About this test
What is the purpose of the test?
This test provides information on what hemolytic enzymes a bacterium possesses. By providing a culture medium enriched with red blood cells, it is possible to determine whether a bacterium can destroy the cells and whether it can digest the hemoglobin inside.
How is hemolysis determined?
Bacteria possessing hemolysins will be able to discolor or clear blood agar in the vicinity of their colonies.
What medium is used?
A nutrient medium augmented with the addition of 5% sheep blood routinely is used. Such a medium is called blood agar .
How is the test performed?
Hemolysis is determined by streaking for isolation on a blood agar plate. In clinical settings, this might also include several stabs of the inoculum into the agar to encourage any anaerobic versions of the enzymes to digest blood cells. After incubation overnight, the medium is inspected for telltale signs of alpha- or beta-hemolysis . If the medium is discolored or darkened after growth, the organism has demonstrated alpha-hemolysis. If the medium has been cleared under growth, the organism is beta-hemolytic . No discernible change in the color of the medium constitutes gamma-hemolysis.
What reagents are added?
Performing this test in the VUMIE Online lab
Inoculation of Medium
1. Select the called blood agar plate medium.
2. Using an inoculating loop, complete the process of a tube-to-plate aseptic transfer to inoculate the medium. Forgotten how to do these things? Watch the “Show Me How To” videos.
Incubation of the Inoculated Medium
3. Place the inoculated tube into the 35-37 C incubator.
Determination of Test Results
5. Incubate this test for only 24 hours.
6. Retrieve the incubated culture from the incubator.
7. Observe the medium surrounding colonies in the plate. The culture showing a darkening or discoloration of the medium in the vicinity of growth demonstrates alpha-hemolysis. Cultures showing clear halos around colonies and under growth is exhibiting beta-hemolysis.
8. Record test result.