TB

Question 1

Causative organism?

Answer 1

Mycobacterium tuberculosis

Question 2

Spread?

Answer 2

Via respiratory droplets so only primary disease is communicable

Question 3

Describe primary disease features

Answer 3

Primary lung infection, small lesion called Gohn focus develops. Made up of tubercule laden macrophages. Gohn focus + hilar lymph nodes = Gohn complex.
Heals via fibrosis.

Question 4

Describe secondary disease features

Answer 4

When the host becomes immunosuppressed.
Initial infection reactivated. Can effect the lungs, CNS (tuberculous meningitis), vertebral bodies (Pott’s disease), cervical lymph nodes, kidneys and GI tract.

Question 5

Describe latent disease features

Answer 5

Persistent immune control, positive on testing but asymptomatic. 5-10% reactivate. Triggers: infection, HIV, transplant, immunosuppressives, drug use, malnutrition.

Question 6

Investigations?

Answer 6

Active TB-
Chest XR will show fibronodular linear opacities in the upper lobes. Bilateral hilar lymph node adenopathy.
Sputum smear- 3 samples needed, poor sensitivty.
Sputum culture- gold standard test, takes 1-3 weeks.
NAAT- instant results.

Latent TB-
Mantoux test- tuberculin skin testing.

Question 7

Active TB treatments

Answer 7

2 months of RIPE:
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol 
THEN...
4 months of 
Rifampicin 
Isoniazid

Question 8

Latent TB treatments

Answer 8

3 months Rifampicin and isoniazid
OR
6 months isoniazid.

Question 9

Tests pre-treatment?

Answer 9

LFTs (rifampicin can cause hepatitis, isoniazid can induce liver enzymes)
U+Es
FBC
Vision test (ethambutol can cause optic neuritis)

Question 10

Side effects of treatment?

Answer 10

Rifampicin- orange secretion, hepatitis, flu like symptoms

Isoniazid- peripheral neuropathy (prevent with VitB6 pyridoxine), hepatitis, liver-enzyme inducer.

Pyrazinamide- hyperuricaemia, gout, arthralgia

Ethambutol- optic neuritis