Introduction to Acid-Fast Staining
The process of staining allows bacteria to be identified by color. Organisms stain different colors based on the makeup of their cell wall and the staining process used. The acid-fast staining process results in the identification of bacteria that are resistant to other types of staining.
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Types
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Different cells react in various ways when stained by different processes. Some staining processes include gram staining, negative staining and acid-fast staining. These are types of differential staining because the results will allow the observer to distinguish cells from one another.
Significance
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Of the many types of bacteria that exist, only a small number can be classified as acid-fast. These organisms possess a strong cell wall that is resistant to other staining processes. Mycobacterium tuberculosis, the cause of tuberculosis, is an example of an acid-fast bacteria.
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Features
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The basic acid-fast staining process consists of three steps: slide preparation, staining and counter-staining. Carbol fuchsin, a red dye, will be used first, followed by the counter-stain methylene blue.
Time Frame
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For one slide, the staining process can be completed in approximately a half hour. The preparation of the heat-fixed slide takes the longest. The time it takes to successful identify a cell will vary case by case.
Warning
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Remember to allow the slide to completely air dry before heat fixing. Also, when completing an acid-fast stain, protective clothing and gloves are recommended. The dyes will stain fabric and skin.
Identification
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After the staining process is complete, viewing the slide under the microscope will show the results. Red-colored cells are the acid-fasts, whereas blue cells are non-acid fast.
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