB (MDR-TB):
• This type of TB doesn’t respond to the most effective drugs, Isoniazid and Rifampin.
• MDR-TB often occurs due to:
• Incomplete or improper treatment.
• Irregular drug intake or poor absorption of medications.
• Drug resistance arises from random mutations in the TB bacteria, making them resistant to certain antibiotics.
• Treating MDR-TB is more challenging, requiring newer and stronger drugs.

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Prevention and Control of TB:

• Vaccination:
• The BCG vaccine is given to infants and children in many countries to prevent severe TB forms like meningitis.
• It provides partial protection but is not 100% effective.
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• Public Health Measures:
• Improving living conditions, reducing homelessness, and minimizing drug abuse can lower TB rates.
• Comprehensive Care for MDR-TB Patients:
• Programs should include proper medication, psychological support, and nutritional care.
• Rapid Treatment:
• Early diagnosis and starting treatment quickly can prevent the spread of TB to others