Path Lab - Microbiology 2 Flashcards
How can you tell the difference between Staph aureus and other Staph species?
S aureus is coagulase positive
Other staph are coagulase negative staph
How can you tell the difference between Strep and Staph?
Using the Catalase test
Staph is catalase positive and causes oxygen bubbles
Which two broad groups of bacteria are differentiated by the oxidase test?
Enterobacteriaceae, and other gram negative rods.
This test is often used to distinguish between Enterobacteriaceae and Pseudomonas aeruginosa
How is a coagulase test performed?
Slide coagulase test: this is the rapid but less reliable form of the test. A portion of a staphylococccal colony is emulsified in a drop of plasma on a glass slide using a wooden toothpick, producing a milky suspension. If coagulase is present, the bacteria and fibrin will clump together within minutes, giving the suspension a granular appearance. The suspension remains homogenous if coagulase is not present.
Vs Tube Coagulase Test
How does the oxidase test work?
The test detects the presence of CYTOCHROME OXIDASE, an enzyme in the electron transport chain of some bacteria but not others. In the test, a colourless compound takes the place of oxygen in the real chemical reaction, and when this is reduced it becomes blue.
