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
What does the vaccine for TB do?
prevents progression to clinical disease
Where is M. Leprae commonly found
in nasal secretions - likely airborne
where can you grow M. Leprae
Footpads of mice
nine-banded armadillo
- better at low temps -
How does M. Leprae resist killing
Surface phenolic glycolipid resists oxidative stress
Which disease has a DTH reaction - tuberculoid or Lepromatous?
Tuberculoid
Which disease has a vigorous CMI reaction (similar to reactivation of TB) tuberculoid or Lepromatous?
Tuberculoid
Lepromatous more IL-10 produced less IL-1
Which disease has a large number of lesions - tuberculoid or Lepromatous?
Lepromatous
Which disease causes local anesthesia - tuberculoid or Lepromatous?
Tuberculoid
Which disease is similar to miliary TB - tuberculoid or Lepromatous?
Lepromatous
which mycobaterium has to be environmentally acquires
M avium complex
M. intracellulare and M. avium
Mycobacterium of which type can look like a disseminated TB infection
M avium complex in HIV positive individuals
which two mycobacteria part of the MtB complex
M. bovis
M. tuberculosis
what % of people will reactivate TB
5% of the 95% that had latent infection
