1. Bacteriology 1
Lab 1

2. Staphylococci
Gram + Cocci
Cluster in arrangement

3. Gram stain

4. mannitol salt agar MSA selective and differential growth medium
high concentration (about 7.5%-10%) of salt
contain carbohydrate mannitol
Ph indicator : phenol red
Staphylococcus aureus produces yellow colonies
S.epidermidis
S. aureus

5. Catalase test Procedure:- 1- add few drops of H2O2 on a slide
Is used to differentiate between staphylocci & streptococcci
Staphylococci give positive result
Use 3% H2O2 (hydrogen peroxide )as substrate
gas bubble is produced for positive results
Procedure:-
1- add few drops of H2O2 on a slide
2- transfer a small amount of colony growth to the slide
3- observe the bubbling reaction

6. Coagulase test
Is used to differentiae between S.aureus and other staphylocci species.
S.aureus gives positive reaction
Fibrinogen (plasma) is the substrate
Fibrin (visible clot) is produced

7. Types of coagulase tests : Slide & Tube
Slide coagulase test :
- Detects cell-bound coagulase enzyme
- fast (within seconds)
- On slide
Tube coagulase test :
- Detects free coagulase enzyme
- Slow (~ 3- 4 hours incubation)
- in a tube

8. DNase test
Is used to differentiae between S.aureus and other staphylocci species.
DNA is the substrate
The hydrolysis of DNA is detected by observing a zone of clearance
Procedure:-
1- Using a sterile loop, inoculate organisms on Dnase plate. Make sure each test area is labelled clearly.
2- Incubate the plate aerobically at 35oC for 13 to 24 hours.
3- Flood the surface of the plate with 1 N hydrochloric acid (HCL )solution. Tip off the excess acid.
4- Look for clearing around the colonies within 5 minutes of adding the acid.
zone of clearance

9. Summary + - Tests S.aureus Other Staphylococci Catalase test
Coagulase test -
Dnase test