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Mycobacterium & Nocardia (Hull)


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Explain what is peptidoglycolipid (that MB Tuberculosis has)
Peptidoglycolipid is peptidoglycan attached to Arabinogalactan (alternating arabinose & galactose), which is then attached to mycolic acid (highly branched fatty acids, can be 60 carbons long). Also, Wax D is a fragment of the peptidoglycolipid and is highly immunogenic (used in Freund's adjuvant)
What is Wax D?
Wax D is a fragment of the peptidoglycolipid and is highly immunogenic (used in Freund's adjuvant)
Why did people used to this Mycobacterium TB was a fungi? (Myco = fungus)
1) It's generation time was so long, ~40 hours which is more like a eukaryotic cell
2) It doesn't take up Gram stain due to its waxy cell wall
All mycobacteria are ___________ aerobes, and because of this they have a strong predilection for the ______.
obligate aerobes, and for this reason they have a strong predilection for the lung
True or false, Mycobacterium TB does NOT make any exotoxins.
True, MB TB makes no exotoxins
What inhibits neutrophil migration?
cord factor, a glycolipid that is lethal when injected into mice
Mycobacterium TB are gram (+/-), niacin (+/-), and have pigmentation/don't have pigmentation
*gram +
*niacin +
*don't have pigmentation
Because they are so sticky, the MB TB show a rope or cording phenomenom that is very characteristic of MB TB. What causes this?
cord factor
What are the functions of the mycolic acid (the fatty acids)?
*prevent dessication
*resistant to lytic enzymes (of the phagocytes), phagocytosis
*resistant to chemicals (ie disinfectants)
*resistance to taking up Gram stains, therefore DO NOT STAIN WITH GRAM STAIN
Mycobacteria are visualized how?
Acid fast stain (Ziehl-Nilsson or Kinyoun), using carbol fuchsin solution that penetrates mycobacteria, especially well if are also heated! Then washed with acidified alcohol, but the red stain remains in the mycobacteria because of the lipid layer keeps the stain in
Laws were developed against spitting on the sidewalk to prevent spread of...
Mycobacterium Tuberculosis
Milk is still pasteurized to prevent the spread of Mycobacterium _______
Mycobacterium bovis is the basis of the ____ vaccine
BCG, but is not used as vaccination in the US (more in other countries across the world)
Why is Auromine-Rhodamine replacing the acid fast stain for diagnosis of MB TB?
1) Normal acid fast stain could only tell you whether you had a Mycobacteria present or not (could not distinguish amongst different species of MB, whether pathogenic or not, in fact some nonpathogenic strands are in tap water and could affect the results of tests performed). the Fluorescent antibody test is specific for Mycobacterium Tuberculosis antigen!!! Will just light up for TB.
2) Easier to see with fluorescence
3) Much more sensitive, requires only 10^3 bacteria present to get a positive result, whereas took 10^5 with acid fast stains
You can get a false - PPD skin test on _____ ?
Immunocompromised patients, especially HIV patients, because their immunity is low, therefore cannot mount an appropriate immune response to the PPD being injected intradermally.
Why is TB very common in HIV patients?
Because, they cannot mount the normal T cell response that you normally see 2-6 weeks after infection where you send in macrophages to kill the mycobacterium. Because the uneducated macrophages cannot kill TB and allow it to persist.
What can lead to a reactivation TB?
alcohol especially suppresses your DTH response, age, underlying disease as well
Treat aggressively with Direct Observed Therapy. Why?
Because people who have it aren't really responsible for their own health care. And because this is such a major public health issue you want to ensure compliance, especially since they will be taking it for such a long time (at least 6 months). So, will even have a nurse go out everyday and give the patient the pills and watch him/her take them.
TB is transmitted via _______
person to person contact, inhalation
Why is resistance common with TB?
Because since the regimens were so long (6 months) people were quitting taking their antibiotics somewhere along the way.
Mycobacterium Tuberculosis is a _____________ intracellular parasite
facultative, therefore can still grow on culture media in the lab.
The only other reservoir for Mycobacterium Leprae is ________
knife bandit armadillo
To get M. Leprae you need (short/prolonged) exposure to an infected person
M. Leprae prefers what parts of the body?
cooler parts (fingers, testicles, toes, eyes, ears, nose, lips)
Why is M. Leprae called the perfect parasite?
Because it doesn't kill the host.
What is the leading cause of death for people with M. leprae infection?
Heart disease, simply from dying of old age (mortality rate of leprosy infection is almost 0)
*Are antibodies against M. TB or M. Leprae diagnostic? Protective?
Discuss the two forms of M. Leprae disease manifestation
Depending on the body's response can have...
1) Tuberculoid leprosy - predominantly a macrophage response to T cells (cell mediated immunity), where granulomas are formed, a lot more damage done, but better for containment of the disease, no skin lesions
2) Lepromatous Leprosy - no granulomas formed, a B cell mediated antibody response, thick skin lesions form, less damage done, but more expansive disease
Why would it not be uncommon to see a Leprosy patient with his hands wrapped entirely in bandages?
Because the lesions may become anasthetic, don't have feelings in them anymore, it is easy to do much more damage to self as a result (ie touching a hot stove and not even realizing it)
PPD test can only tell you how much?
That you HAD a TB infection at some point in the past, or you may have one right now, but cannot definitely say you are dealing with a current infection
What is the concern about Non-TB Mycobacterium being resistant to bleach?
We use bleach to disinfect dialysis equipment (since we can't autoclave it), and because of this it is possible to infect patients with Non-TB MB on subsequent uses of equipment due to its bleach resistance
What is considered the sentinal disease of HIV?
Mycobacterium avium (gets grouped together with M. Intracellulare because they cannot be distinguished by normal laboratory means)
What does M. kansasii produce?
It produces a pulmonary infection very similar to TB, and is very common in the southwest, especially Texas
What is the causative agent of scrofulus?
M. scrofulaceum, which causes a lymph node infection in children
How do kids get scrofulus?
Eating dirt, sand in the sandbox
If you are cleaning your fish tank and cut your finger, you may be at risk for contracting what type if Mycobacterium?
M. marinum, because this lives in water and causes cutaneous infections and abscesses (M. fortuitum does the same, except its found in dirt)
The Non-TB MB do not produce puss in their lesions of the skin. Why not?
Because they also inhibit neutrophil migration according to Dr. Hull
What has the appearance of rosary beads, and smells like dirt, and lives predominantly in dirt, and has a very low virulence for healthy people, but could be dangerous for immunocompromised individuals?

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