Tuberculosis

Question 1

What is the causative agent of TB?

Answer 1

Mycobacterium tuberculosis

Question 2

Describe features of M.tuberculosis

Answer 2

• Weak gram positive bacterium with acid-alcohol fast bacilli
• Slow growing in culture (6-8weeks) so molecular tests like Gene Xpert can identify TB directly from samples

Question 3

What are the different populations of TB?

Answer 3

Actively growing organisms - killed by isoniazid
Semi-dormant organisms inhibited by acid environment (killed by pyrazinamide)
Semi-dormant organisms with spurts of metabolic activity (killed by rifampicin)
Completely dormant cells which cannot be killed by standard drugs

Question 4

What is the immunological hallmark of TB?

Answer 4

Granulomas. These can appear on a CXR as a Ghon complex

Question 5

Describe the clinical presentation of tuberculosis

Answer 5

Pulmonary - cough +/- haemoptysis, SOB.
Systemic - Fever/chills, night sweats, fatigue, loss of apetitie/weight loss, lymphadenopathy.
CNS - Meningitis
Eyes - Choroiditis (blurred vision and red eyes)
CVS - Constrictive pericarditis, chest pain.
Renal - Dysuria, haematuria
GI - Abdo pain, mass in right iliac fossa, ascites,
Skeletal - arthritis and osteomyelitis

Question 6

Explain the presentation of apical disease TB (most common)?

Answer 6

• Cough
• Sputum
• Haemoptysis
• Fever,
• Weight loss
• Night sweats

Question 7

Who is at high risk of developing TB?

Answer 7

• Patients with HIV/AIDS
• Transplantation patients
• Silicosis
• CRF with dialysis
• Recent TB infection
• Patients on TNF alpha inhibitors

Question 8

What are the diagnostic tests for latent TB?

Answer 8

• Mantoux test (intradermal injection of TB antigens)
• Interferon gamma release assay (T-spot-TB and quantiferon)

Question 9

What are methods for diagnosing active TB?

Answer 9

• AFB (acid-fast bacilli) in respiratory samples/smears
• M. tuberculosis growth in liquid or solid cultures
• Clinical and radiological diagnosis

Question 10

What is the treatment for latent TB?

Answer 10

• Isoniazid monotherapy for 6 months for adults and children (strongly recommended).
• Rifampicin and isoniazid for daily 3 months as alternative for children/teens under 15.
• Rifapentine and isoniazid weekly for 3 months as alternative for adults and children

Question 11

What is the treatment for active TB?

Answer 11

6 month treatment - 2 RHEZ/4 RH
- Intensive phase for 2 months with rifampicin, isoniazid, ethambutol and pyrazinamide.
- continuation for 4 months with rifampicin and isoniazid.

Question 12

What are the adverse effects of the drugs used in the intensive phase of active TB treatment

Answer 12

Rifampicin - Enzyme inducer. Turns bodily secretions organ and can cause flu-like illness.
Isoniazid - Liver injury
Ethambutol - Toxic optic neuropathy
Pyrazinamide - liver injury and raised lactate

Question 13

What is the alternative treatment for active TB and why has it been successful?

Answer 13

4 month treatment of rifapentine and moxifloxacin. Shorter duration improved adherence and reduced TB incidence by 25%

Question 14

What is the definition of multi drug resistant TB and how is it treated?

Answer 14

TB which is resistant to both rifampicin and isoniazid.
Treatment is 18-24 months of treatment with an 8 month intensive phase with the following drugs:
- Pyrazinamide
- Fluoroquinolones
- 2nd line injectable
- Ethionamide/prothionamide
- Cycloserine/p-aminosalicylic acid

Question 15

What is extra drug resistant TB?

Answer 15

MDR TB which is also resistant to fluoroquinolones and one of the injectables.