Lab Tests Flashcards
Pseudomonas is oxidase positive or negative
- Oxidase positive
Enterobacteriaceae is oxidase positive or negative
- Oxidase negative
Streptococcus is catalase positive or negative?
- catalase negative
Used to identify gram-negative bacteria
- 3% Potassium hydroxide (KOH) test
Staphylococcus is catalase positive or negative?
- catalase positive
Dissolves a thin layer of peptidoglycan of the cell walls and releases its content including the DNA of the gram negative bacteria, but does not affect gram positive cell walls
- 3% Potassium hydroxide (KOH) test
Used to differentiate between Staphylococcus and Streptococcus
- Catalase test
In a KOH test, if the solution is very viscous and sticky to the plastic loop when touched is the test positive or negative?
- KOH test is positive for gram negative bacteria because the release of DNA from the lysed cell causes this
Produced by Staphylococcus aureus and converts (soluble) fibrinogen in plasma to (insoluble) fibrin
- Coagulase
Used to identify bacteria that produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain
- Oxidase test
Differentiate enterobacteriaceae from Pseudomonas
- Oxidase test
Why will gram positive bacteria not be affected by KOH?
- they have a thicker peptidoglycan layer in the cell wall
If an oxidase test turns the reagent blue/purple what does that mean?
- Oxidase positive test
- > organisms which contain cytochrome c as part of their respiratory chain
Used to differentiate Staphylococcus aureus from negative staphylococci
- Coagulase test
If a catalase test bubbles what does that mean?
- Positive = bubbles
- Negative = bubbles
