Mycobacterium Tuberculosis

Question 1

Mycobacterium tuberculosis

Answer 1

1. Rods
2. Strict aerobes
3. Waxy cell wall –> “acid-fast” on Ziehl-Neelsen stain
4. Transmitted via inhalation

Question 2

CXR findings in TB

Answer 2

1. Ranke complexes / Ghon focus
2. Lower lungs when dormant
3. Cavitating lesions in upper lobes if reactivated

Question 3

Indications for antenatal screening for TB

Answer 3

1. HIV positive or significant immunocompromise
2. Recent close contact with infectious TB
3. Recent arrival from area with high prevalence of TB

Question 4

Tests for TB screening

Answer 4

1. Tuberculin skin test
   - positive in active or latent
   and/or
2. Interferon gamma release assay (IGRA)
   - more specific to TB

If negative, no further action

Question 5

Indication for CXR (TB)

Answer 5

1. Symptoms suggestive of TB
2. Skin test or IGRA positive

Also do clinical examination
Use a chest shield

Question 6

Areas with high prevalence of TB

Answer 6

South East Asia
Pacific Islands
Africa
Eastern Europe
Latin America

Question 7

High risk individuals for latent TB reactivation

Answer 7

HIV postive
Poorly controlled diabetes
Chronic renal failure
Malignancy (etc)

Question 8

TB in pregnancy

Answer 8

The development, clinical presentation and progression are not altered by pregnancy

Question 9

Treatment of TB: No evidence on examination or CXR

Answer 9

Consider isoniazid and/or rifampin prophylaxis post-partum

Question 10

Treatment of TB: Evidence of old/inactive TB, high risk or TST conversion ≤2 years

Answer 10

Consider isoniazid and/or rifampin prophylaxis

Question 11

Treatment of TB: Evidence of active TB

Answer 11

1. Sputum, urine + other investigations as appropriate
2. Treat according to location and drug resistance, liaise with TB expert if required
3. Pulmonary TB no resistance:
   Isoniazid 6 mths
   Rifampicin 6 mths
   Pyrazinamide 2 mths
   Ethambutol 2 mths

Question 12

TB Drugs in pregnancy

Answer 12

All cross the placenta and low concentration in fetal tissues
Isoniazid, rifampicin, ethambutol all safe
Less safety data for pyrazinamide, recommended by WHO

Question 13

Monitoring during TB treatment

Answer 13

Monthly ALT / AST

Question 14

Signs of neonatal TB

Answer 14

Respiratory distress
Hepatosplenomegaly
Fever
Lymphadenopathy
Poor feeding

Question 15

Mechanisms of spread to neonate

Answer 15

1. Airborne spread after delivery (most common)
   - no need to separate unless drug-resistant TB
2. Congenital infection
   - placenta for MCS / histo