Mycobacteria Flashcards
generation time for Mtb
15-20 hours - colonies need 4-6 weeks to appear
Can you culture M. Leprae in vitro?
No
Which mycobaceria have human and animal hosts
M. Leprae, and Mtb complex
NOT NTB - environmental/watery habitats
TB affects what proportion of world’s pop
1/3 - 22 countries bear 80% of burden
reported cases of TB in canada are accounted for by
66% of foreign born indviduals
How is TB transmitted?
Airborne! droplet nuclei
M. bovis can cause infection i
GI and tonsils
Some key factors that increase risk of transmission of TB
cavitary lung disease
laryngeal disease
Primary focus of a TB infection is
Middle and lower lung lobes
Secondary foci of TB infection are
- everywhere! Upper lungs LN vertebral bodies meninges
What % of TB will go on to develop primary disease
only 5%
Miliary TB is
TB in whole body
If you have NO disease or a latent infection your skin test will be
positive
What is the risk if reactivation of latent TB
5% within first 2 years, then then additional 5% for rest of lifetime
In HIV 10% per year
The antibody response to TB has
NO role in host defence
Cell mediated immunity usually plays
The biggest role - delayed type 4 hypersensitivity
How long does cell-mediated immunity take to develop?
3-9 weeks
8% of people revert to negative after 1 year
what immune mechanism inhibits intracellular replication of Mtb
activation of monocytes with TNFa
Which cytokines are preferentially expressed following a Th1 CD4 cell response
IL-2
IFN-gamma
IL-12
What cytokine may suppress the immune response
IL-10
How large is the induration in mantoux test
10mm
5mm if HIV positive
what % of people will be skin test negative with active disease
15-20%
may be falsely negative if immunocompromised
For a latent TB test you can use what to diagnose
IFN-gamma assay production of T cells
Vaccine for TB is
live attenuated M. bovis
60-80% effective in children
DOES NOT prevent infection
