Lab Quizzes and Information Flashcards
What are the laboratory diagnostic methods?
1) In vitro culture based
2) Microscopic methods
3) Molecular-based techniques
4) Serology-based methods (Proteins)
What are the culture based techniques, and what do they tell us?
Typically include growth media and selection; generally tell us about the biology of the organism, site of infection, and immune response to the organism
What is included in microscopy methods?
Direct observation using a microscope and gram staining
What are the molecular based techniques? Why would we use these techniques over other ones?
Restriction Fragment Length Polymorphisms (RFLP/literally just restriction digestion), DNA probes for hybridization (Fluorescent In-Situ Hybridization/FISH), Polymerase chain reaction (PCR), NGS, or Matrix-assisted Laser Desorption/ionization-time of flight (MALDI-TOF)
These techniques are sensitive, specific, and safe, but generally require specialized technical training and can be costly
What do the serological based diagnostics tell us?
They detect and quantitate antigen or antibody in clinical samples; can evaluate patient’s response to infection and history of exposure
What are the methods for serologic-based diagnosis?
Precipitation and immunodiffusion techniques, single radial immunodiffusion (where antigen diffuses into antibody containing agar), and western blotting
Differentiate between immunoelectrophoresis, rocket electrophoresis, and countercurrent electrophoresis
1) Immunoelectrophoresis: Antigen goes into the wells, and an antibody containing trough is put in the agar. The amount of diffusion from the antigen tells us about the reactions between antigen and antibody
2) Rocket electrophoresis: Antigen goes into the wells of an antibody containing gel; can tell us concentration by comparing the smears to a known quantity
3) Countercurrent electrophoresis: Antigen and antibody are loaded into opposite sides of the gel and run towards each other; pretty qualitative, a precipitate line indicates a positive reaction
What is single radial immunodiffusion?
An antigen is put into a well and allowed to diffuse into an antibody-containing agar; allows for the amount of antigen to be quantified in a sample
What are the different types of growth media and what information do they tell us?
Enriched non-selective media: Basic form of media, provides the nutrients needed to grow without distinguishing between what can grow (think LB/TSA agar)
Selective media: Media that is selective for a particular microorganism; can be antibiotics, bile agar to prevent gram + organisms, etc.
Selective and differential media: Media that is selective for a specific organism while also having a distinct change when the selected organism is present (MSA agar turns yellow, bile esculin agar turns black/brown)
Specialized media: Specific media for one microorganism; Lowenstein-Jensen (LJ) agar for mycobacterium/fungus
How should Staphylococcus aureus react to the following tests: hemolysis, TGA agar (coagulase test), MSA agar, Catalase test, Nitrate Reductase test, and Novobiocin Sensitivity test?
Hemolysis: Beta hemolysis (complete clearance)
TGA agar (coagulase test): Shiny black colonies (positive result)
MSA (Mannitol salt) agar: Yellow color (positive result)
Catalase test: Positive result (H2O2)
Nitrate Reductase test: Positive result (turns red)
Novobiocin Sensitivity test: Sensitive, large area of clearance
How should Staphylococcus epidermidis react to the following tests: hemolysis, TGA agar (coagulase test), MSA agar, Catalase test, Nitrate Reductase test, and Novobiocin Sensitivity test?
Hemolysis: Gamma (negative) hemolysis
TGA agar (coagulase test): Grey color (negative result)
MSA (Mannitol salt) agar: Negative (pink color)
Catalase test: Positive result
Nitrate Reductase test: Positive result
Novobiocin Sensitivity test: Sensitive, large area of clearance
How should Staphylococcus saprophyticus react to the following tests: hemolysis, TGA agar (coagulase test), MSA agar, Catalase test, Nitrate Reductase test, and Novobiocin Sensitivity test?
Hemolysis: Gamma (negative) hemolysis
TGA agar (coagulase test): Light black/grey (negative result)
MSA agar: Positive (yellow color)
Catalase test: Positive
Nitrate Reductase test: Negative (no red color)
Novobiocin Sensitivity test: Resistant (small/no area of clearance)
What does the CAMP test do?
It identifies B-hemolytic streptococci based on their formation of a CAMP factor that enlarges the area of hemolysis (the intersection between the two bacteria cultures will be more expanded)
How should Streptococcus pyogenes react to the following tests: hemolysis, bile solubility, bile esculin agar test, catalase test, CAMP test, Bacitracin/Optochin sensitivity tests, and methylene blue milk test?
Hemolysis: Beta hemolysis
Bile solubility: Negative (not soluble)
Bile esculin agar: Negative
Catalase Test: Negative
CAMP Test: Negative
Bacitracin: Sensitive
Optochin: Resistant
Methylene blue milk: Negative
How should Streptococcus agalactiae react to the following tests: hemolysis, bile solubility, bile esculin agar test, catalase test, CAMP test, Bacitracin/Optochin sensitivity tests, and methylene blue milk test?
Hemolysis: Gamma (no) hemolysis
Bile solubility: Negative (not soluble)
Bile esculin agar: Negative
Catalase Test: Negative
Bacitracin: Sensitive
Optochin: Resistant
CAMP Test: Positive
Methylene blue milk: Negative
