Micro Chap 10/Exam 3
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Define Bacterial species
a group of bacterial isoltates with similar characteristics (morphology, metabolic characteristics)
a group of isolates that share a 70% gene sequence similarity
Define Bacterial Isolate
a culture of bacteria obtained from the isolation of a single cell (like a streak plate sample)
Define Bacterial Strain
a group of bacterial isolates within the same species group, yet are distinguishable in some way from other isolates (such as E. coli K12, E. coli 0157, MRSA, VISA, VRSA, etc)
Define Viral species
a group of virus particles with similar morphology, genes, enzymes, and patterns of infection (how transmitted how replicated, symptoms caused, etc)
What is the theory of serological testing?
- 1. Add known antibodies to the sample
- 2. If antibodies bind to the sample, MO present (antibodies stick to the antigens)
- 3. If antibodies do not bind, MO is not present
What are serological methods?
- Use antibodies and antigens
What is an antigen?
- Antibody generators: molecules that, when introduced into a mammal, will cause that mammal's immune system to produces Abs that will bind to those Ag molecules
- -practically, microbial surface proteins and polysaccharides are often antigenic
What is an antibody?
Immunoglobins: are Y-shaped protein molecules, produced by the cells of the mammal's immune system, which chemically bind only to their particular antigen, marking it in some way (in vivo) for destruction
How is a slide-agglutination assay is performed? How is it interpreted?
- 1. Add patient sample to slide
- 2. Add known antibodies
- --> look for clumping to determine positive result
What is an ELISA test?
- E nzyme
- L inked
- I mmuno
- S orbent
- A ssay
How are direct ELISAs performed? How are they interpreted?
* use known antibodies to detect antigens in sample
- 1. Antibody is stuck to the bottom of the well (proteins stick to plastics)
- 2. Another protein like albumin is added to coat the well and protect it form other proteins binding to it
- 3. Patient sample is added, if it contains antigens then they bind to the antibody
- 4. A second antibody with an attached enzyme specific for the same antigen is added. Any unbound enzyme linked antibodies are washed away
- 5. Substrate for the enzyme is added. Conversion of the substrate to product is evidenced by a color change. A color change means the samle has the antigen. No color change is a negative result
How are indirect ELISAs performed? How are they interpreted?
- * use known antigens to detect antibodies in sample
- * used for HIV testing
- 1. The known antigen is stuck to the bottom of the well (proteins stick t plastics)
- 2. A blocking agent, like albumin, is added to coat the rest of the well to prevent the further sticking of proteins
- 3. The patient sample is then added. if the antibody is present, it binds to the antigen
- 4. A antihuman immunoglobin antibody with an attached enzyme is added
- 5. Substrate for the enzyme is added. Conversion of substrate to product is evidenced by a color change. No color change is a negative result
How are fluorescent antibodies used to detect microorganisms?
antibodies are combined with fluorochromes in vitro (in test tubes)
- 1. Add patient sample to the slide and fix
- 2. Add fluorescent antibodies
- 3. Rinse gently
- 4. View with fluorescence microscope
- --> look for fluorescence to indicate a positive result
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