24 Questions
What are the two types of Mycobacterium tuberculosis?
Human type and bovine type
What is the structure of Mycobacterium tuberculosis?
A central core of protein (tuberculoprotein), a polysaccharide fraction, and a lipid capsule
What is the mechanism of granuloma formation in tuberculosis?
Tubercle bacilli enter macrophages, replicate, and then are presented to T cells, leading to a type IV hypersensitivity reaction and formation of granuloma
What is the role of T cells in tuberculosis?
T cells differentiate to T-helper 1 cells, which activate macrophages to kill bacteria
What is caseation necrosis due to?
Hypersensitivity reaction and endarteritis obliterans
What is the type of hypersensitivity reaction that occurs in tuberculosis?
Type IV hypersensitivity reaction
What are the two types of tissue reactions to tuberculosis?
Cellular reaction (tubercle formation) and exudative reaction
What is the effect of pasteurization on Mycobacterium tuberculosis?
Mycobacterium tuberculosis can be killed by pasteurization
What type of organs are affected in exudative tissue reactions?
Serous sacs, lungs
What is a characteristic feature of a microscopic picture of a high immunity response to TB?
Many granulomata, many epithelioid cells, many giant cells, few lymphocytes, and less caseation
What is the outcome of a primary pulmonary TB infection when the bacteria are not fully eliminated?
Latent infection
What is the term for the spread of TB to many organs through the bloodstream?
Miliary tuberculosis
What is the name of the complex that forms in the lungs as a result of primary pulmonary TB?
Ghon’s complex
What is the term for the reactivation of TB due to lowered immunity?
Secondary pulmonary tuberculosis
What are some conditions that can lead to reactivation of TB due to lowered immunity?
AIDS, debilitating diseases, immunosuppressant drugs, and Hodgkin’s lymphoma
What is the term for the spread of TB to a single organ through the bloodstream?
Isolated organ tuberculosis
What is the primary location of Ghon's focus in the lungs?
Lower part of upper lobe or upper part of lower lobe
What is the difference between primary and secondary TB in terms of age of exposure and infection?
Primary TB usually occurs in children, while secondary TB occurs in adults, often due to re-infection or re-activation.
What is the characteristic tissue reaction in secondary TB?
Accelerated tissue reaction
What is the most accurate test for diagnosing tuberculosis?
Identification of TB bacilli through sputum culture or PCR
What is the typical outcome of primary TB in patients with low immunity?
Acute bronchopneumonia
What is the characteristic feature of Ghon's complex?
Coalescent caseating tubercles
What is the difference between lymphadenitis in primary and secondary TB?
Prominent lymphadenitis in primary TB, minimal lymphadenitis in secondary TB
What is the outcome of secondary TB in patients with high immunity?
Chronic fibrocaseous pulmonary TB
Study Notes
Tuberculosis
- Chronic, infective, granulomatous inflammation caused by tubercle bacilli
- Aetiology:
- Predisposing factors: low standard of nutrition and housing, low natural resistance
- Pathogenic organism: Mycobacterium tuberculosis bacilli
- Characteristics of Mycobacterium tuberculosis:
- Aerobic, non-motile organism that can be killed by pasteurization
- Weak gram-positive, stained with Ziehl-Neelsen stain
- Structure: central core of protein (tuberculoprotein), polysaccharide fraction, lipid capsule
Methods of Infection
- Infection occurs through contact with infected individuals or contaminated milk and dairy products
Pathogenesis of Granuloma Formation
- Within 3 weeks of exposure, tubercle bacilli enter macrophages, replicate within phagosomes, and cause bacteremia and seeding of multiple sites
- After 3 weeks, tubercle bacilli are drained to lymph nodes, presented to T cells, and activate macrophages to kill bacteria
- Type IV hypersensitivity reaction develops, leading to granuloma formation and caseous necrosis
Morphology of TB Lesions
- Tissue reaction to tuberculosis:
- Cellular reaction (tubercle formation)
- Exudative reaction
- Characteristics of TB granuloma:
- Many granulomata, epithelioid cells, giant cells, and few lymphocytes
- Caseation necrosis due to hypersensitivity reaction and endarteritis obliterans
Fate of the Tubercle
- Small lesions: replaced by fibrosis, bacteria may remain as latent infection
- Large caseous lesions: reactivate, leading to secondary pulmonary tuberculosis, especially in individuals with lowered immunity (e.g., AIDS, debilitating disease, immunosuppressant drugs)
Primary Pulmonary Tuberculosis
- Mode of transmission: inhalation of infected droplets
- Primary pulmonary complex (Ghon's complex):
- Ghon's focus: small area (1 cm), subpleural, lower part of upper lobe or upper part of lower lobe
- Lymphangitis and lymphadenitis
Secondary Pulmonary Tuberculosis
- Etiology:
- Reactivation of latent infection
- Re-infection
- Pathogenesis:
- Preexisting hypersensitivity induces rapid tissue response, leading to rapid localization of disease with less lymph node involvement
- Marked caseation and destruction lead to cavitations and dissemination of infection
Diagnosis of Tuberculosis
- History of contact with tuberculous patient
- Toxic manifestations
- Productive cough, pleuritic pain, hemoptysis
- Tuberculin test
- Biopsy: characteristic granuloma
- Identification of TB bacilli (sputum culture, PCR): most accurate test for diagnosis
Learn about the causes and characteristics of tuberculosis, a chronic infective granulomatous inflammation caused by Mycobacterium tuberculosis bacilli. Understand predisposing factors, pathogenic organisms, and types of tuberculosis.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
