15- Overview Of The Clinical Microbiology Laboratory Flashcards
What are some indirect identification methods of microbes?
- serology
- immunofluorescence
These bacteria are not routinely cultured and instead are identified with special stains, immunologic tests, or molecular methods such as PCR (3)?
- rickettsias
- chlamydiae
- mycoplasmas
These are produced by hybrids a cells and recognize a single epitope?
Monoclonal antibodies (mAb)
Where would you get chimeric monoclonal antibodies from?
Genetically modified mice that produce AB with a human constant region
What are humanize do monoclonal antibodies?
Monoclonal antibodies that are mostly human, except for mouse antigen-binding
What are fully human antibodies?
Monoclonal antibodies produces from a human gene on a mouse
What are hybridoma cells?
“Immortal” cancerous B cells fused with normal antibody-producing B cells
Immunofluorescence?
- process in which fluorescent dyes are exposed to UV , violet, or blue light to make them fluoresce
- dyes can be coupled to antibody molecules without changing the antibody’ stability to bind to a specific antigen
- can be used as direct fluorescent-antibody (FA) technique or indirect fluorescent-antibody (IFA) technique assay
These methods are used for the detection of parasites?
Histological staining of blood, negative staining of other body fluids, and immunofluorescence staining so are routinely used in identification of parasites
These are some of the molecular genetic methods used in clinical microbiology labs (6)?
- Nucleic acid probes; DNA hybridization
- PCR and real time PCR
- ribotyping (16S rRNA analysis)
- multilocus sequence typing (MLST)
- genomic fingerprinting
- plasmid fingerprinting
Ribotyping?
- used to identify bacterial genera
- based on high levels of 16S rRNA gene conservation among bacteria
- rRNA encoding genes or fragments are amplified by PCR
- the nucleotide sequence of the amplified DNA is determined and compared with those in the National Center for Biotechnology (NCBI)
Plasmid fingerprinting?
Characterizes bacteria based on the number of plasmids and their molecular weight
When would using immunological techniques for the detection of antigens or antibodies in specimens be useful?
When cultural methods are unavailable or impractical or antimicrobial therapy has been started
Advances in clinical immunology has given rise to a marked increase in the number, sensitivity, and specificity of serological tests. This has increased the understanding of what (4)?
- immune cell surface antigens (CDs)
- lymphocyte biology
- production of monoclonal antibodies
- development of sensitive antibody-binding reporter systems
These are essential to the the proper interpretation of immunological tests?
Test selection and timing
Serotyping?
The use of serum or purified antibodies to specifically detect and identify other molecules
How can serotyping be used?
- can be used to differentiate strains (servals or serotyping) of microorganisms that differ in antigenic composition of a structure or product
—-e.g., since virulence factor genes often occur in the same clone with genes for antigenic cell wall material, it is possible to serological identify a pathogen by testing for cell wall antigens–
Quelling reaction?
swelling of capsular material following the addition of antiserum specific for a capsular type
Direct serological tests test for what?
The presence of antigens (from patient sample)
Indirect serological tests test for what?
The presence of antibodies (in patient’s serum)
What are agglutinates?
Visible clumps or aggregates of cells or particles
When does an agglutination reaction occur?
When an immune complex is formed by cross-linking cells or particles with specific antibodies.
Hemagglutination?
Usually results from antibodies cross-linking red blood cells through attachment to surface antigens
- used in blood typing
Widal test?
Reaction involving the agglutination of typhoid bacilli when they are mixed with serum containing typhoid antibodies form an individual who has typhoid fever
- diagnostic for typhoid fever
Antibody titer?
The concentration of antibodies against a particular antigen
T/F: some viruses are able to agglutinate RBCs?
True
The visions of certain viruses can bind to BRCs , causing he agglutination. If serum containing specific antibodies to the virus is mixed with the RBCs, the antibodies will neutralize the virus and inhibit hemagglutination. Is this indicative of a positive or negative test?
Positive
Summarize complement fixation.
- binding of complement to an antigen-antibody complex
- basis of diagnostic tests that determine if antibodies to an antigen are present in patient’s serum
- very sensitive, measure extremely small amounts of antibody
Hemolysis of RBCs ant the indicator stage of the complement fixation test would indicate a positive or a negative test?
Negative test
No hemolysis of RBCs ant the indicator stage of the complement fixation test would indicate a positive or a negative test?
Positive
Summarize Enzyme-linked immunosorbent assay ELISA) test.
- one of the most widely used serological tests
- can be direct (antigens) OR indirect (antibodies)
- reaction visualized by the addition of chromagen
What are some direct identification methods for microbes?
- growth and biochemical characteristics
- microscopy
- molecular methods
- bacteriophage typing
- immunologic tests
Summarize immunoprecipitation (3).
- detects soluble Ag reacting with Ab (precipitins)
- Binding of AB to Ag forms lattice that precipitates
- lattice formation occurs only in optimal ratio of Ag to Ab
This area is where you would see the precipitation of antigens and antibodies?
Zone of equivalence (precipitation bands)
Summarize flow cytometry?
- it detects organisms in clinical samples
- detection is based on cytometry can parameters or by the use of fluorochromes (fluorochromes are often bound to antibodies or oligonucleotides)
What is an antibody neutralization reaction?
Binding of an antibody to biologically active materials (such as bacteria, toxins, or viruses) causes their inactivation.
