Tuberculosis

Question 1

what bacterium causes TB

Answer 1

mycobacterium tuberculosis

- rod shaped bacilli

Question 2

what stain is used to detect TB

Answer 2

Zeihl-Neelson stain

- waxy coat of mycobacterium tuberculosis prevents use of gram stain – known as “acid fast bacilli”

Question 3

what colour does mycobacterium tuberculosis stain on a Zeihl-Neelson stain

Answer 3

red

Question 4

how is TB spread

Answer 4

respiratory transmission

Question 5

what are the stages of TB

Answer 5

primary infection
latent disease
secondary infection
miliary TB

Question 6

what happens in primary TB infection

Answer 6

primary infection enters the lungs – formation of Gohn focus + spread to lymph nodes

Question 7

what is a Gohn focus

Answer 7

lung lesion composed of tubercle- laden macrophages seen in primary TB

Question 8

what kind of necrosis is there in TB

Answer 8

caseous necrosis

Question 9

what is latent TB

Answer 9

immune system encapsulates sites of infection and stops progression of the disease

Question 10

what is secondary TB

Answer 10

latent TB becomes reactivated due to the host becoming immunocompromised

Question 11

where does secondary TB most commonly occur

Answer 11

apex of the lungs

Question 12

what things can trigger secondary TB

Answer 12

immunosuppressive drugs e.g. steroids
HIV infection
malnutrition

Question 13

what is miliary TB

Answer 13

Infection has disseminated in blood/lymphatics to cause multi organ disease

Question 14

where does TB most commonly affect

Answer 14

the lungs

- 60% of TB cases

Question 15

how does pulmonary TB present

Answer 15

chronic productive cough (+/- haemoptysis)
systemic symptoms: 
- fever / night sweats
- weight loss
- malaise

Question 16

what is the second most common presentation of TB

what are the symptoms?

Answer 16

genitourinary TB

- dysuria, loin/back pain, haematuria

Question 17

what is Potts disease

Answer 17

TB affecting the spine

Question 18

features of cutaneous TB

Answer 18

lupus vulgaris
erythema nodosum
erythema multiforme

Question 19

what is the most serious complication of TB

Answer 19

TB meningitis

Question 20

first line investigation for TB

Answer 20

chest XRAY

Question 21

signs of primary TB on CXR

Answer 21

Ghon focus with ipsilateral hilarious lymphadenopathy

pleural effusion

Question 22

signs of secondary TB on CXR

Answer 22

Cavitating lesion in apices

Question 23

signs of miliary TB on CXR

Answer 23

diffuse 1-10mm shadows throughout lung fields

Question 24

how many sputum samples are needed for microbiology

Answer 24

3

Question 25

what tests are done on the sputum samples

Answer 25

microscopy, culture, sensitivities - Zeihl-Neelson stain - Nucleic acid amplification test (NAAT) can replace standard culture for earlier result if patient at high risk complications - PCR for rifampicin resistance

Question 26

what is a Mantoux test

Answer 26

tuberculin skin test - indicates active/latent TB or previous BCG vaccination - induration of 5mm or more = +Ve and patient should be assessed for active disease

Question 27

what is an interferon-Gamma release assays

Answer 27

measures T cell response to TB antigens | - if person has had previous contact with TB then WBCs will release interferon gamma = positive result

Question 28

what is the treatment for active TB

Answer 28

``` RIPE: Rifampicin (6 months) Isoniazid (6 months) Pyrazinamide (2 months) Ethamnutol (2 months) ```

Question 29

what drug should also be co-prescribed in active TB treatment

Answer 29

pyridoxine (vit B6) to prevent peripheral neuropathy caused by isoniazid

Question 30

how are patients with meningeal TB treated

Answer 30

further 6 months of rifampicin + isoniazid plus steroids

Question 31

treatment of latent TB

Answer 31

3 months of rifampicin + isoniazid or 6 months isoniazid (+ pyridoxine)

Question 32

what drug can cause red/orange discolouration of urine/tears

Answer 32

rifampicin

Question 33

what drug can cause optic neuritis / colourblindness

Answer 33

ethambutol

Question 34

what drug induces P450 system and so decreases effectiveness of oral contraceptive pill and warfarin

Answer 34

rifampicin

Question 35

what drug can cause peripheral neuropathy

Answer 35

isoniazid

Question 36

what drag can cause high uric acid levels and precipitate gout

Answer 36

Pyrazinamide

Question 37

what drug can cause agranulocytosis

Answer 37

isoniazid

Question 38

what drugs cause hepatitis

Answer 38

rifampicin isoniazid Pyrazinamide