Term
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Definition
| Waxy substance that gives acid-fast cells a higher affinity for the primary stain and resistance to decolorization by an acid alcohol solution |
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Term
| Name two of the acid-fast staining procedures? |
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Definition
Ziehl-Neelsen (ZN)
Kinyoun (K) method |
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Term
| How do the K and ZN methods differ? |
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Definition
| The ZN method uses heat as part of the staining process whereas K method is a "cold" stain. |
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Term
| Are acid-fast organisms gram + or -? |
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Definition
| They are only weakly gram positive |
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Term
| What is the primary stain used in the ZN method? |
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Definition
| Carbolfuchsin, because it is lipid soluble and penetrates the waxy cell wall. |
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Term
| What color do acid fast cells appear in the ZN method? |
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Definition
| Reddish purple while non acid fast cells are blue |
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Term
| What color do acid-fast cells appear in the K method |
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Definition
| Acid fast will appear reddish, while non acid fast will appear brilliant green, or the color of the counter stain. |
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Term
| What organisms are known to be acid-fast? |
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Definition
Bacteria in the genus Mycobacterium, some of which are pathogens and cause disease such as tuberculosis and leprosy.
Actinomycete Nocardia are partially acid-fast
Crytosoridium
Isospora |
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Term
| How are acid-fast stains useful? |
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Definition
| To identify acid-fast bacilli and in rapid prelim diagnosis of TB, and to track progress of antibiotic therapy, and determine the degree of contagiousness |
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Term
| How long must you steam the slide during the ZN? |
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Definition
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Term
| What is the purpose of the steaming procedure? |
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Definition
| To melt the waxy wall so that carbolfuchsin can get into acid-fast cells |
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Term
| How long do you allow the K carbolfuchsin stain to sit? |
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Definition
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Term
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Definition
| composed of mucoid polysaccharids or polypeptides that repel most stains. |
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Term
| What does the capsule stain technique take advantage of? |
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Definition
| Staining around the cells |
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Term
| What is used in a capsule stain? |
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Definition
| An acidic stain such as congo red or nigrosin, which stains the background, and a basic stain that colorizes the cell proper |
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Term
| How does the capsule appear in a capsule stain? |
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Definition
| It remains colorless and appears as a white halo between the cells and the colored background |
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Term
| In capsule stain why don't you heat fix the cells? |
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Definition
| Because heat fixing causes the cell to shrink leaving an artificactual white halo around them that might be interpreted as a capsule |
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Term
| How do capsules increase virulence? |
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Definition
| By making the cell less vulnerable to phagocytosis |
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