This test is used to differentiate Staphylococcus aureus from S. epidermidis and S. saprophyticus –

    v    Principle:-

          Staphylococcus aureus produces the enzyme coagulase which causes plasma to clot                          converting soluble  fibrinogen to insoluble fibrin.

    v  Requirements:-

1.      Oxalate or citrated plasma

2.      Glass slides

3.      Normal saline

    v Procedure (Slide Method):-

1.      Place a drop of physiological saline on each end of a slide.

2.      Make thick suspensions of the organisms in each drop.

3.      Add a drop of plasma to one of the suspensions. Mix gently. Look for clumping of the organisms within 10 seconds.

     v Results:-

            1.      Clumping within 10 seconds: Staphylococcus aureus

              2.      No clumping within 10 seconds: No production of coagulase

 v Tube test Method:-

1.      Prepare 1.0 ml of saline suspension of the organism

2.      Add 1.0 ml of plasma

3.      Incubate at 37°C for 24 hours.

4.      Observe from clot formation. The formation of a clot indicates the presence of Staphylococcus aureus organism.