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17 Cards in this Set
- Front
- Back
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What is a differential stain? |
Are those that distinguish between different types of organisms . Most importantly used for bacteria are the gram stain and acid fast stain. |
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What is the function of the iodine in a gram stain? |
It increases the cell's affinity for a stain. It allows by crystal violet to stick to the cell wall of a gram (+) bacteria. |
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What is the purpose of the alcohol in a gram stain? |
Removes the purple of the cells from some species but not from others . |
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What is the counterstain in the gram stain? why is it necessary? |
Safranin, it is used to stain pink those cells that have been previously decolorized . |
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What are the major structural differences between gram (+) and gram (-) cell walls? |
Gram (+) retain crystal violet dye,the cell wall is thick of peptidoglycan .In contrats, gram (-) do not retain the violet dye, they are more resistant against antibodies because of their impenetrable cell wall. |
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What effect does the age of a culture have on its gram stain? |
Old cultures of gram positive cells may not retain stain as well as younger cultures and could give false negative results . |
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Is a gram stain an adequate substitute for an acid fast stain? Why? |
No, it won't hold the stain due to the mycolic acid lipid. |
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What are the gram reactions of Mycobacterium spp and Bacillus spp? |
Acid fast stain , purple , garm (+) = Mycobacterium spore- staining , purple , gram (+) = Bacillus |
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When is it appropriate to perform an acid fast stain? |
When dealing with bacteria that have a thick , waxy lipid layer. |
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How might the acid fast stain characteristic of Mycobacterium enhance this bacterium's ability to cause disease ? |
The way cell protects it against phagocytosis and antibodies. |
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What are two acid-fast genera of bacteria? what diseases are associated with each one? |
Mycobacterium ( disease: tuberculosis ) Nocardia ( disease : nocardiosis) |
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Are bacterial endospores a form of reproduction? Why ? |
No , because no new cells are formed Sporulation is only for survival and cells don't replicate . |
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Of what advantage to clostridium is an endospore ? |
It allows clostridium to survive when conditions in the environment become unfavorable |
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Why are endospores important from a clinical viewpoint and in food industry? |
It is important to know that endospores are the cause of diseases such as gangrene , tetanus, botulism, and food poisoning. Knowing about endospores can be helpful when finding ways to kill them or control them so they do not cause diseases. |
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Gram stain |
Primary stain: crystal violet ( 30-60 sec) Mordant : iodine : purple ( 30-60 sec) Decolorizing : 95% ethanol : gram (-) = colorless , gram (+) = remain purple Counterstain : safranin, gram (+) cells retain the purple |
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Acid fast stain |
Primary stain : carbol fuschin ( 20 min) Decolorization : acid alcohol Counterstain : methylene blue ( 30 sec ) when observe : hot pink = acid fast blue = non acid fast |
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Spore stains |
Primary stain : malachite green ( 30 min ) Counterstain : 0.5 % safranin * The safranin will enter the vegetatives cells * spores are green Vegetatives cells are red |
