Tuberculosis Microbiology Of Diagnosis And Management

Question 1

What is the organism that causes tb

Answer 1

Mycobacterium tuberculosis

Question 2

What features can tb cause in the lungs

Answer 2

Granuloma

Question 3

What is a granuloma

Answer 3

When macrophages engulf tb

Question 4

What is a granuloma in the lung known as

Answer 4

Ghon focus

Question 5

What is a ghon complex

Answer 5

Ghon focus and lymphadenopathy

Question 6

What is the role of macrophage

Answer 6

Prevent dissemination of tb

Question 7

What will happen if there is dissemination of tb from the granula

Answer 7

The patient will show symptoms

Question 8

What can a latent tb infection cause

Answer 8

Secondary tb: reactivation of tb

Question 9

When is secondary tb likely to occur

Answer 9

When there is a decline in immunity e.g age, hiv

Question 10

What can a latent infection cause

Answer 10

Nothing: no decrease or decline in the granuloma or immunity

Question 11

What are the 2 tests that we can carry out in latent tb

Answer 11

Tuberculin skin test (tst)

IGRA test

Question 12

What is a tuberculin skin test

Answer 12

When you give a subdermal injection of tuberculin and look at the area if there is a raised reaction

Question 13

When is a tuberculin skin test positive

Answer 13

When there is a reaction

Question 14

What is a IGRA test

Answer 14

Measurement of white cells release of interferon when exposed to tb particles

Question 15

Does the TST and IGRA test test for active tb

Answer 15

No

Question 16

Can people with active tb have negaitve tst and IGRA test

Answer 16

Yes

Question 17

What are the signs and symptoms of active tb

Answer 17

Fever
Weight loss
Night sweats 
Cough or haemoptysis 
Abdominal pain- if in the abdomen 
Headache- if in the meninges
Back pain- if in the spine

Question 18

What changes can you see in a CXR in tb

Answer 18

Upper lobe opafication
Destruction of lung tissue
Miliary tb (seeds in the lung parenchyma)

Question 19

What are the differential diagnosis if tb based on weight loss, night sweats and fever

Answer 19

Cancer: lymphoma, leukemia, lung, bowel or mets
Infection
Autoimmune or rheumatology allergies

Question 20

What are the other causes of granuloma

Answer 20

Sarcoidosis
Crohn’s disease
Granulomatosis with polyangitis 
Infection e.g sphyillis
Foreig body

Question 21

What is the treatment of active tb

Answer 21

RIPE- for 4 months 
Rifampicin
Isoziniade
Pyrazinmaide
Ethambutol 

RI- for 2 months
Rifampicin
Isoniazide

Question 22

What is a common side effect of rifampicin

Answer 22

Orange urine

Question 23

If tb is resistant to treatment how long is the treatment for

Answer 23

9-24 months

Question 24

How do we diagnose active tb

Answer 24

CXR- which will show upper lobe opacity
3 sputum- for ziehlneelsen stain, NAAT and PCR
Or Gastric lavage- in children that swallow sputum
Blood- miliary tb
Csf- meningitis tb
Tissue

Question 25

What type of bacteria is mycobacterium tuberculosis

Answer 25

Acid fast bacilli

Question 26

What are the 2 stains that we can use to stain tb

Answer 26

Auramine stain | Ziehl neelson stain

Question 27

If there is tb what will happen in a auramine stain

Answer 27

1. Auramine is fluorescent yellow 2. Add ethanol to remove the stain 3. Acid fast bacilli (tb) will no decolarise with non fast acid bacilli will 4. You then add potassium permanganate which will stain the non fast acid bacilli black but have no effect for the acid fast bacilli (tb)

Question 28

How does the ziehl neelson stain work in tb

Answer 28

1. You add carbol fluschin which will stain non fast and fast acid bacilli red 2. You then add alcohol to decolourise but the tb will remain red 3. You then add methylene blue which will cause non acid bacilli to stain blue and the acid fast bacilli i.e tb will remain red

Question 29

How do we test for tb drug susceptibility

Answer 29

We grow the tb on liquid media that has antibiotic on it and if the organism grow is will suggest resistant

Question 30

What are the other ways in which we can test for tb

Answer 30

Pcr tb | Whole genome sequencing

Question 31

What is miliary tb

Answer 31

A disseminated (spreader) form of tb that can enter to the bloodstream to spread to the brain, spine etc

Question 32

If a person has positive tst and IGRA test what should we also test for

Answer 32

If the patient has active tb so do a CXR and 3 sputum for pcr, ziehlneelson stain and NAAT

Question 33

If the tuberculin skin test (tst) and IGRA test are negative what can you do for the patient

Answer 33

Offer a BCG test