Tuberculosis

Question 1

What is the name of the pathogen that causes TB?

Answer 1

Mycobacterium tuberculosis

Question 2

How is TB transmitted?

Answer 2

Airborne droplets

Question 3

What are the risk factors for TB

Answer 3

Immunosuppression (HIV, immunosuppressant drugs, TNFalpha inhibitors)
DM, ESRF
Previous lung disease
Smoking
Malnutrition
Drug abuse and alcoholism
Occupational (hospitals)
Living conditions (prisions, homeless shelters)

Question 4

What are the virulence factors for TB?

Answer 4

Mycolic acid glycolipids
Trehalose dimycolate
Catalase-peroxidase
Lipoarabinomannan

Question 5

Explain how the infectious process for TB works

Answer 5

Inhalation of TB droplets > enters alveoli > alveolar macrophages engulf > proliferates in macrophages > release > immune response

Question 6

What are the three stages of TB?

Answer 6

Primary - active TB infection following my
Latent - TH1 response > caseating granuloma
Reactivation - 1) active infection years after latent infection 2) immunosuppression occurs

Question 7

What are the constitutional symptoms of TB?

Answer 7

Fever
Night sweats
Weight loss / anorexia / malaise

Question 8

What are the pulmonary symptoms of TB?

Answer 8

Cough 2-3 weeks
Dry cough then productive
Haemoptysis
Chest sounds - bronchial breath sounds, crackles or NAD

Question 9

Extrapulmonary TB?

Answer 9

Pleura, bones, lymphatic system, liver, CNS, urogenital tract, GI tract, skin

Question 10

What investigations are used for latent TB?

Answer 10

Tuberculin skin test
IGRA - interferon gamma- release assay

Question 11

What is TST?

Answer 11

Purified protein derivative of tuberculin. Injected intradermally.

Question 12

How is TST measured?

Answer 12

48-72hrs after infection, diameter of rash is measured

Question 13

When is IGRA preferred in suspected latent TB ?

Answer 13

BCG vaccinations

Question 14

What is measured in IGRA?

Answer 14

Interferon-y (lambda)

Question 15

What initial scan do you use for TB?

Answer 15

CXR

Question 16

What investigations are used for suspected active TB?

Answer 16

Sputum microscopy - 3 samples TBS
Culture - solid or liquid
NAAT - Xpert MTB / RIF (detects rifampin-resistance mutations or amplified M. tuberculosis direct test

Question 17

What stain is used to identify TB in sputum microscopy?

Answer 17

Ziehl-Neelson stain

Question 18

What is the treatment for latent TB? What is the duration of treatment ?

Answer 18

Isoniazid for 9 months
Rifampin for 4 months

Question 19

What is the treatment for active TB? Duration?

Answer 19

Isoniazid + rifampin + pyrozinamide + ethambutol for 2 months
Isoniazid and rifampin for 4 months

Question 20

How is TB monitored once treatment is started?

Answer 20

Monthly interval sputum samples - 2 consecutive negative samples means the infection has cleared

Question 21

What is the treatment for drug resistant TB (to isoniazid and rifampin)?

Answer 21

Levofloxacin + bedaquiline + linezolid

Question 22

What is the treatment for TB resistant to isoniazid, rifampin, fluoroquinolones and aminoglcyosides ?

Answer 22

Prolonged intensive and continuation treatment:
Five drugs - susceptible first-line drugs, fluoroquinolone, bedaquiline, linezolid and additional oral agents
New alternative is bedaquiline, pretonamid and linezolid

Question 23

Complications of TB?

Answer 23

Pulmonary - pneumothorax, hadmoptysis, pulmonary destruction, fistula, tracheobronchial stenosis, malignancy, chronic pulmonary aspergillosis
Military TB
Septic shock

Question 24

What type of bacteria is M. tuberculosis?

Answer 24

Gram-positive acid-fast bacilli