Tuberculosis (TB)

Question 1

What is TB?

Answer 1

A chronic granulomatous infectious disease caused by the bacteria : Mycobacterium tuberculosis.

Question 2

Epidemiology (& Risk Factors) of TB (3).

Answer 2

More prevalent in :-
1. Non-UK Born Patients (South Asia).
2. Immunocompromised e.g. HIV.
3. Close Contacts with TB.

Question 3

What is Multi-Drug Resistant TB?

Answer 3

Strain resistant to more than one TB drug, making it difficult to treat - use amikacin, macrlides, quinolones and capreomycin.

Question 4

Nature of Mycobacterium tuberculosis (3).

Answer 4

1. Small Rod-Shaped Bacillus.
2. Waxy Coating (makes Gram-Staining Ineffective).
3. Acid-Fast (Resistant to the acids used in the staining procedure).

Question 5

Staining of Mycobacterium tuberculosis.

Answer 5

Ziehl Neelsen Stain : Bright Red against Blue Background.

Question 6

What property of Mycobacterium tuberculosis makes it difficult to culture?

Answer 6

Very slow dividing with high Oxygen demands.

Question 7

Transmission of TB.

Answer 7

Inhalation of saliva droplets from infected people, spreading through lymphatics and blood.

Question 8

What is a Granuloma?

Answer 8

An aggregate of activated epithelioid macrophages - walling off viable organisms in anoxic and acidic environment.

Question 9

Pathophysiology of Pulmonary TB (5).

Answer 9

1. Lung Lesion - Ghon Focus develops (tubercle-laden macrophages).
2. Ghon Complex = Ghon Focus + Hilar Lymph Nodes.
3. Granuloma Formation with Caseous Necrosis in Centre.
4. Inflammatory Response : Type 4 Hypersensitivity Reaction.
5. Th2 Driven (usually Th1 Driven in good health to form granulomas).
6. Immunocompetent = Healing by Fibrosis. Immunocompromised = Disseminated Disease.

Question 10

What is Active TB?

Answer 10

Active infection in various areas within the body.

Question 11

What is Latent TB?

Answer 11

When the immune system encapsulates sites of infection to stop the progression of the disease.

Question 12

What is Secondary TB?

Answer 12

Reactivation of Latent TB.

Question 13

What is Military TB?

Answer 13

When the immune system is unable to control the disease, this causes a disseminated severe disease.

Question 14

Sites of TB Infection (2H).

Answer 14

1. Pulmonary : Lungs (Oxygen Supply).
2. Extrapulmonary :
   2A. Lymph Nodes (Cervical - Scrofuloderma).
   2B. Pleura.
   2C. CNS (Tuberculous Meningitis).
   2D. Pericardium.
   2E. GI System.
   2F. GU System (commonest).
   2G. Bones and Joints.
   2H. Cutaneous TB (Skin).

Question 15

What does TB in the Lymph Nodes cause?

Answer 15

A ‘cold abscess’ - firm painless abscess in the neck with no inflammation, redness and pain (unlike an acutely infected abscess).

Question 16

What is Spinal TB known as?

Answer 16

Pott’s Disease of the Spine.

Question 17

Clinical Presentation of TB (2).

Answer 17

1. Chronic Gradually Worsening Symptoms.
2. 70% Pulmonary TB (but with Systemic Symptoms).

Question 18

Clinical Features of TB (5).

Answer 18

1. Constitutional Symptoms.
2. Cough +/- Haemoptysis.
3. Lymphadenopathy.
4. Erythema Nodosum.
5. Spinal Pain (Spinal TB).

Question 19

Investigations of TB (2B).

Answer 19

1. Ziehl-Neelsen Stain.
2. Immune Response to TB Tests :
   2A. Mantoux Test.
   2B. IGRA Test.

Question 20

Indication of Mantoux Test (3).

Answer 20

1. Previous Vaccination to TB.
2. Latent TB.
3. Active TB.

Question 21

Method of Mantoux Test (2).

Answer 21

1. Inject tuberculin into the intradermal forearm to create a bleb under the skin.
2. After 72 hours, measure the induration of the skin at the site of injection.

Question 22

What is Tuberculin?

Answer 22

A collection of tuberculosis proteins that have been isolated from the bacteria - the infection does not contain any live bacteria.

Question 23

Mantoux Test Results (3).

