21 terms

Micro Lab Unit 2 (Part II)

Acid Fast Stain Endospore Stain Capsule Stain
What is the purpose of the heat during the acid fast staining procedure?
Heat drives the stain into the cells.
What is the function of the counterstain in the acid fast staining procedure?
The counterstain will stick to the non-acid fast microorganism. The stain and the counterstain differentiate between the acid fast and non-acid fast microorganisms.
Are acid fast bacteria gram positive or gram negative? Explain your answer.
They are technically Gram +, but won't test positive in a gram stain. That's because these bacteria have a waxy coat on their cell walls that prevent the stain from entering.
For what diseases would you use an acid fast stain?
TB and leprosy.
What makes a microorganism non-acid fast?
its lacking the mycolic acid which contains 60% lipids.
What chemical is responsible for the acid fast property of mycobacteria?
mycolic acid
Is a Gram stain an adequate substitute for an acid fast stain? Why or why not?
no, it wont hold the stain due to the (mycolic acid) lipid
Why is heat necessary in order to stain endospores?
to provide stain penetration
Where are endospores located within vegetative cells?
Endospores can form within different areas of the vegetative cell. They can be central, subterminal, or terminal. Central endospores are located within the middle of the vegetative cell. Terminal endospores are located at the end of the vegetative cell. Subterminal endospores are located between the middle and the end of the cell.
In the Schaeffer-Fulton endospore stain, what is the primary stain? The counterstain?
primary is malachite green and the counter is safranin
Name two disease causing bacteria that produce endospores.
Tetanus & gangrene
What is the function of an endospore?
to provide protection in unfavorable conditions and at a later time producing a new cell)
Why are endospores so difficult to stain?
Spores have a tough outer covering made of keratin and are highly resistant to heat and chemicals and resists staining.
What do endospore stains have in common with the acid fast (Ziehl-Neelsen) stain?
heat primary stain penetration and then counterstain
What three chemical substances have been identified in bacterial capsules?
polysaccharide, polypeptide, and glycoproteins
What is the relationship between the presence of capsules and bacterial pathogenicity?
increased resistance to phagocytosis by wbc
What is the dual function of copper sulfate in capsule staining?
it is the decolorizing agent after the crystal violet as well as the counterstain for inside the capsule
In staining bacterial capsules, why is heat fixing omitted?
it will melt, distort the cell
How is the capsule stain used in clinical microbiology?
to diagnose and determine organisms virulence (a degree to which a pathogen can cause a disease)
*will it kill you or not
Name several bacteria that have capsules.
klebsiella pneumoniae, bacillus subtillus, streptococcus pneumoniae
Of what value is a capsule to a bacterium?
helps bacteria adhere to surfaces and resist flushing.