What do mycobacteria possess?
A lipid-rich cell wall
What does the lipid-rich cell well of mycobacteria do?
Retains some dyes, even resisting decolourisation with acid (acid-fast)
How is TB spread from person to person?
By the aerosol route
What is the first site of infection for TB?
What is the outcome of primary TB?
Most infections resolve with local scarring
What does TB post-primary infection refer to?
The development of tuberculosis beyond the first few weeks
What may happen in TB post-primary infection?
The infection may progress throughout the body
What is it called when TB spreads throughout the body?
What is the outcome of miliary spread of TB?
- May resolve spontaneously
- May develop into localised infection
Give an example of a localised infection that may result from miliary spread of TB
What happens to Mycobacterium TB once inside the body?
It is ingested by macrophages
What happens to Mycobacterium TB once it has been ingested by macrophages?
It escapes from the phagolysosome to multiply in the cytoplasm
What does the intense immune response to Mycobacterium TB cause?
Local tissue destruction and cytokine-mediated systemic effects
What does local tissue destruction as a result of TB infection cause?
Cavitation in the lung
What cytokine-mediated systemic effects are caused by infection with TB?
Fever and weight loss
What organs may TB affect?
Any organ of the body
What does TB mimic?
Both inflammatory and malignant diseases
How may pulmonary TB present?
- Chronic cough
- Weight loss
- Recurrent bacterial pneumonia
What happens if pulmonary TB is left untreated?
It follows a chronic, deteriorating course
How does tuberculous meningitis present?
- Slowly deteriorating level of consicousness
How may a kidney infection present?
- Local infection
- Weight loss
What are the potential complications of a kidney infection?
- Ureteric fibrosis
What is a common site of bone infection?
The lumbosacral spine
What may progression of a bone infection in the lumbosacral spine cause?
- Vertebral collapse
- Nerve compression
What may inflamamation of large joints lead to?
What does Mycobacterium TB stimulate once it has escaped from macrophages?
An immune response, with the release of IL-12
What is the effect of IL-12?
It drives the release of IFN-γ and TNF-α from NK and CD4 cells
What is the effect of IFN-γ and TNF-α?
They activate and recruit more macrophages to the site of infection, resulting in the formation of granulomas
What are the primary changes in TB?
- Few symptoms
- Lymph nodes may become englarged in young people
What is the classical presentation of post-primary TB?
- Cough (not always productive)
- Fevers towards the end of the day, or at night
- Weight loss and general debility