Respiratory infections: tuberculosis (R1)

Question 1

Pathophysiology
- Gram positive or negative?
- Why is mycobacterium TB an acid fast bacteria? What does this mean?
- Mode of transmission?

Answer 1

Gram positive
Because of its waxy cell wall, it is acid fast - will retain stain even when exposed to acid and alcohol treatment.
Airborne

Question 2

Primary tuberculosis
- Is symptomatic or contagious?
- Describe the 3 main steps
- What are the 3 main outcomes of primary TB?

Answer 2

Asymptomatic and not contagious

1. Alveolar macrophages ingest bacteria. TB produces a protein that inhibits phagosome + lysosome fusion; TB survives and proliferates.
2. Cell mediated immunity occurs (~3 weeks after initial infection). Forms granulomas with caseous necrosis
3. Infection spreads to the hilar lymph nodes, causing caseous necrosis there too.

Outcomes:
1. TB may be killed
2. TB may become dormant
3. TB may spread via blood to body - systemic miliary TB

Question 3

Primary tuberculosis
- Distinguish: granuloma, caseous necrosis, Ghon focus, Ghon complex

Answer 3

Question 4

Granuloma histology
- The outside is made of what cell types?
- The inside is made out of what?

Answer 4

Activated macrophages (aka. epithelioid histiocytes) and lymphocytes (T cells)
–> Activated macrophages can fuse to become a multinucleate giant cell

Macrophages undergoing necrosis –> caseous necrosis

Question 5

Secondary tuberculosis
- Is it symptomatic or contagious?
- Why might a second infection occur?

Answer 5

Both symptomatic and contagious

Due to
- Reinfection
- Reactivation of latent TB - immunosupprseion

Question 6

Secondary tuberculosis
- Steps?

Answer 6

Question 7

What are some complications of systemic miliary TB?

Answer 7

Question 8

What is the vaccine for TB?

Answer 8

BCG vaccine

Question 9

Risk factors for TB?

Answer 9

Question 10

History: symptoms of TB?

Answer 10

Cough tends to be chronic

Question 11

Investigations
- Bedside test?

Answer 11

Question 12

Investigations:
- Laboratory

Answer 12

Question 13

Investigations
- Imaging

Answer 13

CXR

Question 14

Management
- Of latent TB?

Answer 14

3 months of daily rifampicin + isoniazid

Question 15

Management
- Of active TB?

Answer 15

• Intensive phase: 2 months of RIPE (rifampicin, isoniazid, pyrazinamide, ethambutol)
• Continuation phase: rifampicin + isoniazid for 4 months
• Directly observed therapy: HCW watches and confirms you’re taking the medication

Question 16

Management
- Side effects of rifampicin, isoniazid, pyrazinamide, ethambutol?

Answer 16

Question 17

Prognosis
- Without treatment, TB has a mortality rate of __%
- If treated, do patients with TB generally do well?

Answer 17

50%
Yes

Question 18

Patient explanation:
- How would you explain TB to them?

Answer 18

Tuberculosis is a serious infection that usually affects the lungs, but can also affect other organs in the body

Latent TB infection: bacteria causing TB lie dormant in your body without making you ill. Not contagious

Active TB: bacteria can become active at some point, making you ill and contagious.

Without treatment, tuberculosis can be life threatening.

Question 19

Patient explanation
- How would you discuss treatment for TB?

Answer 19

Six months antibiotics. 2 months of intensive treatment with 4 antibiotics; then 4 months with just two

Important you take the medicines exactly as your doctor advises. Stopping treatment too soon or not taking the full dose can allow the bacteria to survive and become resistant to antibiotics.