Mycobacterium and tuberculosis

Question 1

what causes tuberulosis

Answer 1

mycobacterium tuberculosis
obligate aerobe , facultative intracellular parasite
high lipid content

Question 2

how is Tb spread

Answer 2

commonly spread in small droplets being coughed or sneezed in air

Question 3

at risk groups of TB

Answer 3

immunosuppressed
those exposed to TB in youth
high rate country
malnourished

Question 4

primary Tb

Answer 4

droplet nuclei inhaled
if taken up by alveolar macrophages, not activated due to lipids(therefore live within macrophages)
reach the alveoli - infection begins commonly in base of lungs

Question 5

what does the immune system do when reacting to Tb

Answer 5

granuloma in lung (Ghon focus)

Question 6

what is a primary complex

Answer 6

Ghon focus and enlarged lymph nodes

Question 7

how can secondary TB occur

Answer 7

reactivation of dormant mycobacteria

reinfection in person previously sensitised to mycobacterial antigens

Question 8

where is reactivation most common

Answer 8

at apex of lungs

highly oxygenated

Question 9

what happens in the lungs during 2nd TB

Answer 9

caseous centres of tubercles liquefy
large antigen load, bronchi walls become necrotic rupture
cavity formation
oragnsism spills intoairway, coughed out therefore infectious

Question 10

military tuberculosis

Answer 10

immune system overwhelmed
organism into bloodstream
x ray represents milit seeds

Question 11

infection vs disease

Answer 11

1) TB infection
- Organism present
- Tuberculin skin test positive
- Chest X-ray normal
- Sputum smears negative
- Sputum culture negative
- No symptoms
- Not infectious
- Not defined as a case of TB

2) TB lung disease
- Organism present
- Tuberculin skin test positive
- Lesion on chest X-ray
- Sputum smear positive
- Sputum culture positive
- Symptoms
- Infectious
- Defined as a case of TB

Question 12

what are symptoms causes by

Answer 12

cytokine activity

Question 13

symptoms of TB

Answer 13

cough (with/without sputum)
anorexia
swollen glands
fever
night sweats
sense of tiredness and being unwell

Question 14

standard recommend regime for TB

Answer 14

isoniazid
rifampicin
pyraniamide
ethambutol
for 2 months
followed by isoniazid and rifampicin for 4 months
treatment min 6 months to prevent resistance developing

Question 15

how to prevent MDR - TB

Answer 15

standardised drug regimes
directly obeserved treatmetn
good supply of quality drugs
isolation of infectious pts

Question 16

what is the vaccine called and used fro

Answer 16

BCG - bacille calmée gurein
protection in childhood
only prevents disease not infection
invalidates tuberculin skin test

Question 17

HIV and TB

Answer 17

HIV increases risk of acquireing TB

TB makes HIV worse

Question 18

types of drug resistant TB and their treatment ? look lec/ppw when exam

Answer 18

MDR TB -

XDR TB -

Question 19

obstacles to TB control

Answer 19

1) Lack of financial resources
2) social instability
3) HIV epidemic
- HIV/AIDS doubles the TB death rate
4) drug resistance
5) stigma

Question 20

how to diagnose TB

Answer 20

chest x ray
tuberculin ests
blood tests
microscopy 
sputum culture
nucleic acid detection tests  and typing

Question 21

chest x ray

Answer 21

indicates but does not confirm

Question 22

tuberculin tests

Answer 22

heaf, tine Mantoux

ascertains infection rather than disease

Question 23

T spot - TB and quantiferon gold blood tests

Answer 23

Blood tests to replace tuberculin tests

• detects reactive T cells
• specific for MTB
• not affected by BCG – vaccine

Question 24

microscopy

Answer 24

Rhodamine aura mine (fluorescence) more sensitive than ziehl Nelson stain (red)

Question 25

sputum

Answer 25

• homogenise using sputasol
• Decontaminate (4% NaOH Petroff) - to kill all bacteria but leave mycobacterium behind
• concentrate (centrifugation)
• Middlebrooks medium
• Lowerstein Jensen-medium
• 4-6 weeks for visible colonies to form
• liquid media (kirchners)

Question 26

automated culture

Answer 26

can use liquid media - media with fluorescent reaction

can also use laminar strip- looks for specific antigen

Question 27

nucleic acid detection test

Answer 27

specific to DNA of organism
molecular method
look for rifampicin resistant genes, likely to be mutli drug resisant

Question 28

how can you tell if TB is multi drug resistant strain

Answer 28

look for rifampicin resistant gene

Question 29

how do the drugs work

Answer 29

targets the genes

Question 30

typing

Answer 30

once organisms is identified and isolated it can be typed

- can follow epidemic spread via typing

Question 31

methods of typing

Answer 31

methods
1) variable number of tandem repeats
2) Mucobacterial interspersed repetitive units
the number given is the fingerprint of the strain of mycobacteria of TB