Tuberculosis Microbiology Of Diagnosis And Management Flashcards

1
Q

What is the organism that causes tb

A

Mycobacterium tuberculosis

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2
Q

What features can tb cause in the lungs

A

Granuloma

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3
Q

What is a granuloma

A

When macrophages engulf tb

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4
Q

What is a granuloma in the lung known as

A

Ghon focus

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5
Q

What is a ghon complex

A

Ghon focus and lymphadenopathy

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6
Q

What is the role of macrophage

A

Prevent dissemination of tb

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7
Q

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

A

The patient will show symptoms

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8
Q

What can a latent tb infection cause

A

Secondary tb: reactivation of tb

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9
Q

When is secondary tb likely to occur

A

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

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10
Q

What can a latent infection cause

A

Nothing: no decrease or decline in the granuloma or immunity

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11
Q

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

A

Tuberculin skin test (tst)

IGRA test

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12
Q

What is a tuberculin skin test

A

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

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13
Q

When is a tuberculin skin test positive

A

When there is a reaction

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14
Q

What is a IGRA test

A

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

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15
Q

Does the TST and IGRA test test for active tb

A

No

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16
Q

Can people with active tb have negaitve tst and IGRA test

A

Yes

17
Q

What are the signs and symptoms of active tb

A
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
18
Q

What changes can you see in a CXR in tb

A
Upper lobe opafication
Destruction of lung tissue
Miliary tb (seeds in the lung parenchyma)
19
Q

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

A

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

20
Q

What are the other causes of granuloma

A
Sarcoidosis
Crohn’s disease
Granulomatosis with polyangitis 
Infection e.g sphyillis
Foreig body
21
Q

What is the treatment of active tb

A
RIPE- for 4 months 
Rifampicin
Isoziniade
Pyrazinmaide
Ethambutol 

RI- for 2 months
Rifampicin
Isoniazide

22
Q

What is a common side effect of rifampicin

A

Orange urine

23
Q

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

A

9-24 months

24
Q

How do we diagnose active tb

A

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

25
Q

What type of bacteria is mycobacterium tuberculosis

A

Acid fast bacilli

26
Q

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

A

Auramine stain

Ziehl neelson stain

27
Q

If there is tb what will happen in a auramine stain

A
  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)
28
Q

How does the ziehl neelson stain work in tb

A
  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
29
Q

How do we test for tb drug susceptibility

A

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

30
Q

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

A

Pcr tb

Whole genome sequencing

31
Q

What is miliary tb

A

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

32
Q

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

A

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

33
Q

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

A

Offer a BCG test