Tuberculosis

Question 1

What are the risk factors which can turn a primary infection of tuberculosis to an active disease?

Answer 1

• HIV
• TNFa
• IFNy
• Vitamin D
• immune immaturity/deterioration

Question 2

What is the non infectious stage of TB?

Answer 2

primary disease

Question 3

What is the infectious stage of TB?

Answer 3

• secondary disease due to endogenous re-activation

- secondary disease due to exogenous re-infection

Question 4

What are the different tests of TB?

Answer 4

• tuberculin skin test
• interferon gamma release assays
• sputum smear microscopy
• sputum culture
• molecular tests (GeneXpert)

Question 5

What are the symptoms of PTB?

Answer 5

• cough for 2-3 weeks, not responding to antibiotics
• sputum production (maybe with haemoptysis)
• fever
• night sweats
• weightloss

Question 6

What are the advantages and disadvantages of sputum culture?

Answer 6

advantages:

• susceptibility testing
• additional 20-30% diagnostic yield

disadvantages:

• expensive
• slow
• biohazard

Question 7

Describe the X-ray appearance of primary TB

Answer 7

Ghon complex:

• small (often calcified) focus of pulmonary infection
• asasociated lymphadenopathy

Question 8

Describe the X-ray appearances of secondary TB

Answer 8

• cavitation

- miliary TB (primary/post-primary disease)

Question 9

Rifampicin, its action and side effects

Answer 9

• inhibits bacterial DNA-dependent RNA polymerase

Side effects:

• hepatitis
• itch, rash, GI upset
• discolouration of urine, tears, swear
• induces liver enzymes increasing clearance of other drugs
• warfarin, OCP and anti-retroviral therapy interactions

Question 10

Isoniazid, its action and side effects

Answer 10

• inhibits mycolic acid biosynthesis in cell wall

Side effects:

• hepatitis
• peripheral neuropathy
• resistance

Question 11

Pyrazinamide, its action and side effects

Answer 11

• inhibits fatty acid synthase I
• hepatitis
• hyperuricemia
• can exacerbate gout

Question 12

Ethambutamol, its action and side effects

Answer 12

• inhibits arabinosyn transferase
• optic neuritis
• usually added to regimen to help prevent resistance to other drugs

Question 13

Describe the process of prescribing for TB

Answer 13

• intensive phase (2 months): rifampicin, isoniazid, pyrazinamide, ethambutol
• continuation phase (4 months): rifampicin, isoniazid

Question 14

What are the different mutations that can cause antibiotic resistance to anti-TB drugs?

Answer 14

• katG mutations
• inhA mutations
• rpoB mutations