20 Tuberculosis Flashcards
What bacterium caused TB?
Mycobacterium tuberculosis
How many people develop TB daily?
28000
How many people die by tuberculosis daily?
3000-4000
What are the two phases of TB infection?
Primary and secondary
What happens during the primary phase?
the infection process
How is Mycobacterium tuberculosis acquired? (Transmission type)
Aerosols
Where do the bacteria grow?
Bacteria reach the alveoli in lungs and start to grow
What does mycobacterium tuberculosis growth in the alveoli stimulate?
The hosts macrophages
What do the macrophages do?
Form into aggregates (tubercles) and engulf mycobacteria
What happens to some mycobacteria after phagocytosis?
Survive within the macrophage - they do not succumb to the normal lysosomal destruction process
What is the mycobacterial cell wall rich in?
Mycolic acid - a glycolipid
Is mycobacterium tuberculosis Gram positive or negative?
It is neither
Are mycolic acids hydrophilic or hydrophobic?
Hydrophobic
What do these mycobacterial cell walls prevent and what does it limit the entry of?
It prevents phagocytosis from occurring
And limits the entry of antimicrobial compounds
Primary tuberculosis (What happens to a host?)
Primary infection remains undetected in the host. Very rarely will acute pulmonary disease occur leading to destruction of lung tissue and death. The acute form of TB only occurs in unhealthy or already sick individuals
What happens following infection to primary tuberculosis?
Following infection most people become hypersensitised to the bacterium due to cell-mediated immune response. In most people this gives life long (natural immunity) against secondary TB
How can a person develop secondary TB (2 routes)?
Can get a fresh infection from another source or activation of dormant bacteria in lung macrophage
What does secondary tuberculosis lead to?
Death through chronic destruction of lung tissue
What sort of factors is secondary TB linked to?
Aging
Malnutrition
Poor living conditions/poverty
Patients with secondary TB are highly what?
Contagious via aerosols
Heaf test
Spring loaded instrument with 6 needles in a circular pattern used is Scotland on children around 11-12. Positive reactions are screened for TB with xrays and negative reaction gets a BCG vaccine (BCG reserved for those considered in high risk groups since 2005)
What is the treatment for TB?
Treated my antimicrobials
Main drug is Isonazid, used in combination with zifampicin and ethambutol or pyrazinamide
What is Isonazid and what is it activated by?
A prodrug activated by bacterial catalase which inhibits fatty acid synthase
What enzyme does ethambutol inhibit?
Inhibits Arabinosyl transferase which disrupts arabinogalactan synthesis
