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Maddie’s Resp > TB > Flashcards

Flashcards in TB Deck (14)
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1
Q

Describe the Mycobacterium Tuberculosis bacterium. (4)

A

Aerobic, acid and alcohol fast bacilli that can be shown on the smears stained by the Zieglers-Nelson method, and grow very slowly in culture.

2
Q

Describe the pathogenesis of MTB. (5)

A

Alveolar macrophages phagocytise MTB breathed in, but cannot digest them due to the high fatty acid content of the cell wall. This encourages the macrophages to form the characteristic caseous tubercles with a necrotic core surrounded by epitheliod macrophages, Langerhan’s cells and lymphocytes.

3
Q

Describe the primary infection of TB. (5)

A

Inhalation of MTB is followed by development of the sub-pleural primary focus / Ghon’s focus. Bacilli drain from here to the Hilar lymph nodes forming a primary complex (primary focus + hilar lymph nodes). Most heal without calcification, but often has haematogenous spread to extra-pulmonary sites.

4
Q

Describe the latent infection of TB. (3)

A

After the primary infection has been cleared, some bacilli remain. They are latent and so not infection, but can form a post-primary infection if the host becomes immunocompromised

5
Q

Describe types of immunocompromisation needed for latent TB activation. (4)

A

Old age, HIV, malnutrition, diabetes.

6
Q

Explain the differences between the QuantiFERON test and the Mantoux test for TB. (7)

A

QuantiFERON is used to detect the interferon gamma released from T lymphocytes in specific response to TB antigen - these are different antigens to seen in the BCG vaccine or other mycobacterium.
Mantoux is used to detect a sensitivity to tuberculin - this could give false positives (previous BCG vaccination, other not TB mycobacterium infection) or false negatives (immunosuppresion).

7
Q

Describe primary TB. (2)

A

The primary complex causing active TB - about 5% of infected people.

8
Q

Describe post-primary TB. (3)

A

Reactivation of latent TB due to immunocompromisation, mostly in the lungs - about 5% of infected people.

9
Q

Describe the consequences post-primary pulmonary TB. (10)

A

Cavity formation - holes left by liquefaction of caseous material that gets discharged into bronchi.
Haemoptysis - extension of cavity into blood vessel.
Spread - via the bronchial tree to other lung zones
Pleural effusion - seeding in the pleura
Miliary TB - rupture of caseous focus into blood vessel causing dissemination.

10
Q

Describe extra-pulmonary TB. (3)

A

Reactivation of latent TB in other organs eg lymph nodes, bones, CNS, GI, urinary.

11
Q

Describe the clinical features of TB. (6)

A

Gradual onset of malaise, weight loss, any form of cough, sweats.
Recent travel, contact with TB, homelessness, immunocompromisation.
CXR - shadowing with possible lesions calcification or fibrosis.

12
Q

Describe the diagnosis of TB. (3)

A

Identification of the bacillus in a smear, culture (best but slow) or NAAT of the bodily fluid.

13
Q

Describe the treatment of TB. (6)

A
4 antibiotics for 6 months
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol
Can be hepatotoxic or cause visual problems of vitamin D deficiency.
14
Q

Describe the prevention of TB (3)

A

All TB cases notifyable to PHE.

Spread can be prevented with PPE, negative pressure isolation and vaccination.