This test is consistently positive for staphylococci and negative for streptococci. Catalase is an enzyme that splits hydrogen peroxide into water and oxygen. The oxygen released is seen as tiny bubbles. Pick up 1 or 2 isolated colonies with your sterile loop and spread on a slide. Do not add saline.
Bubbles indicate a positive reaction for catalase .
The Coagulase test is the most reliable indicator of pathogenic, toxin-producing strains of Staphylococcus, i.e., for Staphylococcus aureus. Most pathogenic strains of Staphylococcus produce prostaphylocoagulase that reacts with an activator similar to prothrombin, to form the active clotting agent, coagulase. Coagulase in turn reacts with fibrinogen forming fibrin to produce the clotting of plasma. Emulsify this growth into 1 tube of Rabbit plasma, label with your name, and place in the 37 C incubator until the next lab period. Incomplete lysis of RBC's with the formation of a green discoloration surrounding the colony.