We are doing unknowns and we had a couple of media to choose from for streptococ
ID: 65219 • Letter: W
Question
We are doing unknowns and we had a couple of media to choose from for streptococcus. I chose a blood agar with a bacitracin. For my results, my blood agar looks very clear and had no zone of inhibition b/c instead of using bacitracin I had used the wrong pill and comparing to my friend, his blood agar doesn't look as clear but he thinks his blood agar is beta as well.
We have 3 bacteria to choose from Streptococcus Pyogenes, Streptococcus bovis, or enterococcus and Faecalis. Does his look like it has beta, alpha or gamma?
His is on the left. Mine is on the right.
Explanation / Answer
Yes, it is beta hemolysis only, in which a complete or a true lysis of red blood cells can be observed that results in the formation of clear zones which surrounds the colonies (transparent base medium). Many species of bacteria especially streptococcus species (S. pyogenes) produces toxic by-products (streptolysin 'O') that destroy the red blood cells.
Alpha hemolysis is a not true lysis in which, Hb of red blood cells is reduced to methemoglobin that result in the formation of green or brown discoloration of the medium.
Gamma hemolysis has contradictory predictions. In which, no hemolysis can be observed that result in no discoloration of surrounding medium.
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