Mycobacterium & Tuberculosis (TB)

Question 1

Vitamin D link to Tb

Answer 1

Vit D activates macrophages to destroy mycobacteria

Deficienct in ethnic UK pops

Question 2

What is tested if suspected Tb

Answer 2

HIV and Vit D

Question 3

Tx of Tb

Answer 3

Isoniazid, rifampicin, pyrazinamide and ethambutol for 2m

Isoniazid + rifampicin for 4m

Question 4

Min length of Tx, why?

Answer 4

6m to stop resistant strains

Question 5

Why may pt want to stop taking meds after 3 weeks?

Answer 5

Non-infectious after 2 weeks

Feel better after 2-4w

Question 6

BCG vaccine

Answer 6

Child Tb only
No impact of HIV related Tb
Prevents infection only, not disease
Invalidates tuberculin skin test

Question 7

HIV and TB

Answer 7

HIV increase risk of acquiring TB by destroying IS

TB makes HIV worse by increasing replication rate

Question 8

Mycobacterium tuberculosis

Answer 8

Obligate aerobes - upper lobes of lungs.
Facultative intracellular parasite - lipid wall allows it to live in macrophages as it doesn’t activate macro.
Slow generation

Question 9

TB spread

Answer 9

aerosol coughs sneezes
close contact w infected

small so not pulled down by gravity

Question 10

At risk groups

Answer 10

HIV infected
Elderly
Immunosuppressed e.g. chemo, transplants, steroids
Live in crowded unhealthy places
High rate country
TB youth exposure
Prisoners, drug addicts, alcoholic
Malnourished

Question 11

Path of TB to alveoli

Answer 11

Droplet nuclei inhaled
Macrophages take up in alveoli but not activated
Nuclei reach alveoli and infect (usually at base of lung)

Question 12

Gohn focus

Answer 12

Granuloma in lung formed by body IS reacting to infection

Question 13

primary complex

Answer 13

GF + enlarged LN

Question 14

Secondary TB causes

Answer 14

Dormant mycobacteria reactivated

Reinfection of previously infected

Question 15

Secondary TB xray sign

Answer 15

Shadow upper lung on chest xray

Question 16

Ghon complex

Answer 16

Healed area of primary lesion

Question 17

Secondary TB pathway

Answer 17

Caseous centres liquefy
Organism grows rapidly
Large Ag load
Bronchi walls necrotise and rupture leading to a cavity
Allow lots of O2 to organism which it likes as is an aerobe
Organism spills out of rupture into airway and spreads to other areas of lung

Question 18

Miliary TB

Answer 18

IS overwhelmed and organism spreads into blood and therefore to body.
Miliary seeds on xray

Question 19

Infection vs disease

Answer 19

Both have org present and + tuberculin skin test.
Differences:

Infection =
Chest X-ray normal
Sputum smears negative
Sputum culture negative
No symptoms
Not infectious
Not defined as a case of TB

Diseases=
Lesion on chest X-ray
Sputum smear positive
Sputum culture positive
Symptoms
Infectious
Defined as a case of TB

Question 20

What are TB symptoms due to?

Answer 20

Cytokines

Question 21

TB symptoms

Answer 21

Cough (+/- sputum)
WL
Swollen glands
Fever 
Night sweats
Tired + unwell
Cough up blood (Haemoptysis)

Question 22

Stop MDR-TB

Answer 22

standardized drug regimens
directly observed treatment (DOT)
good supply of high quality drugs
isolation of infectious patients

Question 23

Culture media

Answer 23

Ziehl-Neelsen stain - stains red if +

need a large load to get +