||Activity 1.1: Demonstrating Hemolytic Reactions on Blood Agar Inoculums
Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus pneumoniae,
and Streptococcus bovis should be plated to view different hemolytic
- Obtain Blood Agar medium from
refrigerator. Allow medium to adjust to room temperature prior to inoculation.
- Using an appropriate inoculum, perform a four-quadrant streak to obtain
- Incubate at 35°C in an aerobic or CO2-supplemented
environment depending on the organism being cultivated.
- Examine after
18-24 hours. Examine the area immediately surrounding an isolated,
typical colony. Hemolysis is generally visible as a thin "halo" around
a hemolytic colony.
- In your lab report, describe alpha-, beta-, and
gamma-hemolytic reactions. Identify which species produced each type
Interpretation of Results
for growth and observe morphology and hemolysis patterns of the colonies
of interest. There are three main types of hemolysis:
- Beta (β) hemolysis,
where red blood cells around the colony are completely lysed or cleared
- Alpha (α) hemolysis, where red blood cells around the colony are partially
lysed or cleared giving rise to a greenish discoloration.
- Gamma (γ) hemolysis, where red blood cells around the colony remain intact and there is no change in the medium.
Note: Additional biochemical and/or
serological tests must be performed to complete identification.
View an example of hemolytic patterns.