15. Mycobacteria

Question 1

What factors can increase the chances of a TB infection becoming TB disease?

Answer 1

HIV
Corticosteroid therapy
Diabetes

Question 2

What factors does TB need to grow?

Answer 2

Special media
Must be decontaminated with NaOH
Aerobic
3-6 weeks to grow

Question 3

Can TB form spores?

Answer 3

no

Question 4

Why are TB detected as acid-fast bacilli?

Answer 4

The cell wall has a high lipid content and is difficult to stain with conventional dyes
resists decolorisation by acid

Question 5

How is TB transmitted?

Answer 5

Droplet and aerosol

Question 6

What sample should be sent to the lab from a patient with primary TB?

Answer 6

Sputum

Bacteria is not in blood yet

Question 7

When should primary TB be suspected?

Answer 7

Community acquired pneumonia that won’t respond to antibiotics

Question 8

How does primary TB heal?

Answer 8

Calcification fibrosis

Question 9

What parts of the body are involved in miliary TB?

Answer 9

Liver
Spleen
Lymph nodes
Adrenal glands
Bones
Fallopian tubes

Question 10

What is a possible complication of miliary TB?

Answer 10

Pleural effusions

Question 11

What is secondary TB infection?

Answer 11

Reactivation of a dormant infection

Question 12

How can a secondary TB infection be seen on an CXR?

Answer 12

Cavitation of upper lobes

Question 13

What are the extra-pulmonary sites of TB infection?

Answer 13

Pleura
CNS
Lymphatics
Genitourinary
GIT
Bones and joints

Question 14

What tests can be used to detect TB?

Answer 14

Mantoux skin test

IGRA

Question 15

What is the down side of the Mantoux skin test?

Answer 15

will result in false positive for previous infection or BCG vaccine

Question 16

What is the downside of IGRA?

Answer 16

Doesn’t distinguish between an active or latent infection

Question 17

What samples can be sent to the lab to help diagnose TB?

Answer 17

3 sputa 24 hours apart
Early morning urine
CSF

Question 18

What stains are used on TB?

Answer 18

Auramine

Ziehl-Neelsen

Question 19

What might be seen histiologically with a TB tissue sample?

Answer 19

Caseating granuloma

Question 20

What are the first line drugs for TB?

Answer 20

Isoniazid
Rifampicin
Ethambutol
Pyrizinamide

Question 21

How is primary pulmonary TB treated?

Answer 21

4 drugs for 2 months

2 drugs for 4 months

Question 22

Why are regular LFTs taken during the treatment of TB?

Answer 22

Drugs have side effects which may cause hepatitis

Question 23

How is latent TB treated?

Answer 23

Isoniazid for 6 months

or isoniazid and rifampicin for 3 months

Question 24

What is primary drug resistance?

Answer 24

Patient was originally infected with a resistant organism

Question 25

What is secondary drug resistance?

Answer 25

Bacteria become resistant during therapy

Question 26

What is a multi-drug resistant TB defined as?

Answer 26

Resistant to isoniazid and rifampicin

Question 27

What is an extensively drug resistant TB defined as?

Answer 27

Isoniazid, rifampicin and fluroquinones and at least one of: - capreomycin - kanamycin - amikacin

Question 28

What is the BCG vaccine made of?

Answer 28

Live M.bovis

Question 29

Why is the BCG vaccine contraindicated in immunosuppressed?

Answer 29

Causes a delayed-type hypersensitivity reaction

Question 30

What bacterium should be suspected if a patient has HIV and TB is negative?

Answer 30

Mycobacterium avium

Question 31

What is the environmental source of M. Avium?

Answer 31

Water and soil

Question 32

How does an M. Marinum infection present?

Answer 32

'Fishtank granulomas'

Question 33

How does M. Leprae cause anaesthesia and paralysis?

Answer 33

Targets Schwann cells

Question 34

What other defects can M. Leprae cause?

Answer 34

skin lesions Nasal destruction Eye lesions

Question 35

How is M. Leprae diagnosed?

Answer 35

Tissue smears for acid-fast bacilli and histopathology

Question 36

What is the treatment for leprosy?

Answer 36

Dapsone, rifampicin and clofazimine for 6-12 months