Tuberculosis - Types, Pathogenesis, Signs and Symptoms, Diagnosis, Treatment and Prevention

Summary

This video discusses tuberculosis (TB), a serious bacterial infection caused by Mycobacterium tuberculosis. It explores the bacterium's characteristics, how it infects the body, and its various forms, including primary, secondary, and miliary tuberculosis. The video also covers risk factors, pathogenesis, clinical signs, and diagnostic methods. Emphasis is placed on the immune response, granuloma formation, and the potential outcomes of TB. Treatment options, including the standard six-month regimen of four antibiotics, as well as preventive measures like the BCG vaccine, are also outlined, stressing the importance of early detection, isolation, and contact tracing to prevent further spread.

Takeaways

• 😀 Tuberculosis (TB) is caused by *Mycobacterium tuberculosis*, a slow-growing, acid-fast bacterium with high lipid content in its cell wall.
• 😀 TB is transmitted primarily through aerosol droplets when an infected person coughs or sneezes.
• 😀 Risk factors for TB include HIV infection, alcoholism, diabetes, immunosuppressive therapy, and healthcare work exposure.
• 😀 There are two main types of TB: Primary TB (in individuals with no prior exposure) and Secondary TB (due to reactivation of dormant bacteria).
• 😀 Primary TB leads to granuloma formation in the lungs, with the potential for dormant bacteria to cause latent TB.
• 😀 Secondary TB typically affects the upper lobes of the lungs and can lead to cavitation, where lung tissue is destroyed and air spaces form.
• 😀 Miliary TB occurs when bacteria spread through the bloodstream to multiple organs, potentially causing severe, systemic infection.
• 😀 Extrapulmonary TB involves the spread of bacteria to organs outside the lungs, such as the kidneys, bones, and lymph nodes.
• 😀 The clinical signs of TB include a persistent cough, low-grade fever, weight loss, night sweats, and hemoptysis (coughing blood).
• 😀 Diagnosis is made through a combination of clinical symptoms, chest X-rays, sputum tests, bacterial cultures, and the Mantoux tuberculin skin test.
• 😀 TB treatment involves a six-month course of antibiotics (isoniazid, rifampicin, pyrazinamide, and ethambutol), with strict adherence needed to avoid resistance.
• 😀 Prevention of TB includes isolating infected individuals, contact tracing, screening, and vaccination with the BCG vaccine to prevent severe forms of TB.

Q & A

What is the causative organism of tuberculosis?

The causative organism of tuberculosis is Mycobacterium tuberculosis, which is a slow-growing, rod-shaped, obligate aerobic, intracellular bacterium.

Why does Mycobacterium tuberculosis not stain with a Gram stain?

Mycobacterium tuberculosis has a high lipid content, especially mycolic acid, in its cell wall. This prevents it from staining with the Gram stain, making it an acid-fast bacillus.

What is the major virulence factor of Mycobacterium tuberculosis?

The major virulence factor of Mycobacterium tuberculosis is its ability to survive and multiply inside macrophages by avoiding lysosomal killing.

How is tuberculosis primarily transmitted?

Tuberculosis is primarily transmitted via aerosol transmission, where infectious droplets from an infected person are inhaled by others.

What are the key risk factors for tuberculosis?

Key risk factors for tuberculosis include HIV infection, alcoholism, immunosuppressive therapy (e.g., corticosteroids), diabetes mellitus, recent surgery, and exposure in healthcare settings.

What are the two types of tuberculosis based on pathogenesis?

The two types of tuberculosis based on pathogenesis are primary tuberculosis, which occurs in non-sensitized individuals, and secondary tuberculosis, which occurs in previously sensitized individuals.

What is the difference between pulmonary and extrapulmonary tuberculosis?

Pulmonary tuberculosis primarily affects the lungs, while extrapulmonary tuberculosis can affect any organ in the body, including the liver, kidneys, bones, and brain.

What is latent tuberculosis and how does it occur?

Latent tuberculosis occurs when dormant bacilli remain in the body after the initial infection is controlled by the immune system. The person remains asymptomatic until their immunity weakens, at which point the bacilli can become reactivated.

What is the role of the granuloma in tuberculosis?

The granuloma forms as a result of an immune response where macrophages, lymphocytes, and other cells surround and contain the bacteria. It helps to isolate the infection, although some bacilli may remain dormant inside the granuloma.

How is tuberculosis diagnosed?

Tuberculosis is diagnosed through a combination of patient history, clinical signs, radiographic findings, and microbiological tests such as sputum smear for acid-fast bacilli, culture, PCR, and the tuberculin skin test (Mantoux test).

What is the standard treatment for tuberculosis?

The standard treatment for tuberculosis is a six-month regimen of four antibiotics: isoniazid, rifampicin, pyrazinamide, and ethambutol, with treatment closely monitored to prevent antibiotic resistance.

What is the BCG vaccine, and what does it prevent?

The BCG vaccine is a live attenuated vaccine made from a reduced virulence strain of Mycobacterium bovis. It is given at birth to prevent disseminated forms of tuberculosis, such as miliary tuberculosis and TB meningitis, but does not prevent latent or secondary tuberculosis later in life.