15. clinical microbiology Flashcards
What are general requirements to consider when collecting a specimen for microbiological sampling?
- collect from diseased area
- collect enough for all tests
- avoid contamination from other sites
- prompt analysis
- obtain prior to treatment therapy
What are a few direct methods to identify microbes?
- microscopy
- molecular method testing
- bacteriophage typing
- immunologic testing
- culture
Serology and immunofluorescence are what type of microbe identification methods?
- indirect methods
Most bacteria are generally cultured, what are a few exceptions that should undergo stain, immunologic, or PCR for analysis?
- ricketsia
- chlamydiae
- mycoplasmas
Fungi are best identified with what test method?
- sabourad dextrose agar culture
2. tests colony morphology, color and dimorphisms
What types of slides can be made for organisms to be detected with microscopy?
- heat-fixed
- wet-mounted
- chemically fixed
What are the different types of Monoclonal antibodies?
- chimeric
- humanized
- full human
What is a chimeric antibody?
- come from mice that produce antibodies with a human constant region
What is a humanized antibody?
- monoclonal antibody except for the Ag-binding site, which is still mouse derived
What is a full human monoclonal antibody?
- monoclonal antibody that is produced in a mouse from a human genome sequence.
What is the 6 step process for monoclonal Ab production?
- mice injected with Ag, to stimulate Ab production
- spleen is homogenized; B cells are “free”
- B cells are mixed with cancer cells to produce “immortal” hybridomas
- placed in specific medium to only allow growth of hybrid cells
- hybrid cells proliferate
- hybridomas are cultured to increase numbers.
What is the difference between direct and indirect fluorescent antibody detection technique?
- direct: the Ab is fluorescently tagged and binds directly to the Ag ( tests for presence of Ag)
- indirect: the fluorescence comes from an Ab that binds to the Ab that was extracted in the serum of the individual ( tests for presence of the Ab)
What methods can be used to detect the presence/absence of a parasite?
- immunofluorescence
- histological staining
- microscopy
- negative body fluid stain
Ribotyping is a commonly used method of identification that works on what method?
- requires the 16srRNA gene
- amplification of rRNA sequence via PCR
- use to compare sequence of the protein with others in a large database
What are monoclonal antibodies in general?
1.products of hybridoma cells, that allow prolonged lifespan of Ag specific B cells that have been activated
What methods are routinely used to identify parasites?
- blood histology stains
- immunofluorescence
- negative staining of body fluids
What are molecular genetic tests used to identify?
- comparison of proteins
2. detect nucleic acids
What is plasmid fingerprinting?
- characterizing bacteria based on the number of plasmids and their molecular weight
What is sensitivity?
the ability of a test to confirm the presence of a disease
What is specificity?
statistical probability that a person who does not have a disease will show a negative test result
What two features are key to proper immunologic test interpretation?
- test selection and timing of collection
What type of test method uses serum antibodies to detect and identify other molecules?
serotyping
- differentiates microbes that differ in antigen composition structure
Agglutinate
formation of clumps or aggregates of particles in an organized fashion
Widal test
diagnostic test for typhoid fever
Latex agglutination tests
pregnancy test and viral hemagglutination
What type of test will be used to asses antibody titer measures?
agglutination test
In what two ways can indirect agglutination tests be conducted?
- Ag coats a bead, and if Ab is present then agglutination will occur
- bead coated with the Ab, aggregation will indicate Ag presence
Which test uses blood cell lysis or no lysis to determine presence of Ab in the subjects serum?
complement fixation test
Do you know how the complement fixation test works?
Are you sure, be able to walk through it forwards and backwards
What is the indicator in an ELISA test?
peroxidase enzyme
Direct ELISA measures for what?
Ag presence in the sample
Indirect ELISA measures for waht?
Ab presence in the sample, but unable to indicate if the disease is current or from past.
What happens if both the Ag and Ab are present and are subjected to an immunoprecipitation test?
three regions develop.
- is Ab rich region and low Ag
- Ag rich region with low Ab
- proper mix of Ab-Ag that bind and precipitate out of solution in between the other two layers
