mycobacteria Flashcards
most important mycobacfteria
TB
in what environmental or social conditions can leprosy occur
tropical countries
warm climate
illness of poverty
skin lesions cause issues
describe the shape and structure of mycobacteria
-slightly curved beaded bacilli
-high lipid content with mycolic acids in cell wall
-aerobic
-non spore forming
why wont tb show up on gram staining
the high lipid content with mycolic acids in cell wall
challenges of TB
-thick lipid rich cell wall making immune cell killing difficult
-slow growth
- gradual onset of disease
-takes longer to diagnose
-takes longer to treat
WHAT DOES primary tuberculosis INVOLVE
-Initial ‘contact’
made by
alveolar
macrophages
Settles in the apex of the lung and forms a granuloma
-Bacilli taken in
lymphatics
to hilar lymph
node
what does latent tuberculosis involve
Cell mediated
immune (CMI)
response from Tcells
primary
infection
contained but
CMI persists
what does pulmonary tb involve
-Granulomas forms around bacilli that have settled in apex
-In apex of lung there Is more air and less blood supply
(fewer defending
white cells to fight
-necrosis results in abscess forming and caseous material coughed up.
what does our body do to protect us
- Primarily controlled by macrophages
- Requires a CD4 Th1 cell response to be controlled
- Involves many cells of immunity- formation of granulomas
- Granuloma stability controls reactivation of TB
Virulence factors of tb
Cord factor
Catalase peroxidase
Sulfitides
How does the cord factor act as a virulence factor for TB
Evades the immune system
Forms granulomas
Cytokine release
What are the two reasons as to why my bacteria stain poorly on gram staining
Thick Lipid content with my colic acid in well wall
Resistant to decolorisation
What stain do we use tb
Ziehl nessel stain
how does the ziehl neelson stain work
- heat sample with a strong dye, carbol fuchsin
- heat makes the bacteria resistant to decolourisation by acid = acid fast
so when slide is flooded with acid the mycobacteria retain the pink dye - everything else is decolourised.
How is tb transmitted
Through inhalation
