1. Lab 3
streptococci

2. Streptococci
Gram + cocci
Chains in arrangement
Catalase negative

4. Types of hemolysis : Blood agar

5. Alpha hemolysis Partial hemolysis of RBCs
Mainly S.pneumoniae & S. viridans
To differentiate: optochin disc
S.pneumoniae is sensitive while S. viridans is resistant.

6. Beta- hemolysis Complete Hemolysis of RBCs
Mainly GAS (Group A streptococci ) & GBS (Group B streptococci )
To differentiate: bacitracin test
GAS is sensitive while GBS is resistant.

7. Gamma – hemolysis No hemolysis
Mainly Enterococci : E. faecium & E. feacalis
Can grow at 6.5 % salt NACL
Can hydrolyze esculin in 40% bile ( bile esculin)
BILE inhibits gram + bacteria except enterococci & group D streptococci

8. summary

9. Gram stain 1- primary stain: ( crystal violet ) 1 minute
2- mordant : ( iodine ) 1 minute
3- decolorizer : ( alcohol or acetone ) 1-2 seconds
4- counterstain : ( safranin ) 1 minute