practical 3- blood agar Flashcards
Define Hemolysin
exotoxins that have the ability to destroy RBC and hemoglobin
Why is blood agar used for gram positive cocci
because it is used to isolate streptococci
what are the three major types of hemolysis
Beta- hemolysin
Alpha- hemolysin
Gama- hemolysin
Describe Beta- hemolysin
this is the complete destruction of RBC’s
cleans the medium around the colonies
Describe Alpha- hemolysin
partial destruction of RBC’s
produces an olive color around the colonies
describe Gama- hemolysin
non-hemolysis- this appears as simple growth with no change to the medium
what is the term used to describe the hemolysins produced by streptococci
streptolysins
what are the two streptolysins produced by streptococci
streptolysin O
streptolysin S
define streptolysin O
oxygen labile and expresses maximal activity under anaerobic conditions
define streptolysin S
oxygen stable but expresses itself optimally under anaerobic conditions
what is the method used to provide an environment for streptolysins on blood agar
streak stab technique- agar is streaked for isolation then stabbed with loop
what is the % of blood in the agar and where is the blood obtained
5% sheep blood
what type of hemolysis does S. aureus exhibit
B- hemolysis
why is blood agar known as enriched media
it contains nutrients required to support many types of organism growth
what does MRVP stand for
Mannitol red Voges Proskauer test
