TB Flashcards
What are the characteristics of the tuberculosis bacterium?
- Aerobic
- Non - motile
- Slightly curved rods with waxy capsule
- ACID FAST - goes red/pink with ziegler’s-neelsen stain
- Slow growing
- Granulomatous (as resistant to phagocytosis)
- Remain dormant
How is TB spread?
Airbourne infection spread via rest droplets
What is the pathophysiology of primary TB?
- Inhaled, alveolar macrophages ingest bacteria
- Mycobacteria proteins inhibit lysosome fusion with phagosomes so no phagocytosis and survival within the macrophage
- Bacteria proliferate within the macrophage
- Macrophage presents to T lymphocytes - immune response
- Delayed hypersensitivity reaction = tissue necrosis and granuloma formation
What does a granulomatous lesion consist of?
- Central area of necrotic material - caseation
- Surrounded by epithelia cells and longhand giant cells
What is a primary ghon focus?
The initial granuloma
Where is the goon focus located?
In the upper region of the lung in the sub pleural region (as its aerobic, there is most oxygen here)
What is the goon focus seen as on a CXR?
Small calcified nodule
Where do secondary lesions develop?
In the lymph nodes
What is a ghon complex?
The primary Ghon focus and caseous lesions within the lymph nodes
What is a range complex?
When the caveated areas heal completely and become calcified
How can the rank complexes differ?
Sometimes the bacteria are totally killed off and sometimes they lay dormant
What is latent TB?
Immune system contains the infection and develops immunity - 90% of latent TB will never cause any effect to patient
What is reactivation TB
Initial infection many years ago - has laid dormant - usually occurs when there is depression of the host immune system
How is TB transmitted?
- When the cavities erode into the airways, the bacilli can escape and infect more people when the patient coughs
What are the risk factors for TB?
- Origination from high incidence country
- Immunosuppression
- Diabetes
- IV drug user
- Malnutrition
