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25 Cards in this Set
- Front
- Back
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Some group characteristics of Mycobacteria
Are they obligate aerobes? Slow or fast growth Waxy or slimy wall |
Obligate aerobes
Slow growth Even "rapid" growers divide much more slowly than the pyogenic bacteria previously discussed. Waxy cell wall (glycolipid) |
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Mycobacterial Cell Wall
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Waxy coat that makes the class "acid-fast"
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Mycobacterium leprae
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leprosy or Hansen's disease
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Mycobacterium tuberculosis
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Tuberculosis in humans and cows
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Mycobacterium slow growers
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e.g. Mycobacterium avium-intracellulare
e.g. Mycobacterium kansasii |
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Mycobacteria rapid growers..
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e.g. Mycobacterium fortuitum
e.g. Mycobacterium chelonei |
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What is "atypical" about the atypical mycobacteria?
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They can't be distinguished from "typical" ones under the light or electron microscope
They are all obligate aerobes that make waxy cell walls. |
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Atypical Mycobacteria
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They were called atypical by Dr. Runyon in the 1950's who noted that patients with these germs had an atypical response when their disease that looked like ordinary tuberculosis did not respond to the drugs in use at the time (INH, PAS and streptomycin).
Thus, they were "atypical" only in their response to drugs |
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Can PMNs kill mycobacteria?
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No, but macrophages can
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Leprosy is caused by infection with
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Mycobacterium leprae
Which are probably acquired by inhalation or ingestion |
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TB vs. Lepromatous
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Tuberculoid leprosy causes damage to multiple peripheral nerves, but is not usually terribly disfiguring.
Lepromatous leprosy is incredibly disfiguring. Probably no disease is more feared than lepromatous leprosy. |
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Relationship between leprosy type and CD4 count
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The less cd4 cels you have the more likey you are to have lepromatous (vs. tuberculoid)
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Tuberculoid leprosy
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CD4 T-cell immunity strong and appropriate
Activated macrophages restrict growth of M. leprae Bacterial burden in patient is low NOT CONTAGIOUS |
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Lepromatous leprosy
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CD4 T-cell immunity fails to develop
nonactivated macrophages support growth of M. leprae Bacterial burden in patient is very Patients with this kind pass the germ on to others Nasal swab usually shows sheets of M. leprae when stained. |
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Tuberculosis
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Caused by Mycobacterium tuberculosis
M. bovis had been a major cause until the 1930's when a vigorous eradication program was carried out. Spread by inhalation of airborne droplet nuclei from patients with reactivation type pulmonary tuberculosis to uninfected people |
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HIV infection has a profound effect on immunity to tuberculosis
True or False |
TRUE!
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Which lobe does TB live?
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Upper lobe - has more oxygen since it has less perfusion.
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How does TB spread/
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Droplets are too big to reach the alveoli after inhalation and are NOT likely to pass the infection on.
ANS: Evaporation of droplets leads to formation of droplet nuclei (3-5 microns) These will work. |
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How fast can M. tuberculosis grow?
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M. tuberculosis is a slowly growing bacterium that requires ~24 hours to divide
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TB transmission via particles facts
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Particles larger than ~5-10 microns are removed from the airstream in the nose, throat and bronchi.
Particles which land in these zones are removed within hours of their deposition. Particles in the 1-5 micron range will be removed from the airstream in the alveoli. Particles that are deposited in the alveoli must be removed by phagocytes, usually alveolar macrophages. |
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Primary TB is found in upper or lower lobe?
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Lower Lobe
Reactivation TB is usually in the upper lobes and is contagious |
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Mycobacterium avium intracellulare
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Atypical for humans
Not atypica for birds The disease it produces in humans is indistinguishable from true tuberculosis. |
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M. tuberculosis infection - distribution
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Most common on Mexican border and Indian reservations
Note change in scale |
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Whats more common? MAI or M. Tb
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MAI
Everyone in CT has it |
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Persistence of Mycobacteria
why? |
Spores
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