Hemolysis: Click Here to View Images
In this procedure, the unknown bacteria is subcultured onto blood agar and
observed for its ability to lyse red blood cells. Blood agar is composed of a
nutrient agar base enriched with 5-10% sheep, rabbit, or horse blood.
Tips for Success:
Avoid contamination by heat sterilizing the inoculating loop just prior to
streaking plates. After sterilizing the loop, touch it to a portion of the agar
where no growth is present to cool the loop (this avoids "hot looping" the
colony chosen for isolation). After incubation, it is helpful to make
observations with proper back-lighting. Always run positive and negative
controls from known strains.
Procedure:
In this procedure, the unknown bacteria is subcultured onto blood agar and
observed for its ability to lyse red blood cells. Blood agar is composed of a
nutrient agar base enriched with 5-10% sheep, rabbit, or horse blood.
- Bacteria that can completely lyse the blood cells, causing a clearing
around the colony, are called beta hemolytic. - Bacteria that can partially break down the blood cells, causing a
green or brown discoloration of the agar around the colony, are
called alpha hemolytic. - Bacteria that cannot lyse the cells, causing no change in the agar,
are called gamma hemolytic.
Tips for Success:
Avoid contamination by heat sterilizing the inoculating loop just prior to
streaking plates. After sterilizing the loop, touch it to a portion of the agar
where no growth is present to cool the loop (this avoids "hot looping" the
colony chosen for isolation). After incubation, it is helpful to make
observations with proper back-lighting. Always run positive and negative
controls from known strains.
Procedure:
- Touch an isolated colony with a sterile inoculating loop.
- Using the loop, streak for isolation onto a blood agar plate.
- Incubate the plate for 24-48 hours.
- Observe for the presence of a zone of clearing or discoloration
around isolated colonies.
| Hemolysis Procedure For The Identification of Bacteria |
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