Answer 23

1. Negative : Induration < 6mm (no significant hypersensitivity to tuberculin protein - can give BCG if unvaccinated).
2. Positive : Induration of 6-15 mm (hypersensitive - previous TB infection or BCG - don’t give BCG).
3. Strongly Positive : Induration > 15mm (hypersensitive - TB infection).

Question 24

Give 5 false negative causes of the Mantoux test.

Answer 24

1. Military TB.
2. Sarcoidosis.
3. HIV.
4. Lymphoma.
5. Very Young (< 6 Months).

Question 25

Method of IGRA Test (2).

Answer 25

1. Mix TB antigens with a sample of blood. 2. WBCs that are already sensitised will release Interferon-Gamma as part of the immune response.

Question 26

Indication of IGRA Test.

Answer 26

Positive Mantoux test but no features of Active TB in order to confirm a diagnosis of Latent TB.

Question 27

What would a CXR show in TB (3)?

Answer 27

1. Primary : Patchy Consolidation, Pleural Effusions and Bilateral Hilar Lymphadenopathy. 2. Reactivated : Patchy/Nodular Consolidation with Cavitation (Gas Spaces in Lungs) in Upper Zones. 3. Military : 'Millet Seeds' uniformly distributed throughout the lung fields.

Question 28

Cultures in TB (3).

Answer 28

1. Sputum - 3 Samples Collected and Tested (Hypertonic Saline to induce Sputum / Bronchoscopy with Lavage to collect Sputum Samples). 2. Mycobacterium Blood Cultures. 3. Lymph Node Aspiration or Biopsy.

Question 29

When would a NAAT be useful?

Answer 29

Only if the information would affect treatment or the patient is at a higher risk of developing complications e.g. HIV.

Question 30

What can decrease the sensitivity of a sputum smear?

Answer 30

HIV.

Question 31

Management of Latent TB (2B).

Answer 31

1. No Treatment - Healthy. 2. Risk of Reactivation : 2A. Isoniazid and Rifampicin - 3 Months. 2B. Isoniazid - 6 Months.

Question 32

Why are there 2 options in Latent TB management?

Answer 32

A : People Younger than 35 if Hepatotoxicity is a concern. B : Interactions with Rifamycins are a concern e.g. HIV, Transplant.

Question 33

Management of Acute TB (2D).

Answer 33

1. MDT. 2. RIPE Combination : 2A. Rifampicin - 6 Months. 2B. Isoniazid - 6 Months. 2C. Pyrazinamide - 2 Months. 2D. Ethambutol - 2 Months.

Question 34

What is given with Isoniazid Prophylactically?

Answer 34

Pyridoxine (Vitamin B6) - Isoniazid causes peripheral neuropathy.

Question 35

Important Management Considerations of TB (4).

Answer 35

1. Test for Infectious Diseases e.g. HIV. 2. Contact Testing. 3. Public Health England. 4. Isolation until Established on Treatment (2 Weeks).

Question 36

How are patients with Active TB isolated in hospital?

Answer 36

Negative pressure rooms have ventilation systems that actively remove air to prevent it spreading out on to the ward to prevent airborne spread.

Question 37

Management of Meningeal Tuberculosis.

Answer 37

Prolonged period - at least 12 months - with addition of steroids.

Question 38

What is Direct Observed Therapy (DOT) (3)?

Answer 38

3x a weekly dosing regimen indicated in certain groups e.g. :- 1. Homeless People. 2. Poor Concordance. 3. Prisoners.

Question 39

Medication Information for Patient.

Answer 39

Take RIPE all together on empty stomach 1 hour before breakfast.

Question 40

What is the BCG Vaccine?

Answer 40

An intradermal infection of live attenuated TB.

Question 41

What is the BCG Vaccine useful for and not useful for?

Answer 41

Useful : Severe and Complicated TB. Not Useful For : Pulmonary TB (Less Effective).

Question 42

Conditions for the BCG Vaccine (2).

Answer 42

1. Mantoux Test Negative. 2. Immunosuppression and HIV Negative (Live Vaccine).

Question 43

Relationship between HIV and TB (3).

Answer 43

1. Depletion of M. tuberculosis-specific CD4 T Lymphocytes and Type I Cytokine Production. 2. Dysfunction of the CD4 T Lymphocyte-Macrophage Immune Axis. 3. Impairs Host's Ability to Form Granulomas.