Clinical Microbiology Flashcards
Clinical Microbiologist
Isolate and identify microbes from clinical specimens rapidly.
Categories of Testing for a Suspected Infectious Agent
Rapid Tests and Immunoassays Molecular Tests Biochemical Tests Cultures Microscopy
Biosafety Levels
1: Standard practices, basic PPE.
4: BSL-3 practice plus; different clothing; shower to exit; decontamination; glove box work.
Direct Identification of Microbes
Growth/Biochemical Characteristics Microscopy Molecular Methods Bacteriophage Typing Immunologic Tests
Indirect Identification of Microbes
Serology
Immunofluoresence
Dichotomous Keys
Used for identification of bacteria following isolation. Series of choices narrow down the identity of a bacterial pathogen.
Rapid Identification Methods
STAPH-IDENT System, automated systems, immunologic systems.
Microscopy
Dark field for detection of spirochetes; fluorescence for detection of fungi. Often use stains (Gram, acid fast)
Monoclonal Ab
mAbs can be fluorescently labeled and used diagnostically because they can recognize a single epitope.
Immunofluorescence
Fluorescent dyes ca be coupled to antibodies and visualized directly (antibody directly attaches to target) or indirectly (labeled antibody attaches to non-labeled antibody which attaches to target).
Identification of Parasites
Via microscopy. Using histological staining of blood, negative staining of other fluids, or immunofluorescence staining.
Molecular Genetic Identification Methods
Accurate. Compares proteins or nucleic acids. i.e PCR, DNA hybridization, ribotyping (16s rRNA), genomic and plasmid fingerprinting.
Real-Time PCR
Detects, amplifies and quantifies a target DNA molecule.
Immunological Techniques
Detection of antigens or antibodies in a specimen. Useful when culturing is impractical, easy to use, rapid, sensitive, and specific. i.e. OraQuick kit detect HIV antibodies in saliva in 10 minutes.
Serotyping
Use of serum antibodies to detect and identify other molecules. Differentiates serotypes of microbes by analyzing antigenic composition. i.e. testing for cell wall antigens.
Quellung Reaction
Swelling of capsular material following addition of antisera. Used for serotyping.
Agglutination
Generation of visible clumps or aggregates of cells or particles. i.e. Widal test for Typhoid fever, latex agglutination for pregnancy, and antibody titer measurements.
Complement Fixation
Binding of complement to an Ag-Ab complex. Used to determine if antibodies to an antigen are present in a patient’s serum. Very sensitive.
Enzyme-Linked Immunosorbent Assay (ELISA)
Widely used serological test. Detects antigens in a sample directly or antibodies indirectly. Visualized via chromogen.
Western Blotting
Also called immunoblotting. Used to distinguish microbes, and determine prognoses. Proteins are separated by electrophoresis and visualized with enzyme-labeled antibodies.
Immunoprecipitiation
Detects soluble Ag reacting with Ab. Bound Ag-Ab precipitates at optimal ratio due to lattice formation.
Immunodiffusion
Precipitation out of agar. Radial Immunodiffusion assay (RID) precipitates only the antigen. Ouchterlony technique precipitates both Ag and Ab.
Immunoelectrophoresis
Separate Ag by electrophoresis then visualize by precipitation reaction. More accurate resolution than immunodiffusion.
Flow Cytometry
Detects organisms in clinical samples. Often uses fluorochromes. The flow cytometer measures light scattering as a laser is passed through a suspension of cells. Can detect heterogeneous populations.
Radioimmunoassay
Ag labeled with radioactive isotope and binds Ab. Then the amount of radioactivity associated with the Ab is measured.
