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Antigen-Antibody Interactions - Lab #3
Quiz by Ese Ararile
Tag the questions with any skills you have. Your dashboard will track each student's mastery of each skill.
Pick all true about Salmonella spp.
Clinical syndromes caused by Salmonella enterica
A combination of immunochemical, molecular and standardized phenotypic methods is recommended to prevent the misidentification of Salmonella spp. Why?
We used two commercially available qualitative immunoassays: the DynabeadsTM ImmunoMagnetic Separation (IMS) technology and an antibody-based Reveal® 2.0 lateral-flow test, and excluded standard culturing.
DynabeadsTM anti-Salmonella beads are spherical polystyrene hydrophobic 2.8-micron beads that have been made magnetizable and superparamagnetic, i.e. magnetic only in a magnetic field
The beads are coated with mouse polyclonal antibodies specific for LPS of S. enterica.
Organize the Immuno-Magnetic Separation steps accordingly
A lateral flow assay is a rapid, sensitive, low-cost and paper-based immunochromatographic detection system, which uses gold nanoparticles (GNP) as the colour marker.
What physical characteristics of GNPs (gold nanoparticles) used in LFA determine its application?
The core of the LFAs is the detection conjugate on the conjugate pad, which contains antibodies specific to the target, conjugated to colloidal GNPs and are needed to be highly purified and carefully designed
A standard LFA has four parts, namely
A lateral flow assay is based on:
a) a chromatographic separation of components of a mixture based on differences in movement through reaction membrane
b) antigen-antibody reactions
What is represented in this diagram?
Where are the buffer salts and surfactants that make the sample suitable for interaction with the detection system impregnated?
The control line will form in the control zone, indicating the proper liquid flow through the test device, but only if Salmonella is present.
Two red lines indicate a positive result, one each in both the control and test lines, while a negative result shows a control line only.
When is the LFA considered invalid?
Describe the zones of the Lateral Flow Assay
What is contained in the control zone?
In the conjugate pad, colloidal gold conjugates of a second antigen of the sample flow through till they reach the negative control capture zone and are captured by the second antibody.
What is XLD?
What is HEK?
What precautions were taken for this experiment?
Organize the steps of the IMS protocol
On HEK, Salmonella typically appears as green or blue-green colonies with black centers due to its ability to produce hydrogen sulfide (H2S)
On XLD agar, Salmonella will show a black center and red-colored translucent zone because phenol red turns yellow when the pH decreases due to sugar fermentation.
____ colonies have black centers because they metabolize thiosulfate to produce hydrogen sulfide, which reacts with ferric salts to form a black precipitate on XLD.
What woud E. coli colonies look like on XLD?
What is growing on this XLD plate?
Pick all that are accurate about YOUR lab results
I had growth on my bead-bacteria XLD plate
Were the in-lab results for LFA +ve or -ve?
Salmonella is a lactose fermenter
____ Indicates the formation of hydrogen sulfide from thiosulfate in HEK agar
Phenol red: Changes its color to yellow when acid is produced during carbohydrate fermentation of what sugars in XLD?
What do Sodium deoxycholate and Lysine do in XLD?
Bile salts are the inhibitors in HEK agar
Bromothymol blue and acid fuchsin: Indicate carbohydrate dissimilation in HEK