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Cards In This Set
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17.01 Name the 3 major categories of microbe identification techniques?
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1. Phenotypic- macro/microscopic observation of colonies
2. Genotypic- analysis using DNA/RNA
3. Immunologic (aka serology)- analysis of microbe using antibodies
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17.02 Identify some important considerations when collecting samples from patients (for microbial identification)?
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-Aseptic technique
-Must be transported in sterile containers
-Must be incubated correctly
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17.05 Explain the main principle behind biochemical tests?
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Physical reactions of bacteria to nutrients and other substrates provides excellent evidence of the types of enzyme systems present in a particular species.Most of these tests are based on enzymatic reactions visible by a color change.
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17.06 List the major steps in the hybridization method of microbe identification?
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1. Unknown DNA is extracted from cells in specimen and is bound to special blotter paper.
2. Several stock probes are added to the sample and it is observed for evidence that probes have become fixed (DNA is exposed and weak H bonds will let the probes in)
3. The identity of the source organism can be determined by the identity of the known probe used in hybridization.
*probes can now be made fluorescent
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17.07 Provide an explanation of why PCR is useful in ID diagnosis?
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PCR can amplify DNA that is present in sample (even tiny ones), which greatly will improve test sensitivity. Also, this allows for faster diagnosis.
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17.08 Give a thorough definition of the term serology.
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Serology (old term)= the branch of immunology that traditionally deals with in vitro ("in glass") testing in serum
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17.09 Differentiate between sensitivity and specificity?
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All tests have a certain sensitivity and specificity!
Sensitivity= the ability of a test to detect even tiny amounts of antibodies or antigen targets
Specificity= the property of a test to focus on only a certain antibody or antigen and not falsely react to others
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17.11 List the steps of a Western Blot test?
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1. Test serum electrophoresed into a gel to separate particular bands.
2. Gel transsferred to blotter that binds reactants in place.
3. Blot is then developed using fluorescent , radioactive, or luminescent labels.
4. Sites of pecific binding create distinct bands that can then be compared with positive and negative samples.
*Western Blot is currently used as second ID for HIV positive patients that have been diagnosed using ELISA.
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17.13 What are the steps in an ELISA test?
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Enzyme-Linked Immunosorbent Assay
This technique relies on a solid support system such as a plastic microliter plate that can adsorb (attract to its surface) the reactants. The ELISA test contains an enzyme-antibody complex that can be used as a color tracer for antibody reactions.
*AMC uses Sofia test
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