Mycobacterium Flashcards
Generally, what infections do mycobacterium cause?
pulmonary and extrapulmonary infections
Mycobacteria are acid-fast. Why?
because of their high lipid content in their cell walls
How do mycobacteria show up on gram stain?
they are gram negative rods
What type of organisms are Mycobacteria in regards to oxygen?
they are aerobic but they grow better in CO2
What type of media is typically used to grow Mycobacteria?
media that is egg-based
What disinfectants are mycobacteria resistant to?
halogen and quaternary ammonium disinfectants
What can kill mycobacteria?
phenol and substituted cresylic compounds
Are infections caused by Mycobacteria acute or chronic?
chronic
What type of parasites are Mycobacteria?
facultative intracellular parasites
What type of mycobacteria are killed by phagocytic cells and what type kill phagocytic cells?
saprophytic; pathogenic
Where in the cell are mycobacteria found?
in the cytoplasm of the macrophage
When mycobacteria rypture macrophages and adjoining cells are infected, what is formed as a result?
tubercles
Where are lesions from mycobacteria typically localized?
in the lungs, spleen, or liver
What are some immune mechanisms and proposed mechanisms by which mycobacteria are able to resist or alter the immune response?
- promote phagosome-lysosome fusion 2. Aggregate macrophages into epithelioid granulomas to restrict and contain mycobacteria 3. processing and presentation of bacterial antigens 4. Activation of T cells to control infection 5. increase microbicidal capacity of the granuloma by recruiting effector T cells to it
Why is the high lipid content of Mycobacteria important in their resistance to killing?
because they produce a variety of phospholipids, glycolipids, and sulfur-containing glycolypids that may interfere with host immune mechanisms
What is the immune response to Mycobacterium?
it is largely cellular and almost entirely mediated by macrophages. Leukocytes have been known to release reactive nitrogen and oxygen intermediates
What is Freund’s complete adjuvant?
a type of mineral oil that contains killed Mycobacterium smegmatis or M. phlei, but it is not used commercially due to lesions associated with the injection site
How is mycobacteria diagnosed?
since mycobacteria induces a delayed-type hypersensitivity reaction, the DTH reaction (intradermal skin test) is used to expose tubercle bacilli associated with mycobacteria
What antigen is used in the DTH reaction?
tuberculin
What are the different types of tuberculins used in the DTH test?
PPD (purified protein derivative) and OT (old tuberculins)
How are PPDs prepared?
by growing the organism on synthetic culture media, autoclaving, removing the cells, and precipitating the proteins with either ammonium sulfate or TCA
How are OTs prepared?
by growing bacilli on synthetic culture media
What type of tuberculins is used the majority of the time?
PPDs
What do drugs used to treat mycobacteria usually contain?
isoniazid and rifampin
What species does Mycobacterium tuberculosis infect?
primates
What specific disease does Mycobacterium tuberculosis cause?
tuberculosis
What famous scientist is associated with Mycobacterium tuberculosis?
Robert Koch
What other species does Mycobacterium tuberculosis infect?
zoo animals
In humans, tuberculosis is most often _______ in nature.
pulmonary
What lesions are associated with tuberculosis in humans?
lung lesions or cavitations that can develop and progress to the point that large blood vessels are compromised and the patient can bleed to death quickly; lesions occur in the vertebral column, kidneys, bladder, larynx, and other sites
How is tuberculosis treated?
six months of anti-TB drugs (1/3 kilogram a day)
What is the resistant strain of tuberculosis called?
XDR-TB
What is the recommended treatment for extensive drug resistant tuberculosis (XDR-TB)?
removal of lungs
What is the name of the most widely used human immunizing agent for TB in the world?
Bacille Calmette Guerin (BCG)
What does BCG contain?
a weakened live strain of Mycobacterium bovis
Who is BCG effective for?
infants and children