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11 Cards in this Set

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What does acid-fast staining detect the presence of?
The Acid-Fast stain is a differential staining technique that it used to detect the presence
of mycolic acid.
What shape are Mycobacterium? Are they Gram + or -. What is the optimum temperature for their growth?
Mycobacterium are rod-shaped, gram-positive bacteria which like to grow at ~30oC.
The species of this genus have varied rates of growth.
What does the rod shaped mycobacterium genus have that is unique?
Organisms of the genus Mycobacterium have a unique waxy lipid layer called mycolic acid which makes the colonies look waxy and crusty.
What does mycolic acid do for the mycobacterium?
Mycolic acid binds to the peptidoglycan of the cell wall (without mycolic acid, the cell stains Gram-positive) creating a waxy, hydrophobic layer. They are thus resistant to dehydration.
How does the mycolic acid affect staining?
The bacteria require special staining methods
- Gram stains or other stains do not penetrate the waxy layer except if it is removed;
waxy layer repels aqueous stains
what does acid-fast staining require? Stains used?
staining the bacteria requires a mix of phenol and carbolfuchsin (primary stain)
- phenol helps the stain penetrate the waxy layer of the lipid
- carbolfuchsin is lipid soluble so it can enter the waxy layer
What is the mordant used in this genus?
steam and heat act as a mordant and are required to drive the stain into the cell
what is the decolorizer of non-acid fast cells?
acid-alcohol is used as a decolorizer of non acid-fast cells.
What is the counterstain used for non-acid fast cells?
Methylene blue is used as a counterstain in order to stain the non acid-fast bacteria
Mycobacterium tuberculosis
causes tuberculosis; an infection of the lungs where the patient is very sick or dies because of the resulting immune response. Left unchecked, an acute pulmonary infection occurs destroying lung tissue and spreading the disease to other parts of the body resulting in death.
- grows slowly and takes 8 weeks to call a culture negative or positive
- still a prevalent disease in the world
Mycobacterium leprae
- causes leprosy; an infection of the skin where lesions form on the extremities (face,
hands, feet, etc) causing a patient to become very sick or die due to the resulting immune response
can’t be grown on artificial media, only has been cultured on armadillo feet
- still a prevalent disease in parts of the world