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Flashcards in Tuberculosis And Asthma Deck (63)
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1

What are the 3 most common bacteria associated with human TB??

Mycobacterium tuberculosis
Mycobacterium bovids
Mycobacterium africanum

2

Describe some features of mycobacterium tuberculosis

Non-motile
Rod-shaped
Obligate aerobe
Has a very thick layer of fatty acids, glycolipids etc
Need Acid-Fast stain (cannot stain with Gram stain)

3

Why does mycobacterium TB take a long time to culture?

Relatively slow growing bacteria
Generation time 15-20 hours
Takes a minimum of 2 weeks to culture

4

How is TB spread?

Respiratory droplets (coughing/sneezing)
Infectious dose is very low
Air remains infectious for 30 minutes

5

Is it easy to catch TB?

No
Usually need prolonged exposure to catch it

6

What are the classic situations in which TB spreads?

Overcrowding situations:
Poor housing
Prisons
Homeless people

7

Describe the pathogenesis of TB

Inhaled aerosols/droplets
Engulfed by alveolar macrophages
Drainage of lung to local lymph nodes
Primary complex/focus of infection established
Progression to primary active disease or initial containment of infection to latent

8

What are the 2 outcomes of latent infection?

Heals/self cure
Reactivation of post-primary TB

9

What is the commonest type of TB?

Reactivation of latent to post-primary TB

10

Describe how tests for latent TB would appear

TST (mantoux) and IFN gamma tests would be positive
Chest x-ray normal
Sputum smears and cultures normal
Asymptomatic

11

What are the main symptoms of active TB

Cough
Fever
Weight loss

12

What is miliary TB?

TB disseminated wide into the body via the blood stream
(Tiny spots throughout lung fields on x-ray)
Rare

13

What are some of the risk factors for reactivation?

HIV
Substance abuse
Prolonged corticosteroid therapy
Immunosuppressants
TNF alpha antagonist
Low body weight
Organ transplant
Haematological malignancy
Severe kidney disease
Diabetes mellitus
Silicosis

14

What are caseating granulomata in TB?

Lung parenchyma and lymph nodes
Liquified and cheesy looking material
Dead and dying bacilli and inflammatory cells
Langhan's giant cells present

15

What are the common sites for extrapulmonary TB?

Larynx
Lymph nodes
Kidneys
Pleura
Brain
Bones and joints

16

What are some risk factors for TB

Non-Uk born/recent migrants
HIV infected
Immunocompromised
Homeless
Drug users
Prisoners
Close contacts of patients with TB
Young adults

17

What Hx would suggest TB?

Recent arrival/travel
Contacts with TB
BCG vaccination?
Fever
Weight loss
Malissa
Anorexia

18

List some symptoms of pulmonary TB

Fever
Night sweats
Weight loss/anorexia
Tiredness
Malaise
Cough
Haemoptysis
Breathlessness

19

What are some signs on examination of pulmonary TB?

Fever
Often no chest signs
CXR abnormality
May be crackles in infected areas
(Pleural involvement = dullness)

20

What investigations would you run for TB??

CXR
Sputum - 3 early morning samples
Induced sputum via physiotherapy
Bronchoscopy

21

What would you see on a CXR for TB?

Apex of the lung often involved
Ill defined patchy consolidation
Cavities can develop in consolidation
Healing results in fibrosis

22

Why are sputum smears not very good in diagnosing TB?

Not very sensitive
May only have a few bacilli in
Operator dependents

23

What is the gold standard investigation for diagnosis of TB?

Culture (but takes approximately 2 weeks)

24

What are epitheloid cells?

Activated macrophages
(Can fuse together to form giant cells)

25

Describe the tuberculin sensitivity test (TST)/mantoux

Look for latent TB
Challenge with an antigen previously exposed to
Infected intra-dermally
Inflammation, red circle appear at injection site
Read 2-3 days later
(Can get false positives and false negatives)

26

Describe interferon gamma releasing assays (IGRAs)

Buffer test for latent TB
Blood test
No cross reaction with BCG
Cannot distinguish between latent and active TB

27

What is the first line medication for TB?

4 first line medications:
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol

28

What are some problems with Rifampicin?

Can give orange secretions (tears/urine)
Cannot take whilst on the contraceptive pill

29

What is the bad side effect of ethambutol?

Can cause visual disturbance

30

What are the second line drugs for TB?

Quinolones
Clofazamine
PAS
Ethionamide