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Terms in this set (29)
causative agent of tuberculosis
an old-fashioned term for tuberculosis - because the patient was "consumed" by the disease and lost weight and became thinner and thinner
How is Mycobacterium tuberculosis transmitted?
airborne droplets - and the infectious dose is quite low, probably because of the slow-growing nature of Mycobacterium, its waxy coat, and its ability to survive for long periods of time in a dormant state
How is Mycobacterium leprae transmitted?
believed to be airborne droplets (like M.tuberculosis) - and similar to TB, only after long close contact with an infected person
waxy coat advantage for M.tuberculosis
avoiding phagocytosis by our white blood cells because of this virulence factor.
Location of M.tuberculosis infection in the lungs
within the alveolar macrophages
collagen fibers produced by fibroblasts and lymphocytes in order to wall off the macrophages that are infected with M.tuberculosis
non-infectious, does not cause disease, occurs in 90% of infected people
M.tuberculosis in these cases is walled off by granulomas and dormant within the macrophages.
causes tuberculosis; requires acid-fast stain, (weakly) Gram positive rod with a very waxy coat
active tuberculosis symptoms
progressive fatigue, weight loss, low-grade fever, night sweats, cough, bloody sputum
Lymphocyte role in fighting TB
Helper T cells are activated, plasma cells make antibodies, memory cells are produced.
These circulating antibodies help keep Mycobacterium dormant within the macrophage.
tuberculosis skin test, Mantoux test, purified protein derivative (PPD) test
1. proteins from M. tuberculosis are injected under the skin
2. skin is checked for immune reaction 48-72 hours later.
3. the 2-step test requires the procedure to be done again 2 weeks later (Skagit Valley College and most CNA programs in Washington require the 2-step TB test)
Why is a 2-step TB test done?
To identify individuals that had the infection very long ago.
Very long ago infections may no longer have T cell reactivity to the bacteria proteins. The initial test "revives" the T cell population; the second test will have a positive reaction.
Basically, the first test is like a "booster" to adaptive immunity to uncover a previous infection.
Positive TB X-ray situations (granulomas visible)
Positive TB skin test situations
*previous infection of TB
*having been vaccinated to TB
TB Blood Test situations
*best in those that have been vaccinated to TB because they will result in false positives on the skin test.
*measures cytokines released by T cells that stimulate macrophages to become more adept at killing intracellular pathogens (such as Mycobacterium!)
False positive result
result that comes back positive when in reality it is not.
False negative result
result that comes back negative when in reality it is positive
mucous secretion from the lungs, bronchi, and trachea expelled through the mouth
Sputum Test for TB
Sputum is cultured on agar to promote growth of M.tuberculosis. Because it is so slow growing, it can take up to 8 weeks to confirm positive result.
M.tuberculosis oxygen requirements
Obligate aerobe - loves the lungs!
Clostridium oxygen requirements
Obligate anaerobe - can't tolerate oxygen!
Pros and cons of Mycobacterium slow growth (for us)
Pro - the disease is very slow progressing
Con - the slow mitotic rate makes it harder to illicit a strong immune response. Easier for it to hide from our immune system.
Hyperimmune response versus hypoimmune response in responding to Mycobacterium infection
Too MUCH response - so much cellular damage allows the bacteria to spread more easily
Too LITTLE response - the bacteria can grow and spread without inhibition
The best response is appropriate without being excessive. This will either successfully remove the bacteria from the body, or force it into decades of latency.
A skin and nerve disease that causes open sores on the body and can lead to serious complications and death - caused Mycobacterium leprae
Mode of action of TB antibiotics
prevent the dividing Mycobacterium from building its mycolic waxy coat
Why do abx have to be taken so long for TB?
Because the bacteria divides So. Slowly. It takes a long time to have a significant impact on the population of bacteria.
Why does leprosy mostly affect extremities?
Because Mycobacterium leprae is an obligate aerobe.
Other forms of TB
TB may spread to any other organ, although commonly to the skin, the kidneys, or the bones.
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