Tuberculosis

Question 1

Main pathogen

Answer 1

Mycobacterium Tuberculosis

Question 2

Mycobacterium Tuberculosis

Answer 2

• Rod Shaped Gram Positive Bacilli.
• Acid fast characteristics.
• Slow growing.
• 2-4 um by 0.2-0.5 um.

Question 3

Transmission of TB

Answer 3

Aerosol

Question 4

Risk factors

Answer 4

• Visited SE Asia/India (contact with virulent organism).
• Immunosuppression.
• Lifestyle.
• Diabetes.

Question 5

Treatment of Active TB

Answer 5

1. 4 drugs for 2 months: RIPE.

2. 2 drugs for further 4 months: RI.

Question 6

RIPE

Answer 6

Rifampicin, Isoniazid, Pyrazinamide, Ethambutol.

Question 7

Treatment of Latent TB

Answer 7

1. 2 drugs for 3 months: RI.
   or
2. 1 drug for 6 months: Isoniazid.

Question 8

Immune Response to MTB

Answer 8

1. Phagocytosis
2. Immune recognition & innate effector mechanisms.
3. Slow onset of Th1-biased adaptive immunity.
4. Enhanced effector mechanisms.

Question 9

CMI

Answer 9

Cell-Mediated Th1-biased immunity: Key to successful anti-tuberculosis immune response.

Question 10

Defective CMI

Answer 10

E.g. children, HIV affected persons, patients taking anti-TNF-a drugs.

Increased risk of TB.

Question 11

Why is MTB ideally suited to infect & survive within humans?

Answer 11

It is an ancient human pathogen that has co-evolved with modern homosapiens.

Question 12

Symptoms of TB

Answer 12

• Productive, persistent cough >3 weeks.
• Haemoptysis.
• Malaise.
• Weight loss.
• Night sweats.
• Dyspnoea.
• Fever.
• Bone pain.
• Pleuritic pain.

Question 13

Signs of TB

Answer 13

Upper zone crackles.

Question 14

Tests for TB

Answer 14

Sputum culture, PCR, Ziehl Neelson, CXR, Tuberculin skin test, Bronchoscopy, AAFB, GIT.

Question 15

CXR of Patient with MTB

Answer 15

Caseous necrosis, fibrosis and calcification in upper lobes, consolidation.

Question 16

Side effects of Rifampicin

Answer 16

Enzyme induction => orange bodily fluids.

Increased liver metabolism.

Question 17

Side effects of Izoniazid

Answer 17

Neuropathy, hepatitis

Question 18

Side effects of Pyrazinamide

Answer 18

Hepatitis, vomiting, hyperuricaemia

Question 19

Side effects of Ethambutol

Answer 19

Colour blindness

Question 20

Type of hypersensitivity

Answer 20

Type IV (delayed)

Question 21

Other causative organisms

Answer 21

Mycobacterium Bovis

Question 22

Immunity

Answer 22

T-Cell response to organism enhances macrophage ability to kill mycobacteria.

Question 23

Hypersensitivity

Answer 23

T-Cell response causes granulomatous inflammation, tissue necrosis & scarring.

Question 24

Primary TB Pathology

Answer 24

Inhaled organism phagocytosed & carried to hilar lymph nodes. Immune activation (few weeks) leads to granulomatous response in nodes & lungs => leads to killing.

Question 25

Tissue changes in Primary TB

Answer 25

Ghon Focus & large hilar nodes (granulomatous)

Question 26

Latent TB

Answer 26

Symptom free, no evidence of active TB + evidence of previous TB infection.

Question 27

Secondary TB

Answer 27

Latent Reactivation: Reinfection/reactivation of disease in a person with some immunity.

Question 28

Risk Factors of Reactivation of TB

Answer 28

Diabetes, lifestyle, immunosuppression (decreased T cell function), contact with more virulent organism.

Question 29

Tissue Changes in Secondary TB

Answer 29

Fibrosing & cavitation apical lesion.

Question 30

Location of Primary TB

Answer 30

Within lungs, upper lobes principally affected.

Question 31

Location of Secondary TB

Answer 31

Tends to remain localised, often in apices of the lungs but can spread to airways & bloodstream.