Clinical microbiology Flashcards
HAI?
Nosomical infection @ health care fascility
Workflow?
Collect –> Culture –> Microscope –> Detection / Identification
Reliability of a test?
Determined by the specificty and sensitivity
Specificity?
Ability of a test to recognize a single pathogen
Sensitivity?
Smallest quanta of a pathogen detected by a test
Goal?
Low false-positive results
General purpose media?
Blood or chocolate agar
Selective media?
Specific for some organisms. Inhibatory agents that reduces growth for some
Differential media?
Allow identification of organisms based on the appearance after growth.
Blood?
General purpose media - incubate in anoxic and oxid conditions for growth - flourescense / turbidity or O2 or CO2 levels –> Stain –> Selective media - > identification
CSF?
Should be blank and high turbidity usually means high levels of leukocytes. Stain -> incubated with selective media.
UTI’s?
Blood agar and selective/differential media to difference between gram- lactose fermenters from non-fermenters. Including a low growth for gram+ bacteria.
> 10^5 cells / ml
Fecal?
Low pH -> sterile container -> transport and inoculated to suitable media
Wounds?
Syringe/biopsy -> Stain
STI’s?
Stain
Detect Anaerobic pathogens?
For obligate anaerobes. A media with high [] of reducing agent for the reduction of oxygen, and a redox indicator for anoxic conditions.
Skin test?
Th1 cells with DTH respons and a + tuberculine test
mABS?
Monoclonical antibodies produced by a B-cell clone in the area of diagnostic and therapeautic purposes.
Serology?
Study of antigen and antibody reactions in vitro.
Precipation?
Soluble antigen and antibody forms a insoluble complex
Agglutination?
Reaction between antibody and particlebound antigen that forms clumps of particles.
Immunoflourensce?
Conjugated flourescent dyes that detect antigens or intact cells. Under the microscope.
Direct - Antibody + surface antigens coupled to the dye
Indirect - Antibody on cells surface, bind flourescent antibody to the non-flourescent antibody
EIA?
Enzyme immuno assays D I S C
Direct?
Detects Antigen in blood and fecal sample
Antibody and dye binds to second antibody + enzyme and then addition of ES.
Indirect?
Detects Antibody in body fluids
Antigen on supporting matrix and antibodies bind
Antigen sandwich?
Detects Antibody in fluids. Immobilized and serum is added and binds to antigens.
Combination?
Both.
Direct and sandwich in one matrix.
Results EIA?
The coloured products is in proportion to the antigen bound by the E-S complex.
Rapid tests?
Detects Antigens.
Results are absorbed to a fixed support material of paper or plastic .
Point of cause tests - color change in minutes
Antibodies to chromopore that diffuses through a matrix and antigens binds to the chromopore which becomes visible as a line of color.
How does Western-Blotting work?
Antibody that binds to the conjugated enzyme. Coloured bands and after addition of the substrate on the strip @ site. + band matches.
Requires?
S
T
I
Separation?
Of the proteins on a polyacrylamide gel
Transfer?
Or Blotting of the proteins from gel to a nitrocellulorse or nylon membrane.
Identification?
Of proteins using a specific antibody
Nucleic acid based clinical assays?
PCR-techniques with high sensitivity and employ primers for a pathogen specific gene to exam DNA from infected tissue.
Identify viruses and intracellular pathogens that can not be cultured or observed
Nucleic acid hybridization?
Detects pathogens by probes that hybridize, which are labelled with a flourescent compound.
Lysing –> Denaturation NaOH –> Single strands –> Stable duplex
2 component probe –> Reporter and capture
What is qPCR?
Quantitative real time PCR with flourescent probes that labels amplicons that allows target DNA to be visulaized by culturing flourescence.
No gel electrophoresis -> Based on the flourescence in PCR, determined by the amounbt of target DNA present in the ori sample.
RT-PCR?
RNA –> cDNA via reverse transcriptase that detects RNA viruses.
Isolation of RNA sample –> cDNA amplified and employ qPCR –> particular gene from that pathogen.
Qualitative PCR?
Labelled hybridization –> primers are added to a amplicon of a qPCR reaction.
Hybridization probes to the DNA Pol gene and the amplicon is detected by using 2 distinct hybridization probes with flourescent dyes.
Flourescence is measured and after the PCR cycle –> Melting curve analysis for nucleotide polymorphism.
