Tuberculosis - causes, symptoms, diagnosis, treatment, pathology

Summary

This video provides a comprehensive overview of tuberculosis (TB), explaining its transmission, symptoms, and how the immune system responds to the infection. It covers the stages of TB, from primary infection to reactivation in immunocompromised individuals, and the development of conditions like miliary TB. The script also delves into diagnostic tests such as the PPD and IGRA, as well as the treatment protocols for both latent and active TB, including strategies for combating drug-resistant strains like MDR-TB and XDR-TB. The video emphasizes the importance of early detection, proper medication adherence, and the emergence of new therapies for drug-resistant TB.

Takeaways

• 😀 Tuberculosis (TB) is caused by Mycobacterium tuberculosis, which primarily affects the lungs.
• 😀 About 2 billion people worldwide are infected with TB, but most don’t show symptoms due to the latent form of the disease.
• 😀 TB is transmitted through inhalation, and the bacteria can avoid the immune system by residing in the lungs' alveoli.
• 😀 Mycobacterium tuberculosis is acid-fast due to its waxy cell wall, which helps it resist weak disinfectants and survive on dry surfaces for months.
• 😀 Primary tuberculosis may not cause symptoms immediately, but the immune system eventually tries to contain the infection by forming granulomas.
• 😀 Ghon focus is a tissue area with dead cells resulting from TB infection, while Ghon complex includes the infected lymph nodes.
• 😀 In some cases, TB becomes dormant and remains latent, but can reactivate if the immune system weakens due to aging, HIV, or other illnesses.
• 😀 Reactivated TB typically affects the upper lobes of the lungs, forming cavities, and can spread through the body, causing systemic miliary TB.
• 😀 TB spreads to other organs like kidneys, brain, liver, and bones, causing complications such as sterile pyuria, meningitis, hepatitis, and Pott disease.
• 😀 TB testing includes the tuberculin skin test (PPD) and interferon-gamma release assays (IGRAs), with chest X-rays to detect active TB.
• 😀 Treatment for TB involves prolonged use of antibiotics, with special regimens for multi-drug resistant TB (MDR-TB) and extremely drug-resistant TB (XDR-TB).

Q & A

What is tuberculosis (TB), and why is it a major global health concern?

Tuberculosis (TB) is an infection caused by *Mycobacterium tuberculosis*, primarily affecting the lungs. It is a major global health concern due to the vast number of people infected (about two billion), the potential for latent infection, and the emergence of drug-resistant strains such as MDR-TB and XDR-TB.

What does it mean for tuberculosis to be latent, and how does this affect the spread of the disease?

Latent tuberculosis means the bacteria remain dormant in the body without causing symptoms or being contagious. Most individuals with latent TB are unaware of their infection. If the immune system weakens, such as with aging or HIV, the bacteria can reactivate and potentially spread.

What are the unique characteristics of *Mycobacterium tuberculosis* that contribute to its survival and transmission?

*Mycobacterium tuberculosis* has a waxy cell wall due to mycolic acid, which makes it acid-fast, allowing it to resist weak disinfectants and survive on surfaces for months. It is also a strict aerobe, meaning it thrives in oxygen-rich environments, such as the lungs.

How does the immune system typically respond to a tuberculosis infection?

When TB enters the body, macrophages attempt to phagocytize the bacteria. If the immune response is effective, a granuloma forms to wall off the bacteria, creating a Ghon focus. Over time, the body may form scar tissue, and the infection could become dormant or latent.

What is the Ghon complex, and how is it related to tuberculosis?

The Ghon complex consists of a Ghon focus (the area of infection with caseous necrosis) and affected lymph nodes that also undergo caseation. This complex is a hallmark of primary tuberculosis and can be seen on X-rays, often calcified over time, forming a Ranke complex.

Why does tuberculosis tend to affect the upper lobes of the lungs when it reactivates?

When latent TB reactivates, it typically affects the upper lobes of the lungs because these areas have higher oxygen levels, which are more favorable for *Mycobacterium tuberculosis*, a strict aerobe.

What complications can arise when tuberculosis spreads beyond the lungs?

If TB spreads beyond the lungs, it can infect other organs, leading to complications such as kidney damage (sterile pyuria), meningitis, vertebral damage (Pott disease), adrenal gland damage (Addison's disease), liver hepatitis, and cervical lymph node infection (scrofula).

How is tuberculosis diagnosed?

TB can be diagnosed through a variety of tests, including the PPD skin test (tuberculin test), interferon-gamma release assays (IGRAs), chest X-rays, sputum culture, PCR, and bronchoalveolar lavage samples for laboratory testing.

What is the typical treatment approach for active tuberculosis?

Treatment for active TB involves a combination of antibiotics such as isoniazid, rifampin, ethambutol, and pyrazinamide, typically for several months. This regimen helps to ensure that the bacteria are completely eradicated and prevents the development of drug resistance.

What is the significance of directly observed therapy (DOT) in tuberculosis treatment?

Directly observed therapy (DOT) involves a healthcare worker supervising patients to ensure they take their TB medication as prescribed. This helps prevent the development of drug resistance and ensures the complete elimination of the bacteria from the body.