Tuberculosis

Question 1

What is tuberculosis (TB)?

Answer 1

A contagious infectious disease caused mainly by Mycobacterium tuberculosis, primarily affecting the lungs (pulmonary TB) but also other organs (extrapulmonary TB).

Question 2

Why is TB a major global health issue?

Answer 2

Present worldwide, with high mortality, rising drug resistance, and strong links to poverty, HIV, and poor healthcare access.

Question 3

How many people died from TB in 2023?

Answer 3

1.25 million, making TB the world’s leading infectious killer again.

Question 4

What is unique about the TB cell wall?

Answer 4

Thick, waxy, lipid‑rich wall containing mycolic acids, peptidoglycan, arabinogalactan, and lipoarabinomannan (LAM) → highly resistant to disinfectants and antibiotics.

Question 5

What is acid‑fastness?

Answer 5

TB retains dye after acid wash due to its waxy cell wall → requires acid‑fast staining (e.g., Ziehl–Neelsen stain)

Question 6

What is the role of the capsule?

Answer 6

Polysaccharide‑rich layer aiding immune evasion

Question 7

Why does TB grow slowly?

Answer 7

Complex cell wall and metabolic characteristics → doubling time is long → cultures take weeks

Question 8

How does TB survive inside macrophages?

Answer 8

Prevents phagosome–lysosome fusion using the ESX‑1 (Type VII secretion system).

Question 9

What is latent TB?

Answer 9

Infection contained by the immune system; bacteria dormant in granulomas; no symptoms; non‑infectious.

Question 10

What is the lifetime risk of latent TB reactivation?

Answer 10

5–10%, higher with HIV, diabetes, malnutrition, or immunosuppression.

Question 11

What is active TB?

Answer 11

Bacteria multiply, causing symptoms and tissue damage; pulmonary TB is infectious via airborne droplets.

Question 12

How does the TB cell wall contribute to resistance?

Answer 12

Mycolic acid‑rich wall reduces permeability to many antibiotics.

Question 13

What is the role of efflux pumps?

Answer 13

Actively expel drugs → lower intracellular concentrations.

Question 14

Why does slow growth cause resistance?

Answer 14

Many TB drugs (e.g., isoniazid, rifampicin) target actively dividing cells.

Question 15

What factors contribute to acquired resistance?

Answer 15

-Poor adherence

-Incorrect regimens

-Drug shortages

-Delayed diagnosis

-Previous TB treatment

Question 16

What is the role of lipoarabinomannan (LAM)?

Answer 16

Inhibits T‑cell activation and immune signalling → helps TB survive in macrophages

Question 17

What does the ESX‑1 secretion system do?

Answer 17

Prevents phagosome–lysosome fusion → allows intracellular survival and replication.

Question 18

What are granulomas?

Answer 18

Organized immune structures that wall off TB bacteria; hallmark of TB.

Question 19

How does TB acquire iron?

Answer 19

Produces siderophores (e.g., mycobactin) to scavenge iron inside macrophages

Question 20

What is the main source of TB transmission?

Answer 20

Humans with pulmonary or laryngeal TB via airborne droplets.

Question 21

Can animals transmit TB?

Answer 21

Rarely — Mycobacterium bovis from cattle via unpasteurised milk

Question 22

What are common extrapulmonary sites?

Answer 22

Lymph nodes, meninges, bones/joints, genitourinary tract, pericardium, abdomen.

Question 23

What is miliary TB?

Answer 23

Disseminated TB with tiny lesions throughout organs; severe systemic illness

Question 24

Who is high‑risk for TB?

Answer 24

-Born in high‑prevalence countries

-Close contacts

-Children <5

-HIV, CKD, diabetes

-Immunosuppressed

-Homeless, prisoners

-Substance misuse

Question 25

What is the first imaging test for suspected TB?

Answer 25

Chest X‑ray — often shows upper‑lobe consolidation.

Question 26

What is the role of CT?

Answer 26

Provides detailed 3D imaging; identifies cavities and lymph node involvement.

Question 27

What is AFB testing?

Answer 27

Acid‑Fast Bacilli microscopy — rapid but cannot distinguish TB from other mycobacteria.

Question 28

Why are early‑morning sputum samples preferred?

Answer 28

Higher bacterial concentration after overnight accumulation.

Question 29

What is the gold‑standard test?

Answer 29

Culture + susceptibility testing (takes 4–6 weeks).

Question 30

What is the Mantoux test?

Answer 30

Tuberculin skin test measuring delayed hypersensitivity reaction.

Question 31

What is IGRA?

Answer 31

Interferon‑Gamma Release Assay — blood test detecting immune response to TB antigens.

Question 32

What is the standard TB treatment duration?

Answer 32

6 months.

Question 33

What drugs are used in the initial 2‑month phase?

Answer 33

-Rifampicin -Isoniazid (+ pyridoxine) -Pyrazinamide -Ethambutol

Question 34

What drugs are used in the continuation 4‑month phase?

Answer 34

-Rifampicin -Isoniazid (+ pyridoxine)

Question 35

What is DOT?

Answer 35

Directly Observed Therapy — supervised medication administration to ensure adherence.

Question 36

When are corticosteroids used?

Answer 36

TB meningitis or pericarditis.

Question 37

Why give pyridoxine with isoniazid?

Answer 37

Prevents peripheral neuropathy.

Question 38

What are the two regimens for latent TB?

Answer 38

1. Rifampicin + isoniazid (with pyridoxine) for 3 months 2. Isoniazid (with pyridoxine) for 6 months

Question 39

What is MDR‑TB?

Answer 39

Multi‑Drug Resistant TB — resistant to isoniazid and rifampicin.

Question 40

What drugs may be used for MDR‑TB?

Answer 40

Linezolid, clofazimine, bedaquiline, amikacin (specialist‑led).

Question 41

What public health measures reduce TB?

Answer 41

-Awareness and education -Early diagnosis -Reducing stigma -Screening high‑risk groups -Improving ventilation and living conditions

Question 42

What vaccine prevents TB?

Answer 42

BCG vaccine — recommended for infants, children, and high‑risk groups.

Question 43

What is the hallmark of TB pathology?

Answer 43

Granuloma formation

Question 44

What is the most important factor in preventing drug‑resistant TB?

Answer 44

Adherence to treatment.