Diagnostic Immunology (Serology) (BE #6) Flashcards
ID the 3 major methods for identifying the etiologic agent of an infectious disease.
- phenotypic - physical characteristics
- genotype - genetic probes, PCR to ID DNA sequence
- immunological (serological)
What 3 things to phenotypic methods employ?
- cell morphology (under a microscope)
- colony morphology (on agar plates)
- physiology (biochemical tests on selective/differential media)
A bacterial species is found to be an acid-fast G(+) rod. Which method was employed to obtain this information?
phenotypic
Which method uses genetic probes and PCR to identify specific DNA sequences?
genotypic
Which method involves testing the patient’s blood or other body fluids for antibodies against the pathogen?
immunlogical
What 2 things can serological diagnostic methods test for in body fluids?
- antigen (Ag)
2. antbody (Ab)
If you are testing for the presence of antibody (Ab) in body fluids, then you must add __________ to the patient’s sample.
antigen
If you are testing for the presence of antigen (Ag) in body fluids, then you must add
________ to the patient’s sample.
antibody
titer
quantitative results from serological testing are expressed as a titer.
precipitation/gel electrophoresis
- Ag and Ab diffuse from opposite sides of a gel
- a precipitin line forms where they meet and bind
- an electrical current speeds diffusion
agglutination
- Antibody is attached to a latex bead
- Ab- Ag binding causes visible clumping
hemagglutination
- Ab is on a red blood cell
- Ab - Ag binding causes visible clumping of rbi’s
- used for blood typing
complement fixation
- Ab-Ag binding facilitates fixation of complement
- red blood cells are used as an indicator
immunofluorescence assay
- Ab or Ag has a fluorescent tag
- Ab-Ag binding is then visible under a UV light
radioimmunoassay
Ab or Ag has a radioactive tag
enzyme-linked immunosorbent assay (ELISA)
- Ab or Ag has an enzyme tag
- Ab-Ag binding allows enzyme to cleave its substrate
- immunochromatographic
Western blot
proteins separated using gel electrophoresis, then blotted onto filter & inoculated with patients serum
lateral flow test
- immunoassay in a dipstick format
- immunochormatographic
- pregnancy test
complement fixation: + result
Ab-Ag binding facilitates fixation of complement
- red blood cells are not lysed
complement fixation: - result
- Ab and Ab do not bind
- unfixed or free complement causes lysis of red blood cells (hemolysis)
enzyme-linked immunosorbent assay (+ result)
ELISA
Ab-Ag binding allows enzyme to cleave its substrate
color change is visible
enzyme-linked immunosorbent assay (- result)
Ab and Ag do not bind
enzyme is not able to cleave its substrate
no color change is visible
Why is viral culture not a viable option for influenza testing?
expensive & takes too long
ID 2 benefits for influenza testing
- cuts down on prescribing unnecessary antibiotics
2. patients can start antiviral drugs earlier
